diff --git a/llvm/include/llvm/Transforms/Scalar/SCCP.h b/llvm/include/llvm/Transforms/Scalar/SCCP.h --- a/llvm/include/llvm/Transforms/Scalar/SCCP.h +++ b/llvm/include/llvm/Transforms/Scalar/SCCP.h @@ -27,6 +27,7 @@ #include "llvm/IR/Module.h" #include "llvm/IR/PassManager.h" #include "llvm/Transforms/Utils/PredicateInfo.h" +#include "llvm/Transforms/Utils/SCCPSolver.h" namespace llvm { @@ -38,13 +39,6 @@ PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM); }; -/// Helper struct for bundling up the analysis results per function for IPSCCP. -struct AnalysisResultsForFn { - std::unique_ptr PredInfo; - DominatorTree *DT; - PostDominatorTree *PDT; -}; - bool runIPSCCP(Module &M, const DataLayout &DL, std::function GetTLI, function_ref getAnalysis); diff --git a/llvm/include/llvm/Transforms/Utils/SCCPSolver.h b/llvm/include/llvm/Transforms/Utils/SCCPSolver.h new file mode 100644 --- /dev/null +++ b/llvm/include/llvm/Transforms/Utils/SCCPSolver.h @@ -0,0 +1,137 @@ +//===- SCCPSolver.h - SCCP Utility ----------------------------- *- C++ -*-===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// \file +// This file implements Sparse Conditional Constant Propagation (SCCP) utility. +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_TRANSFORMS_UTILS_SCCP_SOLVER_H +#define LLVM_TRANSFORMS_UTILS_SCCP_SOLVER_H + +#include "llvm/ADT/MapVector.h" +#include "llvm/Analysis/DomTreeUpdater.h" +#include "llvm/Analysis/TargetLibraryInfo.h" +#include "llvm/Analysis/ValueLattice.h" +#include "llvm/Analysis/ValueLatticeUtils.h" +#include "llvm/IR/InstVisitor.h" +#include "llvm/Transforms/Utils/PredicateInfo.h" +#include +#include +#include + +namespace llvm { + +/// Helper struct for bundling up the analysis results per function for IPSCCP. +struct AnalysisResultsForFn { + std::unique_ptr PredInfo; + DominatorTree *DT; + PostDominatorTree *PDT; +}; + +class SCCPInstVisitor; + +//===----------------------------------------------------------------------===// +// +/// SCCPSolver - This interface class is a general purpose solver for Sparse +/// Conditional Constant Propagation (SCCP). +/// +class SCCPSolver { + std::unique_ptr Visitor; + +public: + SCCPSolver(const DataLayout &DL, + std::function GetTLI, + LLVMContext &Ctx); + + ~SCCPSolver(); + + void addAnalysis(Function &F, AnalysisResultsForFn A); + + /// MarkBlockExecutable - This method can be used by clients to mark all of + /// the blocks that are known to be intrinsically live in the processed unit. + /// This returns true if the block was not considered live before. + bool MarkBlockExecutable(BasicBlock *BB); + + const PredicateBase *getPredicateInfoFor(Instruction *I); + + DomTreeUpdater getDTU(Function &F); + + /// TrackValueOfGlobalVariable - Clients can use this method to + /// inform the SCCPSolver that it should track loads and stores to the + /// specified global variable if it can. This is only legal to call if + /// performing Interprocedural SCCP. + void TrackValueOfGlobalVariable(GlobalVariable *GV); + + /// AddTrackedFunction - If the SCCP solver is supposed to track calls into + /// and out of the specified function (which cannot have its address taken), + /// this method must be called. + void AddTrackedFunction(Function *F); + + /// Add function to the list of functions whose return cannot be modified. + void addToMustPreserveReturnsInFunctions(Function *F); + + /// Returns true if the return of the given function cannot be modified. + bool mustPreserveReturn(Function *F); + + void AddArgumentTrackedFunction(Function *F); + + /// Returns true if the given function is in the solver's set of + /// argument-tracked functions. + bool isArgumentTrackedFunction(Function *F); + + /// Solve - Solve for constants and executable blocks. + void Solve(); + + /// ResolvedUndefsIn - While solving the dataflow for a function, we assume + /// that branches on undef values cannot reach any of their successors. + /// However, this is not a safe assumption. After we solve dataflow, this + /// method should be use to handle this. If this returns true, the solver + /// should be rerun. + bool ResolvedUndefsIn(Function &F); + + bool isBlockExecutable(BasicBlock *BB) const; + + // isEdgeFeasible - Return true if the control flow edge from the 'From' basic + // block to the 'To' basic block is currently feasible. + bool isEdgeFeasible(BasicBlock *From, BasicBlock *To) const; + + std::vector getStructLatticeValueFor(Value *V) const; + + void removeLatticeValueFor(Value *V); + + const ValueLatticeElement &getLatticeValueFor(Value *V) const; + + /// getTrackedRetVals - Get the inferred return value map. + const MapVector &getTrackedRetVals(); + + /// getTrackedGlobals - Get and return the set of inferred initializers for + /// global variables. + const DenseMap &getTrackedGlobals(); + + /// getMRVFunctionsTracked - Get the set of functions which return multiple + /// values tracked by the pass. + const SmallPtrSet getMRVFunctionsTracked(); + + /// markOverdefined - Mark the specified value overdefined. This + /// works with both scalars and structs. + void markOverdefined(Value *V); + + // isStructLatticeConstant - Return true if all the lattice values + // corresponding to elements of the structure are constants, + // false otherwise. + bool isStructLatticeConstant(Function *F, StructType *STy); + + /// Helper to return a Constant if \p LV is either a constant or a constant + /// range with a single element. + Constant *getConstant(const ValueLatticeElement &LV) const; +}; + +} // namespace llvm + +#endif // LLVM_TRANSFORMS_UTILS_SCCP_SOLVER_H diff --git a/llvm/lib/Transforms/Scalar/SCCP.cpp b/llvm/lib/Transforms/Scalar/SCCP.cpp --- a/llvm/lib/Transforms/Scalar/SCCP.cpp +++ b/llvm/lib/Transforms/Scalar/SCCP.cpp @@ -80,22 +80,11 @@ IPNumInstReplaced, "Number of instructions replaced with (simpler) instruction by IPSCCP"); -// The maximum number of range extensions allowed for operations requiring -// widening. -static const unsigned MaxNumRangeExtensions = 10; - -/// Returns MergeOptions with MaxWidenSteps set to MaxNumRangeExtensions. -static ValueLatticeElement::MergeOptions getMaxWidenStepsOpts() { - return ValueLatticeElement::MergeOptions().setMaxWidenSteps( - MaxNumRangeExtensions); -} -namespace { - // Helper to check if \p LV is either a constant or a constant // range with a single element. This should cover exactly the same cases as the // old ValueLatticeElement::isConstant() and is intended to be used in the // transition to ValueLatticeElement. -bool isConstant(const ValueLatticeElement &LV) { +static bool isConstant(const ValueLatticeElement &LV) { return LV.isConstant() || (LV.isConstantRange() && LV.getConstantRange().isSingleElement()); } @@ -104,1520 +93,12 @@ // than a single element. This should cover exactly the same cases as the old // ValueLatticeElement::isOverdefined() and is intended to be used in the // transition to ValueLatticeElement. -bool isOverdefined(const ValueLatticeElement &LV) { +static bool isOverdefined(const ValueLatticeElement &LV) { return !LV.isUnknownOrUndef() && !isConstant(LV); } -//===----------------------------------------------------------------------===// -// -/// SCCPSolver - This class is a general purpose solver for Sparse Conditional -/// Constant Propagation. -/// -class SCCPSolver : public InstVisitor { - const DataLayout &DL; - std::function GetTLI; - SmallPtrSet BBExecutable; // The BBs that are executable. - DenseMap - ValueState; // The state each value is in. - - /// StructValueState - This maintains ValueState for values that have - /// StructType, for example for formal arguments, calls, insertelement, etc. - DenseMap, ValueLatticeElement> StructValueState; - - /// GlobalValue - If we are tracking any values for the contents of a global - /// variable, we keep a mapping from the constant accessor to the element of - /// the global, to the currently known value. If the value becomes - /// overdefined, it's entry is simply removed from this map. - DenseMap TrackedGlobals; - - /// TrackedRetVals - If we are tracking arguments into and the return - /// value out of a function, it will have an entry in this map, indicating - /// what the known return value for the function is. - MapVector TrackedRetVals; - - /// TrackedMultipleRetVals - Same as TrackedRetVals, but used for functions - /// that return multiple values. - MapVector, ValueLatticeElement> - TrackedMultipleRetVals; - - /// MRVFunctionsTracked - Each function in TrackedMultipleRetVals is - /// represented here for efficient lookup. - SmallPtrSet MRVFunctionsTracked; - - /// A list of functions whose return cannot be modified. - SmallPtrSet MustPreserveReturnsInFunctions; - - /// TrackingIncomingArguments - This is the set of functions for whose - /// arguments we make optimistic assumptions about and try to prove as - /// constants. - SmallPtrSet TrackingIncomingArguments; - - /// The reason for two worklists is that overdefined is the lowest state - /// on the lattice, and moving things to overdefined as fast as possible - /// makes SCCP converge much faster. - /// - /// By having a separate worklist, we accomplish this because everything - /// possibly overdefined will become overdefined at the soonest possible - /// point. - SmallVector OverdefinedInstWorkList; - SmallVector InstWorkList; - - // The BasicBlock work list - SmallVector BBWorkList; - - /// KnownFeasibleEdges - Entries in this set are edges which have already had - /// PHI nodes retriggered. - using Edge = std::pair; - DenseSet KnownFeasibleEdges; - - DenseMap AnalysisResults; - DenseMap> AdditionalUsers; - - LLVMContext &Ctx; - -public: - void addAnalysis(Function &F, AnalysisResultsForFn A) { - AnalysisResults.insert({&F, std::move(A)}); - } - - const PredicateBase *getPredicateInfoFor(Instruction *I) { - auto A = AnalysisResults.find(I->getParent()->getParent()); - if (A == AnalysisResults.end()) - return nullptr; - return A->second.PredInfo->getPredicateInfoFor(I); - } - - DomTreeUpdater getDTU(Function &F) { - auto A = AnalysisResults.find(&F); - assert(A != AnalysisResults.end() && "Need analysis results for function."); - return {A->second.DT, A->second.PDT, DomTreeUpdater::UpdateStrategy::Lazy}; - } - - SCCPSolver(const DataLayout &DL, - std::function GetTLI, - LLVMContext &Ctx) - : DL(DL), GetTLI(std::move(GetTLI)), Ctx(Ctx) {} - - /// MarkBlockExecutable - This method can be used by clients to mark all of - /// the blocks that are known to be intrinsically live in the processed unit. - /// - /// This returns true if the block was not considered live before. - bool MarkBlockExecutable(BasicBlock *BB) { - if (!BBExecutable.insert(BB).second) - return false; - LLVM_DEBUG(dbgs() << "Marking Block Executable: " << BB->getName() << '\n'); - BBWorkList.push_back(BB); // Add the block to the work list! - return true; - } - - /// TrackValueOfGlobalVariable - Clients can use this method to - /// inform the SCCPSolver that it should track loads and stores to the - /// specified global variable if it can. This is only legal to call if - /// performing Interprocedural SCCP. - void TrackValueOfGlobalVariable(GlobalVariable *GV) { - // We only track the contents of scalar globals. - if (GV->getValueType()->isSingleValueType()) { - ValueLatticeElement &IV = TrackedGlobals[GV]; - if (!isa(GV->getInitializer())) - IV.markConstant(GV->getInitializer()); - } - } - - /// AddTrackedFunction - If the SCCP solver is supposed to track calls into - /// and out of the specified function (which cannot have its address taken), - /// this method must be called. - void AddTrackedFunction(Function *F) { - // Add an entry, F -> undef. - if (auto *STy = dyn_cast(F->getReturnType())) { - MRVFunctionsTracked.insert(F); - for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) - TrackedMultipleRetVals.insert( - std::make_pair(std::make_pair(F, i), ValueLatticeElement())); - } else if (!F->getReturnType()->isVoidTy()) - TrackedRetVals.insert(std::make_pair(F, ValueLatticeElement())); - } - - /// Add function to the list of functions whose return cannot be modified. - void addToMustPreserveReturnsInFunctions(Function *F) { - MustPreserveReturnsInFunctions.insert(F); - } - - /// Returns true if the return of the given function cannot be modified. - bool mustPreserveReturn(Function *F) { - return MustPreserveReturnsInFunctions.count(F); - } - - void AddArgumentTrackedFunction(Function *F) { - TrackingIncomingArguments.insert(F); - } - - /// Returns true if the given function is in the solver's set of - /// argument-tracked functions. - bool isArgumentTrackedFunction(Function *F) { - return TrackingIncomingArguments.count(F); - } - - /// Solve - Solve for constants and executable blocks. - void Solve(); - - /// ResolvedUndefsIn - While solving the dataflow for a function, we assume - /// that branches on undef values cannot reach any of their successors. - /// However, this is not a safe assumption. After we solve dataflow, this - /// method should be use to handle this. If this returns true, the solver - /// should be rerun. - bool ResolvedUndefsIn(Function &F); - - bool isBlockExecutable(BasicBlock *BB) const { - return BBExecutable.count(BB); - } - - // isEdgeFeasible - Return true if the control flow edge from the 'From' basic - // block to the 'To' basic block is currently feasible. - bool isEdgeFeasible(BasicBlock *From, BasicBlock *To) const; - - std::vector getStructLatticeValueFor(Value *V) const { - std::vector StructValues; - auto *STy = dyn_cast(V->getType()); - assert(STy && "getStructLatticeValueFor() can be called only on structs"); - for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { - auto I = StructValueState.find(std::make_pair(V, i)); - assert(I != StructValueState.end() && "Value not in valuemap!"); - StructValues.push_back(I->second); - } - return StructValues; - } - - void removeLatticeValueFor(Value *V) { ValueState.erase(V); } - - const ValueLatticeElement &getLatticeValueFor(Value *V) const { - assert(!V->getType()->isStructTy() && - "Should use getStructLatticeValueFor"); - DenseMap::const_iterator I = - ValueState.find(V); - assert(I != ValueState.end() && - "V not found in ValueState nor Paramstate map!"); - return I->second; - } - - /// getTrackedRetVals - Get the inferred return value map. - const MapVector &getTrackedRetVals() { - return TrackedRetVals; - } - - /// getTrackedGlobals - Get and return the set of inferred initializers for - /// global variables. - const DenseMap &getTrackedGlobals() { - return TrackedGlobals; - } - - /// getMRVFunctionsTracked - Get the set of functions which return multiple - /// values tracked by the pass. - const SmallPtrSet getMRVFunctionsTracked() { - return MRVFunctionsTracked; - } - - /// markOverdefined - Mark the specified value overdefined. This - /// works with both scalars and structs. - void markOverdefined(Value *V) { - if (auto *STy = dyn_cast(V->getType())) - for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) - markOverdefined(getStructValueState(V, i), V); - else - markOverdefined(ValueState[V], V); - } - - // isStructLatticeConstant - Return true if all the lattice values - // corresponding to elements of the structure are constants, - // false otherwise. - bool isStructLatticeConstant(Function *F, StructType *STy) { - for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { - const auto &It = TrackedMultipleRetVals.find(std::make_pair(F, i)); - assert(It != TrackedMultipleRetVals.end()); - ValueLatticeElement LV = It->second; - if (!isConstant(LV)) - return false; - } - return true; - } - - /// Helper to return a Constant if \p LV is either a constant or a constant - /// range with a single element. - Constant *getConstant(const ValueLatticeElement &LV) const { - if (LV.isConstant()) - return LV.getConstant(); - - if (LV.isConstantRange()) { - auto &CR = LV.getConstantRange(); - if (CR.getSingleElement()) - return ConstantInt::get(Ctx, *CR.getSingleElement()); - } - return nullptr; - } - -private: - ConstantInt *getConstantInt(const ValueLatticeElement &IV) const { - return dyn_cast_or_null(getConstant(IV)); - } - - // pushToWorkList - Helper for markConstant/markOverdefined - void pushToWorkList(ValueLatticeElement &IV, Value *V) { - if (IV.isOverdefined()) - return OverdefinedInstWorkList.push_back(V); - InstWorkList.push_back(V); - } - - // Helper to push \p V to the worklist, after updating it to \p IV. Also - // prints a debug message with the updated value. - void pushToWorkListMsg(ValueLatticeElement &IV, Value *V) { - LLVM_DEBUG(dbgs() << "updated " << IV << ": " << *V << '\n'); - pushToWorkList(IV, V); - } - - // markConstant - Make a value be marked as "constant". If the value - // is not already a constant, add it to the instruction work list so that - // the users of the instruction are updated later. - bool markConstant(ValueLatticeElement &IV, Value *V, Constant *C, - bool MayIncludeUndef = false) { - if (!IV.markConstant(C, MayIncludeUndef)) - return false; - LLVM_DEBUG(dbgs() << "markConstant: " << *C << ": " << *V << '\n'); - pushToWorkList(IV, V); - return true; - } - - bool markConstant(Value *V, Constant *C) { - assert(!V->getType()->isStructTy() && "structs should use mergeInValue"); - return markConstant(ValueState[V], V, C); - } - - // markOverdefined - Make a value be marked as "overdefined". If the - // value is not already overdefined, add it to the overdefined instruction - // work list so that the users of the instruction are updated later. - bool markOverdefined(ValueLatticeElement &IV, Value *V) { - if (!IV.markOverdefined()) return false; - - LLVM_DEBUG(dbgs() << "markOverdefined: "; - if (auto *F = dyn_cast(V)) dbgs() - << "Function '" << F->getName() << "'\n"; - else dbgs() << *V << '\n'); - // Only instructions go on the work list - pushToWorkList(IV, V); - return true; - } - /// Merge \p MergeWithV into \p IV and push \p V to the worklist, if \p IV - /// changes. - bool mergeInValue(ValueLatticeElement &IV, Value *V, - ValueLatticeElement MergeWithV, - ValueLatticeElement::MergeOptions Opts = { - /*MayIncludeUndef=*/false, /*CheckWiden=*/false}) { - if (IV.mergeIn(MergeWithV, Opts)) { - pushToWorkList(IV, V); - LLVM_DEBUG(dbgs() << "Merged " << MergeWithV << " into " << *V << " : " - << IV << "\n"); - return true; - } - return false; - } - - bool mergeInValue(Value *V, ValueLatticeElement MergeWithV, - ValueLatticeElement::MergeOptions Opts = { - /*MayIncludeUndef=*/false, /*CheckWiden=*/false}) { - assert(!V->getType()->isStructTy() && - "non-structs should use markConstant"); - return mergeInValue(ValueState[V], V, MergeWithV, Opts); - } - - /// getValueState - Return the ValueLatticeElement object that corresponds to - /// the value. This function handles the case when the value hasn't been seen - /// yet by properly seeding constants etc. - ValueLatticeElement &getValueState(Value *V) { - assert(!V->getType()->isStructTy() && "Should use getStructValueState"); - - auto I = ValueState.insert(std::make_pair(V, ValueLatticeElement())); - ValueLatticeElement &LV = I.first->second; - - if (!I.second) - return LV; // Common case, already in the map. - - if (auto *C = dyn_cast(V)) - LV.markConstant(C); // Constants are constant - - // All others are unknown by default. - return LV; - } - - /// getStructValueState - Return the ValueLatticeElement object that - /// corresponds to the value/field pair. This function handles the case when - /// the value hasn't been seen yet by properly seeding constants etc. - ValueLatticeElement &getStructValueState(Value *V, unsigned i) { - assert(V->getType()->isStructTy() && "Should use getValueState"); - assert(i < cast(V->getType())->getNumElements() && - "Invalid element #"); - - auto I = StructValueState.insert( - std::make_pair(std::make_pair(V, i), ValueLatticeElement())); - ValueLatticeElement &LV = I.first->second; - - if (!I.second) - return LV; // Common case, already in the map. - - if (auto *C = dyn_cast(V)) { - Constant *Elt = C->getAggregateElement(i); - - if (!Elt) - LV.markOverdefined(); // Unknown sort of constant. - else if (isa(Elt)) - ; // Undef values remain unknown. - else - LV.markConstant(Elt); // Constants are constant. - } - - // All others are underdefined by default. - return LV; - } - - /// markEdgeExecutable - Mark a basic block as executable, adding it to the BB - /// work list if it is not already executable. - bool markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest) { - if (!KnownFeasibleEdges.insert(Edge(Source, Dest)).second) - return false; // This edge is already known to be executable! - - if (!MarkBlockExecutable(Dest)) { - // If the destination is already executable, we just made an *edge* - // feasible that wasn't before. Revisit the PHI nodes in the block - // because they have potentially new operands. - LLVM_DEBUG(dbgs() << "Marking Edge Executable: " << Source->getName() - << " -> " << Dest->getName() << '\n'); - - for (PHINode &PN : Dest->phis()) - visitPHINode(PN); - } - return true; - } - - // getFeasibleSuccessors - Return a vector of booleans to indicate which - // successors are reachable from a given terminator instruction. - void getFeasibleSuccessors(Instruction &TI, SmallVectorImpl &Succs); - - // OperandChangedState - This method is invoked on all of the users of an - // instruction that was just changed state somehow. Based on this - // information, we need to update the specified user of this instruction. - void OperandChangedState(Instruction *I) { - if (BBExecutable.count(I->getParent())) // Inst is executable? - visit(*I); - } - - // Add U as additional user of V. - void addAdditionalUser(Value *V, User *U) { - auto Iter = AdditionalUsers.insert({V, {}}); - Iter.first->second.insert(U); - } - - // Mark I's users as changed, including AdditionalUsers. - void markUsersAsChanged(Value *I) { - // Functions include their arguments in the use-list. Changed function - // values mean that the result of the function changed. We only need to - // update the call sites with the new function result and do not have to - // propagate the call arguments. - if (isa(I)) { - for (User *U : I->users()) { - if (auto *CB = dyn_cast(U)) - handleCallResult(*CB); - } - } else { - for (User *U : I->users()) - if (auto *UI = dyn_cast(U)) - OperandChangedState(UI); - } - auto Iter = AdditionalUsers.find(I); - if (Iter != AdditionalUsers.end()) { - // Copy additional users before notifying them of changes, because new - // users may be added, potentially invalidating the iterator. - SmallVector ToNotify; - for (User *U : Iter->second) - if (auto *UI = dyn_cast(U)) - ToNotify.push_back(UI); - for (Instruction *UI : ToNotify) - OperandChangedState(UI); - } - } - void handleCallOverdefined(CallBase &CB); - void handleCallResult(CallBase &CB); - void handleCallArguments(CallBase &CB); - -private: - friend class InstVisitor; - - // visit implementations - Something changed in this instruction. Either an - // operand made a transition, or the instruction is newly executable. Change - // the value type of I to reflect these changes if appropriate. - void visitPHINode(PHINode &I); - - // Terminators - - void visitReturnInst(ReturnInst &I); - void visitTerminator(Instruction &TI); - - void visitCastInst(CastInst &I); - void visitSelectInst(SelectInst &I); - void visitUnaryOperator(Instruction &I); - void visitBinaryOperator(Instruction &I); - void visitCmpInst(CmpInst &I); - void visitExtractValueInst(ExtractValueInst &EVI); - void visitInsertValueInst(InsertValueInst &IVI); - - void visitCatchSwitchInst(CatchSwitchInst &CPI) { - markOverdefined(&CPI); - visitTerminator(CPI); - } - - // Instructions that cannot be folded away. - - void visitStoreInst (StoreInst &I); - void visitLoadInst (LoadInst &I); - void visitGetElementPtrInst(GetElementPtrInst &I); - - void visitCallInst (CallInst &I) { - visitCallBase(I); - } - - void visitInvokeInst (InvokeInst &II) { - visitCallBase(II); - visitTerminator(II); - } - - void visitCallBrInst (CallBrInst &CBI) { - visitCallBase(CBI); - visitTerminator(CBI); - } - - void visitCallBase (CallBase &CB); - void visitResumeInst (ResumeInst &I) { /*returns void*/ } - void visitUnreachableInst(UnreachableInst &I) { /*returns void*/ } - void visitFenceInst (FenceInst &I) { /*returns void*/ } - - void visitInstruction(Instruction &I) { - // All the instructions we don't do any special handling for just - // go to overdefined. - LLVM_DEBUG(dbgs() << "SCCP: Don't know how to handle: " << I << '\n'); - markOverdefined(&I); - } -}; - -} // end anonymous namespace - -// getFeasibleSuccessors - Return a vector of booleans to indicate which -// successors are reachable from a given terminator instruction. -void SCCPSolver::getFeasibleSuccessors(Instruction &TI, - SmallVectorImpl &Succs) { - Succs.resize(TI.getNumSuccessors()); - if (auto *BI = dyn_cast(&TI)) { - if (BI->isUnconditional()) { - Succs[0] = true; - return; - } - - ValueLatticeElement BCValue = getValueState(BI->getCondition()); - ConstantInt *CI = getConstantInt(BCValue); - if (!CI) { - // Overdefined condition variables, and branches on unfoldable constant - // conditions, mean the branch could go either way. - if (!BCValue.isUnknownOrUndef()) - Succs[0] = Succs[1] = true; - return; - } - - // Constant condition variables mean the branch can only go a single way. - Succs[CI->isZero()] = true; - return; - } - - // Unwinding instructions successors are always executable. - if (TI.isExceptionalTerminator()) { - Succs.assign(TI.getNumSuccessors(), true); - return; - } - - if (auto *SI = dyn_cast(&TI)) { - if (!SI->getNumCases()) { - Succs[0] = true; - return; - } - const ValueLatticeElement &SCValue = getValueState(SI->getCondition()); - if (ConstantInt *CI = getConstantInt(SCValue)) { - Succs[SI->findCaseValue(CI)->getSuccessorIndex()] = true; - return; - } - - // TODO: Switch on undef is UB. Stop passing false once the rest of LLVM - // is ready. - if (SCValue.isConstantRange(/*UndefAllowed=*/false)) { - const ConstantRange &Range = SCValue.getConstantRange(); - for (const auto &Case : SI->cases()) { - const APInt &CaseValue = Case.getCaseValue()->getValue(); - if (Range.contains(CaseValue)) - Succs[Case.getSuccessorIndex()] = true; - } - - // TODO: Determine whether default case is reachable. - Succs[SI->case_default()->getSuccessorIndex()] = true; - return; - } - - // Overdefined or unknown condition? All destinations are executable! - if (!SCValue.isUnknownOrUndef()) - Succs.assign(TI.getNumSuccessors(), true); - return; - } - - // In case of indirect branch and its address is a blockaddress, we mark - // the target as executable. - if (auto *IBR = dyn_cast(&TI)) { - // Casts are folded by visitCastInst. - ValueLatticeElement IBRValue = getValueState(IBR->getAddress()); - BlockAddress *Addr = dyn_cast_or_null(getConstant(IBRValue)); - if (!Addr) { // Overdefined or unknown condition? - // All destinations are executable! - if (!IBRValue.isUnknownOrUndef()) - Succs.assign(TI.getNumSuccessors(), true); - return; - } - - BasicBlock* T = Addr->getBasicBlock(); - assert(Addr->getFunction() == T->getParent() && - "Block address of a different function ?"); - for (unsigned i = 0; i < IBR->getNumSuccessors(); ++i) { - // This is the target. - if (IBR->getDestination(i) == T) { - Succs[i] = true; - return; - } - } - - // If we didn't find our destination in the IBR successor list, then we - // have undefined behavior. Its ok to assume no successor is executable. - return; - } - - // In case of callbr, we pessimistically assume that all successors are - // feasible. - if (isa(&TI)) { - Succs.assign(TI.getNumSuccessors(), true); - return; - } - - LLVM_DEBUG(dbgs() << "Unknown terminator instruction: " << TI << '\n'); - llvm_unreachable("SCCP: Don't know how to handle this terminator!"); -} - -// isEdgeFeasible - Return true if the control flow edge from the 'From' basic -// block to the 'To' basic block is currently feasible. -bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) const { - // Check if we've called markEdgeExecutable on the edge yet. (We could - // be more aggressive and try to consider edges which haven't been marked - // yet, but there isn't any need.) - return KnownFeasibleEdges.count(Edge(From, To)); -} - -// visit Implementations - Something changed in this instruction, either an -// operand made a transition, or the instruction is newly executable. Change -// the value type of I to reflect these changes if appropriate. This method -// makes sure to do the following actions: -// -// 1. If a phi node merges two constants in, and has conflicting value coming -// from different branches, or if the PHI node merges in an overdefined -// value, then the PHI node becomes overdefined. -// 2. If a phi node merges only constants in, and they all agree on value, the -// PHI node becomes a constant value equal to that. -// 3. If V <- x (op) y && isConstant(x) && isConstant(y) V = Constant -// 4. If V <- x (op) y && (isOverdefined(x) || isOverdefined(y)) V = Overdefined -// 5. If V <- MEM or V <- CALL or V <- (unknown) then V = Overdefined -// 6. If a conditional branch has a value that is constant, make the selected -// destination executable -// 7. If a conditional branch has a value that is overdefined, make all -// successors executable. -void SCCPSolver::visitPHINode(PHINode &PN) { - // If this PN returns a struct, just mark the result overdefined. - // TODO: We could do a lot better than this if code actually uses this. - if (PN.getType()->isStructTy()) - return (void)markOverdefined(&PN); - - if (getValueState(&PN).isOverdefined()) - return; // Quick exit - - // Super-extra-high-degree PHI nodes are unlikely to ever be marked constant, - // and slow us down a lot. Just mark them overdefined. - if (PN.getNumIncomingValues() > 64) - return (void)markOverdefined(&PN); - - unsigned NumActiveIncoming = 0; - - // Look at all of the executable operands of the PHI node. If any of them - // are overdefined, the PHI becomes overdefined as well. If they are all - // constant, and they agree with each other, the PHI becomes the identical - // constant. If they are constant and don't agree, the PHI is a constant - // range. If there are no executable operands, the PHI remains unknown. - ValueLatticeElement PhiState = getValueState(&PN); - for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) { - if (!isEdgeFeasible(PN.getIncomingBlock(i), PN.getParent())) - continue; - - ValueLatticeElement IV = getValueState(PN.getIncomingValue(i)); - PhiState.mergeIn(IV); - NumActiveIncoming++; - if (PhiState.isOverdefined()) - break; - } - - // We allow up to 1 range extension per active incoming value and one - // additional extension. Note that we manually adjust the number of range - // extensions to match the number of active incoming values. This helps to - // limit multiple extensions caused by the same incoming value, if other - // incoming values are equal. - mergeInValue(&PN, PhiState, - ValueLatticeElement::MergeOptions().setMaxWidenSteps( - NumActiveIncoming + 1)); - ValueLatticeElement &PhiStateRef = getValueState(&PN); - PhiStateRef.setNumRangeExtensions( - std::max(NumActiveIncoming, PhiStateRef.getNumRangeExtensions())); -} - -void SCCPSolver::visitReturnInst(ReturnInst &I) { - if (I.getNumOperands() == 0) return; // ret void - - Function *F = I.getParent()->getParent(); - Value *ResultOp = I.getOperand(0); - - // If we are tracking the return value of this function, merge it in. - if (!TrackedRetVals.empty() && !ResultOp->getType()->isStructTy()) { - auto TFRVI = TrackedRetVals.find(F); - if (TFRVI != TrackedRetVals.end()) { - mergeInValue(TFRVI->second, F, getValueState(ResultOp)); - return; - } - } - - // Handle functions that return multiple values. - if (!TrackedMultipleRetVals.empty()) { - if (auto *STy = dyn_cast(ResultOp->getType())) - if (MRVFunctionsTracked.count(F)) - for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) - mergeInValue(TrackedMultipleRetVals[std::make_pair(F, i)], F, - getStructValueState(ResultOp, i)); - } -} - -void SCCPSolver::visitTerminator(Instruction &TI) { - SmallVector SuccFeasible; - getFeasibleSuccessors(TI, SuccFeasible); - - BasicBlock *BB = TI.getParent(); - - // Mark all feasible successors executable. - for (unsigned i = 0, e = SuccFeasible.size(); i != e; ++i) - if (SuccFeasible[i]) - markEdgeExecutable(BB, TI.getSuccessor(i)); -} - -void SCCPSolver::visitCastInst(CastInst &I) { - // ResolvedUndefsIn might mark I as overdefined. Bail out, even if we would - // discover a concrete value later. - if (ValueState[&I].isOverdefined()) - return; - - ValueLatticeElement OpSt = getValueState(I.getOperand(0)); - if (Constant *OpC = getConstant(OpSt)) { - // Fold the constant as we build. - Constant *C = ConstantFoldCastOperand(I.getOpcode(), OpC, I.getType(), DL); - if (isa(C)) - return; - // Propagate constant value - markConstant(&I, C); - } else if (OpSt.isConstantRange() && I.getDestTy()->isIntegerTy()) { - auto &LV = getValueState(&I); - ConstantRange OpRange = OpSt.getConstantRange(); - Type *DestTy = I.getDestTy(); - // Vectors where all elements have the same known constant range are treated - // as a single constant range in the lattice. When bitcasting such vectors, - // there is a mis-match between the width of the lattice value (single - // constant range) and the original operands (vector). Go to overdefined in - // that case. - if (I.getOpcode() == Instruction::BitCast && - I.getOperand(0)->getType()->isVectorTy() && - OpRange.getBitWidth() < DL.getTypeSizeInBits(DestTy)) - return (void)markOverdefined(&I); - - ConstantRange Res = - OpRange.castOp(I.getOpcode(), DL.getTypeSizeInBits(DestTy)); - mergeInValue(LV, &I, ValueLatticeElement::getRange(Res)); - } else if (!OpSt.isUnknownOrUndef()) - markOverdefined(&I); -} - -void SCCPSolver::visitExtractValueInst(ExtractValueInst &EVI) { - // If this returns a struct, mark all elements over defined, we don't track - // structs in structs. - if (EVI.getType()->isStructTy()) - return (void)markOverdefined(&EVI); - - // ResolvedUndefsIn might mark I as overdefined. Bail out, even if we would - // discover a concrete value later. - if (ValueState[&EVI].isOverdefined()) - return (void)markOverdefined(&EVI); - - // If this is extracting from more than one level of struct, we don't know. - if (EVI.getNumIndices() != 1) - return (void)markOverdefined(&EVI); - - Value *AggVal = EVI.getAggregateOperand(); - if (AggVal->getType()->isStructTy()) { - unsigned i = *EVI.idx_begin(); - ValueLatticeElement EltVal = getStructValueState(AggVal, i); - mergeInValue(getValueState(&EVI), &EVI, EltVal); - } else { - // Otherwise, must be extracting from an array. - return (void)markOverdefined(&EVI); - } -} - -void SCCPSolver::visitInsertValueInst(InsertValueInst &IVI) { - auto *STy = dyn_cast(IVI.getType()); - if (!STy) - return (void)markOverdefined(&IVI); - - // ResolvedUndefsIn might mark I as overdefined. Bail out, even if we would - // discover a concrete value later. - if (isOverdefined(ValueState[&IVI])) - return (void)markOverdefined(&IVI); - - // If this has more than one index, we can't handle it, drive all results to - // undef. - if (IVI.getNumIndices() != 1) - return (void)markOverdefined(&IVI); - - Value *Aggr = IVI.getAggregateOperand(); - unsigned Idx = *IVI.idx_begin(); - - // Compute the result based on what we're inserting. - for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { - // This passes through all values that aren't the inserted element. - if (i != Idx) { - ValueLatticeElement EltVal = getStructValueState(Aggr, i); - mergeInValue(getStructValueState(&IVI, i), &IVI, EltVal); - continue; - } - - Value *Val = IVI.getInsertedValueOperand(); - if (Val->getType()->isStructTy()) - // We don't track structs in structs. - markOverdefined(getStructValueState(&IVI, i), &IVI); - else { - ValueLatticeElement InVal = getValueState(Val); - mergeInValue(getStructValueState(&IVI, i), &IVI, InVal); - } - } -} - -void SCCPSolver::visitSelectInst(SelectInst &I) { - // If this select returns a struct, just mark the result overdefined. - // TODO: We could do a lot better than this if code actually uses this. - if (I.getType()->isStructTy()) - return (void)markOverdefined(&I); - - // ResolvedUndefsIn might mark I as overdefined. Bail out, even if we would - // discover a concrete value later. - if (ValueState[&I].isOverdefined()) - return (void)markOverdefined(&I); - - ValueLatticeElement CondValue = getValueState(I.getCondition()); - if (CondValue.isUnknownOrUndef()) - return; - - if (ConstantInt *CondCB = getConstantInt(CondValue)) { - Value *OpVal = CondCB->isZero() ? I.getFalseValue() : I.getTrueValue(); - mergeInValue(&I, getValueState(OpVal)); - return; - } - - // Otherwise, the condition is overdefined or a constant we can't evaluate. - // See if we can produce something better than overdefined based on the T/F - // value. - ValueLatticeElement TVal = getValueState(I.getTrueValue()); - ValueLatticeElement FVal = getValueState(I.getFalseValue()); - - bool Changed = ValueState[&I].mergeIn(TVal); - Changed |= ValueState[&I].mergeIn(FVal); - if (Changed) - pushToWorkListMsg(ValueState[&I], &I); -} - -// Handle Unary Operators. -void SCCPSolver::visitUnaryOperator(Instruction &I) { - ValueLatticeElement V0State = getValueState(I.getOperand(0)); - - ValueLatticeElement &IV = ValueState[&I]; - // ResolvedUndefsIn might mark I as overdefined. Bail out, even if we would - // discover a concrete value later. - if (isOverdefined(IV)) - return (void)markOverdefined(&I); - - if (isConstant(V0State)) { - Constant *C = ConstantExpr::get(I.getOpcode(), getConstant(V0State)); - - // op Y -> undef. - if (isa(C)) - return; - return (void)markConstant(IV, &I, C); - } - - // If something is undef, wait for it to resolve. - if (!isOverdefined(V0State)) - return; - - markOverdefined(&I); -} - -// Handle Binary Operators. -void SCCPSolver::visitBinaryOperator(Instruction &I) { - ValueLatticeElement V1State = getValueState(I.getOperand(0)); - ValueLatticeElement V2State = getValueState(I.getOperand(1)); - - ValueLatticeElement &IV = ValueState[&I]; - if (IV.isOverdefined()) - return; - - // If something is undef, wait for it to resolve. - if (V1State.isUnknownOrUndef() || V2State.isUnknownOrUndef()) - return; - - if (V1State.isOverdefined() && V2State.isOverdefined()) - return (void)markOverdefined(&I); - - // If either of the operands is a constant, try to fold it to a constant. - // TODO: Use information from notconstant better. - if ((V1State.isConstant() || V2State.isConstant())) { - Value *V1 = isConstant(V1State) ? getConstant(V1State) : I.getOperand(0); - Value *V2 = isConstant(V2State) ? getConstant(V2State) : I.getOperand(1); - Value *R = SimplifyBinOp(I.getOpcode(), V1, V2, SimplifyQuery(DL)); - auto *C = dyn_cast_or_null(R); - if (C) { - // X op Y -> undef. - if (isa(C)) - return; - // Conservatively assume that the result may be based on operands that may - // be undef. Note that we use mergeInValue to combine the constant with - // the existing lattice value for I, as different constants might be found - // after one of the operands go to overdefined, e.g. due to one operand - // being a special floating value. - ValueLatticeElement NewV; - NewV.markConstant(C, /*MayIncludeUndef=*/true); - return (void)mergeInValue(&I, NewV); - } - } - - // Only use ranges for binary operators on integers. - if (!I.getType()->isIntegerTy()) - return markOverdefined(&I); - - // Try to simplify to a constant range. - ConstantRange A = ConstantRange::getFull(I.getType()->getScalarSizeInBits()); - ConstantRange B = ConstantRange::getFull(I.getType()->getScalarSizeInBits()); - if (V1State.isConstantRange()) - A = V1State.getConstantRange(); - if (V2State.isConstantRange()) - B = V2State.getConstantRange(); - - ConstantRange R = A.binaryOp(cast(&I)->getOpcode(), B); - mergeInValue(&I, ValueLatticeElement::getRange(R)); - - // TODO: Currently we do not exploit special values that produce something - // better than overdefined with an overdefined operand for vector or floating - // point types, like and <4 x i32> overdefined, zeroinitializer. -} - -// Handle ICmpInst instruction. -void SCCPSolver::visitCmpInst(CmpInst &I) { - // Do not cache this lookup, getValueState calls later in the function might - // invalidate the reference. - if (isOverdefined(ValueState[&I])) - return (void)markOverdefined(&I); - - Value *Op1 = I.getOperand(0); - Value *Op2 = I.getOperand(1); - - // For parameters, use ParamState which includes constant range info if - // available. - auto V1State = getValueState(Op1); - auto V2State = getValueState(Op2); - - Constant *C = V1State.getCompare(I.getPredicate(), I.getType(), V2State); - if (C) { - if (isa(C)) - return; - ValueLatticeElement CV; - CV.markConstant(C); - mergeInValue(&I, CV); - return; - } - - // If operands are still unknown, wait for it to resolve. - if ((V1State.isUnknownOrUndef() || V2State.isUnknownOrUndef()) && - !isConstant(ValueState[&I])) - return; - - markOverdefined(&I); -} - -// Handle getelementptr instructions. If all operands are constants then we -// can turn this into a getelementptr ConstantExpr. -void SCCPSolver::visitGetElementPtrInst(GetElementPtrInst &I) { - if (isOverdefined(ValueState[&I])) - return (void)markOverdefined(&I); - - SmallVector Operands; - Operands.reserve(I.getNumOperands()); - - for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) { - ValueLatticeElement State = getValueState(I.getOperand(i)); - if (State.isUnknownOrUndef()) - return; // Operands are not resolved yet. - - if (isOverdefined(State)) - return (void)markOverdefined(&I); - - if (Constant *C = getConstant(State)) { - Operands.push_back(C); - continue; - } - - return (void)markOverdefined(&I); - } - - Constant *Ptr = Operands[0]; - auto Indices = makeArrayRef(Operands.begin() + 1, Operands.end()); - Constant *C = - ConstantExpr::getGetElementPtr(I.getSourceElementType(), Ptr, Indices); - if (isa(C)) - return; - markConstant(&I, C); -} - -void SCCPSolver::visitStoreInst(StoreInst &SI) { - // If this store is of a struct, ignore it. - if (SI.getOperand(0)->getType()->isStructTy()) - return; - - if (TrackedGlobals.empty() || !isa(SI.getOperand(1))) - return; - - GlobalVariable *GV = cast(SI.getOperand(1)); - auto I = TrackedGlobals.find(GV); - if (I == TrackedGlobals.end()) - return; - - // Get the value we are storing into the global, then merge it. - mergeInValue(I->second, GV, getValueState(SI.getOperand(0)), - ValueLatticeElement::MergeOptions().setCheckWiden(false)); - if (I->second.isOverdefined()) - TrackedGlobals.erase(I); // No need to keep tracking this! -} - -static ValueLatticeElement getValueFromMetadata(const Instruction *I) { - if (MDNode *Ranges = I->getMetadata(LLVMContext::MD_range)) - if (I->getType()->isIntegerTy()) - return ValueLatticeElement::getRange( - getConstantRangeFromMetadata(*Ranges)); - if (I->hasMetadata(LLVMContext::MD_nonnull)) - return ValueLatticeElement::getNot( - ConstantPointerNull::get(cast(I->getType()))); - return ValueLatticeElement::getOverdefined(); -} - -// Handle load instructions. If the operand is a constant pointer to a constant -// global, we can replace the load with the loaded constant value! -void SCCPSolver::visitLoadInst(LoadInst &I) { - // If this load is of a struct or the load is volatile, just mark the result - // as overdefined. - if (I.getType()->isStructTy() || I.isVolatile()) - return (void)markOverdefined(&I); - - // ResolvedUndefsIn might mark I as overdefined. Bail out, even if we would - // discover a concrete value later. - if (ValueState[&I].isOverdefined()) - return (void)markOverdefined(&I); - - ValueLatticeElement PtrVal = getValueState(I.getOperand(0)); - if (PtrVal.isUnknownOrUndef()) - return; // The pointer is not resolved yet! - - ValueLatticeElement &IV = ValueState[&I]; - - if (isConstant(PtrVal)) { - Constant *Ptr = getConstant(PtrVal); - - // load null is undefined. - if (isa(Ptr)) { - if (NullPointerIsDefined(I.getFunction(), I.getPointerAddressSpace())) - return (void)markOverdefined(IV, &I); - else - return; - } - - // Transform load (constant global) into the value loaded. - if (auto *GV = dyn_cast(Ptr)) { - if (!TrackedGlobals.empty()) { - // If we are tracking this global, merge in the known value for it. - auto It = TrackedGlobals.find(GV); - if (It != TrackedGlobals.end()) { - mergeInValue(IV, &I, It->second, getMaxWidenStepsOpts()); - return; - } - } - } - - // Transform load from a constant into a constant if possible. - if (Constant *C = ConstantFoldLoadFromConstPtr(Ptr, I.getType(), DL)) { - if (isa(C)) - return; - return (void)markConstant(IV, &I, C); - } - } - - // Fall back to metadata. - mergeInValue(&I, getValueFromMetadata(&I)); -} - -void SCCPSolver::visitCallBase(CallBase &CB) { - handleCallResult(CB); - handleCallArguments(CB); -} - -void SCCPSolver::handleCallOverdefined(CallBase &CB) { - Function *F = CB.getCalledFunction(); - - // Void return and not tracking callee, just bail. - if (CB.getType()->isVoidTy()) - return; - - // Always mark struct return as overdefined. - if (CB.getType()->isStructTy()) - return (void)markOverdefined(&CB); - - // Otherwise, if we have a single return value case, and if the function is - // a declaration, maybe we can constant fold it. - if (F && F->isDeclaration() && canConstantFoldCallTo(&CB, F)) { - SmallVector Operands; - for (auto AI = CB.arg_begin(), E = CB.arg_end(); AI != E; ++AI) { - if (AI->get()->getType()->isStructTy()) - return markOverdefined(&CB); // Can't handle struct args. - ValueLatticeElement State = getValueState(*AI); - - if (State.isUnknownOrUndef()) - return; // Operands are not resolved yet. - if (isOverdefined(State)) - return (void)markOverdefined(&CB); - assert(isConstant(State) && "Unknown state!"); - Operands.push_back(getConstant(State)); - } - - if (isOverdefined(getValueState(&CB))) - return (void)markOverdefined(&CB); - - // If we can constant fold this, mark the result of the call as a - // constant. - if (Constant *C = ConstantFoldCall(&CB, F, Operands, &GetTLI(*F))) { - // call -> undef. - if (isa(C)) - return; - return (void)markConstant(&CB, C); - } - } - - // Fall back to metadata. - mergeInValue(&CB, getValueFromMetadata(&CB)); -} - -void SCCPSolver::handleCallArguments(CallBase &CB) { - Function *F = CB.getCalledFunction(); - // If this is a local function that doesn't have its address taken, mark its - // entry block executable and merge in the actual arguments to the call into - // the formal arguments of the function. - if (!TrackingIncomingArguments.empty() && - TrackingIncomingArguments.count(F)) { - MarkBlockExecutable(&F->front()); - - // Propagate information from this call site into the callee. - auto CAI = CB.arg_begin(); - for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E; - ++AI, ++CAI) { - // If this argument is byval, and if the function is not readonly, there - // will be an implicit copy formed of the input aggregate. - if (AI->hasByValAttr() && !F->onlyReadsMemory()) { - markOverdefined(&*AI); - continue; - } - - if (auto *STy = dyn_cast(AI->getType())) { - for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { - ValueLatticeElement CallArg = getStructValueState(*CAI, i); - mergeInValue(getStructValueState(&*AI, i), &*AI, CallArg, - getMaxWidenStepsOpts()); - } - } else - mergeInValue(&*AI, getValueState(*CAI), getMaxWidenStepsOpts()); - } - } -} - -void SCCPSolver::handleCallResult(CallBase &CB) { - Function *F = CB.getCalledFunction(); - - if (auto *II = dyn_cast(&CB)) { - if (II->getIntrinsicID() == Intrinsic::ssa_copy) { - if (ValueState[&CB].isOverdefined()) - return; - - Value *CopyOf = CB.getOperand(0); - ValueLatticeElement CopyOfVal = getValueState(CopyOf); - auto *PI = getPredicateInfoFor(&CB); - assert(PI && "Missing predicate info for ssa.copy"); - - const Optional &Constraint = PI->getConstraint(); - if (!Constraint) { - mergeInValue(ValueState[&CB], &CB, CopyOfVal); - return; - } - - CmpInst::Predicate Pred = Constraint->Predicate; - Value *OtherOp = Constraint->OtherOp; - - // Wait until OtherOp is resolved. - if (getValueState(OtherOp).isUnknown()) { - addAdditionalUser(OtherOp, &CB); - return; - } - - // TODO: Actually filp MayIncludeUndef for the created range to false, - // once most places in the optimizer respect the branches on - // undef/poison are UB rule. The reason why the new range cannot be - // undef is as follows below: - // The new range is based on a branch condition. That guarantees that - // neither of the compare operands can be undef in the branch targets, - // unless we have conditions that are always true/false (e.g. icmp ule - // i32, %a, i32_max). For the latter overdefined/empty range will be - // inferred, but the branch will get folded accordingly anyways. - bool MayIncludeUndef = !isa(PI); - - ValueLatticeElement CondVal = getValueState(OtherOp); - ValueLatticeElement &IV = ValueState[&CB]; - if (CondVal.isConstantRange() || CopyOfVal.isConstantRange()) { - auto ImposedCR = - ConstantRange::getFull(DL.getTypeSizeInBits(CopyOf->getType())); - - // Get the range imposed by the condition. - if (CondVal.isConstantRange()) - ImposedCR = ConstantRange::makeAllowedICmpRegion( - Pred, CondVal.getConstantRange()); - - // Combine range info for the original value with the new range from the - // condition. - auto CopyOfCR = CopyOfVal.isConstantRange() - ? CopyOfVal.getConstantRange() - : ConstantRange::getFull( - DL.getTypeSizeInBits(CopyOf->getType())); - auto NewCR = ImposedCR.intersectWith(CopyOfCR); - // If the existing information is != x, do not use the information from - // a chained predicate, as the != x information is more likely to be - // helpful in practice. - if (!CopyOfCR.contains(NewCR) && CopyOfCR.getSingleMissingElement()) - NewCR = CopyOfCR; - - addAdditionalUser(OtherOp, &CB); - mergeInValue( - IV, &CB, - ValueLatticeElement::getRange(NewCR, MayIncludeUndef)); - return; - } else if (Pred == CmpInst::ICMP_EQ && CondVal.isConstant()) { - // For non-integer values or integer constant expressions, only - // propagate equal constants. - addAdditionalUser(OtherOp, &CB); - mergeInValue(IV, &CB, CondVal); - return; - } else if (Pred == CmpInst::ICMP_NE && CondVal.isConstant() && - !MayIncludeUndef) { - // Propagate inequalities. - addAdditionalUser(OtherOp, &CB); - mergeInValue(IV, &CB, - ValueLatticeElement::getNot(CondVal.getConstant())); - return; - } - - return (void)mergeInValue(IV, &CB, CopyOfVal); - } - - if (ConstantRange::isIntrinsicSupported(II->getIntrinsicID())) { - // Compute result range for intrinsics supported by ConstantRange. - // Do this even if we don't know a range for all operands, as we may - // still know something about the result range, e.g. of abs(x). - SmallVector OpRanges; - for (Value *Op : II->args()) { - const ValueLatticeElement &State = getValueState(Op); - if (State.isConstantRange()) - OpRanges.push_back(State.getConstantRange()); - else - OpRanges.push_back( - ConstantRange::getFull(Op->getType()->getScalarSizeInBits())); - } - - ConstantRange Result = - ConstantRange::intrinsic(II->getIntrinsicID(), OpRanges); - return (void)mergeInValue(II, ValueLatticeElement::getRange(Result)); - } - } - - // The common case is that we aren't tracking the callee, either because we - // are not doing interprocedural analysis or the callee is indirect, or is - // external. Handle these cases first. - if (!F || F->isDeclaration()) - return handleCallOverdefined(CB); - - // If this is a single/zero retval case, see if we're tracking the function. - if (auto *STy = dyn_cast(F->getReturnType())) { - if (!MRVFunctionsTracked.count(F)) - return handleCallOverdefined(CB); // Not tracking this callee. - - // If we are tracking this callee, propagate the result of the function - // into this call site. - for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) - mergeInValue(getStructValueState(&CB, i), &CB, - TrackedMultipleRetVals[std::make_pair(F, i)], - getMaxWidenStepsOpts()); - } else { - auto TFRVI = TrackedRetVals.find(F); - if (TFRVI == TrackedRetVals.end()) - return handleCallOverdefined(CB); // Not tracking this callee. - - // If so, propagate the return value of the callee into this call result. - mergeInValue(&CB, TFRVI->second, getMaxWidenStepsOpts()); - } -} - -void SCCPSolver::Solve() { - // Process the work lists until they are empty! - while (!BBWorkList.empty() || !InstWorkList.empty() || - !OverdefinedInstWorkList.empty()) { - // Process the overdefined instruction's work list first, which drives other - // things to overdefined more quickly. - while (!OverdefinedInstWorkList.empty()) { - Value *I = OverdefinedInstWorkList.pop_back_val(); - - LLVM_DEBUG(dbgs() << "\nPopped off OI-WL: " << *I << '\n'); - - // "I" got into the work list because it either made the transition from - // bottom to constant, or to overdefined. - // - // Anything on this worklist that is overdefined need not be visited - // since all of its users will have already been marked as overdefined - // Update all of the users of this instruction's value. - // - markUsersAsChanged(I); - } - - // Process the instruction work list. - while (!InstWorkList.empty()) { - Value *I = InstWorkList.pop_back_val(); - - LLVM_DEBUG(dbgs() << "\nPopped off I-WL: " << *I << '\n'); - - // "I" got into the work list because it made the transition from undef to - // constant. - // - // Anything on this worklist that is overdefined need not be visited - // since all of its users will have already been marked as overdefined. - // Update all of the users of this instruction's value. - // - if (I->getType()->isStructTy() || !getValueState(I).isOverdefined()) - markUsersAsChanged(I); - } - - // Process the basic block work list. - while (!BBWorkList.empty()) { - BasicBlock *BB = BBWorkList.pop_back_val(); - - LLVM_DEBUG(dbgs() << "\nPopped off BBWL: " << *BB << '\n'); - - // Notify all instructions in this basic block that they are newly - // executable. - visit(BB); - } - } -} - -/// ResolvedUndefsIn - While solving the dataflow for a function, we assume -/// that branches on undef values cannot reach any of their successors. -/// However, this is not a safe assumption. After we solve dataflow, this -/// method should be use to handle this. If this returns true, the solver -/// should be rerun. -/// -/// This method handles this by finding an unresolved branch and marking it one -/// of the edges from the block as being feasible, even though the condition -/// doesn't say it would otherwise be. This allows SCCP to find the rest of the -/// CFG and only slightly pessimizes the analysis results (by marking one, -/// potentially infeasible, edge feasible). This cannot usefully modify the -/// constraints on the condition of the branch, as that would impact other users -/// of the value. -/// -/// This scan also checks for values that use undefs. It conservatively marks -/// them as overdefined. -bool SCCPSolver::ResolvedUndefsIn(Function &F) { - bool MadeChange = false; - for (BasicBlock &BB : F) { - if (!BBExecutable.count(&BB)) - continue; - - for (Instruction &I : BB) { - // Look for instructions which produce undef values. - if (I.getType()->isVoidTy()) continue; - - if (auto *STy = dyn_cast(I.getType())) { - // Only a few things that can be structs matter for undef. - - // Tracked calls must never be marked overdefined in ResolvedUndefsIn. - if (auto *CB = dyn_cast(&I)) - if (Function *F = CB->getCalledFunction()) - if (MRVFunctionsTracked.count(F)) - continue; - - // extractvalue and insertvalue don't need to be marked; they are - // tracked as precisely as their operands. - if (isa(I) || isa(I)) - continue; - // Send the results of everything else to overdefined. We could be - // more precise than this but it isn't worth bothering. - for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { - ValueLatticeElement &LV = getStructValueState(&I, i); - if (LV.isUnknownOrUndef()) { - markOverdefined(LV, &I); - MadeChange = true; - } - } - continue; - } - - ValueLatticeElement &LV = getValueState(&I); - if (!LV.isUnknownOrUndef()) - continue; - - // There are two reasons a call can have an undef result - // 1. It could be tracked. - // 2. It could be constant-foldable. - // Because of the way we solve return values, tracked calls must - // never be marked overdefined in ResolvedUndefsIn. - if (auto *CB = dyn_cast(&I)) - if (Function *F = CB->getCalledFunction()) - if (TrackedRetVals.count(F)) - continue; - - if (isa(I)) { - // A load here means one of two things: a load of undef from a global, - // a load from an unknown pointer. Either way, having it return undef - // is okay. - continue; - } - - markOverdefined(&I); - MadeChange = true; - } - - // Check to see if we have a branch or switch on an undefined value. If so - // we force the branch to go one way or the other to make the successor - // values live. It doesn't really matter which way we force it. - Instruction *TI = BB.getTerminator(); - if (auto *BI = dyn_cast(TI)) { - if (!BI->isConditional()) continue; - if (!getValueState(BI->getCondition()).isUnknownOrUndef()) - continue; - - // If the input to SCCP is actually branch on undef, fix the undef to - // false. - if (isa(BI->getCondition())) { - BI->setCondition(ConstantInt::getFalse(BI->getContext())); - markEdgeExecutable(&BB, TI->getSuccessor(1)); - MadeChange = true; - continue; - } - - // Otherwise, it is a branch on a symbolic value which is currently - // considered to be undef. Make sure some edge is executable, so a - // branch on "undef" always flows somewhere. - // FIXME: Distinguish between dead code and an LLVM "undef" value. - BasicBlock *DefaultSuccessor = TI->getSuccessor(1); - if (markEdgeExecutable(&BB, DefaultSuccessor)) - MadeChange = true; - - continue; - } - - if (auto *IBR = dyn_cast(TI)) { - // Indirect branch with no successor ?. Its ok to assume it branches - // to no target. - if (IBR->getNumSuccessors() < 1) - continue; - - if (!getValueState(IBR->getAddress()).isUnknownOrUndef()) - continue; - - // If the input to SCCP is actually branch on undef, fix the undef to - // the first successor of the indirect branch. - if (isa(IBR->getAddress())) { - IBR->setAddress(BlockAddress::get(IBR->getSuccessor(0))); - markEdgeExecutable(&BB, IBR->getSuccessor(0)); - MadeChange = true; - continue; - } - - // Otherwise, it is a branch on a symbolic value which is currently - // considered to be undef. Make sure some edge is executable, so a - // branch on "undef" always flows somewhere. - // FIXME: IndirectBr on "undef" doesn't actually need to go anywhere: - // we can assume the branch has undefined behavior instead. - BasicBlock *DefaultSuccessor = IBR->getSuccessor(0); - if (markEdgeExecutable(&BB, DefaultSuccessor)) - MadeChange = true; - - continue; - } - - if (auto *SI = dyn_cast(TI)) { - if (!SI->getNumCases() || - !getValueState(SI->getCondition()).isUnknownOrUndef()) - continue; - - // If the input to SCCP is actually switch on undef, fix the undef to - // the first constant. - if (isa(SI->getCondition())) { - SI->setCondition(SI->case_begin()->getCaseValue()); - markEdgeExecutable(&BB, SI->case_begin()->getCaseSuccessor()); - MadeChange = true; - continue; - } - - // Otherwise, it is a branch on a symbolic value which is currently - // considered to be undef. Make sure some edge is executable, so a - // branch on "undef" always flows somewhere. - // FIXME: Distinguish between dead code and an LLVM "undef" value. - BasicBlock *DefaultSuccessor = SI->case_begin()->getCaseSuccessor(); - if (markEdgeExecutable(&BB, DefaultSuccessor)) - MadeChange = true; - - continue; - } - } - - return MadeChange; -} static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V) { Constant *Const = nullptr; diff --git a/llvm/lib/Transforms/Utils/CMakeLists.txt b/llvm/lib/Transforms/Utils/CMakeLists.txt --- a/llvm/lib/Transforms/Utils/CMakeLists.txt +++ b/llvm/lib/Transforms/Utils/CMakeLists.txt @@ -56,6 +56,7 @@ PromoteMemoryToRegister.cpp RelLookupTableConverter.cpp ScalarEvolutionExpander.cpp + SCCPSolver.cpp StripGCRelocates.cpp SSAUpdater.cpp SSAUpdaterBulk.cpp diff --git a/llvm/lib/Transforms/Scalar/SCCP.cpp b/llvm/lib/Transforms/Utils/SCCPSolver.cpp copy from llvm/lib/Transforms/Scalar/SCCP.cpp copy to llvm/lib/Transforms/Utils/SCCPSolver.cpp --- a/llvm/lib/Transforms/Scalar/SCCP.cpp +++ b/llvm/lib/Transforms/Utils/SCCPSolver.cpp @@ -1,4 +1,4 @@ -//===- SCCP.cpp - Sparse Conditional Constant Propagation -----------------===// +//===- SCCPSolver.cpp - SCCP Utility --------------------------- *- C++ -*-===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. @@ -6,60 +6,23 @@ // //===----------------------------------------------------------------------===// // -// This file implements sparse conditional constant propagation and merging: -// -// Specifically, this: -// * Assumes values are constant unless proven otherwise -// * Assumes BasicBlocks are dead unless proven otherwise -// * Proves values to be constant, and replaces them with constants -// * Proves conditional branches to be unconditional +// \file +// This file implements the Sparse Conditional Constant Propagation (SCCP) +// utility. // //===----------------------------------------------------------------------===// -#include "llvm/Transforms/Scalar/SCCP.h" -#include "llvm/ADT/ArrayRef.h" -#include "llvm/ADT/DenseMap.h" -#include "llvm/ADT/DenseSet.h" -#include "llvm/ADT/MapVector.h" -#include "llvm/ADT/PointerIntPair.h" -#include "llvm/ADT/STLExtras.h" -#include "llvm/ADT/SetVector.h" -#include "llvm/ADT/SmallPtrSet.h" -#include "llvm/ADT/SmallVector.h" -#include "llvm/ADT/Statistic.h" #include "llvm/Analysis/ConstantFolding.h" -#include "llvm/Analysis/DomTreeUpdater.h" -#include "llvm/Analysis/GlobalsModRef.h" #include "llvm/Analysis/InstructionSimplify.h" -#include "llvm/Analysis/TargetLibraryInfo.h" -#include "llvm/Analysis/ValueLattice.h" -#include "llvm/Analysis/ValueLatticeUtils.h" #include "llvm/Analysis/ValueTracking.h" -#include "llvm/IR/BasicBlock.h" -#include "llvm/IR/Constant.h" -#include "llvm/IR/Constants.h" -#include "llvm/IR/DataLayout.h" -#include "llvm/IR/DerivedTypes.h" -#include "llvm/IR/Function.h" -#include "llvm/IR/GlobalVariable.h" -#include "llvm/IR/InstVisitor.h" -#include "llvm/IR/InstrTypes.h" -#include "llvm/IR/Instruction.h" -#include "llvm/IR/Instructions.h" -#include "llvm/IR/Module.h" -#include "llvm/IR/PassManager.h" -#include "llvm/IR/Type.h" -#include "llvm/IR/User.h" -#include "llvm/IR/Value.h" #include "llvm/InitializePasses.h" #include "llvm/Pass.h" #include "llvm/Support/Casting.h" #include "llvm/Support/Debug.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/raw_ostream.h" -#include "llvm/Transforms/Scalar.h" #include "llvm/Transforms/Utils/Local.h" -#include "llvm/Transforms/Utils/PredicateInfo.h" +#include "llvm/Transforms/Utils/SCCPSolver.h" #include #include #include @@ -68,18 +31,6 @@ #define DEBUG_TYPE "sccp" -STATISTIC(NumInstRemoved, "Number of instructions removed"); -STATISTIC(NumDeadBlocks , "Number of basic blocks unreachable"); -STATISTIC(NumInstReplaced, - "Number of instructions replaced with (simpler) instruction"); - -STATISTIC(IPNumInstRemoved, "Number of instructions removed by IPSCCP"); -STATISTIC(IPNumArgsElimed ,"Number of arguments constant propagated by IPSCCP"); -STATISTIC(IPNumGlobalConst, "Number of globals found to be constant by IPSCCP"); -STATISTIC( - IPNumInstReplaced, - "Number of instructions replaced with (simpler) instruction by IPSCCP"); - // The maximum number of range extensions allowed for operations requiring // widening. static const unsigned MaxNumRangeExtensions = 10; @@ -89,6 +40,7 @@ return ValueLatticeElement::MergeOptions().setMaxWidenSteps( MaxNumRangeExtensions); } + namespace { // Helper to check if \p LV is either a constant or a constant @@ -108,12 +60,13 @@ return !LV.isUnknownOrUndef() && !isConstant(LV); } -//===----------------------------------------------------------------------===// -// -/// SCCPSolver - This class is a general purpose solver for Sparse Conditional -/// Constant Propagation. -/// -class SCCPSolver : public InstVisitor { +} // namespace + +namespace llvm { + +/// Helper class for SCCPSolver. This implements the instruction visitor and +/// holds all the state. +class SCCPInstVisitor : public InstVisitor { const DataLayout &DL; std::function GetTLI; SmallPtrSet BBExecutable; // The BBs that are executable. @@ -163,7 +116,7 @@ SmallVector InstWorkList; // The BasicBlock work list - SmallVector BBWorkList; + SmallVector BBWorkList; /// KnownFeasibleEdges - Entries in this set are edges which have already had /// PHI nodes retriggered. @@ -175,215 +128,23 @@ LLVMContext &Ctx; -public: - void addAnalysis(Function &F, AnalysisResultsForFn A) { - AnalysisResults.insert({&F, std::move(A)}); - } - - const PredicateBase *getPredicateInfoFor(Instruction *I) { - auto A = AnalysisResults.find(I->getParent()->getParent()); - if (A == AnalysisResults.end()) - return nullptr; - return A->second.PredInfo->getPredicateInfoFor(I); - } - - DomTreeUpdater getDTU(Function &F) { - auto A = AnalysisResults.find(&F); - assert(A != AnalysisResults.end() && "Need analysis results for function."); - return {A->second.DT, A->second.PDT, DomTreeUpdater::UpdateStrategy::Lazy}; - } - - SCCPSolver(const DataLayout &DL, - std::function GetTLI, - LLVMContext &Ctx) - : DL(DL), GetTLI(std::move(GetTLI)), Ctx(Ctx) {} - - /// MarkBlockExecutable - This method can be used by clients to mark all of - /// the blocks that are known to be intrinsically live in the processed unit. - /// - /// This returns true if the block was not considered live before. - bool MarkBlockExecutable(BasicBlock *BB) { - if (!BBExecutable.insert(BB).second) - return false; - LLVM_DEBUG(dbgs() << "Marking Block Executable: " << BB->getName() << '\n'); - BBWorkList.push_back(BB); // Add the block to the work list! - return true; - } - - /// TrackValueOfGlobalVariable - Clients can use this method to - /// inform the SCCPSolver that it should track loads and stores to the - /// specified global variable if it can. This is only legal to call if - /// performing Interprocedural SCCP. - void TrackValueOfGlobalVariable(GlobalVariable *GV) { - // We only track the contents of scalar globals. - if (GV->getValueType()->isSingleValueType()) { - ValueLatticeElement &IV = TrackedGlobals[GV]; - if (!isa(GV->getInitializer())) - IV.markConstant(GV->getInitializer()); - } - } - - /// AddTrackedFunction - If the SCCP solver is supposed to track calls into - /// and out of the specified function (which cannot have its address taken), - /// this method must be called. - void AddTrackedFunction(Function *F) { - // Add an entry, F -> undef. - if (auto *STy = dyn_cast(F->getReturnType())) { - MRVFunctionsTracked.insert(F); - for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) - TrackedMultipleRetVals.insert( - std::make_pair(std::make_pair(F, i), ValueLatticeElement())); - } else if (!F->getReturnType()->isVoidTy()) - TrackedRetVals.insert(std::make_pair(F, ValueLatticeElement())); - } - - /// Add function to the list of functions whose return cannot be modified. - void addToMustPreserveReturnsInFunctions(Function *F) { - MustPreserveReturnsInFunctions.insert(F); - } - - /// Returns true if the return of the given function cannot be modified. - bool mustPreserveReturn(Function *F) { - return MustPreserveReturnsInFunctions.count(F); - } - - void AddArgumentTrackedFunction(Function *F) { - TrackingIncomingArguments.insert(F); - } - - /// Returns true if the given function is in the solver's set of - /// argument-tracked functions. - bool isArgumentTrackedFunction(Function *F) { - return TrackingIncomingArguments.count(F); - } - - /// Solve - Solve for constants and executable blocks. - void Solve(); - - /// ResolvedUndefsIn - While solving the dataflow for a function, we assume - /// that branches on undef values cannot reach any of their successors. - /// However, this is not a safe assumption. After we solve dataflow, this - /// method should be use to handle this. If this returns true, the solver - /// should be rerun. - bool ResolvedUndefsIn(Function &F); - - bool isBlockExecutable(BasicBlock *BB) const { - return BBExecutable.count(BB); - } - - // isEdgeFeasible - Return true if the control flow edge from the 'From' basic - // block to the 'To' basic block is currently feasible. - bool isEdgeFeasible(BasicBlock *From, BasicBlock *To) const; - - std::vector getStructLatticeValueFor(Value *V) const { - std::vector StructValues; - auto *STy = dyn_cast(V->getType()); - assert(STy && "getStructLatticeValueFor() can be called only on structs"); - for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { - auto I = StructValueState.find(std::make_pair(V, i)); - assert(I != StructValueState.end() && "Value not in valuemap!"); - StructValues.push_back(I->second); - } - return StructValues; - } - - void removeLatticeValueFor(Value *V) { ValueState.erase(V); } - - const ValueLatticeElement &getLatticeValueFor(Value *V) const { - assert(!V->getType()->isStructTy() && - "Should use getStructLatticeValueFor"); - DenseMap::const_iterator I = - ValueState.find(V); - assert(I != ValueState.end() && - "V not found in ValueState nor Paramstate map!"); - return I->second; - } - - /// getTrackedRetVals - Get the inferred return value map. - const MapVector &getTrackedRetVals() { - return TrackedRetVals; - } - - /// getTrackedGlobals - Get and return the set of inferred initializers for - /// global variables. - const DenseMap &getTrackedGlobals() { - return TrackedGlobals; - } - - /// getMRVFunctionsTracked - Get the set of functions which return multiple - /// values tracked by the pass. - const SmallPtrSet getMRVFunctionsTracked() { - return MRVFunctionsTracked; - } - - /// markOverdefined - Mark the specified value overdefined. This - /// works with both scalars and structs. - void markOverdefined(Value *V) { - if (auto *STy = dyn_cast(V->getType())) - for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) - markOverdefined(getStructValueState(V, i), V); - else - markOverdefined(ValueState[V], V); - } - - // isStructLatticeConstant - Return true if all the lattice values - // corresponding to elements of the structure are constants, - // false otherwise. - bool isStructLatticeConstant(Function *F, StructType *STy) { - for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { - const auto &It = TrackedMultipleRetVals.find(std::make_pair(F, i)); - assert(It != TrackedMultipleRetVals.end()); - ValueLatticeElement LV = It->second; - if (!isConstant(LV)) - return false; - } - return true; - } - - /// Helper to return a Constant if \p LV is either a constant or a constant - /// range with a single element. - Constant *getConstant(const ValueLatticeElement &LV) const { - if (LV.isConstant()) - return LV.getConstant(); - - if (LV.isConstantRange()) { - auto &CR = LV.getConstantRange(); - if (CR.getSingleElement()) - return ConstantInt::get(Ctx, *CR.getSingleElement()); - } - return nullptr; - } - private: ConstantInt *getConstantInt(const ValueLatticeElement &IV) const { return dyn_cast_or_null(getConstant(IV)); } // pushToWorkList - Helper for markConstant/markOverdefined - void pushToWorkList(ValueLatticeElement &IV, Value *V) { - if (IV.isOverdefined()) - return OverdefinedInstWorkList.push_back(V); - InstWorkList.push_back(V); - } + void pushToWorkList(ValueLatticeElement &IV, Value *V); // Helper to push \p V to the worklist, after updating it to \p IV. Also // prints a debug message with the updated value. - void pushToWorkListMsg(ValueLatticeElement &IV, Value *V) { - LLVM_DEBUG(dbgs() << "updated " << IV << ": " << *V << '\n'); - pushToWorkList(IV, V); - } + void pushToWorkListMsg(ValueLatticeElement &IV, Value *V); // markConstant - Make a value be marked as "constant". If the value // is not already a constant, add it to the instruction work list so that // the users of the instruction are updated later. bool markConstant(ValueLatticeElement &IV, Value *V, Constant *C, - bool MayIncludeUndef = false) { - if (!IV.markConstant(C, MayIncludeUndef)) - return false; - LLVM_DEBUG(dbgs() << "markConstant: " << *C << ": " << *V << '\n'); - pushToWorkList(IV, V); - return true; - } + bool MayIncludeUndef = false); bool markConstant(Value *V, Constant *C) { assert(!V->getType()->isStructTy() && "structs should use mergeInValue"); @@ -393,32 +154,14 @@ // markOverdefined - Make a value be marked as "overdefined". If the // value is not already overdefined, add it to the overdefined instruction // work list so that the users of the instruction are updated later. - bool markOverdefined(ValueLatticeElement &IV, Value *V) { - if (!IV.markOverdefined()) return false; - - LLVM_DEBUG(dbgs() << "markOverdefined: "; - if (auto *F = dyn_cast(V)) dbgs() - << "Function '" << F->getName() << "'\n"; - else dbgs() << *V << '\n'); - // Only instructions go on the work list - pushToWorkList(IV, V); - return true; - } + bool markOverdefined(ValueLatticeElement &IV, Value *V); /// Merge \p MergeWithV into \p IV and push \p V to the worklist, if \p IV /// changes. bool mergeInValue(ValueLatticeElement &IV, Value *V, ValueLatticeElement MergeWithV, ValueLatticeElement::MergeOptions Opts = { - /*MayIncludeUndef=*/false, /*CheckWiden=*/false}) { - if (IV.mergeIn(MergeWithV, Opts)) { - pushToWorkList(IV, V); - LLVM_DEBUG(dbgs() << "Merged " << MergeWithV << " into " << *V << " : " - << IV << "\n"); - return true; - } - return false; - } + /*MayIncludeUndef=*/false, /*CheckWiden=*/false}); bool mergeInValue(Value *V, ValueLatticeElement MergeWithV, ValueLatticeElement::MergeOptions Opts = { @@ -438,10 +181,10 @@ ValueLatticeElement &LV = I.first->second; if (!I.second) - return LV; // Common case, already in the map. + return LV; // Common case, already in the map. if (auto *C = dyn_cast(V)) - LV.markConstant(C); // Constants are constant + LV.markConstant(C); // Constants are constant // All others are unknown by default. return LV; @@ -460,17 +203,17 @@ ValueLatticeElement &LV = I.first->second; if (!I.second) - return LV; // Common case, already in the map. + return LV; // Common case, already in the map. if (auto *C = dyn_cast(V)) { Constant *Elt = C->getAggregateElement(i); if (!Elt) - LV.markOverdefined(); // Unknown sort of constant. + LV.markOverdefined(); // Unknown sort of constant. else if (isa(Elt)) ; // Undef values remain unknown. else - LV.markConstant(Elt); // Constants are constant. + LV.markConstant(Elt); // Constants are constant. } // All others are underdefined by default. @@ -479,22 +222,7 @@ /// markEdgeExecutable - Mark a basic block as executable, adding it to the BB /// work list if it is not already executable. - bool markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest) { - if (!KnownFeasibleEdges.insert(Edge(Source, Dest)).second) - return false; // This edge is already known to be executable! - - if (!MarkBlockExecutable(Dest)) { - // If the destination is already executable, we just made an *edge* - // feasible that wasn't before. Revisit the PHI nodes in the block - // because they have potentially new operands. - LLVM_DEBUG(dbgs() << "Marking Edge Executable: " << Source->getName() - << " -> " << Dest->getName() << '\n'); - - for (PHINode &PN : Dest->phis()) - visitPHINode(PN); - } - return true; - } + bool markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest); // getFeasibleSuccessors - Return a vector of booleans to indicate which // successors are reachable from a given terminator instruction. @@ -504,7 +232,7 @@ // instruction that was just changed state somehow. Based on this // information, we need to update the specified user of this instruction. void OperandChangedState(Instruction *I) { - if (BBExecutable.count(I->getParent())) // Inst is executable? + if (BBExecutable.count(I->getParent())) // Inst is executable? visit(*I); } @@ -548,7 +276,7 @@ void handleCallArguments(CallBase &CB); private: - friend class InstVisitor; + friend class InstVisitor; // visit implementations - Something changed in this instruction. Either an // operand made a transition, or the instruction is newly executable. Change @@ -575,43 +303,258 @@ // Instructions that cannot be folded away. - void visitStoreInst (StoreInst &I); - void visitLoadInst (LoadInst &I); + void visitStoreInst(StoreInst &I); + void visitLoadInst(LoadInst &I); void visitGetElementPtrInst(GetElementPtrInst &I); - void visitCallInst (CallInst &I) { - visitCallBase(I); - } + void visitCallInst(CallInst &I) { visitCallBase(I); } - void visitInvokeInst (InvokeInst &II) { + void visitInvokeInst(InvokeInst &II) { visitCallBase(II); visitTerminator(II); } - void visitCallBrInst (CallBrInst &CBI) { + void visitCallBrInst(CallBrInst &CBI) { visitCallBase(CBI); visitTerminator(CBI); } - void visitCallBase (CallBase &CB); - void visitResumeInst (ResumeInst &I) { /*returns void*/ } - void visitUnreachableInst(UnreachableInst &I) { /*returns void*/ } - void visitFenceInst (FenceInst &I) { /*returns void*/ } + void visitCallBase(CallBase &CB); + void visitResumeInst(ResumeInst &I) { /*returns void*/ + } + void visitUnreachableInst(UnreachableInst &I) { /*returns void*/ + } + void visitFenceInst(FenceInst &I) { /*returns void*/ + } - void visitInstruction(Instruction &I) { - // All the instructions we don't do any special handling for just - // go to overdefined. - LLVM_DEBUG(dbgs() << "SCCP: Don't know how to handle: " << I << '\n'); - markOverdefined(&I); + void visitInstruction(Instruction &I); + +public: + void addAnalysis(Function &F, AnalysisResultsForFn A) { + AnalysisResults.insert({&F, std::move(A)}); + } + + bool MarkBlockExecutable(BasicBlock *BB); + + const PredicateBase *getPredicateInfoFor(Instruction *I) { + auto A = AnalysisResults.find(I->getParent()->getParent()); + if (A == AnalysisResults.end()) + return nullptr; + return A->second.PredInfo->getPredicateInfoFor(I); + } + + DomTreeUpdater getDTU(Function &F) { + auto A = AnalysisResults.find(&F); + assert(A != AnalysisResults.end() && "Need analysis results for function."); + return {A->second.DT, A->second.PDT, DomTreeUpdater::UpdateStrategy::Lazy}; + } + + SCCPInstVisitor(const DataLayout &DL, + std::function GetTLI, + LLVMContext &Ctx) + : DL(DL), GetTLI(GetTLI), Ctx(Ctx) {} + + void TrackValueOfGlobalVariable(GlobalVariable *GV) { + // We only track the contents of scalar globals. + if (GV->getValueType()->isSingleValueType()) { + ValueLatticeElement &IV = TrackedGlobals[GV]; + if (!isa(GV->getInitializer())) + IV.markConstant(GV->getInitializer()); + } + } + + void AddTrackedFunction(Function *F) { + // Add an entry, F -> undef. + if (auto *STy = dyn_cast(F->getReturnType())) { + MRVFunctionsTracked.insert(F); + for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) + TrackedMultipleRetVals.insert( + std::make_pair(std::make_pair(F, i), ValueLatticeElement())); + } else if (!F->getReturnType()->isVoidTy()) + TrackedRetVals.insert(std::make_pair(F, ValueLatticeElement())); + } + + void addToMustPreserveReturnsInFunctions(Function *F) { + MustPreserveReturnsInFunctions.insert(F); + } + + bool mustPreserveReturn(Function *F) { + return MustPreserveReturnsInFunctions.count(F); + } + + void AddArgumentTrackedFunction(Function *F) { + TrackingIncomingArguments.insert(F); + } + + bool isArgumentTrackedFunction(Function *F) { + return TrackingIncomingArguments.count(F); } + + void Solve(); + + bool ResolvedUndefsIn(Function &F); + + bool isBlockExecutable(BasicBlock *BB) const { + return BBExecutable.count(BB); + } + + bool isEdgeFeasible(BasicBlock *From, BasicBlock *To) const; + + std::vector getStructLatticeValueFor(Value *V) const { + std::vector StructValues; + auto *STy = dyn_cast(V->getType()); + assert(STy && "getStructLatticeValueFor() can be called only on structs"); + for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { + auto I = StructValueState.find(std::make_pair(V, i)); + assert(I != StructValueState.end() && "Value not in valuemap!"); + StructValues.push_back(I->second); + } + return StructValues; + } + + void removeLatticeValueFor(Value *V) { ValueState.erase(V); } + + const ValueLatticeElement &getLatticeValueFor(Value *V) const { + assert(!V->getType()->isStructTy() && + "Should use getStructLatticeValueFor"); + DenseMap::const_iterator I = + ValueState.find(V); + assert(I != ValueState.end() && + "V not found in ValueState nor Paramstate map!"); + return I->second; + } + + const MapVector &getTrackedRetVals() { + return TrackedRetVals; + } + + const DenseMap &getTrackedGlobals() { + return TrackedGlobals; + } + + const SmallPtrSet getMRVFunctionsTracked() { + return MRVFunctionsTracked; + } + + void markOverdefined(Value *V) { + if (auto *STy = dyn_cast(V->getType())) + for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) + markOverdefined(getStructValueState(V, i), V); + else + markOverdefined(ValueState[V], V); + } + + bool isStructLatticeConstant(Function *F, StructType *STy); + + Constant *getConstant(const ValueLatticeElement &LV) const; }; -} // end anonymous namespace +} // namespace llvm + +bool SCCPInstVisitor::MarkBlockExecutable(BasicBlock *BB) { + if (!BBExecutable.insert(BB).second) + return false; + LLVM_DEBUG(dbgs() << "Marking Block Executable: " << BB->getName() << '\n'); + BBWorkList.push_back(BB); // Add the block to the work list! + return true; +} + +void SCCPInstVisitor::pushToWorkList(ValueLatticeElement &IV, Value *V) { + if (IV.isOverdefined()) + return OverdefinedInstWorkList.push_back(V); + InstWorkList.push_back(V); +} + +void SCCPInstVisitor::pushToWorkListMsg(ValueLatticeElement &IV, Value *V) { + LLVM_DEBUG(dbgs() << "updated " << IV << ": " << *V << '\n'); + pushToWorkList(IV, V); +} + +bool SCCPInstVisitor::markConstant(ValueLatticeElement &IV, Value *V, + Constant *C, bool MayIncludeUndef) { + if (!IV.markConstant(C, MayIncludeUndef)) + return false; + LLVM_DEBUG(dbgs() << "markConstant: " << *C << ": " << *V << '\n'); + pushToWorkList(IV, V); + return true; +} + +bool SCCPInstVisitor::markOverdefined(ValueLatticeElement &IV, Value *V) { + if (!IV.markOverdefined()) + return false; + + LLVM_DEBUG(dbgs() << "markOverdefined: "; + if (auto *F = dyn_cast(V)) dbgs() + << "Function '" << F->getName() << "'\n"; + else dbgs() << *V << '\n'); + // Only instructions go on the work list + pushToWorkList(IV, V); + return true; +} + +bool SCCPInstVisitor::isStructLatticeConstant(Function *F, StructType *STy) { + for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { + const auto &It = TrackedMultipleRetVals.find(std::make_pair(F, i)); + assert(It != TrackedMultipleRetVals.end()); + ValueLatticeElement LV = It->second; + if (!isConstant(LV)) + return false; + } + return true; +} + +Constant *SCCPInstVisitor::getConstant(const ValueLatticeElement &LV) const { + if (LV.isConstant()) + return LV.getConstant(); + + if (LV.isConstantRange()) { + auto &CR = LV.getConstantRange(); + if (CR.getSingleElement()) + return ConstantInt::get(Ctx, *CR.getSingleElement()); + } + return nullptr; +} + +void SCCPInstVisitor::visitInstruction(Instruction &I) { + // All the instructions we don't do any special handling for just + // go to overdefined. + LLVM_DEBUG(dbgs() << "SCCP: Don't know how to handle: " << I << '\n'); + markOverdefined(&I); +} + +bool SCCPInstVisitor::mergeInValue(ValueLatticeElement &IV, Value *V, + ValueLatticeElement MergeWithV, + ValueLatticeElement::MergeOptions Opts) { + if (IV.mergeIn(MergeWithV, Opts)) { + pushToWorkList(IV, V); + LLVM_DEBUG(dbgs() << "Merged " << MergeWithV << " into " << *V << " : " + << IV << "\n"); + return true; + } + return false; +} + +bool SCCPInstVisitor::markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest) { + if (!KnownFeasibleEdges.insert(Edge(Source, Dest)).second) + return false; // This edge is already known to be executable! + + if (!MarkBlockExecutable(Dest)) { + // If the destination is already executable, we just made an *edge* + // feasible that wasn't before. Revisit the PHI nodes in the block + // because they have potentially new operands. + LLVM_DEBUG(dbgs() << "Marking Edge Executable: " << Source->getName() + << " -> " << Dest->getName() << '\n'); + + for (PHINode &PN : Dest->phis()) + visitPHINode(PN); + } + return true; +} // getFeasibleSuccessors - Return a vector of booleans to indicate which // successors are reachable from a given terminator instruction. -void SCCPSolver::getFeasibleSuccessors(Instruction &TI, - SmallVectorImpl &Succs) { +void SCCPInstVisitor::getFeasibleSuccessors(Instruction &TI, + SmallVectorImpl &Succs) { Succs.resize(TI.getNumSuccessors()); if (auto *BI = dyn_cast(&TI)) { if (BI->isUnconditional()) { @@ -678,14 +621,14 @@ // Casts are folded by visitCastInst. ValueLatticeElement IBRValue = getValueState(IBR->getAddress()); BlockAddress *Addr = dyn_cast_or_null(getConstant(IBRValue)); - if (!Addr) { // Overdefined or unknown condition? + if (!Addr) { // Overdefined or unknown condition? // All destinations are executable! if (!IBRValue.isUnknownOrUndef()) Succs.assign(TI.getNumSuccessors(), true); return; } - BasicBlock* T = Addr->getBasicBlock(); + BasicBlock *T = Addr->getBasicBlock(); assert(Addr->getFunction() == T->getParent() && "Block address of a different function ?"); for (unsigned i = 0; i < IBR->getNumSuccessors(); ++i) { @@ -714,7 +657,7 @@ // isEdgeFeasible - Return true if the control flow edge from the 'From' basic // block to the 'To' basic block is currently feasible. -bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) const { +bool SCCPInstVisitor::isEdgeFeasible(BasicBlock *From, BasicBlock *To) const { // Check if we've called markEdgeExecutable on the edge yet. (We could // be more aggressive and try to consider edges which haven't been marked // yet, but there isn't any need.) @@ -738,7 +681,7 @@ // destination executable // 7. If a conditional branch has a value that is overdefined, make all // successors executable. -void SCCPSolver::visitPHINode(PHINode &PN) { +void SCCPInstVisitor::visitPHINode(PHINode &PN) { // If this PN returns a struct, just mark the result overdefined. // TODO: We could do a lot better than this if code actually uses this. if (PN.getType()->isStructTy()) @@ -784,8 +727,9 @@ std::max(NumActiveIncoming, PhiStateRef.getNumRangeExtensions())); } -void SCCPSolver::visitReturnInst(ReturnInst &I) { - if (I.getNumOperands() == 0) return; // ret void +void SCCPInstVisitor::visitReturnInst(ReturnInst &I) { + if (I.getNumOperands() == 0) + return; // ret void Function *F = I.getParent()->getParent(); Value *ResultOp = I.getOperand(0); @@ -809,7 +753,7 @@ } } -void SCCPSolver::visitTerminator(Instruction &TI) { +void SCCPInstVisitor::visitTerminator(Instruction &TI) { SmallVector SuccFeasible; getFeasibleSuccessors(TI, SuccFeasible); @@ -821,7 +765,7 @@ markEdgeExecutable(BB, TI.getSuccessor(i)); } -void SCCPSolver::visitCastInst(CastInst &I) { +void SCCPInstVisitor::visitCastInst(CastInst &I) { // ResolvedUndefsIn might mark I as overdefined. Bail out, even if we would // discover a concrete value later. if (ValueState[&I].isOverdefined()) @@ -856,7 +800,7 @@ markOverdefined(&I); } -void SCCPSolver::visitExtractValueInst(ExtractValueInst &EVI) { +void SCCPInstVisitor::visitExtractValueInst(ExtractValueInst &EVI) { // If this returns a struct, mark all elements over defined, we don't track // structs in structs. if (EVI.getType()->isStructTy()) @@ -882,7 +826,7 @@ } } -void SCCPSolver::visitInsertValueInst(InsertValueInst &IVI) { +void SCCPInstVisitor::visitInsertValueInst(InsertValueInst &IVI) { auto *STy = dyn_cast(IVI.getType()); if (!STy) return (void)markOverdefined(&IVI); @@ -920,7 +864,7 @@ } } -void SCCPSolver::visitSelectInst(SelectInst &I) { +void SCCPInstVisitor::visitSelectInst(SelectInst &I) { // If this select returns a struct, just mark the result overdefined. // TODO: We could do a lot better than this if code actually uses this. if (I.getType()->isStructTy()) @@ -954,7 +898,7 @@ } // Handle Unary Operators. -void SCCPSolver::visitUnaryOperator(Instruction &I) { +void SCCPInstVisitor::visitUnaryOperator(Instruction &I) { ValueLatticeElement V0State = getValueState(I.getOperand(0)); ValueLatticeElement &IV = ValueState[&I]; @@ -980,7 +924,7 @@ } // Handle Binary Operators. -void SCCPSolver::visitBinaryOperator(Instruction &I) { +void SCCPInstVisitor::visitBinaryOperator(Instruction &I) { ValueLatticeElement V1State = getValueState(I.getOperand(0)); ValueLatticeElement V2State = getValueState(I.getOperand(1)); @@ -1038,7 +982,7 @@ } // Handle ICmpInst instruction. -void SCCPSolver::visitCmpInst(CmpInst &I) { +void SCCPInstVisitor::visitCmpInst(CmpInst &I) { // Do not cache this lookup, getValueState calls later in the function might // invalidate the reference. if (isOverdefined(ValueState[&I])) @@ -1072,17 +1016,17 @@ // Handle getelementptr instructions. If all operands are constants then we // can turn this into a getelementptr ConstantExpr. -void SCCPSolver::visitGetElementPtrInst(GetElementPtrInst &I) { +void SCCPInstVisitor::visitGetElementPtrInst(GetElementPtrInst &I) { if (isOverdefined(ValueState[&I])) return (void)markOverdefined(&I); - SmallVector Operands; + SmallVector Operands; Operands.reserve(I.getNumOperands()); for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) { ValueLatticeElement State = getValueState(I.getOperand(i)); if (State.isUnknownOrUndef()) - return; // Operands are not resolved yet. + return; // Operands are not resolved yet. if (isOverdefined(State)) return (void)markOverdefined(&I); @@ -1100,11 +1044,11 @@ Constant *C = ConstantExpr::getGetElementPtr(I.getSourceElementType(), Ptr, Indices); if (isa(C)) - return; + return; markConstant(&I, C); } -void SCCPSolver::visitStoreInst(StoreInst &SI) { +void SCCPInstVisitor::visitStoreInst(StoreInst &SI) { // If this store is of a struct, ignore it. if (SI.getOperand(0)->getType()->isStructTy()) return; @@ -1121,7 +1065,7 @@ mergeInValue(I->second, GV, getValueState(SI.getOperand(0)), ValueLatticeElement::MergeOptions().setCheckWiden(false)); if (I->second.isOverdefined()) - TrackedGlobals.erase(I); // No need to keep tracking this! + TrackedGlobals.erase(I); // No need to keep tracking this! } static ValueLatticeElement getValueFromMetadata(const Instruction *I) { @@ -1137,7 +1081,7 @@ // Handle load instructions. If the operand is a constant pointer to a constant // global, we can replace the load with the loaded constant value! -void SCCPSolver::visitLoadInst(LoadInst &I) { +void SCCPInstVisitor::visitLoadInst(LoadInst &I) { // If this load is of a struct or the load is volatile, just mark the result // as overdefined. if (I.getType()->isStructTy() || I.isVolatile()) @@ -1189,12 +1133,12 @@ mergeInValue(&I, getValueFromMetadata(&I)); } -void SCCPSolver::visitCallBase(CallBase &CB) { +void SCCPInstVisitor::visitCallBase(CallBase &CB) { handleCallResult(CB); handleCallArguments(CB); } -void SCCPSolver::handleCallOverdefined(CallBase &CB) { +void SCCPInstVisitor::handleCallOverdefined(CallBase &CB) { Function *F = CB.getCalledFunction(); // Void return and not tracking callee, just bail. @@ -1239,7 +1183,7 @@ mergeInValue(&CB, getValueFromMetadata(&CB)); } -void SCCPSolver::handleCallArguments(CallBase &CB) { +void SCCPInstVisitor::handleCallArguments(CallBase &CB) { Function *F = CB.getCalledFunction(); // If this is a local function that doesn't have its address taken, mark its // entry block executable and merge in the actual arguments to the call into @@ -1271,7 +1215,7 @@ } } -void SCCPSolver::handleCallResult(CallBase &CB) { +void SCCPInstVisitor::handleCallResult(CallBase &CB) { Function *F = CB.getCalledFunction(); if (auto *II = dyn_cast(&CB)) { @@ -1335,9 +1279,8 @@ NewCR = CopyOfCR; addAdditionalUser(OtherOp, &CB); - mergeInValue( - IV, &CB, - ValueLatticeElement::getRange(NewCR, MayIncludeUndef)); + mergeInValue(IV, &CB, + ValueLatticeElement::getRange(NewCR, MayIncludeUndef)); return; } else if (Pred == CmpInst::ICMP_EQ && CondVal.isConstant()) { // For non-integer values or integer constant expressions, only @@ -1404,7 +1347,7 @@ } } -void SCCPSolver::Solve() { +void SCCPInstVisitor::Solve() { // Process the work lists until they are empty! while (!BBWorkList.empty() || !InstWorkList.empty() || !OverdefinedInstWorkList.empty()) { @@ -1471,7 +1414,7 @@ /// /// This scan also checks for values that use undefs. It conservatively marks /// them as overdefined. -bool SCCPSolver::ResolvedUndefsIn(Function &F) { +bool SCCPInstVisitor::ResolvedUndefsIn(Function &F) { bool MadeChange = false; for (BasicBlock &BB : F) { if (!BBExecutable.count(&BB)) @@ -1479,7 +1422,8 @@ for (Instruction &I : BB) { // Look for instructions which produce undef values. - if (I.getType()->isVoidTy()) continue; + if (I.getType()->isVoidTy()) + continue; if (auto *STy = dyn_cast(I.getType())) { // Only a few things that can be structs matter for undef. @@ -1536,7 +1480,8 @@ // values live. It doesn't really matter which way we force it. Instruction *TI = BB.getTerminator(); if (auto *BI = dyn_cast(TI)) { - if (!BI->isConditional()) continue; + if (!BI->isConditional()) + continue; if (!getValueState(BI->getCondition()).isUnknownOrUndef()) continue; @@ -1560,7 +1505,7 @@ continue; } - if (auto *IBR = dyn_cast(TI)) { + if (auto *IBR = dyn_cast(TI)) { // Indirect branch with no successor ?. Its ok to assume it branches // to no target. if (IBR->getNumSuccessors() < 1) @@ -1619,572 +1564,103 @@ return MadeChange; } -static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V) { - Constant *Const = nullptr; - if (V->getType()->isStructTy()) { - std::vector IVs = Solver.getStructLatticeValueFor(V); - if (any_of(IVs, - [](const ValueLatticeElement &LV) { return isOverdefined(LV); })) - return false; - std::vector ConstVals; - auto *ST = cast(V->getType()); - for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { - ValueLatticeElement V = IVs[i]; - ConstVals.push_back(isConstant(V) - ? Solver.getConstant(V) - : UndefValue::get(ST->getElementType(i))); - } - Const = ConstantStruct::get(ST, ConstVals); - } else { - const ValueLatticeElement &IV = Solver.getLatticeValueFor(V); - if (isOverdefined(IV)) - return false; - - Const = - isConstant(IV) ? Solver.getConstant(IV) : UndefValue::get(V->getType()); - } - assert(Const && "Constant is nullptr here!"); - - // Replacing `musttail` instructions with constant breaks `musttail` invariant - // unless the call itself can be removed. - // Calls with "clang.arc.attachedcall" implicitly use the return value and - // those uses cannot be updated with a constant. - CallBase *CB = dyn_cast(V); - if (CB && ((CB->isMustTailCall() && !CB->isSafeToRemove()) || - CB->getOperandBundle(LLVMContext::OB_clang_arc_attachedcall))) { - Function *F = CB->getCalledFunction(); - - // Don't zap returns of the callee - if (F) - Solver.addToMustPreserveReturnsInFunctions(F); - - LLVM_DEBUG(dbgs() << " Can\'t treat the result of call " << *CB - << " as a constant\n"); - return false; - } +//===----------------------------------------------------------------------===// +// +// SCCPSolver implementations +// +SCCPSolver::SCCPSolver( + const DataLayout &DL, + std::function GetTLI, + LLVMContext &Ctx) + : Visitor(new SCCPInstVisitor(DL, std::move(GetTLI), Ctx)) {} - LLVM_DEBUG(dbgs() << " Constant: " << *Const << " = " << *V << '\n'); +SCCPSolver::~SCCPSolver() { } - // Replaces all of the uses of a variable with uses of the constant. - V->replaceAllUsesWith(Const); - return true; +void SCCPSolver::addAnalysis(Function &F, AnalysisResultsForFn A) { + return Visitor->addAnalysis(F, std::move(A)); } -static bool simplifyInstsInBlock(SCCPSolver &Solver, BasicBlock &BB, - SmallPtrSetImpl &InsertedValues, - Statistic &InstRemovedStat, - Statistic &InstReplacedStat) { - bool MadeChanges = false; - for (Instruction &Inst : make_early_inc_range(BB)) { - if (Inst.getType()->isVoidTy()) - continue; - if (tryToReplaceWithConstant(Solver, &Inst)) { - if (Inst.isSafeToRemove()) - Inst.eraseFromParent(); - // Hey, we just changed something! - MadeChanges = true; - ++InstRemovedStat; - } else if (isa(&Inst)) { - Value *ExtOp = Inst.getOperand(0); - if (isa(ExtOp) || InsertedValues.count(ExtOp)) - continue; - const ValueLatticeElement &IV = Solver.getLatticeValueFor(ExtOp); - if (!IV.isConstantRange(/*UndefAllowed=*/false)) - continue; - if (IV.getConstantRange().isAllNonNegative()) { - auto *ZExt = new ZExtInst(ExtOp, Inst.getType(), "", &Inst); - InsertedValues.insert(ZExt); - Inst.replaceAllUsesWith(ZExt); - Solver.removeLatticeValueFor(&Inst); - Inst.eraseFromParent(); - InstReplacedStat++; - MadeChanges = true; - } - } - } - return MadeChanges; +bool SCCPSolver::MarkBlockExecutable(BasicBlock *BB) { + return Visitor->MarkBlockExecutable(BB); } -// runSCCP() - Run the Sparse Conditional Constant Propagation algorithm, -// and return true if the function was modified. -static bool runSCCP(Function &F, const DataLayout &DL, - const TargetLibraryInfo *TLI) { - LLVM_DEBUG(dbgs() << "SCCP on function '" << F.getName() << "'\n"); - SCCPSolver Solver( - DL, [TLI](Function &F) -> const TargetLibraryInfo & { return *TLI; }, - F.getContext()); - - // Mark the first block of the function as being executable. - Solver.MarkBlockExecutable(&F.front()); - - // Mark all arguments to the function as being overdefined. - for (Argument &AI : F.args()) - Solver.markOverdefined(&AI); - - // Solve for constants. - bool ResolvedUndefs = true; - while (ResolvedUndefs) { - Solver.Solve(); - LLVM_DEBUG(dbgs() << "RESOLVING UNDEFs\n"); - ResolvedUndefs = Solver.ResolvedUndefsIn(F); - } - - bool MadeChanges = false; - - // If we decided that there are basic blocks that are dead in this function, - // delete their contents now. Note that we cannot actually delete the blocks, - // as we cannot modify the CFG of the function. - - SmallPtrSet InsertedValues; - for (BasicBlock &BB : F) { - if (!Solver.isBlockExecutable(&BB)) { - LLVM_DEBUG(dbgs() << " BasicBlock Dead:" << BB); - - ++NumDeadBlocks; - NumInstRemoved += removeAllNonTerminatorAndEHPadInstructions(&BB).first; - - MadeChanges = true; - continue; - } - - MadeChanges |= simplifyInstsInBlock(Solver, BB, InsertedValues, - NumInstRemoved, NumInstReplaced); - } - - return MadeChanges; +const PredicateBase *SCCPSolver::getPredicateInfoFor(Instruction *I) { + return Visitor->getPredicateInfoFor(I); } -PreservedAnalyses SCCPPass::run(Function &F, FunctionAnalysisManager &AM) { - const DataLayout &DL = F.getParent()->getDataLayout(); - auto &TLI = AM.getResult(F); - if (!runSCCP(F, DL, &TLI)) - return PreservedAnalyses::all(); +DomTreeUpdater SCCPSolver::getDTU(Function &F) { return Visitor->getDTU(F); } - auto PA = PreservedAnalyses(); - PA.preserve(); - PA.preserveSet(); - return PA; +void SCCPSolver::TrackValueOfGlobalVariable(GlobalVariable *GV) { + Visitor->TrackValueOfGlobalVariable(GV); } -namespace { - -//===--------------------------------------------------------------------===// -// -/// SCCP Class - This class uses the SCCPSolver to implement a per-function -/// Sparse Conditional Constant Propagator. -/// -class SCCPLegacyPass : public FunctionPass { -public: - // Pass identification, replacement for typeid - static char ID; - - SCCPLegacyPass() : FunctionPass(ID) { - initializeSCCPLegacyPassPass(*PassRegistry::getPassRegistry()); - } - - void getAnalysisUsage(AnalysisUsage &AU) const override { - AU.addRequired(); - AU.addPreserved(); - AU.setPreservesCFG(); - } - - // runOnFunction - Run the Sparse Conditional Constant Propagation - // algorithm, and return true if the function was modified. - bool runOnFunction(Function &F) override { - if (skipFunction(F)) - return false; - const DataLayout &DL = F.getParent()->getDataLayout(); - const TargetLibraryInfo *TLI = - &getAnalysis().getTLI(F); - return runSCCP(F, DL, TLI); - } -}; - -} // end anonymous namespace - -char SCCPLegacyPass::ID = 0; - -INITIALIZE_PASS_BEGIN(SCCPLegacyPass, "sccp", - "Sparse Conditional Constant Propagation", false, false) -INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass) -INITIALIZE_PASS_END(SCCPLegacyPass, "sccp", - "Sparse Conditional Constant Propagation", false, false) - -// createSCCPPass - This is the public interface to this file. -FunctionPass *llvm::createSCCPPass() { return new SCCPLegacyPass(); } - -static void findReturnsToZap(Function &F, - SmallVector &ReturnsToZap, - SCCPSolver &Solver) { - // We can only do this if we know that nothing else can call the function. - if (!Solver.isArgumentTrackedFunction(&F)) - return; - - if (Solver.mustPreserveReturn(&F)) { - LLVM_DEBUG( - dbgs() - << "Can't zap returns of the function : " << F.getName() - << " due to present musttail or \"clang.arc.attachedcall\" call of " - "it\n"); - return; - } - - assert( - all_of(F.users(), - [&Solver](User *U) { - if (isa(U) && - !Solver.isBlockExecutable(cast(U)->getParent())) - return true; - // Non-callsite uses are not impacted by zapping. Also, constant - // uses (like blockaddresses) could stuck around, without being - // used in the underlying IR, meaning we do not have lattice - // values for them. - if (!isa(U)) - return true; - if (U->getType()->isStructTy()) { - return all_of(Solver.getStructLatticeValueFor(U), - [](const ValueLatticeElement &LV) { - return !isOverdefined(LV); - }); - } - return !isOverdefined(Solver.getLatticeValueFor(U)); - }) && - "We can only zap functions where all live users have a concrete value"); - - for (BasicBlock &BB : F) { - if (CallInst *CI = BB.getTerminatingMustTailCall()) { - LLVM_DEBUG(dbgs() << "Can't zap return of the block due to present " - << "musttail call : " << *CI << "\n"); - (void)CI; - return; - } - - if (auto *RI = dyn_cast(BB.getTerminator())) - if (!isa(RI->getOperand(0))) - ReturnsToZap.push_back(RI); - } +void SCCPSolver::AddTrackedFunction(Function *F) { + Visitor->AddTrackedFunction(F); } -static bool removeNonFeasibleEdges(const SCCPSolver &Solver, BasicBlock *BB, - DomTreeUpdater &DTU) { - SmallPtrSet FeasibleSuccessors; - bool HasNonFeasibleEdges = false; - for (BasicBlock *Succ : successors(BB)) { - if (Solver.isEdgeFeasible(BB, Succ)) - FeasibleSuccessors.insert(Succ); - else - HasNonFeasibleEdges = true; - } - - // All edges feasible, nothing to do. - if (!HasNonFeasibleEdges) - return false; - - // SCCP can only determine non-feasible edges for br, switch and indirectbr. - Instruction *TI = BB->getTerminator(); - assert((isa(TI) || isa(TI) || - isa(TI)) && - "Terminator must be a br, switch or indirectbr"); - - if (FeasibleSuccessors.size() == 1) { - // Replace with an unconditional branch to the only feasible successor. - BasicBlock *OnlyFeasibleSuccessor = *FeasibleSuccessors.begin(); - SmallVector Updates; - bool HaveSeenOnlyFeasibleSuccessor = false; - for (BasicBlock *Succ : successors(BB)) { - if (Succ == OnlyFeasibleSuccessor && !HaveSeenOnlyFeasibleSuccessor) { - // Don't remove the edge to the only feasible successor the first time - // we see it. We still do need to remove any multi-edges to it though. - HaveSeenOnlyFeasibleSuccessor = true; - continue; - } - - Succ->removePredecessor(BB); - Updates.push_back({DominatorTree::Delete, BB, Succ}); - } - - BranchInst::Create(OnlyFeasibleSuccessor, BB); - TI->eraseFromParent(); - DTU.applyUpdatesPermissive(Updates); - } else if (FeasibleSuccessors.size() > 1) { - SwitchInstProfUpdateWrapper SI(*cast(TI)); - SmallVector Updates; - for (auto CI = SI->case_begin(); CI != SI->case_end();) { - if (FeasibleSuccessors.contains(CI->getCaseSuccessor())) { - ++CI; - continue; - } - - BasicBlock *Succ = CI->getCaseSuccessor(); - Succ->removePredecessor(BB); - Updates.push_back({DominatorTree::Delete, BB, Succ}); - SI.removeCase(CI); - // Don't increment CI, as we removed a case. - } - - DTU.applyUpdatesPermissive(Updates); - } else { - llvm_unreachable("Must have at least one feasible successor"); - } - return true; +void SCCPSolver::addToMustPreserveReturnsInFunctions(Function *F) { + Visitor->addToMustPreserveReturnsInFunctions(F); } -bool llvm::runIPSCCP( - Module &M, const DataLayout &DL, - std::function GetTLI, - function_ref getAnalysis) { - SCCPSolver Solver(DL, GetTLI, M.getContext()); - - // Loop over all functions, marking arguments to those with their addresses - // taken or that are external as overdefined. - for (Function &F : M) { - if (F.isDeclaration()) - continue; - - Solver.addAnalysis(F, getAnalysis(F)); - - // Determine if we can track the function's return values. If so, add the - // function to the solver's set of return-tracked functions. - if (canTrackReturnsInterprocedurally(&F)) - Solver.AddTrackedFunction(&F); - - // Determine if we can track the function's arguments. If so, add the - // function to the solver's set of argument-tracked functions. - if (canTrackArgumentsInterprocedurally(&F)) { - Solver.AddArgumentTrackedFunction(&F); - continue; - } - - // Assume the function is called. - Solver.MarkBlockExecutable(&F.front()); - - // Assume nothing about the incoming arguments. - for (Argument &AI : F.args()) - Solver.markOverdefined(&AI); - } - - // Determine if we can track any of the module's global variables. If so, add - // the global variables we can track to the solver's set of tracked global - // variables. - for (GlobalVariable &G : M.globals()) { - G.removeDeadConstantUsers(); - if (canTrackGlobalVariableInterprocedurally(&G)) - Solver.TrackValueOfGlobalVariable(&G); - } - - // Solve for constants. - bool ResolvedUndefs = true; - Solver.Solve(); - while (ResolvedUndefs) { - LLVM_DEBUG(dbgs() << "RESOLVING UNDEFS\n"); - ResolvedUndefs = false; - for (Function &F : M) { - if (Solver.ResolvedUndefsIn(F)) - ResolvedUndefs = true; - } - if (ResolvedUndefs) - Solver.Solve(); - } - - bool MadeChanges = false; - - // Iterate over all of the instructions in the module, replacing them with - // constants if we have found them to be of constant values. - - for (Function &F : M) { - if (F.isDeclaration()) - continue; - - SmallVector BlocksToErase; - - if (Solver.isBlockExecutable(&F.front())) { - bool ReplacedPointerArg = false; - for (Argument &Arg : F.args()) { - if (!Arg.use_empty() && tryToReplaceWithConstant(Solver, &Arg)) { - ReplacedPointerArg |= Arg.getType()->isPointerTy(); - ++IPNumArgsElimed; - } - } - - // If we replaced an argument, the argmemonly and - // inaccessiblemem_or_argmemonly attributes do not hold any longer. Remove - // them from both the function and callsites. - if (ReplacedPointerArg) { - AttrBuilder AttributesToRemove; - AttributesToRemove.addAttribute(Attribute::ArgMemOnly); - AttributesToRemove.addAttribute(Attribute::InaccessibleMemOrArgMemOnly); - F.removeAttributes(AttributeList::FunctionIndex, AttributesToRemove); - - for (User *U : F.users()) { - auto *CB = dyn_cast(U); - if (!CB || CB->getCalledFunction() != &F) - continue; - - CB->removeAttributes(AttributeList::FunctionIndex, - AttributesToRemove); - } - } - } +bool SCCPSolver::mustPreserveReturn(Function *F) { + return Visitor->mustPreserveReturn(F); +} - SmallPtrSet InsertedValues; - for (BasicBlock &BB : F) { - if (!Solver.isBlockExecutable(&BB)) { - LLVM_DEBUG(dbgs() << " BasicBlock Dead:" << BB); - ++NumDeadBlocks; +void SCCPSolver::AddArgumentTrackedFunction(Function *F) { + Visitor->AddArgumentTrackedFunction(F); +} - MadeChanges = true; +bool SCCPSolver::isArgumentTrackedFunction(Function *F) { + return Visitor->isArgumentTrackedFunction(F); +} - if (&BB != &F.front()) - BlocksToErase.push_back(&BB); - continue; - } +void SCCPSolver::Solve() { Visitor->Solve(); } - MadeChanges |= simplifyInstsInBlock(Solver, BB, InsertedValues, - IPNumInstRemoved, IPNumInstReplaced); - } +bool SCCPSolver::ResolvedUndefsIn(Function &F) { + return Visitor->ResolvedUndefsIn(F); +} - DomTreeUpdater DTU = Solver.getDTU(F); - // Change dead blocks to unreachable. We do it after replacing constants - // in all executable blocks, because changeToUnreachable may remove PHI - // nodes in executable blocks we found values for. The function's entry - // block is not part of BlocksToErase, so we have to handle it separately. - for (BasicBlock *BB : BlocksToErase) { - NumInstRemoved += - changeToUnreachable(BB->getFirstNonPHI(), /*UseLLVMTrap=*/false, - /*PreserveLCSSA=*/false, &DTU); - } - if (!Solver.isBlockExecutable(&F.front())) - NumInstRemoved += changeToUnreachable(F.front().getFirstNonPHI(), - /*UseLLVMTrap=*/false, - /*PreserveLCSSA=*/false, &DTU); - - for (BasicBlock &BB : F) - MadeChanges |= removeNonFeasibleEdges(Solver, &BB, DTU); - - for (BasicBlock *DeadBB : BlocksToErase) - DTU.deleteBB(DeadBB); - - for (BasicBlock &BB : F) { - for (BasicBlock::iterator BI = BB.begin(), E = BB.end(); BI != E;) { - Instruction *Inst = &*BI++; - if (Solver.getPredicateInfoFor(Inst)) { - if (auto *II = dyn_cast(Inst)) { - if (II->getIntrinsicID() == Intrinsic::ssa_copy) { - Value *Op = II->getOperand(0); - Inst->replaceAllUsesWith(Op); - Inst->eraseFromParent(); - } - } - } - } - } - } +bool SCCPSolver::isBlockExecutable(BasicBlock *BB) const { + return Visitor->isBlockExecutable(BB); +} - // If we inferred constant or undef return values for a function, we replaced - // all call uses with the inferred value. This means we don't need to bother - // actually returning anything from the function. Replace all return - // instructions with return undef. - // - // Do this in two stages: first identify the functions we should process, then - // actually zap their returns. This is important because we can only do this - // if the address of the function isn't taken. In cases where a return is the - // last use of a function, the order of processing functions would affect - // whether other functions are optimizable. - SmallVector ReturnsToZap; - - for (const auto &I : Solver.getTrackedRetVals()) { - Function *F = I.first; - const ValueLatticeElement &ReturnValue = I.second; - - // If there is a known constant range for the return value, add !range - // metadata to the function's call sites. - if (ReturnValue.isConstantRange() && - !ReturnValue.getConstantRange().isSingleElement()) { - // Do not add range metadata if the return value may include undef. - if (ReturnValue.isConstantRangeIncludingUndef()) - continue; +bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) const { + return Visitor->isEdgeFeasible(From, To); +} - auto &CR = ReturnValue.getConstantRange(); - for (User *User : F->users()) { - auto *CB = dyn_cast(User); - if (!CB || CB->getCalledFunction() != F) - continue; +std::vector +SCCPSolver::getStructLatticeValueFor(Value *V) const { + return Visitor->getStructLatticeValueFor(V); +} - // Limit to cases where the return value is guaranteed to be neither - // poison nor undef. Poison will be outside any range and currently - // values outside of the specified range cause immediate undefined - // behavior. - if (!isGuaranteedNotToBeUndefOrPoison(CB, nullptr, CB)) - continue; +void SCCPSolver::removeLatticeValueFor(Value *V) { + return Visitor->removeLatticeValueFor(V); +} - // Do not touch existing metadata for now. - // TODO: We should be able to take the intersection of the existing - // metadata and the inferred range. - if (CB->getMetadata(LLVMContext::MD_range)) - continue; +const ValueLatticeElement &SCCPSolver::getLatticeValueFor(Value *V) const { + return Visitor->getLatticeValueFor(V); +} - LLVMContext &Context = CB->getParent()->getContext(); - Metadata *RangeMD[] = { - ConstantAsMetadata::get(ConstantInt::get(Context, CR.getLower())), - ConstantAsMetadata::get(ConstantInt::get(Context, CR.getUpper()))}; - CB->setMetadata(LLVMContext::MD_range, MDNode::get(Context, RangeMD)); - } - continue; - } - if (F->getReturnType()->isVoidTy()) - continue; - if (isConstant(ReturnValue) || ReturnValue.isUnknownOrUndef()) - findReturnsToZap(*F, ReturnsToZap, Solver); - } +const MapVector & +SCCPSolver::getTrackedRetVals() { + return Visitor->getTrackedRetVals(); +} - for (auto F : Solver.getMRVFunctionsTracked()) { - assert(F->getReturnType()->isStructTy() && - "The return type should be a struct"); - StructType *STy = cast(F->getReturnType()); - if (Solver.isStructLatticeConstant(F, STy)) - findReturnsToZap(*F, ReturnsToZap, Solver); - } +const DenseMap & +SCCPSolver::getTrackedGlobals() { + return Visitor->getTrackedGlobals(); +} - // Zap all returns which we've identified as zap to change. - SmallSetVector FuncZappedReturn; - for (unsigned i = 0, e = ReturnsToZap.size(); i != e; ++i) { - Function *F = ReturnsToZap[i]->getParent()->getParent(); - ReturnsToZap[i]->setOperand(0, UndefValue::get(F->getReturnType())); - // Record all functions that are zapped. - FuncZappedReturn.insert(F); - } +const SmallPtrSet SCCPSolver::getMRVFunctionsTracked() { + return Visitor->getMRVFunctionsTracked(); +} - // Remove the returned attribute for zapped functions and the - // corresponding call sites. - for (Function *F : FuncZappedReturn) { - for (Argument &A : F->args()) - F->removeParamAttr(A.getArgNo(), Attribute::Returned); - for (Use &U : F->uses()) { - // Skip over blockaddr users. - if (isa(U.getUser())) - continue; - CallBase *CB = cast(U.getUser()); - for (Use &Arg : CB->args()) - CB->removeParamAttr(CB->getArgOperandNo(&Arg), Attribute::Returned); - } - } +void SCCPSolver::markOverdefined(Value *V) { Visitor->markOverdefined(V); } - // If we inferred constant or undef values for globals variables, we can - // delete the global and any stores that remain to it. - for (auto &I : make_early_inc_range(Solver.getTrackedGlobals())) { - GlobalVariable *GV = I.first; - if (isOverdefined(I.second)) - continue; - LLVM_DEBUG(dbgs() << "Found that GV '" << GV->getName() - << "' is constant!\n"); - while (!GV->use_empty()) { - StoreInst *SI = cast(GV->user_back()); - SI->eraseFromParent(); - MadeChanges = true; - } - M.getGlobalList().erase(GV); - ++IPNumGlobalConst; - } +bool SCCPSolver::isStructLatticeConstant(Function *F, StructType *STy) { + return Visitor->isStructLatticeConstant(F, STy); +} - return MadeChanges; +Constant *SCCPSolver::getConstant(const ValueLatticeElement &LV) const { + return Visitor->getConstant(LV); }