Index: include/llvm/Analysis/AliasAnalysis.h =================================================================== --- include/llvm/Analysis/AliasAnalysis.h +++ include/llvm/Analysis/AliasAnalysis.h @@ -141,6 +141,21 @@ } }; + Location getLocation(Instruction *Inst) { + if (auto *I = dyn_cast(Inst)) + return getLocation(I); + else if (auto *I = dyn_cast(Inst)) + return getLocation(I); + else if (auto *I = dyn_cast(Inst)) + return getLocation(I); + else if (auto *I = dyn_cast(Inst)) + return getLocation(I); + else if (auto *I = dyn_cast(Inst)) + return getLocation(I); + else + llvm_unreachable("unsupported memory instruction"); + } + /// getLocation - Fill in Loc with information about the memory reference by /// the given instruction. Location getLocation(const LoadInst *LI); @@ -357,6 +372,24 @@ return (MRB & ModRef) && (MRB & ArgumentPointees); } + // getModRefInfo - Return information about whether or not an + // instruction may read or write memory (without regard to a + // specific location) + ModRefResult getModRefInfo(const Instruction *I) { + if (isa(I) || isa(I)) { + auto MRB = getModRefBehavior(I); + if (MRB & ModRef) + return ModRef; + else if (MRB & Ref) + return Ref; + else if (MRB & Mod) + return Mod; + return NoModRef; + } + + return getModRefInfo(I, Location()); + } + /// getModRefInfo - Return information about whether or not an instruction may /// read or write the specified memory location. An instruction /// that doesn't read or write memory may be trivially LICM'd for example. Index: include/llvm/IR/Function.h =================================================================== --- include/llvm/IR/Function.h +++ include/llvm/IR/Function.h @@ -472,6 +472,10 @@ Constant *getPrologueData() const; void setPrologueData(Constant *PrologueData); + /// Print the function to an output stream with an optional + /// AssemblyAnnotationWriter. + void print(raw_ostream &OS, AssemblyAnnotationWriter *AAW = nullptr) const; + /// viewCFG - This function is meant for use from the debugger. You can just /// say 'call F->viewCFG()' and a ghostview window should pop up from the /// program, displaying the CFG of the current function with the code for each Index: include/llvm/InitializePasses.h =================================================================== --- include/llvm/InitializePasses.h +++ include/llvm/InitializePasses.h @@ -201,6 +201,7 @@ void initializeMemDepPrinterPass(PassRegistry&); void initializeMemDerefPrinterPass(PassRegistry&); void initializeMemoryDependenceAnalysisPass(PassRegistry&); +void initializeMemorySSAPass(PassRegistry&); void initializeMergedLoadStoreMotionPass(PassRegistry &); void initializeMetaRenamerPass(PassRegistry&); void initializeMergeFunctionsPass(PassRegistry&); Index: include/llvm/Transforms/Utils/MemorySSA.h =================================================================== --- /dev/null +++ include/llvm/Transforms/Utils/MemorySSA.h @@ -0,0 +1,296 @@ +//===- MemorySSA.h - Build Memory SSA ----------------------------*- C++ +//-*-===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file exposes an interface to building/using memory SSA to walk memory +// instructions using a use/def graph + +// Memory SSA class builds an SSA form that links together memory +// access instructions such loads, stores, and clobbers (atomics, +// calls, etc), so they can be walked easily. Additionally, it does a +// trivial form of "heap versioning" Every time the memory state +// changes in the program, we generate a new heap version It generates +// MemoryDef/Uses/Phis that are overlayed on top of the existing +// instructions + +// As a trivial example, +// define i32 @main() #0 { +// entry: +// %call = call noalias i8* @_Znwm(i64 4) #2 +// %0 = bitcast i8* %call to i32* +// %call1 = call noalias i8* @_Znwm(i64 4) #2 +// %1 = bitcast i8* %call1 to i32* +// store i32 5, i32* %0, align 4 +// store i32 7, i32* %1, align 4 +// %2 = load i32* %0, align 4 +// %3 = load i32* %1, align 4 +// %add = add nsw i32 %2, %3 +// ret i32 %add +// } +// Will become +// define i32 @main() #0 { +// entry: +// ; 1 = MemoryDef(0) +// %call = call noalias i8* @_Znwm(i64 4) #3 +// %2 = bitcast i8* %call to i32* +// ; 2 = MemoryDef(1) +// %call1 = call noalias i8* @_Znwm(i64 4) #3 +// %4 = bitcast i8* %call1 to i32* +// ; 3 = MemoryDef(2) +// store i32 5, i32* %2, align 4 +// ; 4 = MemoryDef(3) +// store i32 7, i32* %4, align 4 +// ; MemoryUse(4) +// %7 = load i32* %2, align 4 +// ; MemoryUse(4) +// %8 = load i32* %4, align 4 +// %add = add nsw i32 %7, %8 +// ret i32 %add +// } +// Given this form, all the stores that could ever effect the load +// at %8 can be gotten by using the memory use associated with it, +// and walking from use to def until you hit the top of the function. + +// Each def also has a list of uses +// Also note that it does not attempt any disambiguation, it is simply +// linking together the instructions. + +// +//===----------------------------------------------------------------------===// +#ifndef LLVM_TRANSFORMS_UTILS_MEMORYSSA_H +#define LLVM_TRANSFORMS_UTILS_MEMORYSSA_H +#include "llvm/Analysis/AliasAnalysis.h" +#include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/SmallVector.h" +#include "llvm/ADT/SmallPtrSet.h" +#include "llvm/ADT/UniqueVector.h" +#include "llvm/Support/Allocator.h" +#include +namespace llvm { + +class BasicBlock; +class DominatorTree; +class Function; + +class MemoryAccess { +public: + enum AccessType { AccessUse, AccessDef, AccessPhi }; + + // Methods for support type inquiry through isa, cast, and + // dyn_cast + static inline bool classof(const MemoryAccess *) { return true; } + + AccessType getAccessType() const { return AccessType; } + virtual ~MemoryAccess() {} + BasicBlock *getBlock() const { return Block; } + + typedef UniqueVector SlotInfoType; + virtual void print(raw_ostream &OS, SlotInfoType &SlotInfo) {} + typedef MemoryAccess **iterator; + typedef MemoryAccess **const const_iterator; + + // The use list is immutable because it is allocated in a + // BumpPtrAllocator + + const_iterator use_begin() const { return UseList; } + const_iterator use_end() const { return UseList + NumUses; } + +protected: + friend class MemorySSA; + // We automatically allocate the right amount of space + void addUse(MemoryAccess *Use) { UseList[NumUses++] = Use; } + MemoryAccess(AccessType AT, BasicBlock *BB) + : AccessType(AT), Block(BB), NumUses(0), UseList(nullptr) {} + +private: + MemoryAccess(const MemoryAccess &); + void operator=(const MemoryAccess &); + AccessType AccessType; + BasicBlock *Block; + unsigned int NumUses; + MemoryAccess **UseList; +}; + +class MemoryUse : public MemoryAccess { +public: + MemoryUse(MemoryAccess *DMA, Instruction *MI, BasicBlock *BB) + : MemoryUse(DMA, AccessUse, MI, BB) {} + + MemoryAccess *getDefiningAccess() const { return DefiningAccess; } + void setDefiningAccess(MemoryAccess *DMA) { DefiningAccess = DMA; } + Instruction *getMemoryInst() const { return MemoryInst; } + void setMemoryInst(Instruction *MI) { MemoryInst = MI; } + + static inline bool classof(const MemoryUse *) { return true; } + static inline bool classof(const MemoryAccess *MA) { + return MA->getAccessType() == AccessUse; + } + virtual void print(raw_ostream &OS, SlotInfoType &SlotInfo); + +protected: + MemoryUse(MemoryAccess *DMA, enum AccessType AT, Instruction *MI, + BasicBlock *BB) + : MemoryAccess(AT, BB), DefiningAccess(DMA), MemoryInst(MI) {} + +private: + MemoryAccess *DefiningAccess; + Instruction *MemoryInst; +}; + +// All defs also have a use +class MemoryDef : public MemoryUse { +public: + MemoryDef(MemoryAccess *DMA, Instruction *MI, BasicBlock *BB) + : MemoryUse(DMA, AccessDef, MI, BB) {} + + static inline bool classof(const MemoryDef *) { return true; } + static inline bool classof(const MemoryUse *MA) { + return MA->getAccessType() == AccessDef; + } + + static inline bool classof(const MemoryAccess *MA) { + return MA->getAccessType() == AccessDef; + } + virtual void print(raw_ostream &OS, SlotInfoType &SlotInfo); + typedef MemoryAccess **iterator; + typedef const MemoryAccess **const_iterator; +}; +class MemoryPhi : public MemoryAccess { +public: + MemoryPhi(BasicBlock *BB, unsigned int NumPreds) + : MemoryAccess(AccessPhi, BB) { + Args.reserve(NumPreds); + } + unsigned int getNumIncomingValues() { return Args.size(); } + void addIncoming(MemoryAccess *MA, BasicBlock *BB) { + Args.push_back(std::make_pair(BB, MA)); + } + void setIncomingValue(unsigned int v, MemoryAccess *MA) { + std::pair &Val = Args[v]; + Val.second = MA; + } + MemoryAccess *getIncomingValue(unsigned int v) { return Args[v].second; } + void setIncomingBlock(unsigned int v, BasicBlock *BB) { + std::pair &Val = Args[v]; + Val.first = BB; + } + BasicBlock *getIncomingBlock(unsigned int v) { return Args[v].first; } + static inline bool classof(const MemoryPhi *) { return true; } + static inline bool classof(const MemoryAccess *MA) { + return MA->getAccessType() == AccessPhi; + } + + virtual void print(raw_ostream &OS, SlotInfoType &SlotInfo); + +private: + SmallVector, 8> Args; +}; + +class MemorySSA : public FunctionPass { + +private: + AliasAnalysis *AA; + DominatorTree *DT; + BumpPtrAllocator MemoryAccessAllocator; + Function *F; + + // Memory SSA mappings + DenseMap InstructionToMemoryAccess; + DenseMap, MemoryAccess *> + CachedClobberingAccess; + DenseMap CachedClobberingCall; + + // Memory SSA building info + typedef DenseMap *> AccessMap; + MemoryAccess *LiveOnEntryDef; + +public: + MemorySSA(); + ~MemorySSA(); + static char ID; + + bool runOnFunction(Function &) override; + + void releaseMemory() override; + + void getAnalysisUsage(AnalysisUsage &AU) const override; + + // Memory SSA related stuff + void buildMemorySSA(Function &F); + // Given a memory defining/using/clobbering instruction, give you + // the nearest dominating clobbering Memory Access (by skipping non-aliasing + // def links) + MemoryAccess *getClobberingMemoryAccess(Instruction *); + // Given a memory using/clobbering/etc instruction, get the + // MemorySSA access associaed with it + MemoryAccess *getMemoryAccess(const Value *I) const; + void dump(Function &F); + void print(raw_ostream &OS, const Module *M) const override; + inline bool isLiveOnEntryDef(const MemoryAccess *MA) const { + return MA == LiveOnEntryDef; + } + inline const MemoryAccess *getLiveOnEntryDef() const { + assert(LiveOnEntryDef && "Live on entry def not initialized yet"); + return LiveOnEntryDef; + } + +private: + void verifyUseInDefs(MemoryAccess *Def, MemoryAccess *Use); + typedef DenseMap *> UseMap; + MemoryAccess *doCacheLookup(MemoryAccess *, const AliasAnalysis::Location &, + bool); + void doCacheInsert(MemoryAccess *, const AliasAnalysis::Location &, + MemoryAccess *, bool); + std::pair + getClobberingMemoryAccess(MemoryPhi *Phi, const AliasAnalysis::Location &, + bool, SmallPtrSet &); + std::pair + getClobberingMemoryAccess(MemoryAccess *, const AliasAnalysis::Location &, + bool, SmallPtrSet &); + + void computeLiveInBlocks(const AccessMap &BlockAccesses, + const SmallPtrSetImpl &DefBlocks, + const SmallVector &UseBlocks, + SmallPtrSetImpl &LiveInBlocks); + void + determineInsertionPoint(Function &F, AccessMap &BlockAccesses, + const SmallPtrSetImpl &DefiningBlocks, + const SmallVector &UsingBlocks); + void computeDomLevels(DenseMap &DomLevels); + void computeBBNumbers(Function &F, + DenseMap &BBNumbers); + void markUnreachableAsLiveOnEntry(AccessMap &BlockAccesses, BasicBlock *BB, + UseMap &Uses); + void addUses(UseMap &Uses); + void addUseToMap(UseMap &, MemoryAccess *, MemoryAccess *); + void verifyDefUses(Function &F); + + struct RenamePassData { + BasicBlock *BB; + BasicBlock *Pred; + MemoryAccess *MA; + + RenamePassData() : BB(nullptr), Pred(nullptr), MA(nullptr) {} + + RenamePassData(BasicBlock *B, BasicBlock *P, MemoryAccess *M) + : BB(B), Pred(P), MA(M) {} + void swap(RenamePassData &RHS) { + std::swap(BB, RHS.BB); + std::swap(Pred, RHS.Pred); + std::swap(MA, RHS.MA); + } + }; + + void renamePass(BasicBlock *BB, BasicBlock *Pred, MemoryAccess *IncomingVal, + AccessMap &BlockAccesses, + std::vector &Worklist, + SmallPtrSet &Visited, UseMap &Uses); +}; +} +#endif Index: lib/Analysis/Analysis.cpp =================================================================== --- lib/Analysis/Analysis.cpp +++ lib/Analysis/Analysis.cpp @@ -56,6 +56,7 @@ initializeMemDepPrinterPass(Registry); initializeMemDerefPrinterPass(Registry); initializeMemoryDependenceAnalysisPass(Registry); + initializeMemorySSAPass(Registry); initializeModuleDebugInfoPrinterPass(Registry); initializePostDominatorTreePass(Registry); initializeRegionInfoPassPass(Registry); Index: lib/IR/AsmWriter.cpp =================================================================== --- lib/IR/AsmWriter.cpp +++ lib/IR/AsmWriter.cpp @@ -3084,6 +3084,13 @@ // External Interface declarations //===----------------------------------------------------------------------===// +void Function::print(raw_ostream &ROS, AssemblyAnnotationWriter *AAW) const { + SlotTracker SlotTable(this->getParent()); + formatted_raw_ostream OS(ROS); + AssemblyWriter W(OS, SlotTable, this->getParent(), AAW); + W.printFunction(this); +} + void Module::print(raw_ostream &ROS, AssemblyAnnotationWriter *AAW) const { SlotTracker SlotTable(this); formatted_raw_ostream OS(ROS); Index: lib/Transforms/Utils/CMakeLists.txt =================================================================== --- lib/Transforms/Utils/CMakeLists.txt +++ lib/Transforms/Utils/CMakeLists.txt @@ -24,6 +24,7 @@ LowerInvoke.cpp LowerSwitch.cpp Mem2Reg.cpp + MemorySSA.cpp MetaRenamer.cpp ModuleUtils.cpp PromoteMemoryToRegister.cpp Index: lib/Transforms/Utils/MemorySSA.cpp =================================================================== --- /dev/null +++ lib/Transforms/Utils/MemorySSA.cpp @@ -0,0 +1,837 @@ + +//===- MemorySSA.cpp - Memory SSA Builder----------------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements the MemorySSA class. +// +//===----------------------------------------------------------------------===// +#include "llvm/Transforms/Scalar.h" +#include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/PostOrderIterator.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/ADT/UniqueVector.h" +#include "llvm/Analysis/AliasAnalysis.h" +#include "llvm/Analysis/CFG.h" +#include "llvm/IR/AssemblyAnnotationWriter.h" +#include "llvm/IR/DataLayout.h" +#include "llvm/IR/Dominators.h" +#include "llvm/IR/GlobalVariable.h" +#include "llvm/IR/IRBuilder.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/IR/Metadata.h" +#include "llvm/IR/Module.h" +#include "llvm/IR/PatternMatch.h" +#include "llvm/Support/Allocator.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/FormattedStream.h" +#include "llvm/Transforms/Utils/MemorySSA.h" +#include +#include +#define DEBUG_TYPE "memoryssa" +using namespace llvm; +STATISTIC(NumClobberCacheLookups, "Number of Memory SSA version cache lookups"); +STATISTIC(NumClobberCacheHits, "Number of Memory SSA version cache hits"); + +INITIALIZE_PASS_BEGIN(MemorySSA, "memoryssa", "Memory SSA", false, true) +INITIALIZE_AG_DEPENDENCY(AliasAnalysis) +INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) +INITIALIZE_PASS_END(MemorySSA, "memoryssa", "Memory SSA", false, true); + +// This is a temporary (IE will be deleted once consensus is reached +// in the review) flag to determine whether we should optimize uses +// while building so they point to the nearest actual clobber +#define OPTIMIZE_USES 1 + +namespace llvm { +// An annotator class to print memory ssa information in comments +class MemorySSAAnnotatedWriter : public AssemblyAnnotationWriter { + const MemorySSA *MSSA; + MemoryAccess::SlotInfoType SlotInfo; + +public: + MemorySSAAnnotatedWriter(const MemorySSA *M) : MSSA(M) { + // Always want the live on entry def to print out as the lowest number + SlotInfo.insert(M->getLiveOnEntryDef()); + } + + virtual void emitBasicBlockStartAnnot(const BasicBlock *BB, + formatted_raw_ostream &OS) { + MemoryAccess *MA = MSSA->getMemoryAccess(BB); + if (MA) { + OS << "; "; + MA->print(OS, SlotInfo); + OS << "\n"; + } + } + + virtual void emitInstructionAnnot(const Instruction *I, + formatted_raw_ostream &OS) { + MemoryAccess *MA = MSSA->getMemoryAccess(I); + if (MA) { + OS << "; "; + MA->print(OS, SlotInfo); + OS << "\n"; + } + } +}; +} + +void MemorySSA::doCacheInsert(MemoryAccess *M, + const AliasAnalysis::Location &Loc, + MemoryAccess *Result, bool AskingAboutCall) { + if (!AskingAboutCall) + CachedClobberingAccess.insert( + std::make_pair(std::make_pair(M, Loc), Result)); + else + CachedClobberingCall.insert(std::make_pair(M, Result)); +} + +MemoryAccess *MemorySSA::doCacheLookup(MemoryAccess *M, + const AliasAnalysis::Location &Loc, + bool AskingAboutCall) { + ++NumClobberCacheLookups; + MemoryAccess *Result; + if (AskingAboutCall) + Result = CachedClobberingCall.lookup(getMemoryAccess(Loc.Ptr)); + else + Result = CachedClobberingAccess.lookup(std::make_pair(M, Loc)); + + if (Result) { + ++NumClobberCacheHits; + return Result; + } + return nullptr; +} + +// Get the clobbering memory access for a phi node and alias location +std::pair MemorySSA::getClobberingMemoryAccess( + MemoryPhi *P, const AliasAnalysis::Location &Loc, bool AskingAboutCall, + SmallPtrSet &Visited) { + + bool HitVisited = false; + + ++NumClobberCacheLookups; + auto CacheResult = doCacheLookup(P, Loc, AskingAboutCall); + if (CacheResult) + return std::make_pair(CacheResult, false); + + // The algorithm here is fairly simple. The goal is to prove that + // the phi node doesn't matter for this alias location, and to get + // to whatever Access occurs before the *split* point that caused + // the phi node. + // There are only two cases we can walk through: + // 1. One argument dominates the other, and the other's argument + // defining memory access is non-aliasing with our location. + // 2. All of the arguments are non-aliasing with our location, and + // eventually lead back to the same defining memory access + MemoryAccess *Result = nullptr; + + // If we already got here once, and didn't get to an answer (if we + // did, it would have been cached below), we must be stuck in + // mutually recursive phi nodes. In that case, the correct answer + // is "we can ignore the phi node if all the other arguments turn + // out okay" (since it cycles between itself and the other + // arguments). We return true here, and are careful to make sure we + // only pass through "true" when we are giving results + // for the cycle itself. + if (!Visited.insert(P).second) + return std::make_pair(P, true); + + // Look through 1 argument phi nodes + if (P->getNumIncomingValues() == 1) { + auto SingleResult = getClobberingMemoryAccess(P->getIncomingValue(0), Loc, + AskingAboutCall, Visited); + HitVisited = SingleResult.second; + Result = SingleResult.first; + } else { + MemoryAccess *TargetResult = nullptr; + + // This is true if we hit ourselves from every argument + bool AllVisited = true; + for (unsigned i = 0; i < P->getNumIncomingValues(); ++i) { + MemoryAccess *Arg = P->getIncomingValue(i); + auto ArgResult = + getClobberingMemoryAccess(Arg, Loc, AskingAboutCall, Visited); + if (!ArgResult.second) { + AllVisited = false; + // Fill in target result we are looking for if we haven't so far + // Otherwise check the argument is equal to the last one + if (!TargetResult) { + TargetResult = ArgResult.first; + } else if (TargetResult != ArgResult.first) { + Result = P; + HitVisited = false; + break; + } + } + } + // See if we completed either with all visited, or with success + if (!Result && AllVisited) { + Result = P; + HitVisited = true; + } else if (!Result && TargetResult) { + Result = TargetResult; + HitVisited = false; + } + } + doCacheInsert(P, Loc, Result, AskingAboutCall); + + return std::make_pair(Result, HitVisited); +} + +// For a given MemoryAccess, walk backwards using Memory SSA and find +// the MemoryAccess that actually clobbers Loc. The second part of +// the pair we return is whether we hit a cyclic phi node. +std::pair MemorySSA::getClobberingMemoryAccess( + MemoryAccess *MA, const AliasAnalysis::Location &Loc, bool AskingAboutCall, + SmallPtrSet &Visited) { + MemoryAccess *CurrAccess = MA; + while (true) { + // If we started with a heap use, walk to the def + if (MemoryUse *MU = dyn_cast(CurrAccess)) + CurrAccess = MU->getDefiningAccess(); + + // Should be either a Memory Def or a Phi node at this point + if (MemoryPhi *P = dyn_cast(CurrAccess)) + return getClobberingMemoryAccess(P, Loc, AskingAboutCall, Visited); + else { + MemoryDef *MD = dyn_cast(CurrAccess); + assert(MD && "Use linked to something that is not a def"); + // If we hit the top, stop + if (isLiveOnEntryDef(MD)) + return std::make_pair(CurrAccess, false); + Instruction *DefMemoryInst = MD->getMemoryInst(); + assert(DefMemoryInst && + "Defining instruction not actually an instruction"); + + // While we can do lookups, we can't sanely do inserts here unless we + // were to track every thing we saw along the way, since we don't + // know where we will stop. + // Note: There is no point in doing lookups for calls at this + // stage. If we knew a better result for the initial call, we + // would have found it in the function that calls this one. + if (!AskingAboutCall) { + if (auto CacheResult = doCacheLookup(CurrAccess, Loc, AskingAboutCall)) + return std::make_pair(CacheResult, false); + // Check whether our memory location is modified by this instruction + if (AA->getModRefInfo(DefMemoryInst, Loc) & AliasAnalysis::Mod) + break; + } else { + if (isa(DefMemoryInst) || isa(DefMemoryInst)) { + // Check if the two calls touch the same memory + if (AA->getModRefInfo(Loc.Ptr, DefMemoryInst) & AliasAnalysis::Mod) + break; + } else { + // Otherwise, check if the call modifies or references this + // location (The best we can say is that if the call + // references what this instruction defines, it + // must be clobbered by this location,. + const AliasAnalysis::Location DefLoc = AA->getLocation(DefMemoryInst); + if (AA->getModRefInfo(cast(Loc.Ptr), DefLoc) & + AliasAnalysis::Mod) + break; + } + } + } + + MemoryAccess *NextAccess = cast(CurrAccess)->getDefiningAccess(); + // Walk from def to def + CurrAccess = NextAccess; + } + doCacheInsert(MA, Loc, CurrAccess, AskingAboutCall); + return std::make_pair(CurrAccess, false); +} + +// For a given instruction, walk backwards using Memory SSA and find +// the memory access that actually clobbers this one, skipping non-aliasing +// ones along the way +MemoryAccess *MemorySSA::getClobberingMemoryAccess(Instruction *I) { + MemoryAccess *StartingAccess = getMemoryAccess(I); + bool AskingAboutCall = false; + + // First extract our location, then start walking until it is + // clobbered + + AliasAnalysis::Location Loc(I); + + // We can't sanely do anything with a FenceInst, they conservatively + // clobber all memory + if (isa(I)) { + return StartingAccess; + } else if (!isa(I) && !isa(I)) { + Loc = AA->getLocation(I); + } else { + AskingAboutCall = true; + } + auto CacheResult = doCacheLookup(StartingAccess, Loc, AskingAboutCall); + if (CacheResult) + return CacheResult; + SmallPtrSet Visited; + MemoryAccess *FinalAccess = + getClobberingMemoryAccess(StartingAccess, Loc, AskingAboutCall, Visited) + .first; + doCacheInsert(StartingAccess, Loc, FinalAccess, AskingAboutCall); + DEBUG(dbgs() << "Starting Memory SSA clobber for " << (uintptr_t)I << " is "); + DEBUG(dbgs() << (uintptr_t)StartingAccess); + DEBUG(dbgs() << "\n"); + DEBUG(dbgs() << "Final Memory SSA clobber for " << (uintptr_t)I << " is "); + DEBUG(dbgs() << (uintptr_t)FinalAccess); + DEBUG(dbgs() << "\n"); + + return FinalAccess; +} + +// This is the same as PromoteMemoryToRegister's Access. The goal is +// to compute blocks in which a memory-access is Live-In. + +void MemorySSA::computeLiveInBlocks( + const AccessMap &BlockAccesses, + const SmallPtrSetImpl &DefBlocks, + const SmallVector &UseBlocks, + SmallPtrSetImpl &LiveInBlocks) { + + // To determine liveness, we must iterate through the predecessors of blocks + // where the def is live. Blocks are added to the worklist if we need to + // check their predecessors. Start with all the using blocks. + SmallVector LiveInBlockWorklist(UseBlocks.begin(), + UseBlocks.end()); + // If any of the using blocks is also a definition block, check to see if the + // definition occurs before or after the use. If it happens before the use, + // the value isn't really live-in. + for (unsigned i = 0, e = LiveInBlockWorklist.size(); i != e; ++i) { + BasicBlock *BB = LiveInBlockWorklist[i]; + if (!DefBlocks.count(BB)) + continue; + + // Okay, this is a block that both uses and defines the value. If the first + // reference to the alloca is a def (store), then we know it isn't + // live-in. + auto AccessList = BlockAccesses.lookup(BB); + + if (AccessList && isa(AccessList->front())) { + LiveInBlockWorklist[i] = LiveInBlockWorklist.back(); + LiveInBlockWorklist.pop_back(); + --i, --e; + } + } + + // Now that we have a set of blocks where the phi is live-in, recursively add + // their predecessors until we find the full region the value is live. + while (!LiveInBlockWorklist.empty()) { + BasicBlock *BB = LiveInBlockWorklist.pop_back_val(); + + // The block really is live in here, insert it into the set. If already in + // the set, then it has already been processed. + if (!LiveInBlocks.insert(BB).second) + continue; + + // Since the value is live into BB, it is either defined in a predecessor or + // live into it to. Add the preds to the worklist unless they are a + // defining block. + for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { + BasicBlock *P = *PI; + + // The value is not live into a predecessor if it defines the value. + if (DefBlocks.count(P)) + continue; + + // Otherwise it is, add to the worklist. + LiveInBlockWorklist.push_back(P); + } + } +} + +// We need a unique numbering for each BB. + +void MemorySSA::computeBBNumbers(Function &F, + DenseMap &BBNumbers) { + // Assign unique ids to basic blocks + unsigned ID = 0; + for (auto &I : F) + BBNumbers[&I] = ID++; +} + +// This is the same algorithm as PromoteMemoryToRegister's phi +// placement algorithm. + +void MemorySSA::determineInsertionPoint( + Function &F, AccessMap &BlockAccesses, + const SmallPtrSetImpl &DefBlocks, + const SmallVector &UsingBlocks) { + // Compute dominator levels and BB numbers + DenseMap DomLevels; + computeDomLevels(DomLevels); + + DenseMap BBNumbers; + computeBBNumbers(F, BBNumbers); + + SmallPtrSet LiveInBlocks; + + computeLiveInBlocks(BlockAccesses, DefBlocks, UsingBlocks, LiveInBlocks); + // Use a priority queue keyed on dominator tree level so that inserted nodes + // are handled from the bottom of the dominator tree upwards. + typedef std::pair DomTreeNodePair; + typedef std::priority_queue, + less_second> IDFPriorityQueue; + IDFPriorityQueue PQ; + + for (BasicBlock *BB : DefBlocks) { + if (DomTreeNode *Node = DT->getNode(BB)) + PQ.push(std::make_pair(Node, DomLevels[Node])); + } + + SmallVector, 32> DFBlocks; + SmallPtrSet Visited; + SmallVector Worklist; + while (!PQ.empty()) { + DomTreeNodePair RootPair = PQ.top(); + PQ.pop(); + DomTreeNode *Root = RootPair.first; + unsigned RootLevel = RootPair.second; + + // Walk all dominator tree children of Root, inspecting their CFG edges with + // targets elsewhere on the dominator tree. Only targets whose level is at + // most Root's level are added to the iterated dominance frontier of the + // definition set. + + Worklist.clear(); + Worklist.push_back(Root); + + while (!Worklist.empty()) { + DomTreeNode *Node = Worklist.pop_back_val(); + BasicBlock *BB = Node->getBlock(); + + for (auto S : successors(BB)) { + DomTreeNode *SuccNode = DT->getNode(S); + + // Quickly skip all CFG edges that are also dominator tree edges instead + // of catching them below. + if (SuccNode->getIDom() == Node) + continue; + + unsigned SuccLevel = DomLevels[SuccNode]; + if (SuccLevel > RootLevel) + continue; + + if (!Visited.insert(SuccNode).second) + continue; + + BasicBlock *SuccBB = SuccNode->getBlock(); + if (!LiveInBlocks.count(SuccBB)) + continue; + + DFBlocks.push_back(std::make_pair(BBNumbers[SuccBB], SuccBB)); + if (!DefBlocks.count(SuccBB)) + PQ.push(std::make_pair(SuccNode, SuccLevel)); + } + + for (auto &C : *Node) + if (!Visited.count(C)) + Worklist.push_back(C); + } + } + + if (DFBlocks.size() > 1) + std::sort(DFBlocks.begin(), DFBlocks.end()); + for (unsigned i = 0, e = DFBlocks.size(); i != e; ++i) { + // Insert phi node + BasicBlock *BB = DFBlocks[i].second; + auto Accesses = BlockAccesses.lookup(BB); + if (!Accesses) { + Accesses = new std::list; + BlockAccesses.insert(std::make_pair(BB, Accesses)); + } + MemoryPhi *Phi = new (MemoryAccessAllocator) + MemoryPhi(BB, std::distance(pred_begin(BB), pred_end(BB))); + InstructionToMemoryAccess.insert(std::make_pair(BB, Phi)); + // Phi goes first + Accesses->push_front(Phi); + } +} + +// Standard SSA renaming pass. Same algorithm as +// PromoteMemoryToRegisters + +void MemorySSA::renamePass(BasicBlock *BB, BasicBlock *Pred, + MemoryAccess *IncomingVal, AccessMap &BlockAccesses, + std::vector &Worklist, + SmallPtrSet &Visited, + UseMap &Uses) { +NextIteration: + auto Accesses = BlockAccesses.lookup(BB); + + // First rename the phi nodes + if (Accesses && isa(Accesses->front())) { + MemoryPhi *Phi = cast(Accesses->front()); + unsigned NumEdges = std::count(succ_begin(Pred), succ_end(Pred), BB); + assert(NumEdges && "Must be at least one edge from Pred to BB!"); + for (unsigned i = 0; i != NumEdges; ++i) + Phi->addIncoming(IncomingVal, Pred); + addUseToMap(Uses, IncomingVal, Phi); + + IncomingVal = Phi; + } + + // Don't revisit blocks. + if (!Visited.insert(BB).second) + return; + + // Skip if the list is empty, but we still have to pass thru the + // incoming value info/etc to successors + if (Accesses) + for (auto &L : *Accesses) { + if (isa(L)) + continue; + + if (MemoryUse *MU = dyn_cast(L)) { +#if OPTIMIZE_USES + MU->setDefiningAccess(IncomingVal); + auto RealVal = getClobberingMemoryAccess(MU->getMemoryInst()); +#else + auto RealVal = IncomingVal; +#endif + MU->setDefiningAccess(RealVal); + addUseToMap(Uses, RealVal, MU); + } else if (MemoryDef *MD = dyn_cast(L)) { +#if OPTIMIZE_USES + MD->setDefiningAccess(IncomingVal); + auto RealVal = getClobberingMemoryAccess(MD->getMemoryInst()); + if (RealVal == MD) + RealVal = IncomingVal; +#else + auto RealVal = IncomingVal; +#endif + MD->setDefiningAccess(RealVal); + addUseToMap(Uses, RealVal, MD); + IncomingVal = MD; + } + } + // 'Recurse' to our successors. + succ_iterator I = succ_begin(BB), E = succ_end(BB); + if (I == E) + return; + + // Keep track of the successors so we don't visit the same successor twice + SmallPtrSet VisitedSuccs; + + // Handle the first successor without using the worklist. + VisitedSuccs.insert(*I); + Pred = BB; + BB = *I; + ++I; + + for (; I != E; ++I) + if (VisitedSuccs.insert(*I).second) + Worklist.push_back(RenamePassData(*I, Pred, IncomingVal)); + goto NextIteration; +} + +void MemorySSA::computeDomLevels(DenseMap &DomLevels) { + SmallVector Worklist; + + DomTreeNode *Root = DT->getRootNode(); + DomLevels[Root] = 0; + Worklist.push_back(Root); + + while (!Worklist.empty()) { + DomTreeNode *Node = Worklist.pop_back_val(); + unsigned ChildLevel = DomLevels[Node] + 1; + for (auto CI = Node->begin(), CE = Node->end(); CI != CE; ++CI) { + DomLevels[*CI] = ChildLevel; + Worklist.push_back(*CI); + } + } +} + +// Handle unreachable block acccesses by deleting phi nodes in +// unreachable blocks, and marking all other unreachable +// memoryaccesses as being uses of the live on entry definition +void MemorySSA::markUnreachableAsLiveOnEntry(AccessMap &BlockAccesses, + BasicBlock *BB, UseMap &Uses) { + assert(!DT->isReachableFromEntry(BB) && + "Reachable block found while handling unreachable blocks"); + + auto Accesses = BlockAccesses.lookup(BB); + if (!Accesses) + return; + + for (auto AI = Accesses->begin(), AE = Accesses->end(); AI != AE;) { + auto Next = std::next(AI); + // If we have a phi, just remove it. We are going to replace all + // users with live on entry. + if (MemoryPhi *P = dyn_cast(*AI)) { + delete P; + Accesses->erase(AI); + } else if (MemoryUse *U = dyn_cast(*AI)) { + U->setDefiningAccess(LiveOnEntryDef); + addUseToMap(Uses, LiveOnEntryDef, U); + } else if (MemoryDef *D = dyn_cast(*AI)) { + D->setDefiningAccess(LiveOnEntryDef); + addUseToMap(Uses, LiveOnEntryDef, D); + } + AI = Next; + } +} + +char MemorySSA::ID = 0; + +MemorySSA::MemorySSA() : FunctionPass(ID), LiveOnEntryDef(nullptr) { + initializeMemorySSAPass(*PassRegistry::getPassRegistry()); +} + +MemorySSA::~MemorySSA() {} + +void MemorySSA::releaseMemory() { + CachedClobberingAccess.clear(); + CachedClobberingCall.clear(); + InstructionToMemoryAccess.clear(); + MemoryAccessAllocator.Reset(); +} + +void MemorySSA::getAnalysisUsage(AnalysisUsage &AU) const { + AU.setPreservesAll(); + AU.addRequiredTransitive(); + AU.addRequired(); +} + +void MemorySSA::addUseToMap(UseMap &Uses, MemoryAccess *User, + MemoryAccess *Use) { + std::list *UseList; + UseList = Uses.lookup(User); + if (!UseList) { + UseList = new std::list; + Uses.insert(std::make_pair(User, UseList)); + } + + UseList->push_back(Use); +} + +// Build the actual use lists out of the use map +void MemorySSA::addUses(UseMap &Uses) { + for (auto &D : Uses) { + std::list *UseList = D.second; + MemoryAccess *User = D.first; + User->UseList = + MemoryAccessAllocator.Allocate(UseList->size()); + for (auto &U : *UseList) + User->addUse(U); + } +} + +bool MemorySSA::runOnFunction(Function &F) { + this->F = &F; + AA = &getAnalysis(); + DT = &getAnalysis().getDomTree(); + buildMemorySSA(F); + return false; +} + +void MemorySSA::buildMemorySSA(Function &F) { + // We temporarily maintain lists of memory accesses per-block, + // trading time for memory. We could just look up the memory access + // for every possible instruction in the stream. Instead, we build + // lists, and then throw it out once the use-def form is built. + AccessMap PerBlockAccesses; + SmallPtrSet DefiningBlocks; + SmallVector UsingBlocks; + + for (auto &B : F) { + std::list *Accesses = nullptr; + for (auto &I : B) { + bool use = false; + bool def = false; + if (isa(&I)) { + use = true; + def = false; + } else if (isa(&I)) { + use = false; + def = true; + } else { + AliasAnalysis::ModRefResult ModRef = AA->getModRefInfo(&I); + if (ModRef & AliasAnalysis::Mod) + def = true; + if (ModRef & AliasAnalysis::Ref) + use = true; + } + + // Defs are already uses, so use && def == def + if (use && !def) { + MemoryUse *MU = new (MemoryAccessAllocator) MemoryUse(nullptr, &I, &B); + InstructionToMemoryAccess.insert(std::make_pair(&I, MU)); + UsingBlocks.push_back(&B); + if (!Accesses) { + Accesses = new std::list; + PerBlockAccesses.insert(std::make_pair(&B, Accesses)); + } + Accesses->push_back(MU); + } + if (def) { + MemoryDef *MD = new (MemoryAccessAllocator) MemoryDef(nullptr, &I, &B); + InstructionToMemoryAccess.insert(std::make_pair(&I, MD)); + DefiningBlocks.insert(&B); + if (!Accesses) { + Accesses = new std::list; + PerBlockAccesses.insert(std::make_pair(&B, Accesses)); + } + Accesses->push_back(MD); + } + } + } + // Determine where our PHI's should go + determineInsertionPoint(F, PerBlockAccesses, DefiningBlocks, UsingBlocks); + + // We create an access to represent "live on entry", for things like + // arguments or users of globals. We do not actually insert it in to + // the IR. + BasicBlock &StartingPoint = F.getEntryBlock(); + LiveOnEntryDef = + new (MemoryAccessAllocator) MemoryDef(nullptr, nullptr, &StartingPoint); + + // Now do regular SSA renaming + SmallPtrSet Visited; + + // Uses are allocated and built once for a memory access, then are + // immutable. In order to count how many we need for a given memory + // access, we first add all the uses to lists in a densemap, then + // later we will convert it into an array and place it in the right + // place + UseMap Uses; + + std::vector RenamePassWorklist; + RenamePassWorklist.push_back({F.begin(), nullptr, LiveOnEntryDef}); + do { + RenamePassData RPD; + RPD.swap(RenamePassWorklist.back()); + RenamePassWorklist.pop_back(); + renamePass(RPD.BB, RPD.Pred, RPD.MA, PerBlockAccesses, RenamePassWorklist, + Visited, Uses); + } while (!RenamePassWorklist.empty()); + + // At this point, we may have unreachable blocks with unreachable accesses + // Given any uses in unreachable blocks the live on entry definition + if (Visited.size() != F.size()) { + for (auto &B : F) + if (!Visited.count(&B)) + markUnreachableAsLiveOnEntry(PerBlockAccesses, &B, Uses); + } + + // Now convert our use lists into real uses + addUses(Uses); + DEBUG(dump(F)); + DEBUG(verifyDefUses(F)); + + // Delete our access lists + for (auto &D : PerBlockAccesses) + delete D.second; + + // Densemap does not like when you delete or change the value during + // iteration. + std::vector *> UseListsToDelete; + for (auto &D : Uses) + UseListsToDelete.push_back(D.second); + + Uses.clear(); + for (unsigned i = 0, e = UseListsToDelete.size(); i != e; ++i) { + delete UseListsToDelete[i]; + UseListsToDelete[i] = nullptr; + } +} + +void MemorySSA::print(raw_ostream &OS, const Module *M) const { + F->print(OS, new MemorySSAAnnotatedWriter(this)); +} +void MemorySSA::dump(Function &F) { + F.print(dbgs(), new MemorySSAAnnotatedWriter(this)); +} + +void MemorySSA::verifyUseInDefs(MemoryAccess *Def, MemoryAccess *Use) { + // The live on entry use may cause us to get a NULL def here + if (Def == nullptr) { + assert(isLiveOnEntryDef(Use) && + "Null def but use not point to live on entry def"); + return; + } + assert(std::find(Def->use_begin(), Def->use_end(), Use) != Def->use_end() && + "Did not find use in def's use list"); +} + +// Verify the immediate use information, by walking all the memory +// accesses and verifying that, for each use, it appears in the +// appropriate def's use list + +void MemorySSA::verifyDefUses(Function &F) { + for (auto &B : F) { + // Phi nodes are attached to basic blocks + MemoryAccess *MA = getMemoryAccess(&B); + if (MA) { + assert(isa(MA) && + "Something other than phi node on basic block"); + MemoryPhi *MP = cast(MA); + for (unsigned i = 0, e = MP->getNumIncomingValues(); i != e; ++i) + verifyUseInDefs(MP->getIncomingValue(i), MP); + } + for (auto &I : B) { + MA = getMemoryAccess(&I); + if (MA) { + if (MemoryUse *MU = dyn_cast(MA)) + verifyUseInDefs(MU->getDefiningAccess(), MU); + else if (MemoryDef *MD = dyn_cast(MA)) + verifyUseInDefs(MD->getDefiningAccess(), MD); + else if (MemoryPhi *MP = dyn_cast(MA)) { + for (unsigned i = 0, e = MP->getNumIncomingValues(); i != e; ++i) + verifyUseInDefs(MP->getIncomingValue(i), MP); + } + } + } + } +} + +// Get a memory access for an instruction +MemoryAccess *MemorySSA::getMemoryAccess(const Value *I) const { + return InstructionToMemoryAccess.lookup(I); +} + +void MemoryDef::print(raw_ostream &OS, SlotInfoType &SlotInfo) { + MemoryAccess *UO = getDefiningAccess(); + OS << SlotInfo.insert(this) << " = " + << "MemoryDef("; + OS << SlotInfo.insert(UO) << ")"; +} + +void MemoryPhi::print(raw_ostream &OS, SlotInfoType &SlotInfo) { + OS << SlotInfo.insert(this) << " = " + << "MemoryPhi("; + for (unsigned int i = 0, e = getNumIncomingValues(); i != e; ++i) { + BasicBlock *BB = getIncomingBlock(i); + MemoryAccess *MA = getIncomingValue(i); + OS << "{"; + if (BB->hasName()) + OS << BB->getName(); + else + BB->printAsOperand(OS, false); + OS << ","; + assert((isa(MA) || isa(MA)) && + "Phi node should have referred to def or another phi"); + OS << SlotInfo.insert(MA); + OS << "}"; + if (i + 1 < e) + OS << ","; + } + OS << ")"; +} + +void MemoryUse::print(raw_ostream &OS, SlotInfoType &SlotInfo) { + MemoryAccess *UO = getDefiningAccess(); + OS << "MemoryUse("; + OS << SlotInfo.insert(UO); + OS << ")"; +}