Index: llvm/include/llvm/InitializePasses.h
===================================================================
--- llvm/include/llvm/InitializePasses.h
+++ llvm/include/llvm/InitializePasses.h
@@ -124,6 +124,7 @@
void initializeDAEPass(PassRegistry&);
void initializeDAHPass(PassRegistry&);
void initializeDCELegacyPassPass(PassRegistry&);
+void initializeDFAJumpThreadingLegacyPassPass(PassRegistry &);
void initializeDSELegacyPassPass(PassRegistry&);
void initializeDataFlowSanitizerLegacyPassPass(PassRegistry &);
void initializeDeadMachineInstructionElimPass(PassRegistry&);
Index: llvm/include/llvm/LinkAllPasses.h
===================================================================
--- llvm/include/llvm/LinkAllPasses.h
+++ llvm/include/llvm/LinkAllPasses.h
@@ -174,6 +174,7 @@
(void) llvm::createStripDeadPrototypesPass();
(void) llvm::createTailCallEliminationPass();
(void) llvm::createJumpThreadingPass();
+ (void) llvm::createDFAJumpThreadingPass();
(void) llvm::createUnifyFunctionExitNodesPass();
(void) llvm::createInstCountPass();
(void) llvm::createConstantHoistingPass();
Index: llvm/include/llvm/Transforms/Scalar.h
===================================================================
--- llvm/include/llvm/Transforms/Scalar.h
+++ llvm/include/llvm/Transforms/Scalar.h
@@ -253,6 +253,14 @@
FunctionPass *createJumpThreadingPass(bool FreezeSelectCond = false,
int Threshold = -1);
+//===----------------------------------------------------------------------===//
+//
+// DFAJumpThreading - When a switch statement inside a loop is used to
+// implement a deterministic finite automata we can jump thread the switch
+// statement reducing number of conditional jumps.
+//
+FunctionPass *createDFAJumpThreadingPass();
+
//===----------------------------------------------------------------------===//
//
// CFGSimplification - Merge basic blocks, eliminate unreachable blocks,
Index: llvm/include/llvm/Transforms/Scalar/DFAJumpThreading.h
===================================================================
--- /dev/null
+++ llvm/include/llvm/Transforms/Scalar/DFAJumpThreading.h
@@ -0,0 +1,27 @@
+//===- DFAJumpThreading.h - Threads a switch statement inside a loop ------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file provides the interface for the DFAJumpThreading pass.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_SCALAR_DFAJUMPTHREADING_H
+#define LLVM_TRANSFORMS_SCALAR_DFAJUMPTHREADING_H
+
+#include "llvm/IR/Function.h"
+#include "llvm/IR/PassManager.h"
+
+namespace llvm {
+
+struct DFAJumpThreadingPass : PassInfoMixin<DFAJumpThreadingPass> {
+ PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
+};
+
+} // end namespace llvm
+
+#endif // LLVM_TRANSFORMS_SCALAR_DFAJUMPTHREADING_H
Index: llvm/lib/Passes/PassBuilder.cpp
===================================================================
--- llvm/lib/Passes/PassBuilder.cpp
+++ llvm/lib/Passes/PassBuilder.cpp
@@ -145,6 +145,7 @@
#include "llvm/Transforms/Scalar/ConstraintElimination.h"
#include "llvm/Transforms/Scalar/CorrelatedValuePropagation.h"
#include "llvm/Transforms/Scalar/DCE.h"
+#include "llvm/Transforms/Scalar/DFAJumpThreading.h"
#include "llvm/Transforms/Scalar/DeadStoreElimination.h"
#include "llvm/Transforms/Scalar/DivRemPairs.h"
#include "llvm/Transforms/Scalar/EarlyCSE.h"
@@ -303,6 +304,7 @@
extern cl::opt<bool> EnableLoopInterchange;
extern cl::opt<bool> EnableUnrollAndJam;
extern cl::opt<bool> EnableLoopFlatten;
+extern cl::opt<bool> EnableDFAJumpThreading;
extern cl::opt<bool> RunNewGVN;
extern cl::opt<bool> RunPartialInlining;
extern cl::opt<bool> ExtraVectorizerPasses;
@@ -827,6 +829,9 @@
// Re-consider control flow based optimizations after redundancy elimination,
// redo DCE, etc.
+ if (EnableDFAJumpThreading && Level.getSizeLevel() == 0)
+ FPM.addPass(DFAJumpThreadingPass());
+
FPM.addPass(JumpThreadingPass());
FPM.addPass(CorrelatedValuePropagationPass());
Index: llvm/lib/Passes/PassRegistry.def
===================================================================
--- llvm/lib/Passes/PassRegistry.def
+++ llvm/lib/Passes/PassRegistry.def
@@ -211,6 +211,7 @@
FUNCTION_PASS("coro-cleanup", CoroCleanupPass())
FUNCTION_PASS("correlated-propagation", CorrelatedValuePropagationPass())
FUNCTION_PASS("dce", DCEPass())
+FUNCTION_PASS("dfa-jump-threading", DFAJumpThreadingPass())
FUNCTION_PASS("div-rem-pairs", DivRemPairsPass())
FUNCTION_PASS("dse", DSEPass())
FUNCTION_PASS("dot-cfg", CFGPrinterPass())
Index: llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
===================================================================
--- llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -97,6 +97,10 @@
cl::Hidden,
cl::desc("Enable the LoopFlatten Pass"));
+cl::opt<bool> EnableDFAJumpThreading("enable-dfa-jump-thread",
+ cl::desc("Enable DFA jump threading."),
+ cl::init(true), cl::Hidden);
+
static cl::opt<bool>
EnablePrepareForThinLTO("prepare-for-thinlto", cl::init(false), cl::Hidden,
cl::desc("Enable preparation for ThinLTO."));
@@ -494,6 +498,9 @@
MPM.add(createInstructionCombiningPass());
addExtensionsToPM(EP_Peephole, MPM);
if (OptLevel > 1) {
+ if (EnableDFAJumpThreading && SizeLevel == 0)
+ MPM.add(createDFAJumpThreadingPass());
+
MPM.add(createJumpThreadingPass()); // Thread jumps
MPM.add(createCorrelatedValuePropagationPass());
}
Index: llvm/lib/Transforms/Scalar/CMakeLists.txt
===================================================================
--- llvm/lib/Transforms/Scalar/CMakeLists.txt
+++ llvm/lib/Transforms/Scalar/CMakeLists.txt
@@ -9,6 +9,7 @@
CorrelatedValuePropagation.cpp
DCE.cpp
DeadStoreElimination.cpp
+ DFAJumpThreading.cpp
DivRemPairs.cpp
EarlyCSE.cpp
FlattenCFGPass.cpp
Index: llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
===================================================================
--- /dev/null
+++ llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
@@ -0,0 +1,1207 @@
+//===- DFAJumpThreading.cpp - Threads a switch statement inside a loop ----===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// When a switch statement inside a loop is used to implement a deterministic
+// finite automaton, we can jump thread the switch statement reducing number of
+// conditional jumps. Currently this does not happen in LLVM jump threading.
+// For example the code pattern on the left could functionally be transformed
+// to the right pattern if the switch condition is predictable.
+//
+// X = A goto A
+// for (...) A:
+// switch (X) ...
+// case A goto B
+// X = B B:
+// case B ...
+// X = C goto C
+//
+// The pass first checks that a switch variable is decided by the control flow
+// path taken in the loop. It then enumerates through all paths in the loop and
+// labels the basic blocks where the next state is decided.
+//
+// Using this information it creates new paths that unconditionally branch to
+// the next case. This involves cloning code, so it only runs if the amount of
+// code duplicated is below a threshold.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar/DFAJumpThreading.h"
+#include "llvm/ADT/APInt.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/AssumptionCache.h"
+#include "llvm/Analysis/CodeMetrics.h"
+#include "llvm/Analysis/LoopIterator.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/CFG.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Verifier.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/Cloning.h"
+#include "llvm/Transforms/Utils/SSAUpdaterBulk.h"
+#include "llvm/Transforms/Utils/ValueMapper.h"
+#include <algorithm>
+#include <deque>
+#include <unordered_map>
+#include <unordered_set>
+
+using namespace llvm;
+
+#define DEBUG_TYPE "dfa-jump-threading"
+
+STATISTIC(NumTransforms, "Number of transformations done");
+STATISTIC(NumCloned, "Number of blocks cloned");
+STATISTIC(NumPaths, "Number of individual paths threaded");
+
+static cl::opt<bool>
+ IsViewCFGBefore("dfa-jump-view-cfg-before",
+ cl::desc("View the CFG before DFA Jump Threading"),
+ cl::Hidden, cl::init(false));
+
+static cl::opt<unsigned> MaxPathDepth(
+ "dfa-max-path-length",
+ cl::desc("Max number of blocks searched to find threadable path"),
+ cl::Hidden, cl::init(20));
+
+static cl::opt<unsigned>
+ CostThreshold("dfa-cost-threshold",
+ cl::desc("Maximum cost accepted for the transformation"),
+ cl::Hidden, cl::init(50));
+
+namespace {
+
+class SelectInstToUnfold {
+ SelectInst *SI;
+ PHINode *SIUse;
+
+public:
+ SelectInstToUnfold(SelectInst *SI, PHINode *SIUse) : SI(SI), SIUse(SIUse) {}
+
+ SelectInst *getInst() { return SI; }
+ PHINode *getUse() { return SIUse; }
+
+ explicit operator bool() const { return SI && SIUse; }
+};
+
+void unfold(DomTreeUpdater *DTU, SelectInstToUnfold SIToUnfold,
+ std::vector<SelectInstToUnfold> *NewSIsToUnfold,
+ std::vector<BasicBlock *> *NewBBs);
+
+class DFAJumpThreading {
+public:
+ DFAJumpThreading(AssumptionCache *AC, DominatorTree *DT,
+ TargetTransformInfo *TTI)
+ : AC(AC), DT(DT), TTI(TTI) {}
+
+ bool run(Function &F);
+
+private:
+ void
+ unfoldSelectInstrs(DominatorTree *DT,
+ const SmallVector<SelectInstToUnfold, 4> &SelectInsts) {
+ DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Eager);
+ SmallVector<SelectInstToUnfold, 4> Stack;
+ for (SelectInstToUnfold SIToUnfold : SelectInsts) {
+ Stack.push_back(SIToUnfold);
+ }
+
+ while (!Stack.empty()) {
+ SelectInstToUnfold SIToUnfold = Stack.back();
+ Stack.pop_back();
+
+ std::vector<SelectInstToUnfold> NewSIsToUnfold;
+ std::vector<BasicBlock *> NewBBs;
+ unfold(&DTU, SIToUnfold, &NewSIsToUnfold, &NewBBs);
+
+ // Put newly discovered select instructions into the work list.
+ for (const SelectInstToUnfold &NewSIToUnfold : NewSIsToUnfold) {
+ Stack.push_back(NewSIToUnfold);
+ }
+ }
+ }
+
+ AssumptionCache *AC;
+ DominatorTree *DT;
+ TargetTransformInfo *TTI;
+};
+
+class DFAJumpThreadingLegacyPass : public FunctionPass {
+public:
+ static char ID; // Pass identification
+ DFAJumpThreadingLegacyPass() : FunctionPass(ID) {}
+
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.addRequired<AssumptionCacheTracker>();
+ AU.addRequired<DominatorTreeWrapperPass>();
+ AU.addRequired<TargetTransformInfoWrapperPass>();
+ }
+
+ bool runOnFunction(Function &F) override {
+ if (skipFunction(F))
+ return false;
+
+ AssumptionCache *AC =
+ &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
+ DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+ TargetTransformInfo *TTI =
+ &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
+
+ return DFAJumpThreading(AC, DT, TTI).run(F);
+ }
+};
+} // end anonymous namespace
+
+char DFAJumpThreadingLegacyPass::ID = 0;
+INITIALIZE_PASS_BEGIN(DFAJumpThreadingLegacyPass, "dfa-jump-threading",
+ "DFA Jump Threading", false, false)
+INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
+INITIALIZE_PASS_END(DFAJumpThreadingLegacyPass, "dfa-jump-threading",
+ "DFA Jump Threading", false, false)
+
+// Public interface to the DFA Jump Threading pass
+FunctionPass *llvm::createDFAJumpThreadingPass() {
+ return new DFAJumpThreadingLegacyPass();
+}
+
+namespace {
+
+/// Unfold the select instruction held in \p SIToUnfold.
+///
+/// Put newly discovered select instructions into \p NewSIsToUnfold. Put newly
+/// created basic blocks into \p NewBBs.
+///
+/// This routine is inspired by CodeGenPrepare::optimizeSelectInst().
+void unfold(DomTreeUpdater *DTU, SelectInstToUnfold SIToUnfold,
+ std::vector<SelectInstToUnfold> *NewSIsToUnfold,
+ std::vector<BasicBlock *> *NewBBs) {
+ SelectInst *SI = SIToUnfold.getInst();
+ PHINode *SIUse = SIToUnfold.getUse();
+ BasicBlock *StartBlock = SI->getParent();
+ BasicBlock *EndBlock = SIUse->getParent();
+ BranchInst *StartBlockTerm =
+ dyn_cast<BranchInst>(StartBlock->getTerminator());
+
+ assert(StartBlockTerm && StartBlockTerm->isUnconditional());
+ assert(SI->hasOneUse());
+
+ // These are the new basic blocks for the conditional branch.
+ // At least one will become an actual new basic block.
+ BasicBlock *TrueBlock = nullptr;
+ BasicBlock *FalseBlock = nullptr;
+ BranchInst *TrueBranch = nullptr;
+ BranchInst *FalseBranch = nullptr;
+
+ // Sink select instructions to be able to unfold them later.
+ if (SelectInst *SIOp = dyn_cast<SelectInst>(SI->getTrueValue())) {
+ assert(SIOp->hasOneUse());
+ TrueBlock = BasicBlock::Create(SI->getContext(), "si.unfold.true",
+ EndBlock->getParent(), EndBlock);
+ NewBBs->push_back(TrueBlock);
+ TrueBranch = BranchInst::Create(EndBlock, TrueBlock);
+ SIOp->moveBefore(TrueBranch);
+ NewSIsToUnfold->push_back(SelectInstToUnfold(SIOp, SIUse));
+ DTU->applyUpdates({{DominatorTree::Insert, TrueBlock, EndBlock}});
+ }
+ if (SelectInst *SIOp = dyn_cast<SelectInst>(SI->getFalseValue())) {
+ assert(SIOp->hasOneUse());
+ FalseBlock = BasicBlock::Create(SI->getContext(), "si.unfold.false",
+ EndBlock->getParent(), EndBlock);
+ NewBBs->push_back(FalseBlock);
+ FalseBranch = BranchInst::Create(EndBlock, FalseBlock);
+ SIOp->moveBefore(FalseBranch);
+ NewSIsToUnfold->push_back(SelectInstToUnfold(SIOp, SIUse));
+ DTU->applyUpdates({{DominatorTree::Insert, FalseBlock, EndBlock}});
+ }
+
+ // If there was nothing to sink, then arbitrarily choose the 'false' side
+ // for a new input value to the PHI.
+ if (!TrueBlock && !FalseBlock) {
+ FalseBlock = BasicBlock::Create(SI->getContext(), "si.unfold.false",
+ EndBlock->getParent(), EndBlock);
+ NewBBs->push_back(FalseBlock);
+ BranchInst::Create(EndBlock, FalseBlock);
+ DTU->applyUpdates({{DominatorTree::Insert, FalseBlock, EndBlock}});
+ }
+
+ // Insert the real conditional branch based on the original condition.
+ // If we did not create a new block for one of the 'true' or 'false' paths
+ // of the condition, it means that side of the branch goes to the end block
+ // directly and the path originates from the start block from the point of
+ // view of the new PHI.
+ BasicBlock *TT = EndBlock;
+ BasicBlock *FT = EndBlock;
+ if (TrueBlock && FalseBlock) {
+ // A diamond.
+ TT = TrueBlock;
+ FT = FalseBlock;
+
+ // Update the phi node of SI.
+ SIUse->removeIncomingValue(StartBlock, /* DeletePHIIfEmpty = */ false);
+ SIUse->addIncoming(SI->getTrueValue(), TrueBlock);
+ SIUse->addIncoming(SI->getFalseValue(), FalseBlock);
+
+ // Update any other PHI nodes in EndBlock.
+ for (auto II = EndBlock->begin(); PHINode *Phi = dyn_cast<PHINode>(II);
+ ++II) {
+ if (Phi != SIUse) {
+ Phi->addIncoming(Phi->getIncomingValueForBlock(StartBlock), TrueBlock);
+ Phi->addIncoming(Phi->getIncomingValueForBlock(StartBlock), FalseBlock);
+ }
+ }
+ } else {
+ BasicBlock *NewBlock = nullptr;
+ Value *SIOp1 = SI->getTrueValue();
+ Value *SIOp2 = SI->getFalseValue();
+
+ // A triangle pointing right.
+ if (!TrueBlock) {
+ NewBlock = FalseBlock;
+ FT = FalseBlock;
+ }
+ // A triangle pointing left.
+ else {
+ NewBlock = TrueBlock;
+ TT = TrueBlock;
+ std::swap(SIOp1, SIOp2);
+ }
+
+ // Update the phi node of SI.
+ for (unsigned Idx = 0; Idx < SIUse->getNumIncomingValues(); ++Idx) {
+ if (SIUse->getIncomingBlock(Idx) == StartBlock) {
+ SIUse->setIncomingValue(Idx, SIOp1);
+ }
+ }
+ SIUse->addIncoming(SIOp2, NewBlock);
+
+ // Update any other PHI nodes in EndBlock.
+ for (auto II = EndBlock->begin(); PHINode *Phi = dyn_cast<PHINode>(II);
+ ++II) {
+ if (Phi != SIUse) {
+ Phi->addIncoming(Phi->getIncomingValueForBlock(StartBlock), NewBlock);
+ }
+ }
+ }
+ StartBlockTerm->eraseFromParent();
+ BranchInst::Create(TT, FT, SI->getCondition(), StartBlock);
+ DTU->applyUpdates({{DominatorTree::Insert, StartBlock, TT},
+ {DominatorTree::Insert, StartBlock, FT}});
+
+ // The select is now dead.
+ SI->eraseFromParent();
+}
+
+struct ClonedBlock {
+ BasicBlock *BB;
+ uint64_t State;
+};
+
+typedef std::deque<BasicBlock *> PathType;
+typedef std::vector<PathType> PathsType;
+typedef std::set<const BasicBlock *> VisitedBlocks;
+typedef std::vector<ClonedBlock> CloneList;
+
+// This data structure keeps track of all blocks that have been cloned in the
+// optimization. If two different ThreadingPaths clone the same block for a
+// certain state it should be reused, and it can be looked up in this map.
+typedef DenseMap<BasicBlock *, CloneList> DuplicateBlockMap;
+
+// This map keeps track of all the new definitions for an instruction. This
+// information is needed when restoring SSA form after cloning blocks.
+typedef DenseMap<Instruction *, std::vector<Instruction *>> DefMap;
+
+inline raw_ostream &operator<<(raw_ostream &OS, const PathType &Path) {
+ OS << "< ";
+ for (const BasicBlock *BB : Path) {
+ std::string BBName;
+ if (BB->hasName())
+ raw_string_ostream(BBName) << BB->getName();
+ else
+ raw_string_ostream(BBName) << BB;
+ OS << BBName << " ";
+ }
+ OS << ">";
+ return OS;
+}
+
+struct ThreadingPath {
+ uint64_t getExitValue() const { return ExitVal; }
+ void setExitValue(const ConstantInt *V) {
+ ExitVal = V->getZExtValue();
+ IsExitValSet = true;
+ }
+ bool isExitValueSet() const { return IsExitValSet; }
+
+ const BasicBlock *getDeterminatorBB() const { return DBB; }
+ void setDeterminator(const BasicBlock *BB) { DBB = BB; }
+
+ const PathType &getPath() const { return Path; }
+ void setPath(const PathType &NewPath) { Path = NewPath; }
+
+ void print(raw_ostream &OS) const {
+ OS << Path << " [ " << ExitVal << ", " << DBB->getName() << " ]";
+ }
+
+private:
+ PathType Path;
+ uint64_t ExitVal;
+ const BasicBlock *DBB = nullptr;
+ bool IsExitValSet = false;
+};
+
+#ifndef NDEBUG
+inline raw_ostream &operator<<(raw_ostream &OS, const ThreadingPath &TPath) {
+ TPath.print(OS);
+ return OS;
+}
+#endif
+
+struct MainSwitch {
+ MainSwitch(SwitchInst *SI) {
+ if (isPredictable(SI))
+ Instr = SI;
+ }
+
+ virtual ~MainSwitch() = default;
+
+ SwitchInst *getInstr() const { return Instr; }
+ const SmallVector<SelectInstToUnfold, 4> getSelectInsts() {
+ return SelectInsts;
+ }
+
+private:
+ /// Do a use-def chain traversal. Make sure the value of the switch variable
+ /// is always a known constant. This means that all conditional jumps based on
+ /// switch variable can be converted to unconditional jump.
+ bool isPredictable(const SwitchInst *SI) {
+ std::deque<Instruction *> Q;
+ SmallSet<Value *, 16> SeenValues;
+ SelectInsts.clear();
+
+ Value *FirstDef = SI->getOperand(0);
+ auto *Inst = dyn_cast<Instruction>(FirstDef);
+
+ // If this is a function argument or another non-instruction, then give up.
+ // We are interested in loop local variables.
+ if (!Inst)
+ return false;
+
+ // Require the first definition to be a PHINode
+ if (!isa<PHINode>(Inst))
+ return false;
+
+ LLVM_DEBUG(dbgs() << "\tisPredictable() FirstDef: " << *Inst << "\n");
+
+ Q.push_back(Inst);
+ SeenValues.insert(FirstDef);
+
+ while (!Q.empty()) {
+ Instruction *Current = Q.front();
+ Q.pop_front();
+
+ if (auto *Phi = dyn_cast<PHINode>(Current)) {
+ for (Value *Incoming : Phi->incoming_values()) {
+ if (!isValidValue(Incoming, SeenValues)) {
+ return false;
+ }
+ addInstToQueue(Incoming, Q, SeenValues);
+ }
+ LLVM_DEBUG(dbgs() << "\tisPredictable() phi: " << *Phi << "\n");
+ } else if (SelectInst *SelI = dyn_cast<SelectInst>(Current)) {
+ if (!isValidSelectInst(SelI)) {
+ return false;
+ }
+ if (!isValidValue(SelI->getTrueValue(), SeenValues) ||
+ !isValidValue(SelI->getFalseValue(), SeenValues)) {
+ return false;
+ }
+ addInstToQueue(SelI->getTrueValue(), Q, SeenValues);
+ addInstToQueue(SelI->getFalseValue(), Q, SeenValues);
+ LLVM_DEBUG(dbgs() << "\tisPredictable() select: " << *SelI << "\n");
+ if (auto *SelIUse = dyn_cast<PHINode>(SelI->user_back())) {
+ SelectInsts.push_back(SelectInstToUnfold(SelI, SelIUse));
+ }
+ } else {
+ // If it is neither a phi nor a select, then we give up.
+ return false;
+ }
+ }
+
+ return true;
+ }
+
+ bool isValidValue(Value *InpVal, SmallSet<Value *, 16> &SeenValues) {
+ if (SeenValues.find(InpVal) != SeenValues.end())
+ return true;
+
+ if (isa<ConstantInt>(InpVal))
+ return true;
+
+ // If this is a function argument or another non-instruction, then give up.
+ if (!isa<Instruction>(InpVal))
+ return false;
+
+ return true;
+ }
+
+ void addInstToQueue(Value *Val, std::deque<Instruction *> &Q,
+ SmallSet<Value *, 16> &SeenValues) {
+ if (SeenValues.find(Val) != SeenValues.end())
+ return;
+ if (Instruction *I = dyn_cast<Instruction>(Val)) {
+ Q.push_back(I);
+ }
+ SeenValues.insert(Val);
+ }
+
+ bool isValidSelectInst(SelectInst *SI) {
+ if (!SI->hasOneUse()) {
+ return false;
+ }
+
+ Instruction *SIUse = dyn_cast<Instruction>(SI->user_back());
+ // The use of the select inst should be either a phi or another select.
+ if (!SIUse && !(isa<PHINode>(SIUse) || isa<SelectInst>(SIUse))) {
+ return false;
+ }
+
+ BasicBlock *SIBB = SI->getParent();
+
+ // Currently, we can only expand select instructions in basic blocks with
+ // one successor.
+ BranchInst *SITerm = dyn_cast<BranchInst>(SIBB->getTerminator());
+ if (!SITerm || !SITerm->isUnconditional()) {
+ return false;
+ }
+
+ if (isa<PHINode>(SIUse) && SIBB->getSingleSuccessor() !=
+ dyn_cast<Instruction>(SIUse)->getParent()) {
+ return false;
+ }
+
+ // If select will not be sunk during unfolding, and it is in the same basic
+ // block as another state defining select, then cannot unfold both.
+ for (SelectInstToUnfold SIToUnfold : SelectInsts) {
+ SelectInst *PrevSI = SIToUnfold.getInst();
+ if (PrevSI->getTrueValue() != SI && PrevSI->getFalseValue() != SI &&
+ PrevSI->getParent() == SI->getParent())
+ return false;
+ }
+
+ return true;
+ }
+
+ SwitchInst *Instr = nullptr;
+ SmallVector<SelectInstToUnfold, 4> SelectInsts;
+};
+
+struct AllSwitchPaths {
+ AllSwitchPaths(const MainSwitch *MSwitch)
+ : Switch(MSwitch->getInstr()), SwitchBlock(Switch->getParent()) {}
+
+ std::vector<ThreadingPath> &getThreadingPaths() { return TPaths; }
+ unsigned getNumThreadingPaths() { return TPaths.size(); }
+ SwitchInst *getSwitchInst() { return Switch; }
+ BasicBlock *getSwitchBlock() { return SwitchBlock; }
+
+ void run() {
+ VisitedBlocks Visited;
+ PathsType LoopPaths = paths(SwitchBlock, Visited, /* PathDepth = */ 1);
+ StateDefMap StateDef = getStateDefMap();
+
+ for (PathType Path : LoopPaths) {
+ ThreadingPath TPath;
+
+ const BasicBlock *PrevBB = Path.back();
+ for (const BasicBlock *BB : Path) {
+ if (StateDef.count(BB) != 0) {
+ const PHINode *Phi = dyn_cast<PHINode>(StateDef[BB]);
+ assert(Phi && "Expected a state-defining instr to be a phi node.");
+
+ const Value *V = Phi->getIncomingValueForBlock(PrevBB);
+ if (const ConstantInt *C = dyn_cast<const ConstantInt>(V)) {
+ TPath.setExitValue(C);
+ TPath.setDeterminator(BB);
+ TPath.setPath(Path);
+ }
+ }
+
+ // Switch block is the determinator, this is the final exit value.
+ if (TPath.isExitValueSet() && BB == Path.front())
+ break;
+
+ PrevBB = BB;
+ }
+
+ if (TPath.isExitValueSet())
+ TPaths.push_back(TPath);
+ }
+ }
+
+private:
+ // Value: an instruction that defines a switch state;
+ // Key: the parent basic block of that instruction.
+ typedef DenseMap<const BasicBlock *, const PHINode *> StateDefMap;
+
+ PathsType paths(BasicBlock *BB, VisitedBlocks &Visited,
+ unsigned PathDepth) const {
+ PathsType Res;
+
+ // Stop exploring paths after visiting MaxPathLength blocks
+ if (PathDepth > MaxPathDepth)
+ return Res;
+
+ Visited.insert(BB);
+
+ // Some blocks have multiple edges to the same successor, and this set
+ // is used to prevent a duplicate path from being generated
+ SmallSet<BasicBlock *, 4> Successors;
+
+ for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI) {
+ BasicBlock *Succ = *SI;
+
+ if (Successors.find(Succ) != Successors.end())
+ continue;
+ Successors.insert(Succ);
+
+ // Found a cycle through the SwitchBlock
+ if (Succ == SwitchBlock) {
+ Res.push_back({BB});
+ continue;
+ }
+
+ // We have encountered a cycle, do not get caught in it
+ if (Visited.find(Succ) != Visited.end())
+ continue;
+
+ PathsType SuccPaths = paths(Succ, Visited, PathDepth + 1);
+ for (PathType Path : SuccPaths) {
+ PathType NewPath(Path);
+ NewPath.push_front(BB);
+ Res.push_back(NewPath);
+ }
+ }
+ // This block could now be visited again from a different predecessor. Note
+ // that this will result in exponential runtime. Subpaths could possibly be
+ // cached but it takes a lot of memory to store them.
+ Visited.erase(BB);
+ return Res;
+ }
+
+ /// Walk the use-def chain and collect all the state-defining instructions.
+ StateDefMap getStateDefMap() const {
+ StateDefMap Res;
+
+ Value *FirstDef = Switch->getOperand(0);
+
+ assert(isa<PHINode>(FirstDef) && "After select unfolding, all state "
+ "definitions are expected to be phi "
+ "nodes.");
+
+ SmallVector<PHINode *, 8> Stack;
+ Stack.push_back(dyn_cast<PHINode>(FirstDef));
+ SmallSet<Value *, 16> SeenValues;
+
+ while (!Stack.empty()) {
+ PHINode *CurPhi = Stack.back();
+ Stack.pop_back();
+
+ Res[CurPhi->getParent()] = CurPhi;
+ SeenValues.insert(CurPhi);
+
+ for (Value *Incoming : CurPhi->incoming_values()) {
+ if (Incoming == FirstDef || isa<ConstantInt>(Incoming) ||
+ SeenValues.find(Incoming) != SeenValues.end()) {
+ continue;
+ }
+
+ assert(isa<PHINode>(Incoming) && "After select unfolding, all state "
+ "definitions are expected to be phi "
+ "nodes.");
+
+ Stack.push_back(cast<PHINode>(Incoming));
+ }
+ }
+
+ return Res;
+ }
+
+ SwitchInst *Switch;
+ BasicBlock *SwitchBlock;
+ std::vector<ThreadingPath> TPaths;
+};
+
+struct TransformFSM {
+ TransformFSM(AllSwitchPaths *SwitchPaths, DominatorTree *DT,
+ AssumptionCache *AC, TargetTransformInfo *TTI,
+ SmallPtrSet<const Value *, 32> EphValues)
+ : SwitchPaths(SwitchPaths), DT(DT), AC(AC), TTI(TTI),
+ EphValues(EphValues) {}
+
+ void run() {
+ if (isLegalAndProfitableToTransform()) {
+ createAllExitPaths();
+ }
+ }
+
+private:
+ /// This function performs both a legality check and profitability check at
+ /// the same time since it is convenient to do so. It iterates through all
+ /// blocks that will be cloned, and keeps track of the duplication cost. It
+ /// also returns false if it is illegal to clone some required block.
+ bool isLegalAndProfitableToTransform() {
+ CodeMetrics Metrics;
+ SwitchInst *Switch = SwitchPaths->getSwitchInst();
+
+ // Note that DuplicateBlockMap is not being used as intended here. It is
+ // just being used to ensure (BB, State) pairs are only counted once.
+ DuplicateBlockMap DuplicateMap;
+
+ for (ThreadingPath &TPath : SwitchPaths->getThreadingPaths()) {
+ PathType PathBBs = TPath.getPath();
+ uint64_t NextState = TPath.getExitValue();
+ const BasicBlock *Determinator = TPath.getDeterminatorBB();
+
+ // Update Metrics for the Switch block, this is always cloned
+ BasicBlock *BB = SwitchPaths->getSwitchBlock();
+ BasicBlock *VisitedBB = getClonedBB(BB, NextState, DuplicateMap);
+ if (!VisitedBB) {
+ Metrics.analyzeBasicBlock(BB, *TTI, EphValues);
+ DuplicateMap[BB].push_back({BB, NextState});
+ }
+
+ // If the Switch block is the Determinator, then we can continue since
+ // this is the only block that is cloned and we already counted for it.
+ if (PathBBs.front() == Determinator) {
+ continue;
+ }
+
+ // Otherwise update Metrics for all blocks that will be cloned. If any
+ // block is already cloned and would be reused, don't double count it.
+ auto DetIt = std::find(PathBBs.begin(), PathBBs.end(), Determinator);
+ for (auto BBIt = DetIt; BBIt != PathBBs.end(); BBIt++) {
+ BB = *BBIt;
+ VisitedBB = getClonedBB(BB, NextState, DuplicateMap);
+ if (VisitedBB)
+ continue;
+ Metrics.analyzeBasicBlock(BB, *TTI, EphValues);
+ DuplicateMap[BB].push_back({BB, NextState});
+ }
+
+ if (Metrics.notDuplicatable) {
+ LLVM_DEBUG(dbgs() << "DFA Jump Threading: Not jump threading, contains "
+ << "non-duplicatable instructions.\n");
+ return false;
+ }
+
+ if (Metrics.convergent) {
+ LLVM_DEBUG(dbgs() << "DFA Jump Threading: Not jump threading, contains "
+ << "convergent instructions.\n");
+ return false;
+ }
+ }
+
+ // Factor in the number of conditional branches reduced from jump threading
+ unsigned CondBranches =
+ APInt(32, Switch->getNumSuccessors()).ceilLogBase2();
+ unsigned NumInsts = Metrics.NumInsts;
+ unsigned DuplicationCost = NumInsts / CondBranches;
+
+ LLVM_DEBUG(dbgs() << "\nDFA Jump Threading: Cost to jump thread block "
+ << SwitchPaths->getSwitchBlock()->getName()
+ << " is: " << DuplicationCost << "\n\n");
+
+ if (DuplicationCost > CostThreshold) {
+ LLVM_DEBUG(dbgs() << "Not jump threading, duplication cost exceeds the "
+ << "cost threshold.\n");
+ return false;
+ }
+
+ return true;
+ }
+
+ /// Transform each threading path to effectively jump thread the FSM. For
+ /// example the CFG below could be transformed as follows, where the cloned
+ /// blocks unconditionally branch to the next correct case based on what is
+ /// identified in the analysis.
+ /// sw.bb sw.bb
+ /// / | \ / | \
+ /// case1 case2 case3 case1 case2 case3
+ /// \ | / | | |
+ /// determinator det.2 det.3 det.1
+ /// br sw.bb / | \
+ /// sw.bb.2 sw.bb.3 sw.bb.1
+ /// br case2 br case3 br case1
+ void createAllExitPaths() {
+ DomTreeUpdater DTU(*DT, DomTreeUpdater::UpdateStrategy::Eager);
+
+ // Move the switch block to the end of the path, since it will be duplicated
+ BasicBlock *SwitchBlock = SwitchPaths->getSwitchBlock();
+ for (ThreadingPath &TPath : SwitchPaths->getThreadingPaths()) {
+ LLVM_DEBUG(dbgs() << TPath << "\n");
+ PathType NewPath(TPath.getPath());
+ NewPath.push_back(SwitchBlock);
+ TPath.setPath(NewPath);
+ }
+
+ // Transform the ThreadingPaths and keep track of the cloned values
+ DuplicateBlockMap DuplicateMap;
+ DefMap NewDefs;
+
+ SmallSet<BasicBlock *, 16> BlocksToClean;
+ for (BasicBlock *BB : successors(SwitchBlock)) {
+ BlocksToClean.insert(BB);
+ }
+
+ for (ThreadingPath &TPath : SwitchPaths->getThreadingPaths()) {
+ createExitPath(NewDefs, TPath, DuplicateMap, BlocksToClean, &DTU);
+ NumPaths++;
+ }
+
+ // After all paths are cloned, now update the last successor of the cloned
+ // path so it skips over the switch statement
+ for (ThreadingPath &TPath : SwitchPaths->getThreadingPaths()) {
+ updateLastSuccessor(TPath, DuplicateMap, &DTU);
+ }
+
+ // For each instruction that was cloned and used outside, update its uses
+ updateSSA(NewDefs);
+
+ // Clean PHI Nodes for the newly created blocks
+ for (BasicBlock *BB : BlocksToClean) {
+ cleanPhiNodes(BB);
+ }
+ }
+
+ /// For a specific ThreadingPath, create an exit path starting from the
+ /// determinator block. To remember the correct destination, we have to
+ /// duplicate blocks corresponding to each state. Also update the terminating
+ /// instruction of the predecessors, and phis in the successor blocks.
+ void createExitPath(DefMap &NewDefs, ThreadingPath &Path,
+ DuplicateBlockMap &DuplicateMap,
+ SmallSet<BasicBlock *, 16> &BlocksToClean,
+ DomTreeUpdater *DTU) {
+ uint64_t NextState = Path.getExitValue();
+ const BasicBlock *Determinator = Path.getDeterminatorBB();
+ PathType PathBBs = Path.getPath();
+
+ // Don't select the placeholder block in front
+ if (PathBBs.front() == Determinator)
+ PathBBs.pop_front();
+
+ auto DetIt = std::find(PathBBs.begin(), PathBBs.end(), Determinator);
+ auto Prev = std::prev(DetIt);
+ BasicBlock *PrevBB = *Prev;
+ for (auto BBIt = DetIt; BBIt != PathBBs.end(); BBIt++) {
+ BasicBlock *BB = *BBIt;
+ BlocksToClean.insert(BB);
+
+ // We already cloned BB for this NextState, now just update the branch
+ // and continue.
+ BasicBlock *NextBB = getClonedBB(BB, NextState, DuplicateMap);
+ if (NextBB) {
+ updatePredecessor(PrevBB, BB, NextBB, DTU);
+ PrevBB = NextBB;
+ continue;
+ }
+
+ // Clone the BB and update the successor of Prev to jump to the new block
+ BasicBlock *NewBB = cloneBlockAndUpdatePredecessor(
+ BB, PrevBB, NextState, DuplicateMap, NewDefs, DTU);
+ DuplicateMap[BB].push_back({NewBB, NextState});
+ BlocksToClean.insert(NewBB);
+ PrevBB = NewBB;
+ }
+ }
+
+ /// Restore SSA form after cloning blocks. Each cloned block creates new defs
+ /// for a variable, and the uses need to be updated to reflect this. The uses
+ /// may be replaced with a cloned value, or some derived phi instruction. Note
+ /// that all uses of a value defined in the same block were already remapped
+ /// when cloning the block.
+ void updateSSA(DefMap &NewDefs) {
+ SSAUpdaterBulk SSAUpdate;
+ SmallVector<Use *, 16> UsesToRename;
+
+ for (auto KV : NewDefs) {
+ Instruction *I = KV.first;
+ BasicBlock *BB = I->getParent();
+ std::vector<Instruction *> Cloned = KV.second;
+
+ // Scan all uses of this instruction to see if it is used outside of its
+ // block, and if so, record them in UsesToRename.
+ for (Use &U : I->uses()) {
+ Instruction *User = cast<Instruction>(U.getUser());
+ if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
+ if (UserPN->getIncomingBlock(U) == BB)
+ continue;
+ } else if (User->getParent() == BB) {
+ continue;
+ }
+
+ UsesToRename.push_back(&U);
+ }
+
+ // If there are no uses outside the block, we're done with this
+ // instruction.
+ if (UsesToRename.empty())
+ continue;
+ LLVM_DEBUG(dbgs() << "DFA-JT: Renaming non-local uses of: " << *I
+ << "\n");
+
+ // We found a use of I outside of BB. Rename all uses of I that are
+ // outside its block to be uses of the appropriate PHI node etc. See
+ // ValuesInBlocks with the values we know.
+ unsigned VarNum = SSAUpdate.AddVariable(I->getName(), I->getType());
+ SSAUpdate.AddAvailableValue(VarNum, BB, I);
+ for (Instruction *New : Cloned)
+ SSAUpdate.AddAvailableValue(VarNum, New->getParent(), New);
+
+ while (!UsesToRename.empty())
+ SSAUpdate.AddUse(VarNum, UsesToRename.pop_back_val());
+
+ LLVM_DEBUG(dbgs() << "\n");
+ }
+ // SSAUpdater handles phi placement and renaming uses with the appropriate
+ // value.
+ SSAUpdate.RewriteAllUses(DT);
+ }
+
+ /// Clones a basic block, and adds it to the CFG. This function also includes
+ /// updating phi nodes in the successors of the BB, and remapping uses that
+ /// were defined locally in the cloned BB.
+ BasicBlock *cloneBlockAndUpdatePredecessor(BasicBlock *BB, BasicBlock *PrevBB,
+ uint64_t NextState,
+ DuplicateBlockMap &DuplicateMap,
+ DefMap &NewDefs,
+ DomTreeUpdater *DTU) {
+ ValueToValueMapTy VMap;
+ BasicBlock *NewBB = CloneBasicBlock(
+ BB, VMap, ".jt" + std::to_string(NextState), BB->getParent());
+ NewBB->moveAfter(BB);
+ NumCloned++;
+
+ for (Instruction &I : *NewBB) {
+ // Do not remap operands of PHINode in case a definition in BB is an
+ // incoming value to a phi in the same block. This incoming value will
+ // be renamed later while restoring SSA.
+ if (isa<PHINode>(&I))
+ continue;
+ RemapInstruction(&I, VMap,
+ RF_IgnoreMissingLocals | RF_NoModuleLevelChanges);
+ if (AssumeInst *II = dyn_cast<AssumeInst>(&I))
+ AC->registerAssumption(II);
+ }
+
+ updateSuccessorPhis(BB, NewBB, NextState, VMap, DuplicateMap);
+ updatePredecessor(PrevBB, BB, NewBB, DTU);
+ updateDefMap(NewDefs, VMap);
+
+ // Add all successors to the DominatorTree
+ SmallPtrSet<BasicBlock *, 4> SuccSet;
+ for (auto *SuccBB : successors(NewBB)) {
+ if (SuccSet.insert(SuccBB).second)
+ DTU->applyUpdates({{DominatorTree::Insert, NewBB, SuccBB}});
+ }
+ SuccSet.clear();
+ return NewBB;
+ }
+
+ /// Update the phi nodes in BB's successors. This means creating a new
+ /// incoming value from NewBB with the new instruction wherever there is
+ /// an incoming value from BB.
+ void updateSuccessorPhis(BasicBlock *BB, BasicBlock *ClonedBB,
+ uint64_t NextState, ValueToValueMapTy &VMap,
+ DuplicateBlockMap &DuplicateMap) {
+ std::vector<BasicBlock *> BlocksToUpdate;
+
+ // If BB is the last block in the path, we can simply update the one case
+ // successor that will be reached.
+ if (BB == SwitchPaths->getSwitchBlock()) {
+ SwitchInst *Switch = SwitchPaths->getSwitchInst();
+ BasicBlock *NextCase = getNextCaseSuccessor(Switch, NextState);
+ BlocksToUpdate.push_back(NextCase);
+ BasicBlock *ClonedSucc = getClonedBB(NextCase, NextState, DuplicateMap);
+ if (ClonedSucc) {
+ BlocksToUpdate.push_back(ClonedSucc);
+ }
+ }
+ // Otherwise update phis in all successors.
+ else {
+ for (BasicBlock *Succ : successors(BB)) {
+ BlocksToUpdate.push_back(Succ);
+
+ // Check if a successor has already been cloned for the particular exit
+ // value. In this case if a successor was already cloned, the phi nodes
+ // in the cloned block should be updated directly.
+ BasicBlock *ClonedSucc = getClonedBB(Succ, NextState, DuplicateMap);
+ if (ClonedSucc) {
+ BlocksToUpdate.push_back(ClonedSucc);
+ }
+ }
+ }
+
+ // If there is a phi with an incoming value from BB, create a new incoming
+ // value for the new predecessor ClonedBB. The value will either be the same
+ // value from BB or a cloned value.
+ for (BasicBlock *Succ : BlocksToUpdate) {
+ for (auto II = Succ->begin(); PHINode *Phi = dyn_cast<PHINode>(II);
+ ++II) {
+ Value *Incoming = Phi->getIncomingValueForBlock(BB);
+ if (Incoming) {
+ if (isa<Constant>(Incoming)) {
+ Phi->addIncoming(Incoming, ClonedBB);
+ continue;
+ }
+ Value *ClonedVal = VMap[Incoming];
+ if (ClonedVal) {
+ Phi->addIncoming(ClonedVal, ClonedBB);
+ } else {
+ Phi->addIncoming(Incoming, ClonedBB);
+ }
+ }
+ }
+ }
+ }
+
+ /// Sets the successor of PrevBB to be NewBB instead of OldBB. Note that all
+ /// other successors are kept as well.
+ void updatePredecessor(BasicBlock *PrevBB, BasicBlock *OldBB,
+ BasicBlock *NewBB, DomTreeUpdater *DTU) {
+ // When a path is reused, there is a chance that predecessors were already
+ // updated before. Check if the predecessor needs to be updated first.
+ if (!isPredecessor(OldBB, PrevBB))
+ return;
+
+ Instruction *PrevTerm = PrevBB->getTerminator();
+ for (unsigned Idx = 0; Idx < PrevTerm->getNumSuccessors(); Idx++) {
+ if (PrevTerm->getSuccessor(Idx) == OldBB) {
+ OldBB->removePredecessor(PrevBB, /* KeepOneInputPHIs = */ true);
+ PrevTerm->setSuccessor(Idx, NewBB);
+ }
+ }
+ DTU->applyUpdates({{DominatorTree::Delete, PrevBB, OldBB},
+ {DominatorTree::Insert, PrevBB, NewBB}});
+ }
+
+ /// Add new value mappings to the DefMap to keep track of all new definitions
+ /// for a particular instruction. These will be used while updating SSA form.
+ void updateDefMap(DefMap &NewDefs, ValueToValueMapTy &VMap) {
+ for (auto Entry : VMap) {
+ Instruction *Inst =
+ dyn_cast<Instruction>(const_cast<Value *>(Entry.first));
+ if (!Inst || !Entry.second || isa<BranchInst>(Inst) ||
+ isa<SwitchInst>(Inst)) {
+ continue;
+ }
+
+ Instruction *Cloned = dyn_cast<Instruction>(Entry.second);
+ if (!Cloned)
+ continue;
+
+ if (NewDefs.find(Inst) == NewDefs.end())
+ NewDefs[Inst] = {Cloned};
+ else
+ NewDefs[Inst].push_back(Cloned);
+ }
+ }
+
+ /// Update the last branch of a particular cloned path to point to the correct
+ /// case successor. Note that this is an optional step and would have been
+ /// done in later optimizations, but it makes the CFG significantly easier to
+ /// work with.
+ void updateLastSuccessor(ThreadingPath &TPath,
+ DuplicateBlockMap &DuplicateMap,
+ DomTreeUpdater *DTU) {
+ uint64_t NextState = TPath.getExitValue();
+ BasicBlock *BB = TPath.getPath().back();
+ BasicBlock *LastBlock = getClonedBB(BB, NextState, DuplicateMap);
+
+ // Note multiple paths can end at the same block so check that it is not
+ // updated yet
+ if (!isa<SwitchInst>(LastBlock->getTerminator()))
+ return;
+ SwitchInst *Switch = cast<SwitchInst>(LastBlock->getTerminator());
+ BasicBlock *NextCase = getNextCaseSuccessor(Switch, NextState);
+
+ std::vector<DominatorTree::UpdateType> DTUpdates;
+ SmallPtrSet<BasicBlock *, 4> SuccSet;
+ for (BasicBlock *Succ : successors(LastBlock)) {
+ if (Succ != NextCase && SuccSet.insert(Succ).second)
+ DTUpdates.push_back({DominatorTree::Delete, LastBlock, Succ});
+ }
+
+ Switch->eraseFromParent();
+ BranchInst::Create(NextCase, LastBlock);
+
+ DTU->applyUpdates(DTUpdates);
+ }
+
+ /// After cloning blocks, some of the phi nodes have extra incoming values
+ /// that are no longer used. This function removes them.
+ void cleanPhiNodes(BasicBlock *BB) {
+ // If BB is no longer reachable, remove any remaining phi nodes
+ if (pred_empty(BB)) {
+ std::vector<PHINode *> PhiToRemove;
+ for (auto II = BB->begin(); PHINode *Phi = dyn_cast<PHINode>(II); ++II) {
+ PhiToRemove.push_back(Phi);
+ }
+ for (PHINode *PN : PhiToRemove) {
+ PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
+ PN->eraseFromParent();
+ }
+ return;
+ }
+
+ // Remove any incoming values that come from an invalid predecessor
+ for (auto II = BB->begin(); PHINode *Phi = dyn_cast<PHINode>(II); ++II) {
+ std::vector<BasicBlock *> BlocksToRemove;
+ for (BasicBlock *IncomingBB : Phi->blocks()) {
+ if (!isPredecessor(BB, IncomingBB))
+ BlocksToRemove.push_back(IncomingBB);
+ }
+ for (BasicBlock *BB : BlocksToRemove) {
+ Phi->removeIncomingValue(BB);
+ }
+ }
+ }
+
+ /// Checks if BB was already cloned for a particular next state value. If it
+ /// was then it returns this cloned block, and otherwise null.
+ BasicBlock *getClonedBB(BasicBlock *BB, uint64_t NextState,
+ DuplicateBlockMap &DuplicateMap) {
+ CloneList ClonedBBs = DuplicateMap[BB];
+
+ // Find an entry in the CloneList with this NextState. If it exists then
+ // return the corresponding BB
+ auto It = llvm::find_if(ClonedBBs, [NextState](const ClonedBlock &C) {
+ return C.State == NextState;
+ });
+ return It != ClonedBBs.end() ? (*It).BB : nullptr;
+ }
+
+ /// Helper to get the successor corresponding to a particular case value for
+ /// a switch statement.
+ BasicBlock *getNextCaseSuccessor(SwitchInst *Switch, uint64_t NextState) {
+ BasicBlock *NextCase = nullptr;
+ for (auto Case : Switch->cases()) {
+ if (Case.getCaseValue()->getZExtValue() == NextState) {
+ NextCase = Case.getCaseSuccessor();
+ break;
+ }
+ }
+ if (!NextCase) {
+ NextCase = Switch->getDefaultDest();
+ }
+ return NextCase;
+ }
+
+ /// Returns true if IncomingBB is a predecessor of BB.
+ bool isPredecessor(BasicBlock *BB, BasicBlock *IncomingBB) {
+ return llvm::find(predecessors(BB), IncomingBB) != pred_end(BB);
+ }
+
+ AllSwitchPaths *SwitchPaths;
+ DominatorTree *DT;
+ AssumptionCache *AC;
+ TargetTransformInfo *TTI;
+ SmallPtrSet<const Value *, 32> EphValues;
+ std::vector<ThreadingPath> TPaths;
+};
+
+bool DFAJumpThreading::run(Function &F) {
+ LLVM_DEBUG(dbgs() << "\nDFA Jump threading: " << F.getName() << "\n");
+
+ if (IsViewCFGBefore) {
+ F.viewCFG();
+ }
+
+ SmallVector<AllSwitchPaths, 2> ThreadableLoops;
+ bool MadeChanges = false;
+
+ for (Function::iterator B = F.begin(), BE = F.end(); B != BE; B++) {
+ if (auto *SI = dyn_cast<SwitchInst>(B->getTerminator())) {
+
+ LLVM_DEBUG(dbgs() << "\nCheck if SwitchInst in BB " << B->getName()
+ << " is predictable\n");
+ MainSwitch Switch(SI);
+
+ if (!Switch.getInstr())
+ continue;
+
+ LLVM_DEBUG(dbgs() << "\nSwitchInst in BB " << B->getName() << " is a "
+ << "candidate for jump threading\n");
+ LLVM_DEBUG(SI->dump());
+
+ unfoldSelectInstrs(DT, Switch.getSelectInsts());
+ if (!Switch.getSelectInsts().empty())
+ MadeChanges = true;
+
+ AllSwitchPaths SwitchPaths(&Switch);
+ SwitchPaths.run();
+
+ if (SwitchPaths.getNumThreadingPaths() > 0) {
+ ThreadableLoops.push_back(SwitchPaths);
+
+ // For the time being limit this optimization to occurring once in a
+ // function since it can change the CFG significantly. This is not a
+ // strict requirement but it can cause buggy behavior if there is an
+ // overlap of blocks in different opportunities. There is a lot of room
+ // to experiment with catching more opportunities here.
+ break;
+ }
+ }
+ }
+
+ SmallPtrSet<const Value *, 32> EphValues;
+ if (ThreadableLoops.size() > 0) {
+ CodeMetrics::collectEphemeralValues(&F, AC, EphValues);
+ }
+
+ for (AllSwitchPaths SwitchPaths : ThreadableLoops) {
+ TransformFSM Transform(&SwitchPaths, DT, AC, TTI, EphValues);
+ Transform.run();
+ MadeChanges = true;
+ NumTransforms++;
+ }
+
+#ifdef EXPENSIVE_CHECKS
+ assert(DT->verify(DominatorTree::VerificationLevel::Full));
+ verifyFunction(F, &dbgs());
+#endif
+
+ return MadeChanges;
+}
+
+} // end anonymous namespace
+
+/// Integrate with the new Pass Manager
+PreservedAnalyses DFAJumpThreadingPass::run(Function &F,
+ FunctionAnalysisManager &AM) {
+ AssumptionCache &AC = AM.getResult<AssumptionAnalysis>(F);
+ DominatorTree &DT = AM.getResult<DominatorTreeAnalysis>(F);
+ TargetTransformInfo &TTI = AM.getResult<TargetIRAnalysis>(F);
+
+ if (!DFAJumpThreading(&AC, &DT, &TTI).run(F))
+ return PreservedAnalyses::all();
+
+ PreservedAnalyses PA;
+ PA.preserve<DominatorTreeAnalysis>();
+ return PA;
+}
Index: llvm/lib/Transforms/Scalar/Scalar.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/Scalar.cpp
+++ llvm/lib/Transforms/Scalar/Scalar.cpp
@@ -60,6 +60,7 @@
initializeInferAddressSpacesPass(Registry);
initializeInstSimplifyLegacyPassPass(Registry);
initializeJumpThreadingPass(Registry);
+ initializeDFAJumpThreadingLegacyPassPass(Registry);
initializeLegacyLICMPassPass(Registry);
initializeLegacyLoopSinkPassPass(Registry);
initializeLoopFuseLegacyPass(Registry);
Index: llvm/test/CodeGen/AMDGPU/opt-pipeline.ll
===================================================================
--- llvm/test/CodeGen/AMDGPU/opt-pipeline.ll
+++ llvm/test/CodeGen/AMDGPU/opt-pipeline.ll
@@ -508,6 +508,10 @@
; GCN-O2-NEXT: Lazy Block Frequency Analysis
; GCN-O2-NEXT: Optimization Remark Emitter
; GCN-O2-NEXT: Combine redundant instructions
+; GCN-O2-NEXT: DFA Jump Threading
+; GCN-O2-NEXT: Dominator Tree Construction
+; GCN-O2-NEXT: Basic Alias Analysis (stateless AA impl)
+; GCN-O2-NEXT: Function Alias Analysis Results
; GCN-O2-NEXT: Lazy Value Information Analysis
; GCN-O2-NEXT: Jump Threading
; GCN-O2-NEXT: Value Propagation
@@ -868,6 +872,10 @@
; GCN-O3-NEXT: Lazy Block Frequency Analysis
; GCN-O3-NEXT: Optimization Remark Emitter
; GCN-O3-NEXT: Combine redundant instructions
+; GCN-O3-NEXT: DFA Jump Threading
+; GCN-O3-NEXT: Dominator Tree Construction
+; GCN-O3-NEXT: Basic Alias Analysis (stateless AA impl)
+; GCN-O3-NEXT: Function Alias Analysis Results
; GCN-O3-NEXT: Lazy Value Information Analysis
; GCN-O3-NEXT: Jump Threading
; GCN-O3-NEXT: Value Propagation
Index: llvm/test/Other/new-pm-defaults.ll
===================================================================
--- llvm/test/Other/new-pm-defaults.ll
+++ llvm/test/Other/new-pm-defaults.ll
@@ -180,6 +180,8 @@
; CHECK-O-NEXT: Running analysis: DemandedBitsAnalysis
; CHECK-O-NEXT: Running pass: InstCombinePass
; CHECK-EP-PEEPHOLE-NEXT: Running pass: NoOpFunctionPass
+; CHECK-O2-NEXT: Running pass: DFAJumpThreadingPass
+; CHECK-O3-NEXT: Running pass: DFAJumpThreadingPass
; CHECK-O23SZ-NEXT: Running pass: JumpThreadingPass
; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
Index: llvm/test/Other/new-pm-thinlto-defaults.ll
===================================================================
--- llvm/test/Other/new-pm-thinlto-defaults.ll
+++ llvm/test/Other/new-pm-thinlto-defaults.ll
@@ -167,6 +167,8 @@
; CHECK-O-NEXT: Running pass: BDCEPass
; CHECK-O-NEXT: Running analysis: DemandedBitsAnalysis
; CHECK-O-NEXT: Running pass: InstCombinePass
+; CHECK-O2-NEXT: Running pass: DFAJumpThreadingPass
+; CHECK-O3-NEXT: Running pass: DFAJumpThreadingPass
; CHECK-O23SZ-NEXT: Running pass: JumpThreadingPass
; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
Index: llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
===================================================================
--- llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
+++ llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
@@ -140,6 +140,8 @@
; CHECK-O-NEXT: Running pass: BDCEPass
; CHECK-O-NEXT: Running analysis: DemandedBitsAnalysis
; CHECK-O-NEXT: Running pass: InstCombinePass
+; CHECK-O2-NEXT: Running pass: DFAJumpThreadingPass
+; CHECK-O3-NEXT: Running pass: DFAJumpThreadingPass
; CHECK-O23SZ-NEXT: Running pass: JumpThreadingPass
; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
Index: llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
===================================================================
--- llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
+++ llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
@@ -149,6 +149,8 @@
; CHECK-O-NEXT: Running pass: BDCEPass
; CHECK-O-NEXT: Running analysis: DemandedBitsAnalysis
; CHECK-O-NEXT: Running pass: InstCombinePass
+; CHECK-O2-NEXT: Running pass: DFAJumpThreadingPass
+; CHECK-O3-NEXT: Running pass: DFAJumpThreadingPass
; CHECK-O23SZ-NEXT: Running pass: JumpThreadingPass
; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
Index: llvm/test/Other/new-pm-thinlto-prelink-pgo-defaults.ll
===================================================================
--- llvm/test/Other/new-pm-thinlto-prelink-pgo-defaults.ll
+++ llvm/test/Other/new-pm-thinlto-prelink-pgo-defaults.ll
@@ -180,6 +180,8 @@
; CHECK-O-NEXT: Running pass: BDCEPass
; CHECK-O-NEXT: Running analysis: DemandedBitsAnalysis
; CHECK-O-NEXT: Running pass: InstCombinePass
+; CHECK-O2-NEXT: Running pass: DFAJumpThreadingPass
+; CHECK-O3-NEXT: Running pass: DFAJumpThreadingPass
; CHECK-O23SZ-NEXT: Running pass: JumpThreadingPass
; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
Index: llvm/test/Other/new-pm-thinlto-prelink-samplepgo-defaults.ll
===================================================================
--- llvm/test/Other/new-pm-thinlto-prelink-samplepgo-defaults.ll
+++ llvm/test/Other/new-pm-thinlto-prelink-samplepgo-defaults.ll
@@ -143,6 +143,8 @@
; CHECK-O-NEXT: Running pass: BDCEPass
; CHECK-O-NEXT: Running analysis: DemandedBitsAnalysis
; CHECK-O-NEXT: Running pass: InstCombinePass
+; CHECK-O2-NEXT: Running pass: DFAJumpThreadingPass
+; CHECK-O3-NEXT: Running pass: DFAJumpThreadingPass
; CHECK-O23SZ-NEXT: Running pass: JumpThreadingPass
; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
Index: llvm/test/Other/opt-O2-pipeline.ll
===================================================================
--- llvm/test/Other/opt-O2-pipeline.ll
+++ llvm/test/Other/opt-O2-pipeline.ll
@@ -153,6 +153,10 @@
; CHECK-NEXT: Lazy Block Frequency Analysis
; CHECK-NEXT: Optimization Remark Emitter
; CHECK-NEXT: Combine redundant instructions
+; CHECK-NEXT: DFA Jump Threading
+; CHECK-NEXT: Dominator Tree Construction
+; CHECK-NEXT: Basic Alias Analysis (stateless AA impl)
+; CHECK-NEXT: Function Alias Analysis Results
; CHECK-NEXT: Lazy Value Information Analysis
; CHECK-NEXT: Jump Threading
; CHECK-NEXT: Value Propagation
Index: llvm/test/Other/opt-O3-pipeline-enable-matrix.ll
===================================================================
--- llvm/test/Other/opt-O3-pipeline-enable-matrix.ll
+++ llvm/test/Other/opt-O3-pipeline-enable-matrix.ll
@@ -158,6 +158,10 @@
; CHECK-NEXT: Lazy Block Frequency Analysis
; CHECK-NEXT: Optimization Remark Emitter
; CHECK-NEXT: Combine redundant instructions
+; CHECK-NEXT: DFA Jump Threading
+; CHECK-NEXT: Dominator Tree Construction
+; CHECK-NEXT: Basic Alias Analysis (stateless AA impl)
+; CHECK-NEXT: Function Alias Analysis Results
; CHECK-NEXT: Lazy Value Information Analysis
; CHECK-NEXT: Jump Threading
; CHECK-NEXT: Value Propagation
Index: llvm/test/Other/opt-O3-pipeline.ll
===================================================================
--- llvm/test/Other/opt-O3-pipeline.ll
+++ llvm/test/Other/opt-O3-pipeline.ll
@@ -158,6 +158,10 @@
; CHECK-NEXT: Lazy Block Frequency Analysis
; CHECK-NEXT: Optimization Remark Emitter
; CHECK-NEXT: Combine redundant instructions
+; CHECK-NEXT: DFA Jump Threading
+; CHECK-NEXT: Dominator Tree Construction
+; CHECK-NEXT: Basic Alias Analysis (stateless AA impl)
+; CHECK-NEXT: Function Alias Analysis Results
; CHECK-NEXT: Lazy Value Information Analysis
; CHECK-NEXT: Jump Threading
; CHECK-NEXT: Value Propagation
Index: llvm/test/Transforms/DFAJumpThreading/dfa-constant-propagation.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/DFAJumpThreading/dfa-constant-propagation.ll
@@ -0,0 +1,31 @@
+; RUN: opt -S -dfa-jump-threading -sccp -simplifycfg %s | FileCheck %s
+
+; CHECK: define i32 @test
+; CHECK-NEXT: entry:
+; CHECK-NEXT: ret i32 3
+
+; This test checks that a constant propagation is applied for a basic loop.
+; Related to bug 44679.
+define i32 @test(i32 %a) {
+entry:
+ br label %while.cond
+
+while.cond:
+ %num = phi i32 [ 0, %entry ], [ %add, %case1 ]
+ %state = phi i32 [ 1, %entry ], [ %state.next, %case1 ]
+ switch i32 %state, label %end [
+ i32 1, label %case1
+ i32 2, label %case2
+ ]
+
+case1:
+ %state.next = phi i32 [ 3, %case2 ], [ 2, %while.cond ]
+ %add = add nsw i32 %num, %state
+ br label %while.cond
+
+case2:
+ br label %case1
+
+end:
+ ret i32 %num
+}
Index: llvm/test/Transforms/DFAJumpThreading/dfa-jump-threading-analysis.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/DFAJumpThreading/dfa-jump-threading-analysis.ll
@@ -0,0 +1,180 @@
+; REQUIRES: asserts
+; RUN: opt -S -dfa-jump-threading -debug-only=dfa-jump-threading -disable-output %s 2>&1 | FileCheck %s
+
+; This test checks that the analysis identifies all threadable paths in a
+; simple CFG. A threadable path includes a list of basic blocks, the exit
+; state, and the block that determines the next state.
+; < path of BBs that form a cycle > [ state, determinator ]
+define i32 @test1(i32 %num) {
+; CHECK: < for.body for.inc > [ 1, for.inc ]
+; CHECK-NEXT: < for.body case1 for.inc > [ 2, for.inc ]
+; CHECK-NEXT: < for.body case2 for.inc > [ 1, for.inc ]
+; CHECK-NEXT: < for.body case2 si.unfold.false for.inc > [ 2, for.inc ]
+entry:
+ br label %for.body
+
+for.body:
+ %count = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
+ %state = phi i32 [ 1, %entry ], [ %state.next, %for.inc ]
+ switch i32 %state, label %for.inc [
+ i32 1, label %case1
+ i32 2, label %case2
+ ]
+
+case1:
+ br label %for.inc
+
+case2:
+ %cmp = icmp eq i32 %count, 50
+ %sel = select i1 %cmp, i32 1, i32 2
+ br label %for.inc
+
+for.inc:
+ %state.next = phi i32 [ %sel, %case2 ], [ 1, %for.body ], [ 2, %case1 ]
+ %inc = add nsw i32 %count, 1
+ %cmp.exit = icmp slt i32 %inc, %num
+ br i1 %cmp.exit, label %for.body, label %for.end
+
+for.end:
+ ret i32 0
+}
+
+; This test checks that the analysis finds threadable paths in a more
+; complicated CFG. Here the FSM is represented as a nested loop, with
+; fallthrough cases.
+define i32 @test2(i32 %init) {
+; CHECK: < loop.3 case2 > [ 3, loop.3 ]
+; CHECK-NEXT: < loop.3 case2 loop.1.backedge loop.1 loop.2 > [ 1, loop.1 ]
+; CHECK-NEXT: < loop.3 case2 loop.1.backedge si.unfold.false loop.1 loop.2 > [ 4, loop.1.backedge ]
+; CHECK-NEXT: < loop.3 case3 loop.2.backedge loop.2 > [ 0, loop.2.backedge ]
+; CHECK-NEXT: < loop.3 case3 case4 loop.2.backedge loop.2 > [ 3, loop.2.backedge ]
+; CHECK-NEXT: < loop.3 case3 case4 loop.1.backedge loop.1 loop.2 > [ 1, loop.1 ]
+; CHECK-NEXT: < loop.3 case3 case4 loop.1.backedge si.unfold.false loop.1 loop.2 > [ 2, loop.1.backedge ]
+; CHECK-NEXT: < loop.3 case4 loop.2.backedge loop.2 > [ 3, loop.2.backedge ]
+; CHECK-NEXT: < loop.3 case4 loop.1.backedge loop.1 loop.2 > [ 1, loop.1 ]
+; CHECK-NEXT: < loop.3 case4 loop.1.backedge si.unfold.false loop.1 loop.2 > [ 2, loop.1.backedge ]
+entry:
+ %cmp = icmp eq i32 %init, 0
+ %sel = select i1 %cmp, i32 0, i32 2
+ br label %loop.1
+
+loop.1:
+ %state.1 = phi i32 [ %sel, %entry ], [ %state.1.be2, %loop.1.backedge ]
+ br label %loop.2
+
+loop.2:
+ %state.2 = phi i32 [ %state.1, %loop.1 ], [ %state.2.be, %loop.2.backedge ]
+ br label %loop.3
+
+loop.3:
+ %state = phi i32 [ %state.2, %loop.2 ], [ 3, %case2 ]
+ switch i32 %state, label %infloop.i [
+ i32 2, label %case2
+ i32 3, label %case3
+ i32 4, label %case4
+ i32 0, label %case0
+ i32 1, label %case1
+ ]
+
+case2:
+ br i1 %cmp, label %loop.3, label %loop.1.backedge
+
+case3:
+ br i1 %cmp, label %loop.2.backedge, label %case4
+
+case4:
+ br i1 %cmp, label %loop.2.backedge, label %loop.1.backedge
+
+loop.1.backedge:
+ %state.1.be = phi i32 [ 2, %case4 ], [ 4, %case2 ]
+ %state.1.be2 = select i1 %cmp, i32 1, i32 %state.1.be
+ br label %loop.1
+
+loop.2.backedge:
+ %state.2.be = phi i32 [ 3, %case4 ], [ 0, %case3 ]
+ br label %loop.2
+
+case0:
+ br label %exit
+
+case1:
+ br label %exit
+
+infloop.i:
+ br label %infloop.i
+
+exit:
+ ret i32 0
+}
+
+declare void @baz()
+
+; Verify that having the switch block as a determinator is handled correctly.
+define i32 @main() {
+; CHECK: < bb43 bb59 bb3 bb31 bb41 > [ 77, bb43 ]
+; CHECK-NEXT: < bb43 bb49 bb59 bb3 bb31 bb41 > [ 77, bb43 ]
+bb:
+ %i = alloca [420 x i8], align 1
+ %i2 = getelementptr inbounds [420 x i8], [420 x i8]* %i, i64 0, i64 390
+ br label %bb3
+
+bb3: ; preds = %bb59, %bb
+ %i4 = phi i8* [ %i2, %bb ], [ %i60, %bb59 ]
+ %i5 = phi i8 [ 77, %bb ], [ %i64, %bb59 ]
+ %i6 = phi i32 [ 2, %bb ], [ %i63, %bb59 ]
+ %i7 = phi i32 [ 26, %bb ], [ %i62, %bb59 ]
+ %i8 = phi i32 [ 25, %bb ], [ %i61, %bb59 ]
+ %i9 = icmp sgt i32 %i7, 2
+ %i10 = select i1 %i9, i32 %i7, i32 2
+ %i11 = add i32 %i8, 2
+ %i12 = sub i32 %i11, %i10
+ %i13 = mul nsw i32 %i12, 3
+ %i14 = add nsw i32 %i13, %i6
+ %i15 = sext i32 %i14 to i64
+ %i16 = getelementptr inbounds i8, i8* %i4, i64 %i15
+ %i17 = load i8, i8* %i16, align 1
+ %i18 = icmp sgt i8 %i17, 0
+ br i1 %i18, label %bb21, label %bb31
+
+bb21: ; preds = %bb3
+ br i1 true, label %bb59, label %bb43
+
+bb59: ; preds = %bb49, %bb43, %bb31, %bb21
+ %i60 = phi i8* [ %i44, %bb49 ], [ %i44, %bb43 ], [ %i34, %bb31 ], [ %i4, %bb21 ]
+ %i61 = phi i32 [ %i45, %bb49 ], [ %i45, %bb43 ], [ %i33, %bb31 ], [ %i8, %bb21 ]
+ %i62 = phi i32 [ %i47, %bb49 ], [ %i47, %bb43 ], [ %i32, %bb31 ], [ %i7, %bb21 ]
+ %i63 = phi i32 [ %i48, %bb49 ], [ %i48, %bb43 ], [ 2, %bb31 ], [ %i6, %bb21 ]
+ %i64 = phi i8 [ %i46, %bb49 ], [ %i46, %bb43 ], [ 77, %bb31 ], [ %i5, %bb21 ]
+ %i65 = icmp sgt i32 %i62, 0
+ br i1 %i65, label %bb3, label %bb66
+
+bb31: ; preds = %bb3
+ %i32 = add nsw i32 %i7, -1
+ %i33 = add nsw i32 %i8, -1
+ %i34 = getelementptr inbounds i8, i8* %i4, i64 -15
+ %i35 = icmp eq i8 %i5, 77
+ br i1 %i35, label %bb59, label %bb41
+
+bb41: ; preds = %bb31
+ tail call void @baz()
+ br label %bb43
+
+bb43: ; preds = %bb41, %bb21
+ %i44 = phi i8* [ %i34, %bb41 ], [ %i4, %bb21 ]
+ %i45 = phi i32 [ %i33, %bb41 ], [ %i8, %bb21 ]
+ %i46 = phi i8 [ 77, %bb41 ], [ %i5, %bb21 ]
+ %i47 = phi i32 [ %i32, %bb41 ], [ %i7, %bb21 ]
+ %i48 = phi i32 [ 2, %bb41 ], [ %i6, %bb21 ]
+ tail call void @baz()
+ switch i8 %i5, label %bb59 [
+ i8 68, label %bb49
+ i8 73, label %bb49
+ ]
+
+bb49: ; preds = %bb43, %bb43
+ tail call void @baz()
+ br label %bb59
+
+bb66: ; preds = %bb59
+ ret i32 0
+}
Index: llvm/test/Transforms/DFAJumpThreading/dfa-jump-threading-transform.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/DFAJumpThreading/dfa-jump-threading-transform.ll
@@ -0,0 +1,175 @@
+; RUN: opt -S -dfa-jump-threading %s | FileCheck %s
+
+; These tests check that the DFA jump threading transformation is applied
+; properly to two CFGs. It checks that blocks are cloned, branches are updated,
+; and SSA form is restored.
+define i32 @test1(i32 %num) {
+entry:
+ br label %for.body
+
+for.body:
+ %count = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
+ %state = phi i32 [ 1, %entry ], [ %state.next, %for.inc ]
+ switch i32 %state, label %for.inc [
+ i32 1, label %case1
+ i32 2, label %case2
+ ]
+
+; CHECK: for.body.jt2:
+; CHECK-NEXT: %count.jt2
+; CHECK-NEXT: %state.jt2
+; CHECK-NEXT: br label %case2
+
+; CHECK: for.body.jt1:
+; CHECK-NEXT: %count.jt1
+; CHECK-NEXT: %state.jt1
+; CHECK-NEXT: br label %case1
+
+case1:
+ br label %for.inc
+
+; CHECK: case1:
+; CHECK-NEXT: %count2 = phi i32 [ %count.jt1, %for.body.jt1 ], [ %count, %for.body ]
+
+case2:
+ %cmp = icmp eq i32 %count, 50
+ %sel = select i1 %cmp, i32 1, i32 2
+ br label %for.inc
+
+; CHECK: case2:
+; CHECK-NEXT: %count1 = phi i32 [ %count.jt2, %for.body.jt2 ], [ %count, %for.body ]
+; CHECK: br i1 %cmp, label %for.inc.jt1, label %si.unfold.false
+
+; CHECK: si.unfold.false:
+; CHECK-NEXT: br label %for.inc.jt2
+
+for.inc:
+ %state.next = phi i32 [ %sel, %case2 ], [ 1, %for.body ], [ 2, %case1 ]
+ %inc = add nsw i32 %count, 1
+ %cmp.exit = icmp slt i32 %inc, %num
+ br i1 %cmp.exit, label %for.body, label %for.end
+
+; CHECK: for.inc.jt2:
+; CHECK-NEXT: %count4 = phi i32 [ %count1, %si.unfold.false ], [ %count2, %case1 ]
+; CHECK: br i1 %cmp.exit.jt2, label %for.body.jt2, label %for.end
+
+; CHECK: for.inc.jt1:
+; CHECK-NEXT: %count3 = phi i32 [ %count1, %case2 ], [ %count, %for.body ]
+; CHECK: br i1 %cmp.exit.jt1, label %for.body.jt1, label %for.end
+
+for.end:
+ ret i32 0
+}
+
+
+define i32 @test2(i32 %init) {
+entry:
+ %cmp = icmp eq i32 %init, 0
+ %sel = select i1 %cmp, i32 0, i32 2
+ br label %loop.1
+
+; CHECK: si.unfold.false:
+; CHECK-NEXT: br label %loop.1
+; CHECK: si.unfold.false.jt2:
+; CHECK-NEXT: br label %loop.1.jt2
+; CHECK: si.unfold.false.jt4:
+; CHECK-NEXT: br label %loop.1.jt4
+; CHECK: si.unfold.false1:
+; CHECK-NEXT: br label %loop.1
+
+loop.1:
+ %state.1 = phi i32 [ %sel, %entry ], [ %state.1.be2, %loop.1.backedge ]
+ br label %loop.2
+
+; CHECK: loop.1.jt2:
+; CHECK :br label %loop.2.jt2
+; CHECK: loop.1.jt4:
+; CHECK: br label %loop.2.jt4
+; CHECK: loop.1.jt1:
+; CHECK: br label %loop.2.jt1
+
+loop.2:
+ %state.2 = phi i32 [ %state.1, %loop.1 ], [ %state.2.be, %loop.2.backedge ]
+ br label %loop.3
+
+; CHECK: loop.2.jt2:
+; CHECK: br label %loop.3.jt2
+; CHECK: loop.2.jt3:
+; CHECK: br label %loop.3.jt3
+; CHECK: loop.2.jt0:
+; CHECK: br label %loop.3.jt0
+; CHECK: loop.2.jt4:
+; CHECK: br label %loop.3.jt4
+; CHECK: loop.2.jt1:
+; CHECK: br label %loop.3.jt1
+
+loop.3:
+ %state = phi i32 [ %state.2, %loop.2 ], [ 3, %case2 ]
+ switch i32 %state, label %infloop.i [
+ i32 2, label %case2
+ i32 3, label %case3
+ i32 4, label %case4
+ i32 0, label %case0
+ i32 1, label %case1
+ ]
+
+; CHECK: loop.3.jt2:
+; CHECK: br label %case2
+; CHECK: loop.3.jt0:
+; CHECK: br label %case0
+; CHECK: loop.3.jt4:
+; CHECK: br label %case4
+; CHECK: loop.3.jt1:
+; CHECK: br label %case1
+; CHECK: loop.3.jt3:
+; CHECK: br label %case3
+
+case2:
+ br i1 %cmp, label %loop.3, label %loop.1.backedge
+
+; CHECK: case2:
+; CHECK-NEXT: br i1 %cmp, label %loop.3.jt3, label %loop.1.backedge.jt4
+
+case3:
+ br i1 %cmp, label %loop.2.backedge, label %case4
+
+; CHECK: case3:
+; CHECK-NEXT: br i1 %cmp, label %loop.2.backedge.jt0, label %case4
+
+case4:
+ br i1 %cmp, label %loop.2.backedge, label %loop.1.backedge
+
+; CHECK: case4:
+; CHECK-NEXT: br i1 %cmp, label %loop.2.backedge.jt3, label %loop.1.backedge.jt2
+
+loop.1.backedge:
+ %state.1.be = phi i32 [ 2, %case4 ], [ 4, %case2 ]
+ %state.1.be2 = select i1 %cmp, i32 1, i32 %state.1.be
+ br label %loop.1
+
+; CHECK: loop.1.backedge.jt2:
+; CHECK: br i1 %cmp, label %loop.1.jt1, label %si.unfold.false.jt2
+; CHECK: loop.1.backedge.jt4:
+; CHECK: br i1 %cmp, label %loop.1.jt1, label %si.unfold.false.jt4
+
+loop.2.backedge:
+ %state.2.be = phi i32 [ 3, %case4 ], [ 0, %case3 ]
+ br label %loop.2
+
+; CHECK: loop.2.backedge.jt3:
+; CHECK: br label %loop.2.jt3
+; CHECK: loop.2.backedge.jt0:
+; CHECK: br label %loop.2.jt0
+
+case0:
+ br label %exit
+
+case1:
+ br label %exit
+
+infloop.i:
+ br label %infloop.i
+
+exit:
+ ret i32 0
+}
Index: llvm/test/Transforms/DFAJumpThreading/dfa-unfold-select.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/DFAJumpThreading/dfa-unfold-select.ll
@@ -0,0 +1,164 @@
+; RUN: opt -S -dfa-jump-threading %s | FileCheck %s
+
+; These tests check if selects are unfolded properly for jump threading
+; opportunities. There are three different patterns to consider:
+; 1) Both operands are constant and the false branch is unfolded by default
+; 2) One operand is constant and the other is another select to be unfolded. In
+; this case a single select is sunk to a new block to unfold.
+; 3) Both operands are a select, and both should be sunk to new blocks.
+define i32 @test1(i32 %num) {
+entry:
+ br label %for.body
+
+for.body:
+ %count = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
+ %state = phi i32 [ 1, %entry ], [ %state.next, %for.inc ]
+ switch i32 %state, label %for.inc [
+ i32 1, label %case1
+ i32 2, label %case2
+ ]
+
+case1:
+ br label %for.inc
+
+case2:
+; CHECK: %cmp = icmp
+; CHECK-NOT: %sel = select i1 %cmp, i32 1, i32 2
+; CHECK-NEXT: br i1 %cmp, label %for.inc
+; CHECK: si.unfold.false
+ %cmp = icmp slt i32 %count, 50
+ %sel = select i1 %cmp, i32 1, i32 2
+ br label %for.inc
+
+; CHECK: si.unfold.false:
+; CHECK-NEXT: br label %for.inc
+
+for.inc:
+; CHECK: for.inc.jt2:
+; CHECK: %state.next.jt2 = phi i32
+; CHECK: [ 2, %si.unfold.false ]
+; CHECK: for.inc.jt1:
+; CHECK: %state.next.jt1 = phi i32
+; CHECK: [ 1, %case2 ]
+ %state.next = phi i32 [ %sel, %case2 ], [ 1, %for.body ], [ 2, %case1 ]
+ %inc = add nsw i32 %count, 1
+ %cmp.exit = icmp slt i32 %inc, %num
+ br i1 %cmp.exit, label %for.body, label %for.end
+
+for.end:
+ ret i32 0
+}
+
+define i32 @test2(i32 %num) {
+entry:
+ br label %for.body
+
+for.body:
+ %count = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
+ %state = phi i32 [ 1, %entry ], [ %state.next, %for.inc ]
+ switch i32 %state, label %for.inc [
+ i32 1, label %case1
+ i32 2, label %case2
+ ]
+
+case1:
+; CHECK: %cmp.c1 = icmp
+; CHECK: %cmp2.c1 = icmp
+; CHECK-NOT: select i1
+; CHECK-NEXT: br i1 %cmp2.c1
+ %cmp.c1 = icmp slt i32 %count, 50
+ %cmp2.c1 = icmp slt i32 %count, 100
+ %state1.1 = select i1 %cmp.c1, i32 1, i32 2
+ %state1.2 = select i1 %cmp2.c1, i32 %state1.1, i32 3
+ br label %for.inc
+
+case2:
+; CHECK: %cmp.c2 = icmp
+; CHECK: %cmp2.c2 = icmp
+; CHECK-NOT: select i1
+; CHECK-NEXT: br i1 %cmp2.c2
+ %cmp.c2 = icmp slt i32 %count, 50
+ %cmp2.c2 = icmp sgt i32 %count, 100
+ %state2.1 = select i1 %cmp.c2, i32 1, i32 2
+ %state2.2 = select i1 %cmp2.c2, i32 3, i32 %state2.1
+ br label %for.inc
+
+; CHECK: si.unfold.false:
+; CHECK-NEXT: br i1 %cmp.c2
+; CHECK: si.unfold.false1:
+; CHECK-NEXT: br label %for.inc
+; CHECK: si.unfold.true:
+; CHECK-NEXT: br i1 %cmp.c1
+; CHECK: si.unfold.false2:
+; CHECK-NEXT: br label %for.inc
+
+for.inc:
+; CHECK: for.inc.jt3:
+; CHECK: [ 3, %case1 ], [ 3, %case2 ]
+; CHECK: for.inc.jt2:
+; CHECK: [ 2, %si.unfold.false1 ], [ 2, %si.unfold.false2 ]
+; CHECK: for.inc.jt1:
+; CHECK: [ 1, %si.unfold.false ], [ 1, %si.unfold.true ]
+ %state.next = phi i32 [ %state1.2, %case1 ], [ %state2.2, %case2 ], [ 1, %for.body ]
+ %inc = add nsw i32 %count, 1
+ %cmp.exit = icmp slt i32 %inc, %num
+ br i1 %cmp.exit, label %for.body, label %for.end
+
+for.end:
+ ret i32 0
+}
+
+define i32 @test3(i32 %num) {
+entry:
+ br label %for.body
+
+for.body:
+ %count = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
+ %state = phi i32 [ 1, %entry ], [ %state.next, %for.inc ]
+ switch i32 %state, label %for.inc [
+ i32 1, label %case1
+ i32 2, label %case2
+ ]
+
+case1:
+ br label %for.inc
+
+case2:
+; CHECK: %cmp.3 = icmp eq i32 %0, 0
+; CHECK-NOT: select i1
+; CHECK-NEXT: br i1 %cmp.3, label %si.unfold.true, label %si.unfold.false
+ %cmp.1 = icmp slt i32 %count, 50
+ %cmp.2 = icmp slt i32 %count, 100
+ %0 = and i32 %count, 1
+ %cmp.3 = icmp eq i32 %0, 0
+ %sel.1 = select i1 %cmp.1, i32 1, i32 2
+ %sel.2 = select i1 %cmp.2, i32 3, i32 4
+ %sel.3 = select i1 %cmp.3, i32 %sel.1, i32 %sel.2
+ br label %for.inc
+
+; CHECK: si.unfold.true:
+; CHECK-NEXT: br i1 %cmp.1
+; CHECK: si.unfold.false:
+; CHECK-NEXT: br i1 %cmp.2
+; CHECK: si.unfold.false1:
+; CHECK-NEXT: br label %for.inc
+; CHECK: si.unfold.false2:
+; CHECK-NEXT: br label %for.inc
+
+for.inc:
+; CHECK: for.inc.jt4:
+; CHECK: [ 4, %si.unfold.false1 ]
+; CHECK: for.inc.jt3:
+; CHECK: [ 3, %si.unfold.false ]
+; CHECK: for.inc.jt2:
+; CHECK: [ 2, %si.unfold.false2 ]
+; CHECK: for.inc.jt1:
+; CHECK: [ 1, %si.unfold.true ]
+ %state.next = phi i32 [ %sel.3, %case2 ], [ 1, %for.body ], [ 2, %case1 ]
+ %inc = add nsw i32 %count, 1
+ %cmp.exit = icmp slt i32 %inc, %num
+ br i1 %cmp.exit, label %for.body, label %for.end
+
+for.end:
+ ret i32 0
+}