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https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151262 91177308-0d34-0410-b5e6-96231b3b80d8
2597 lines
101 KiB
C++
2597 lines
101 KiB
C++
//===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This transformation implements the well known scalar replacement of
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// aggregates transformation. This xform breaks up alloca instructions of
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// aggregate type (structure or array) into individual alloca instructions for
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// each member (if possible). Then, if possible, it transforms the individual
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// alloca instructions into nice clean scalar SSA form.
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//
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// This combines a simple SRoA algorithm with the Mem2Reg algorithm because
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// often interact, especially for C++ programs. As such, iterating between
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// SRoA, then Mem2Reg until we run out of things to promote works well.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "scalarrepl"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Function.h"
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#include "llvm/GlobalVariable.h"
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#include "llvm/Instructions.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/LLVMContext.h"
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#include "llvm/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Analysis/DebugInfo.h"
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#include "llvm/Analysis/DIBuilder.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Analysis/Loads.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Transforms/Utils/PromoteMemToReg.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/Transforms/Utils/SSAUpdater.h"
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#include "llvm/Support/CallSite.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/GetElementPtrTypeIterator.h"
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#include "llvm/Support/IRBuilder.h"
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#include "llvm/Support/MathExtras.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Statistic.h"
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using namespace llvm;
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STATISTIC(NumReplaced, "Number of allocas broken up");
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STATISTIC(NumPromoted, "Number of allocas promoted");
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STATISTIC(NumAdjusted, "Number of scalar allocas adjusted to allow promotion");
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STATISTIC(NumConverted, "Number of aggregates converted to scalar");
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STATISTIC(NumGlobals, "Number of allocas copied from constant global");
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namespace {
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struct SROA : public FunctionPass {
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SROA(int T, bool hasDT, char &ID)
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: FunctionPass(ID), HasDomTree(hasDT) {
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if (T == -1)
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SRThreshold = 128;
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else
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SRThreshold = T;
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}
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bool runOnFunction(Function &F);
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bool performScalarRepl(Function &F);
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bool performPromotion(Function &F);
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private:
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bool HasDomTree;
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TargetData *TD;
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/// DeadInsts - Keep track of instructions we have made dead, so that
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/// we can remove them after we are done working.
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SmallVector<Value*, 32> DeadInsts;
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/// AllocaInfo - When analyzing uses of an alloca instruction, this captures
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/// information about the uses. All these fields are initialized to false
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/// and set to true when something is learned.
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struct AllocaInfo {
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/// The alloca to promote.
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AllocaInst *AI;
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/// CheckedPHIs - This is a set of verified PHI nodes, to prevent infinite
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/// looping and avoid redundant work.
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SmallPtrSet<PHINode*, 8> CheckedPHIs;
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/// isUnsafe - This is set to true if the alloca cannot be SROA'd.
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bool isUnsafe : 1;
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/// isMemCpySrc - This is true if this aggregate is memcpy'd from.
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bool isMemCpySrc : 1;
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/// isMemCpyDst - This is true if this aggregate is memcpy'd into.
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bool isMemCpyDst : 1;
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/// hasSubelementAccess - This is true if a subelement of the alloca is
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/// ever accessed, or false if the alloca is only accessed with mem
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/// intrinsics or load/store that only access the entire alloca at once.
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bool hasSubelementAccess : 1;
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/// hasALoadOrStore - This is true if there are any loads or stores to it.
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/// The alloca may just be accessed with memcpy, for example, which would
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/// not set this.
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bool hasALoadOrStore : 1;
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explicit AllocaInfo(AllocaInst *ai)
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: AI(ai), isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false),
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hasSubelementAccess(false), hasALoadOrStore(false) {}
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};
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unsigned SRThreshold;
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void MarkUnsafe(AllocaInfo &I, Instruction *User) {
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I.isUnsafe = true;
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DEBUG(dbgs() << " Transformation preventing inst: " << *User << '\n');
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}
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bool isSafeAllocaToScalarRepl(AllocaInst *AI);
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void isSafeForScalarRepl(Instruction *I, uint64_t Offset, AllocaInfo &Info);
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void isSafePHISelectUseForScalarRepl(Instruction *User, uint64_t Offset,
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AllocaInfo &Info);
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void isSafeGEP(GetElementPtrInst *GEPI, uint64_t &Offset, AllocaInfo &Info);
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void isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
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Type *MemOpType, bool isStore, AllocaInfo &Info,
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Instruction *TheAccess, bool AllowWholeAccess);
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bool TypeHasComponent(Type *T, uint64_t Offset, uint64_t Size);
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uint64_t FindElementAndOffset(Type *&T, uint64_t &Offset,
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Type *&IdxTy);
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void DoScalarReplacement(AllocaInst *AI,
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std::vector<AllocaInst*> &WorkList);
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void DeleteDeadInstructions();
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void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
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SmallVector<AllocaInst*, 32> &NewElts);
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void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
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SmallVector<AllocaInst*, 32> &NewElts);
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void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
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SmallVector<AllocaInst*, 32> &NewElts);
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void RewriteLifetimeIntrinsic(IntrinsicInst *II, AllocaInst *AI,
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uint64_t Offset,
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SmallVector<AllocaInst*, 32> &NewElts);
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void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
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AllocaInst *AI,
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SmallVector<AllocaInst*, 32> &NewElts);
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void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
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SmallVector<AllocaInst*, 32> &NewElts);
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void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
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SmallVector<AllocaInst*, 32> &NewElts);
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static MemTransferInst *isOnlyCopiedFromConstantGlobal(
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AllocaInst *AI, SmallVector<Instruction*, 4> &ToDelete);
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};
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// SROA_DT - SROA that uses DominatorTree.
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struct SROA_DT : public SROA {
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static char ID;
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public:
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SROA_DT(int T = -1) : SROA(T, true, ID) {
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initializeSROA_DTPass(*PassRegistry::getPassRegistry());
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}
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// getAnalysisUsage - This pass does not require any passes, but we know it
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// will not alter the CFG, so say so.
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<DominatorTree>();
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AU.setPreservesCFG();
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}
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};
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// SROA_SSAUp - SROA that uses SSAUpdater.
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struct SROA_SSAUp : public SROA {
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static char ID;
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public:
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SROA_SSAUp(int T = -1) : SROA(T, false, ID) {
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initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry());
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}
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// getAnalysisUsage - This pass does not require any passes, but we know it
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// will not alter the CFG, so say so.
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesCFG();
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}
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};
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}
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char SROA_DT::ID = 0;
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char SROA_SSAUp::ID = 0;
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INITIALIZE_PASS_BEGIN(SROA_DT, "scalarrepl",
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"Scalar Replacement of Aggregates (DT)", false, false)
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INITIALIZE_PASS_DEPENDENCY(DominatorTree)
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INITIALIZE_PASS_END(SROA_DT, "scalarrepl",
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"Scalar Replacement of Aggregates (DT)", false, false)
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INITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa",
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"Scalar Replacement of Aggregates (SSAUp)", false, false)
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INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa",
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"Scalar Replacement of Aggregates (SSAUp)", false, false)
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// Public interface to the ScalarReplAggregates pass
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FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold,
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bool UseDomTree) {
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if (UseDomTree)
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return new SROA_DT(Threshold);
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return new SROA_SSAUp(Threshold);
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}
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//===----------------------------------------------------------------------===//
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// Convert To Scalar Optimization.
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//===----------------------------------------------------------------------===//
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namespace {
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/// ConvertToScalarInfo - This class implements the "Convert To Scalar"
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/// optimization, which scans the uses of an alloca and determines if it can
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/// rewrite it in terms of a single new alloca that can be mem2reg'd.
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class ConvertToScalarInfo {
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/// AllocaSize - The size of the alloca being considered in bytes.
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unsigned AllocaSize;
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const TargetData &TD;
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/// IsNotTrivial - This is set to true if there is some access to the object
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/// which means that mem2reg can't promote it.
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bool IsNotTrivial;
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/// ScalarKind - Tracks the kind of alloca being considered for promotion,
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/// computed based on the uses of the alloca rather than the LLVM type system.
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enum {
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Unknown,
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// Accesses via GEPs that are consistent with element access of a vector
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// type. This will not be converted into a vector unless there is a later
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// access using an actual vector type.
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ImplicitVector,
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// Accesses via vector operations and GEPs that are consistent with the
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// layout of a vector type.
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Vector,
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// An integer bag-of-bits with bitwise operations for insertion and
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// extraction. Any combination of types can be converted into this kind
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// of scalar.
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Integer
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} ScalarKind;
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/// VectorTy - This tracks the type that we should promote the vector to if
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/// it is possible to turn it into a vector. This starts out null, and if it
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/// isn't possible to turn into a vector type, it gets set to VoidTy.
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VectorType *VectorTy;
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/// HadNonMemTransferAccess - True if there is at least one access to the
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/// alloca that is not a MemTransferInst. We don't want to turn structs into
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/// large integers unless there is some potential for optimization.
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bool HadNonMemTransferAccess;
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public:
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explicit ConvertToScalarInfo(unsigned Size, const TargetData &td)
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: AllocaSize(Size), TD(td), IsNotTrivial(false), ScalarKind(Unknown),
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VectorTy(0), HadNonMemTransferAccess(false) { }
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AllocaInst *TryConvert(AllocaInst *AI);
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private:
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bool CanConvertToScalar(Value *V, uint64_t Offset);
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void MergeInTypeForLoadOrStore(Type *In, uint64_t Offset);
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bool MergeInVectorType(VectorType *VInTy, uint64_t Offset);
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void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
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Value *ConvertScalar_ExtractValue(Value *NV, Type *ToType,
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uint64_t Offset, IRBuilder<> &Builder);
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Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
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uint64_t Offset, IRBuilder<> &Builder);
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};
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} // end anonymous namespace.
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/// TryConvert - Analyze the specified alloca, and if it is safe to do so,
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/// rewrite it to be a new alloca which is mem2reg'able. This returns the new
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/// alloca if possible or null if not.
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AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) {
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// If we can't convert this scalar, or if mem2reg can trivially do it, bail
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// out.
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if (!CanConvertToScalar(AI, 0) || !IsNotTrivial)
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return 0;
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// If an alloca has only memset / memcpy uses, it may still have an Unknown
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// ScalarKind. Treat it as an Integer below.
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if (ScalarKind == Unknown)
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ScalarKind = Integer;
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if (ScalarKind == Vector && VectorTy->getBitWidth() != AllocaSize * 8)
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ScalarKind = Integer;
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// If we were able to find a vector type that can handle this with
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// insert/extract elements, and if there was at least one use that had
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// a vector type, promote this to a vector. We don't want to promote
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// random stuff that doesn't use vectors (e.g. <9 x double>) because then
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// we just get a lot of insert/extracts. If at least one vector is
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// involved, then we probably really do have a union of vector/array.
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Type *NewTy;
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if (ScalarKind == Vector) {
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assert(VectorTy && "Missing type for vector scalar.");
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DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
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<< *VectorTy << '\n');
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NewTy = VectorTy; // Use the vector type.
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} else {
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unsigned BitWidth = AllocaSize * 8;
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if ((ScalarKind == ImplicitVector || ScalarKind == Integer) &&
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!HadNonMemTransferAccess && !TD.fitsInLegalInteger(BitWidth))
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return 0;
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DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
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// Create and insert the integer alloca.
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NewTy = IntegerType::get(AI->getContext(), BitWidth);
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}
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AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
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ConvertUsesToScalar(AI, NewAI, 0);
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return NewAI;
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}
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/// MergeInTypeForLoadOrStore - Add the 'In' type to the accumulated vector type
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/// (VectorTy) so far at the offset specified by Offset (which is specified in
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/// bytes).
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///
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/// There are two cases we handle here:
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/// 1) A union of vector types of the same size and potentially its elements.
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/// Here we turn element accesses into insert/extract element operations.
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/// This promotes a <4 x float> with a store of float to the third element
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/// into a <4 x float> that uses insert element.
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/// 2) A fully general blob of memory, which we turn into some (potentially
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/// large) integer type with extract and insert operations where the loads
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/// and stores would mutate the memory. We mark this by setting VectorTy
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/// to VoidTy.
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void ConvertToScalarInfo::MergeInTypeForLoadOrStore(Type *In,
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uint64_t Offset) {
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// If we already decided to turn this into a blob of integer memory, there is
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// nothing to be done.
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if (ScalarKind == Integer)
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return;
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// If this could be contributing to a vector, analyze it.
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// If the In type is a vector that is the same size as the alloca, see if it
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// matches the existing VecTy.
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if (VectorType *VInTy = dyn_cast<VectorType>(In)) {
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if (MergeInVectorType(VInTy, Offset))
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return;
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} else if (In->isFloatTy() || In->isDoubleTy() ||
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(In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 &&
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isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
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// Full width accesses can be ignored, because they can always be turned
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// into bitcasts.
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unsigned EltSize = In->getPrimitiveSizeInBits()/8;
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if (EltSize == AllocaSize)
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return;
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// If we're accessing something that could be an element of a vector, see
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// if the implied vector agrees with what we already have and if Offset is
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// compatible with it.
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if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 &&
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(!VectorTy || EltSize == VectorTy->getElementType()
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->getPrimitiveSizeInBits()/8)) {
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if (!VectorTy) {
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ScalarKind = ImplicitVector;
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VectorTy = VectorType::get(In, AllocaSize/EltSize);
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}
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return;
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}
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}
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// Otherwise, we have a case that we can't handle with an optimized vector
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// form. We can still turn this into a large integer.
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ScalarKind = Integer;
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}
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/// MergeInVectorType - Handles the vector case of MergeInTypeForLoadOrStore,
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/// returning true if the type was successfully merged and false otherwise.
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bool ConvertToScalarInfo::MergeInVectorType(VectorType *VInTy,
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uint64_t Offset) {
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if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
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// If we're storing/loading a vector of the right size, allow it as a
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// vector. If this the first vector we see, remember the type so that
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// we know the element size. If this is a subsequent access, ignore it
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// even if it is a differing type but the same size. Worst case we can
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// bitcast the resultant vectors.
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if (!VectorTy)
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VectorTy = VInTy;
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ScalarKind = Vector;
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return true;
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}
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return false;
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}
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/// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
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/// its accesses to a single vector type, return true and set VecTy to
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/// the new type. If we could convert the alloca into a single promotable
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/// integer, return true but set VecTy to VoidTy. Further, if the use is not a
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/// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
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/// is the current offset from the base of the alloca being analyzed.
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///
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/// If we see at least one access to the value that is as a vector type, set the
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/// SawVec flag.
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bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) {
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for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
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Instruction *User = cast<Instruction>(*UI);
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if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
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// Don't break volatile loads.
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if (!LI->isSimple())
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return false;
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// Don't touch MMX operations.
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if (LI->getType()->isX86_MMXTy())
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return false;
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HadNonMemTransferAccess = true;
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MergeInTypeForLoadOrStore(LI->getType(), Offset);
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continue;
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}
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if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
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// Storing the pointer, not into the value?
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if (SI->getOperand(0) == V || !SI->isSimple()) return false;
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// Don't touch MMX operations.
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if (SI->getOperand(0)->getType()->isX86_MMXTy())
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return false;
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HadNonMemTransferAccess = true;
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MergeInTypeForLoadOrStore(SI->getOperand(0)->getType(), Offset);
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continue;
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}
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if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
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if (!onlyUsedByLifetimeMarkers(BCI))
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IsNotTrivial = true; // Can't be mem2reg'd.
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if (!CanConvertToScalar(BCI, Offset))
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return false;
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continue;
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}
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if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
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// If this is a GEP with a variable indices, we can't handle it.
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if (!GEP->hasAllConstantIndices())
|
|
return false;
|
|
|
|
// Compute the offset that this GEP adds to the pointer.
|
|
SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
|
|
if (!GEP->getPointerOperandType()->isPointerTy())
|
|
return false;
|
|
uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
|
|
Indices);
|
|
// See if all uses can be converted.
|
|
if (!CanConvertToScalar(GEP, Offset+GEPOffset))
|
|
return false;
|
|
IsNotTrivial = true; // Can't be mem2reg'd.
|
|
HadNonMemTransferAccess = true;
|
|
continue;
|
|
}
|
|
|
|
// If this is a constant sized memset of a constant value (e.g. 0) we can
|
|
// handle it.
|
|
if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
|
|
// Store of constant value.
|
|
if (!isa<ConstantInt>(MSI->getValue()))
|
|
return false;
|
|
|
|
// Store of constant size.
|
|
ConstantInt *Len = dyn_cast<ConstantInt>(MSI->getLength());
|
|
if (!Len)
|
|
return false;
|
|
|
|
// If the size differs from the alloca, we can only convert the alloca to
|
|
// an integer bag-of-bits.
|
|
// FIXME: This should handle all of the cases that are currently accepted
|
|
// as vector element insertions.
|
|
if (Len->getZExtValue() != AllocaSize || Offset != 0)
|
|
ScalarKind = Integer;
|
|
|
|
IsNotTrivial = true; // Can't be mem2reg'd.
|
|
HadNonMemTransferAccess = true;
|
|
continue;
|
|
}
|
|
|
|
// If this is a memcpy or memmove into or out of the whole allocation, we
|
|
// can handle it like a load or store of the scalar type.
|
|
if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
|
|
ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength());
|
|
if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0)
|
|
return false;
|
|
|
|
IsNotTrivial = true; // Can't be mem2reg'd.
|
|
continue;
|
|
}
|
|
|
|
// If this is a lifetime intrinsic, we can handle it.
|
|
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
|
|
if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
|
|
II->getIntrinsicID() == Intrinsic::lifetime_end) {
|
|
continue;
|
|
}
|
|
}
|
|
|
|
// Otherwise, we cannot handle this!
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
|
|
/// directly. This happens when we are converting an "integer union" to a
|
|
/// single integer scalar, or when we are converting a "vector union" to a
|
|
/// vector with insert/extractelement instructions.
|
|
///
|
|
/// Offset is an offset from the original alloca, in bits that need to be
|
|
/// shifted to the right. By the end of this, there should be no uses of Ptr.
|
|
void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI,
|
|
uint64_t Offset) {
|
|
while (!Ptr->use_empty()) {
|
|
Instruction *User = cast<Instruction>(Ptr->use_back());
|
|
|
|
if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
|
|
ConvertUsesToScalar(CI, NewAI, Offset);
|
|
CI->eraseFromParent();
|
|
continue;
|
|
}
|
|
|
|
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
|
|
// Compute the offset that this GEP adds to the pointer.
|
|
SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
|
|
uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
|
|
Indices);
|
|
ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
|
|
GEP->eraseFromParent();
|
|
continue;
|
|
}
|
|
|
|
IRBuilder<> Builder(User);
|
|
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
|
|
// The load is a bit extract from NewAI shifted right by Offset bits.
|
|
Value *LoadedVal = Builder.CreateLoad(NewAI);
|
|
Value *NewLoadVal
|
|
= ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
|
|
LI->replaceAllUsesWith(NewLoadVal);
|
|
LI->eraseFromParent();
|
|
continue;
|
|
}
|
|
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
|
|
assert(SI->getOperand(0) != Ptr && "Consistency error!");
|
|
Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
|
|
Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
|
|
Builder);
|
|
Builder.CreateStore(New, NewAI);
|
|
SI->eraseFromParent();
|
|
|
|
// If the load we just inserted is now dead, then the inserted store
|
|
// overwrote the entire thing.
|
|
if (Old->use_empty())
|
|
Old->eraseFromParent();
|
|
continue;
|
|
}
|
|
|
|
// If this is a constant sized memset of a constant value (e.g. 0) we can
|
|
// transform it into a store of the expanded constant value.
|
|
if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
|
|
assert(MSI->getRawDest() == Ptr && "Consistency error!");
|
|
unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
|
|
if (NumBytes != 0) {
|
|
unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
|
|
|
|
// Compute the value replicated the right number of times.
|
|
APInt APVal(NumBytes*8, Val);
|
|
|
|
// Splat the value if non-zero.
|
|
if (Val)
|
|
for (unsigned i = 1; i != NumBytes; ++i)
|
|
APVal |= APVal << 8;
|
|
|
|
Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
|
|
Value *New = ConvertScalar_InsertValue(
|
|
ConstantInt::get(User->getContext(), APVal),
|
|
Old, Offset, Builder);
|
|
Builder.CreateStore(New, NewAI);
|
|
|
|
// If the load we just inserted is now dead, then the memset overwrote
|
|
// the entire thing.
|
|
if (Old->use_empty())
|
|
Old->eraseFromParent();
|
|
}
|
|
MSI->eraseFromParent();
|
|
continue;
|
|
}
|
|
|
|
// If this is a memcpy or memmove into or out of the whole allocation, we
|
|
// can handle it like a load or store of the scalar type.
|
|
if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
|
|
assert(Offset == 0 && "must be store to start of alloca");
|
|
|
|
// If the source and destination are both to the same alloca, then this is
|
|
// a noop copy-to-self, just delete it. Otherwise, emit a load and store
|
|
// as appropriate.
|
|
AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, &TD, 0));
|
|
|
|
if (GetUnderlyingObject(MTI->getSource(), &TD, 0) != OrigAI) {
|
|
// Dest must be OrigAI, change this to be a load from the original
|
|
// pointer (bitcasted), then a store to our new alloca.
|
|
assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
|
|
Value *SrcPtr = MTI->getSource();
|
|
PointerType* SPTy = cast<PointerType>(SrcPtr->getType());
|
|
PointerType* AIPTy = cast<PointerType>(NewAI->getType());
|
|
if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
|
|
AIPTy = PointerType::get(AIPTy->getElementType(),
|
|
SPTy->getAddressSpace());
|
|
}
|
|
SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy);
|
|
|
|
LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
|
|
SrcVal->setAlignment(MTI->getAlignment());
|
|
Builder.CreateStore(SrcVal, NewAI);
|
|
} else if (GetUnderlyingObject(MTI->getDest(), &TD, 0) != OrigAI) {
|
|
// Src must be OrigAI, change this to be a load from NewAI then a store
|
|
// through the original dest pointer (bitcasted).
|
|
assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
|
|
LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
|
|
|
|
PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType());
|
|
PointerType* AIPTy = cast<PointerType>(NewAI->getType());
|
|
if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
|
|
AIPTy = PointerType::get(AIPTy->getElementType(),
|
|
DPTy->getAddressSpace());
|
|
}
|
|
Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy);
|
|
|
|
StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
|
|
NewStore->setAlignment(MTI->getAlignment());
|
|
} else {
|
|
// Noop transfer. Src == Dst
|
|
}
|
|
|
|
MTI->eraseFromParent();
|
|
continue;
|
|
}
|
|
|
|
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
|
|
if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
|
|
II->getIntrinsicID() == Intrinsic::lifetime_end) {
|
|
// There's no need to preserve these, as the resulting alloca will be
|
|
// converted to a register anyways.
|
|
II->eraseFromParent();
|
|
continue;
|
|
}
|
|
}
|
|
|
|
llvm_unreachable("Unsupported operation!");
|
|
}
|
|
}
|
|
|
|
/// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
|
|
/// or vector value FromVal, extracting the bits from the offset specified by
|
|
/// Offset. This returns the value, which is of type ToType.
|
|
///
|
|
/// This happens when we are converting an "integer union" to a single
|
|
/// integer scalar, or when we are converting a "vector union" to a vector with
|
|
/// insert/extractelement instructions.
|
|
///
|
|
/// Offset is an offset from the original alloca, in bits that need to be
|
|
/// shifted to the right.
|
|
Value *ConvertToScalarInfo::
|
|
ConvertScalar_ExtractValue(Value *FromVal, Type *ToType,
|
|
uint64_t Offset, IRBuilder<> &Builder) {
|
|
// If the load is of the whole new alloca, no conversion is needed.
|
|
Type *FromType = FromVal->getType();
|
|
if (FromType == ToType && Offset == 0)
|
|
return FromVal;
|
|
|
|
// If the result alloca is a vector type, this is either an element
|
|
// access or a bitcast to another vector type of the same size.
|
|
if (VectorType *VTy = dyn_cast<VectorType>(FromType)) {
|
|
unsigned FromTypeSize = TD.getTypeAllocSize(FromType);
|
|
unsigned ToTypeSize = TD.getTypeAllocSize(ToType);
|
|
if (FromTypeSize == ToTypeSize)
|
|
return Builder.CreateBitCast(FromVal, ToType);
|
|
|
|
// Otherwise it must be an element access.
|
|
unsigned Elt = 0;
|
|
if (Offset) {
|
|
unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
|
|
Elt = Offset/EltSize;
|
|
assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
|
|
}
|
|
// Return the element extracted out of it.
|
|
Value *V = Builder.CreateExtractElement(FromVal, Builder.getInt32(Elt));
|
|
if (V->getType() != ToType)
|
|
V = Builder.CreateBitCast(V, ToType);
|
|
return V;
|
|
}
|
|
|
|
// If ToType is a first class aggregate, extract out each of the pieces and
|
|
// use insertvalue's to form the FCA.
|
|
if (StructType *ST = dyn_cast<StructType>(ToType)) {
|
|
const StructLayout &Layout = *TD.getStructLayout(ST);
|
|
Value *Res = UndefValue::get(ST);
|
|
for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
|
|
Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
|
|
Offset+Layout.getElementOffsetInBits(i),
|
|
Builder);
|
|
Res = Builder.CreateInsertValue(Res, Elt, i);
|
|
}
|
|
return Res;
|
|
}
|
|
|
|
if (ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
|
|
uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
|
|
Value *Res = UndefValue::get(AT);
|
|
for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
|
|
Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
|
|
Offset+i*EltSize, Builder);
|
|
Res = Builder.CreateInsertValue(Res, Elt, i);
|
|
}
|
|
return Res;
|
|
}
|
|
|
|
// Otherwise, this must be a union that was converted to an integer value.
|
|
IntegerType *NTy = cast<IntegerType>(FromVal->getType());
|
|
|
|
// If this is a big-endian system and the load is narrower than the
|
|
// full alloca type, we need to do a shift to get the right bits.
|
|
int ShAmt = 0;
|
|
if (TD.isBigEndian()) {
|
|
// On big-endian machines, the lowest bit is stored at the bit offset
|
|
// from the pointer given by getTypeStoreSizeInBits. This matters for
|
|
// integers with a bitwidth that is not a multiple of 8.
|
|
ShAmt = TD.getTypeStoreSizeInBits(NTy) -
|
|
TD.getTypeStoreSizeInBits(ToType) - Offset;
|
|
} else {
|
|
ShAmt = Offset;
|
|
}
|
|
|
|
// Note: we support negative bitwidths (with shl) which are not defined.
|
|
// We do this to support (f.e.) loads off the end of a structure where
|
|
// only some bits are used.
|
|
if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
|
|
FromVal = Builder.CreateLShr(FromVal,
|
|
ConstantInt::get(FromVal->getType(), ShAmt));
|
|
else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
|
|
FromVal = Builder.CreateShl(FromVal,
|
|
ConstantInt::get(FromVal->getType(), -ShAmt));
|
|
|
|
// Finally, unconditionally truncate the integer to the right width.
|
|
unsigned LIBitWidth = TD.getTypeSizeInBits(ToType);
|
|
if (LIBitWidth < NTy->getBitWidth())
|
|
FromVal =
|
|
Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
|
|
LIBitWidth));
|
|
else if (LIBitWidth > NTy->getBitWidth())
|
|
FromVal =
|
|
Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
|
|
LIBitWidth));
|
|
|
|
// If the result is an integer, this is a trunc or bitcast.
|
|
if (ToType->isIntegerTy()) {
|
|
// Should be done.
|
|
} else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) {
|
|
// Just do a bitcast, we know the sizes match up.
|
|
FromVal = Builder.CreateBitCast(FromVal, ToType);
|
|
} else {
|
|
// Otherwise must be a pointer.
|
|
FromVal = Builder.CreateIntToPtr(FromVal, ToType);
|
|
}
|
|
assert(FromVal->getType() == ToType && "Didn't convert right?");
|
|
return FromVal;
|
|
}
|
|
|
|
/// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
|
|
/// or vector value "Old" at the offset specified by Offset.
|
|
///
|
|
/// This happens when we are converting an "integer union" to a
|
|
/// single integer scalar, or when we are converting a "vector union" to a
|
|
/// vector with insert/extractelement instructions.
|
|
///
|
|
/// Offset is an offset from the original alloca, in bits that need to be
|
|
/// shifted to the right.
|
|
Value *ConvertToScalarInfo::
|
|
ConvertScalar_InsertValue(Value *SV, Value *Old,
|
|
uint64_t Offset, IRBuilder<> &Builder) {
|
|
// Convert the stored type to the actual type, shift it left to insert
|
|
// then 'or' into place.
|
|
Type *AllocaType = Old->getType();
|
|
LLVMContext &Context = Old->getContext();
|
|
|
|
if (VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
|
|
uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy);
|
|
uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType());
|
|
|
|
// Changing the whole vector with memset or with an access of a different
|
|
// vector type?
|
|
if (ValSize == VecSize)
|
|
return Builder.CreateBitCast(SV, AllocaType);
|
|
|
|
// Must be an element insertion.
|
|
Type *EltTy = VTy->getElementType();
|
|
if (SV->getType() != EltTy)
|
|
SV = Builder.CreateBitCast(SV, EltTy);
|
|
uint64_t EltSize = TD.getTypeAllocSizeInBits(EltTy);
|
|
unsigned Elt = Offset/EltSize;
|
|
return Builder.CreateInsertElement(Old, SV, Builder.getInt32(Elt));
|
|
}
|
|
|
|
// If SV is a first-class aggregate value, insert each value recursively.
|
|
if (StructType *ST = dyn_cast<StructType>(SV->getType())) {
|
|
const StructLayout &Layout = *TD.getStructLayout(ST);
|
|
for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
|
|
Value *Elt = Builder.CreateExtractValue(SV, i);
|
|
Old = ConvertScalar_InsertValue(Elt, Old,
|
|
Offset+Layout.getElementOffsetInBits(i),
|
|
Builder);
|
|
}
|
|
return Old;
|
|
}
|
|
|
|
if (ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
|
|
uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
|
|
for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
|
|
Value *Elt = Builder.CreateExtractValue(SV, i);
|
|
Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
|
|
}
|
|
return Old;
|
|
}
|
|
|
|
// If SV is a float, convert it to the appropriate integer type.
|
|
// If it is a pointer, do the same.
|
|
unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType());
|
|
unsigned DestWidth = TD.getTypeSizeInBits(AllocaType);
|
|
unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType());
|
|
unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType);
|
|
if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy())
|
|
SV = Builder.CreateBitCast(SV, IntegerType::get(SV->getContext(),SrcWidth));
|
|
else if (SV->getType()->isPointerTy())
|
|
SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()));
|
|
|
|
// Zero extend or truncate the value if needed.
|
|
if (SV->getType() != AllocaType) {
|
|
if (SV->getType()->getPrimitiveSizeInBits() <
|
|
AllocaType->getPrimitiveSizeInBits())
|
|
SV = Builder.CreateZExt(SV, AllocaType);
|
|
else {
|
|
// Truncation may be needed if storing more than the alloca can hold
|
|
// (undefined behavior).
|
|
SV = Builder.CreateTrunc(SV, AllocaType);
|
|
SrcWidth = DestWidth;
|
|
SrcStoreWidth = DestStoreWidth;
|
|
}
|
|
}
|
|
|
|
// If this is a big-endian system and the store is narrower than the
|
|
// full alloca type, we need to do a shift to get the right bits.
|
|
int ShAmt = 0;
|
|
if (TD.isBigEndian()) {
|
|
// On big-endian machines, the lowest bit is stored at the bit offset
|
|
// from the pointer given by getTypeStoreSizeInBits. This matters for
|
|
// integers with a bitwidth that is not a multiple of 8.
|
|
ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
|
|
} else {
|
|
ShAmt = Offset;
|
|
}
|
|
|
|
// Note: we support negative bitwidths (with shr) which are not defined.
|
|
// We do this to support (f.e.) stores off the end of a structure where
|
|
// only some bits in the structure are set.
|
|
APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
|
|
if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
|
|
SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), ShAmt));
|
|
Mask <<= ShAmt;
|
|
} else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
|
|
SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), -ShAmt));
|
|
Mask = Mask.lshr(-ShAmt);
|
|
}
|
|
|
|
// Mask out the bits we are about to insert from the old value, and or
|
|
// in the new bits.
|
|
if (SrcWidth != DestWidth) {
|
|
assert(DestWidth > SrcWidth);
|
|
Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
|
|
SV = Builder.CreateOr(Old, SV, "ins");
|
|
}
|
|
return SV;
|
|
}
|
|
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// SRoA Driver
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
|
|
bool SROA::runOnFunction(Function &F) {
|
|
TD = getAnalysisIfAvailable<TargetData>();
|
|
|
|
bool Changed = performPromotion(F);
|
|
|
|
// FIXME: ScalarRepl currently depends on TargetData more than it
|
|
// theoretically needs to. It should be refactored in order to support
|
|
// target-independent IR. Until this is done, just skip the actual
|
|
// scalar-replacement portion of this pass.
|
|
if (!TD) return Changed;
|
|
|
|
while (1) {
|
|
bool LocalChange = performScalarRepl(F);
|
|
if (!LocalChange) break; // No need to repromote if no scalarrepl
|
|
Changed = true;
|
|
LocalChange = performPromotion(F);
|
|
if (!LocalChange) break; // No need to re-scalarrepl if no promotion
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
namespace {
|
|
class AllocaPromoter : public LoadAndStorePromoter {
|
|
AllocaInst *AI;
|
|
DIBuilder *DIB;
|
|
SmallVector<DbgDeclareInst *, 4> DDIs;
|
|
SmallVector<DbgValueInst *, 4> DVIs;
|
|
public:
|
|
AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S,
|
|
DIBuilder *DB)
|
|
: LoadAndStorePromoter(Insts, S), AI(0), DIB(DB) {}
|
|
|
|
void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) {
|
|
// Remember which alloca we're promoting (for isInstInList).
|
|
this->AI = AI;
|
|
if (MDNode *DebugNode = MDNode::getIfExists(AI->getContext(), AI)) {
|
|
for (Value::use_iterator UI = DebugNode->use_begin(),
|
|
E = DebugNode->use_end(); UI != E; ++UI)
|
|
if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(*UI))
|
|
DDIs.push_back(DDI);
|
|
else if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(*UI))
|
|
DVIs.push_back(DVI);
|
|
}
|
|
|
|
LoadAndStorePromoter::run(Insts);
|
|
AI->eraseFromParent();
|
|
for (SmallVector<DbgDeclareInst *, 4>::iterator I = DDIs.begin(),
|
|
E = DDIs.end(); I != E; ++I) {
|
|
DbgDeclareInst *DDI = *I;
|
|
DDI->eraseFromParent();
|
|
}
|
|
for (SmallVector<DbgValueInst *, 4>::iterator I = DVIs.begin(),
|
|
E = DVIs.end(); I != E; ++I) {
|
|
DbgValueInst *DVI = *I;
|
|
DVI->eraseFromParent();
|
|
}
|
|
}
|
|
|
|
virtual bool isInstInList(Instruction *I,
|
|
const SmallVectorImpl<Instruction*> &Insts) const {
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(I))
|
|
return LI->getOperand(0) == AI;
|
|
return cast<StoreInst>(I)->getPointerOperand() == AI;
|
|
}
|
|
|
|
virtual void updateDebugInfo(Instruction *Inst) const {
|
|
for (SmallVector<DbgDeclareInst *, 4>::const_iterator I = DDIs.begin(),
|
|
E = DDIs.end(); I != E; ++I) {
|
|
DbgDeclareInst *DDI = *I;
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
|
|
ConvertDebugDeclareToDebugValue(DDI, SI, *DIB);
|
|
else if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
|
|
ConvertDebugDeclareToDebugValue(DDI, LI, *DIB);
|
|
}
|
|
for (SmallVector<DbgValueInst *, 4>::const_iterator I = DVIs.begin(),
|
|
E = DVIs.end(); I != E; ++I) {
|
|
DbgValueInst *DVI = *I;
|
|
Value *Arg = NULL;
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
|
|
// If an argument is zero extended then use argument directly. The ZExt
|
|
// may be zapped by an optimization pass in future.
|
|
if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
|
|
Arg = dyn_cast<Argument>(ZExt->getOperand(0));
|
|
if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
|
|
Arg = dyn_cast<Argument>(SExt->getOperand(0));
|
|
if (!Arg)
|
|
Arg = SI->getOperand(0);
|
|
} else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
|
|
Arg = LI->getOperand(0);
|
|
} else {
|
|
continue;
|
|
}
|
|
Instruction *DbgVal =
|
|
DIB->insertDbgValueIntrinsic(Arg, 0, DIVariable(DVI->getVariable()),
|
|
Inst);
|
|
DbgVal->setDebugLoc(DVI->getDebugLoc());
|
|
}
|
|
}
|
|
};
|
|
} // end anon namespace
|
|
|
|
/// isSafeSelectToSpeculate - Select instructions that use an alloca and are
|
|
/// subsequently loaded can be rewritten to load both input pointers and then
|
|
/// select between the result, allowing the load of the alloca to be promoted.
|
|
/// From this:
|
|
/// %P2 = select i1 %cond, i32* %Alloca, i32* %Other
|
|
/// %V = load i32* %P2
|
|
/// to:
|
|
/// %V1 = load i32* %Alloca -> will be mem2reg'd
|
|
/// %V2 = load i32* %Other
|
|
/// %V = select i1 %cond, i32 %V1, i32 %V2
|
|
///
|
|
/// We can do this to a select if its only uses are loads and if the operand to
|
|
/// the select can be loaded unconditionally.
|
|
static bool isSafeSelectToSpeculate(SelectInst *SI, const TargetData *TD) {
|
|
bool TDerefable = SI->getTrueValue()->isDereferenceablePointer();
|
|
bool FDerefable = SI->getFalseValue()->isDereferenceablePointer();
|
|
|
|
for (Value::use_iterator UI = SI->use_begin(), UE = SI->use_end();
|
|
UI != UE; ++UI) {
|
|
LoadInst *LI = dyn_cast<LoadInst>(*UI);
|
|
if (LI == 0 || !LI->isSimple()) return false;
|
|
|
|
// Both operands to the select need to be dereferencable, either absolutely
|
|
// (e.g. allocas) or at this point because we can see other accesses to it.
|
|
if (!TDerefable && !isSafeToLoadUnconditionally(SI->getTrueValue(), LI,
|
|
LI->getAlignment(), TD))
|
|
return false;
|
|
if (!FDerefable && !isSafeToLoadUnconditionally(SI->getFalseValue(), LI,
|
|
LI->getAlignment(), TD))
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/// isSafePHIToSpeculate - PHI instructions that use an alloca and are
|
|
/// subsequently loaded can be rewritten to load both input pointers in the pred
|
|
/// blocks and then PHI the results, allowing the load of the alloca to be
|
|
/// promoted.
|
|
/// From this:
|
|
/// %P2 = phi [i32* %Alloca, i32* %Other]
|
|
/// %V = load i32* %P2
|
|
/// to:
|
|
/// %V1 = load i32* %Alloca -> will be mem2reg'd
|
|
/// ...
|
|
/// %V2 = load i32* %Other
|
|
/// ...
|
|
/// %V = phi [i32 %V1, i32 %V2]
|
|
///
|
|
/// We can do this to a select if its only uses are loads and if the operand to
|
|
/// the select can be loaded unconditionally.
|
|
static bool isSafePHIToSpeculate(PHINode *PN, const TargetData *TD) {
|
|
// For now, we can only do this promotion if the load is in the same block as
|
|
// the PHI, and if there are no stores between the phi and load.
|
|
// TODO: Allow recursive phi users.
|
|
// TODO: Allow stores.
|
|
BasicBlock *BB = PN->getParent();
|
|
unsigned MaxAlign = 0;
|
|
for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end();
|
|
UI != UE; ++UI) {
|
|
LoadInst *LI = dyn_cast<LoadInst>(*UI);
|
|
if (LI == 0 || !LI->isSimple()) return false;
|
|
|
|
// For now we only allow loads in the same block as the PHI. This is a
|
|
// common case that happens when instcombine merges two loads through a PHI.
|
|
if (LI->getParent() != BB) return false;
|
|
|
|
// Ensure that there are no instructions between the PHI and the load that
|
|
// could store.
|
|
for (BasicBlock::iterator BBI = PN; &*BBI != LI; ++BBI)
|
|
if (BBI->mayWriteToMemory())
|
|
return false;
|
|
|
|
MaxAlign = std::max(MaxAlign, LI->getAlignment());
|
|
}
|
|
|
|
// Okay, we know that we have one or more loads in the same block as the PHI.
|
|
// We can transform this if it is safe to push the loads into the predecessor
|
|
// blocks. The only thing to watch out for is that we can't put a possibly
|
|
// trapping load in the predecessor if it is a critical edge.
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
|
|
BasicBlock *Pred = PN->getIncomingBlock(i);
|
|
Value *InVal = PN->getIncomingValue(i);
|
|
|
|
// If the terminator of the predecessor has side-effects (an invoke),
|
|
// there is no safe place to put a load in the predecessor.
|
|
if (Pred->getTerminator()->mayHaveSideEffects())
|
|
return false;
|
|
|
|
// If the value is produced by the terminator of the predecessor
|
|
// (an invoke), there is no valid place to put a load in the predecessor.
|
|
if (Pred->getTerminator() == InVal)
|
|
return false;
|
|
|
|
// If the predecessor has a single successor, then the edge isn't critical.
|
|
if (Pred->getTerminator()->getNumSuccessors() == 1)
|
|
continue;
|
|
|
|
// If this pointer is always safe to load, or if we can prove that there is
|
|
// already a load in the block, then we can move the load to the pred block.
|
|
if (InVal->isDereferenceablePointer() ||
|
|
isSafeToLoadUnconditionally(InVal, Pred->getTerminator(), MaxAlign, TD))
|
|
continue;
|
|
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
|
|
/// tryToMakeAllocaBePromotable - This returns true if the alloca only has
|
|
/// direct (non-volatile) loads and stores to it. If the alloca is close but
|
|
/// not quite there, this will transform the code to allow promotion. As such,
|
|
/// it is a non-pure predicate.
|
|
static bool tryToMakeAllocaBePromotable(AllocaInst *AI, const TargetData *TD) {
|
|
SetVector<Instruction*, SmallVector<Instruction*, 4>,
|
|
SmallPtrSet<Instruction*, 4> > InstsToRewrite;
|
|
|
|
for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end();
|
|
UI != UE; ++UI) {
|
|
User *U = *UI;
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
|
|
if (!LI->isSimple())
|
|
return false;
|
|
continue;
|
|
}
|
|
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
|
|
if (SI->getOperand(0) == AI || !SI->isSimple())
|
|
return false; // Don't allow a store OF the AI, only INTO the AI.
|
|
continue;
|
|
}
|
|
|
|
if (SelectInst *SI = dyn_cast<SelectInst>(U)) {
|
|
// If the condition being selected on is a constant, fold the select, yes
|
|
// this does (rarely) happen early on.
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition())) {
|
|
Value *Result = SI->getOperand(1+CI->isZero());
|
|
SI->replaceAllUsesWith(Result);
|
|
SI->eraseFromParent();
|
|
|
|
// This is very rare and we just scrambled the use list of AI, start
|
|
// over completely.
|
|
return tryToMakeAllocaBePromotable(AI, TD);
|
|
}
|
|
|
|
// If it is safe to turn "load (select c, AI, ptr)" into a select of two
|
|
// loads, then we can transform this by rewriting the select.
|
|
if (!isSafeSelectToSpeculate(SI, TD))
|
|
return false;
|
|
|
|
InstsToRewrite.insert(SI);
|
|
continue;
|
|
}
|
|
|
|
if (PHINode *PN = dyn_cast<PHINode>(U)) {
|
|
if (PN->use_empty()) { // Dead PHIs can be stripped.
|
|
InstsToRewrite.insert(PN);
|
|
continue;
|
|
}
|
|
|
|
// If it is safe to turn "load (phi [AI, ptr, ...])" into a PHI of loads
|
|
// in the pred blocks, then we can transform this by rewriting the PHI.
|
|
if (!isSafePHIToSpeculate(PN, TD))
|
|
return false;
|
|
|
|
InstsToRewrite.insert(PN);
|
|
continue;
|
|
}
|
|
|
|
if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
|
|
if (onlyUsedByLifetimeMarkers(BCI)) {
|
|
InstsToRewrite.insert(BCI);
|
|
continue;
|
|
}
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
// If there are no instructions to rewrite, then all uses are load/stores and
|
|
// we're done!
|
|
if (InstsToRewrite.empty())
|
|
return true;
|
|
|
|
// If we have instructions that need to be rewritten for this to be promotable
|
|
// take care of it now.
|
|
for (unsigned i = 0, e = InstsToRewrite.size(); i != e; ++i) {
|
|
if (BitCastInst *BCI = dyn_cast<BitCastInst>(InstsToRewrite[i])) {
|
|
// This could only be a bitcast used by nothing but lifetime intrinsics.
|
|
for (BitCastInst::use_iterator I = BCI->use_begin(), E = BCI->use_end();
|
|
I != E;) {
|
|
Use &U = I.getUse();
|
|
++I;
|
|
cast<Instruction>(U.getUser())->eraseFromParent();
|
|
}
|
|
BCI->eraseFromParent();
|
|
continue;
|
|
}
|
|
|
|
if (SelectInst *SI = dyn_cast<SelectInst>(InstsToRewrite[i])) {
|
|
// Selects in InstsToRewrite only have load uses. Rewrite each as two
|
|
// loads with a new select.
|
|
while (!SI->use_empty()) {
|
|
LoadInst *LI = cast<LoadInst>(SI->use_back());
|
|
|
|
IRBuilder<> Builder(LI);
|
|
LoadInst *TrueLoad =
|
|
Builder.CreateLoad(SI->getTrueValue(), LI->getName()+".t");
|
|
LoadInst *FalseLoad =
|
|
Builder.CreateLoad(SI->getFalseValue(), LI->getName()+".f");
|
|
|
|
// Transfer alignment and TBAA info if present.
|
|
TrueLoad->setAlignment(LI->getAlignment());
|
|
FalseLoad->setAlignment(LI->getAlignment());
|
|
if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) {
|
|
TrueLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
|
|
FalseLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
|
|
}
|
|
|
|
Value *V = Builder.CreateSelect(SI->getCondition(), TrueLoad, FalseLoad);
|
|
V->takeName(LI);
|
|
LI->replaceAllUsesWith(V);
|
|
LI->eraseFromParent();
|
|
}
|
|
|
|
// Now that all the loads are gone, the select is gone too.
|
|
SI->eraseFromParent();
|
|
continue;
|
|
}
|
|
|
|
// Otherwise, we have a PHI node which allows us to push the loads into the
|
|
// predecessors.
|
|
PHINode *PN = cast<PHINode>(InstsToRewrite[i]);
|
|
if (PN->use_empty()) {
|
|
PN->eraseFromParent();
|
|
continue;
|
|
}
|
|
|
|
Type *LoadTy = cast<PointerType>(PN->getType())->getElementType();
|
|
PHINode *NewPN = PHINode::Create(LoadTy, PN->getNumIncomingValues(),
|
|
PN->getName()+".ld", PN);
|
|
|
|
// Get the TBAA tag and alignment to use from one of the loads. It doesn't
|
|
// matter which one we get and if any differ, it doesn't matter.
|
|
LoadInst *SomeLoad = cast<LoadInst>(PN->use_back());
|
|
MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa);
|
|
unsigned Align = SomeLoad->getAlignment();
|
|
|
|
// Rewrite all loads of the PN to use the new PHI.
|
|
while (!PN->use_empty()) {
|
|
LoadInst *LI = cast<LoadInst>(PN->use_back());
|
|
LI->replaceAllUsesWith(NewPN);
|
|
LI->eraseFromParent();
|
|
}
|
|
|
|
// Inject loads into all of the pred blocks. Keep track of which blocks we
|
|
// insert them into in case we have multiple edges from the same block.
|
|
DenseMap<BasicBlock*, LoadInst*> InsertedLoads;
|
|
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
|
|
BasicBlock *Pred = PN->getIncomingBlock(i);
|
|
LoadInst *&Load = InsertedLoads[Pred];
|
|
if (Load == 0) {
|
|
Load = new LoadInst(PN->getIncomingValue(i),
|
|
PN->getName() + "." + Pred->getName(),
|
|
Pred->getTerminator());
|
|
Load->setAlignment(Align);
|
|
if (TBAATag) Load->setMetadata(LLVMContext::MD_tbaa, TBAATag);
|
|
}
|
|
|
|
NewPN->addIncoming(Load, Pred);
|
|
}
|
|
|
|
PN->eraseFromParent();
|
|
}
|
|
|
|
++NumAdjusted;
|
|
return true;
|
|
}
|
|
|
|
bool SROA::performPromotion(Function &F) {
|
|
std::vector<AllocaInst*> Allocas;
|
|
DominatorTree *DT = 0;
|
|
if (HasDomTree)
|
|
DT = &getAnalysis<DominatorTree>();
|
|
|
|
BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
|
|
DIBuilder DIB(*F.getParent());
|
|
bool Changed = false;
|
|
SmallVector<Instruction*, 64> Insts;
|
|
while (1) {
|
|
Allocas.clear();
|
|
|
|
// Find allocas that are safe to promote, by looking at all instructions in
|
|
// the entry node
|
|
for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
|
|
if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
|
|
if (tryToMakeAllocaBePromotable(AI, TD))
|
|
Allocas.push_back(AI);
|
|
|
|
if (Allocas.empty()) break;
|
|
|
|
if (HasDomTree)
|
|
PromoteMemToReg(Allocas, *DT);
|
|
else {
|
|
SSAUpdater SSA;
|
|
for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
|
|
AllocaInst *AI = Allocas[i];
|
|
|
|
// Build list of instructions to promote.
|
|
for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
|
|
UI != E; ++UI)
|
|
Insts.push_back(cast<Instruction>(*UI));
|
|
AllocaPromoter(Insts, SSA, &DIB).run(AI, Insts);
|
|
Insts.clear();
|
|
}
|
|
}
|
|
NumPromoted += Allocas.size();
|
|
Changed = true;
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
|
|
/// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for
|
|
/// SROA. It must be a struct or array type with a small number of elements.
|
|
static bool ShouldAttemptScalarRepl(AllocaInst *AI) {
|
|
Type *T = AI->getAllocatedType();
|
|
// Do not promote any struct into more than 32 separate vars.
|
|
if (StructType *ST = dyn_cast<StructType>(T))
|
|
return ST->getNumElements() <= 32;
|
|
// Arrays are much less likely to be safe for SROA; only consider
|
|
// them if they are very small.
|
|
if (ArrayType *AT = dyn_cast<ArrayType>(T))
|
|
return AT->getNumElements() <= 8;
|
|
return false;
|
|
}
|
|
|
|
|
|
// performScalarRepl - This algorithm is a simple worklist driven algorithm,
|
|
// which runs on all of the alloca instructions in the function, removing them
|
|
// if they are only used by getelementptr instructions.
|
|
//
|
|
bool SROA::performScalarRepl(Function &F) {
|
|
std::vector<AllocaInst*> WorkList;
|
|
|
|
// Scan the entry basic block, adding allocas to the worklist.
|
|
BasicBlock &BB = F.getEntryBlock();
|
|
for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
|
|
if (AllocaInst *A = dyn_cast<AllocaInst>(I))
|
|
WorkList.push_back(A);
|
|
|
|
// Process the worklist
|
|
bool Changed = false;
|
|
while (!WorkList.empty()) {
|
|
AllocaInst *AI = WorkList.back();
|
|
WorkList.pop_back();
|
|
|
|
// Handle dead allocas trivially. These can be formed by SROA'ing arrays
|
|
// with unused elements.
|
|
if (AI->use_empty()) {
|
|
AI->eraseFromParent();
|
|
Changed = true;
|
|
continue;
|
|
}
|
|
|
|
// If this alloca is impossible for us to promote, reject it early.
|
|
if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
|
|
continue;
|
|
|
|
// Check to see if this allocation is only modified by a memcpy/memmove from
|
|
// a constant global. If this is the case, we can change all users to use
|
|
// the constant global instead. This is commonly produced by the CFE by
|
|
// constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
|
|
// is only subsequently read.
|
|
SmallVector<Instruction *, 4> ToDelete;
|
|
if (MemTransferInst *Copy = isOnlyCopiedFromConstantGlobal(AI, ToDelete)) {
|
|
DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n');
|
|
DEBUG(dbgs() << " memcpy = " << *Copy << '\n');
|
|
for (unsigned i = 0, e = ToDelete.size(); i != e; ++i)
|
|
ToDelete[i]->eraseFromParent();
|
|
Constant *TheSrc = cast<Constant>(Copy->getSource());
|
|
AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
|
|
Copy->eraseFromParent(); // Don't mutate the global.
|
|
AI->eraseFromParent();
|
|
++NumGlobals;
|
|
Changed = true;
|
|
continue;
|
|
}
|
|
|
|
// Check to see if we can perform the core SROA transformation. We cannot
|
|
// transform the allocation instruction if it is an array allocation
|
|
// (allocations OF arrays are ok though), and an allocation of a scalar
|
|
// value cannot be decomposed at all.
|
|
uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
|
|
|
|
// Do not promote [0 x %struct].
|
|
if (AllocaSize == 0) continue;
|
|
|
|
// Do not promote any struct whose size is too big.
|
|
if (AllocaSize > SRThreshold) continue;
|
|
|
|
// If the alloca looks like a good candidate for scalar replacement, and if
|
|
// all its users can be transformed, then split up the aggregate into its
|
|
// separate elements.
|
|
if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) {
|
|
DoScalarReplacement(AI, WorkList);
|
|
Changed = true;
|
|
continue;
|
|
}
|
|
|
|
// If we can turn this aggregate value (potentially with casts) into a
|
|
// simple scalar value that can be mem2reg'd into a register value.
|
|
// IsNotTrivial tracks whether this is something that mem2reg could have
|
|
// promoted itself. If so, we don't want to transform it needlessly. Note
|
|
// that we can't just check based on the type: the alloca may be of an i32
|
|
// but that has pointer arithmetic to set byte 3 of it or something.
|
|
if (AllocaInst *NewAI =
|
|
ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) {
|
|
NewAI->takeName(AI);
|
|
AI->eraseFromParent();
|
|
++NumConverted;
|
|
Changed = true;
|
|
continue;
|
|
}
|
|
|
|
// Otherwise, couldn't process this alloca.
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
/// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
|
|
/// predicate, do SROA now.
|
|
void SROA::DoScalarReplacement(AllocaInst *AI,
|
|
std::vector<AllocaInst*> &WorkList) {
|
|
DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
|
|
SmallVector<AllocaInst*, 32> ElementAllocas;
|
|
if (StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
|
|
ElementAllocas.reserve(ST->getNumContainedTypes());
|
|
for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
|
|
AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
|
|
AI->getAlignment(),
|
|
AI->getName() + "." + Twine(i), AI);
|
|
ElementAllocas.push_back(NA);
|
|
WorkList.push_back(NA); // Add to worklist for recursive processing
|
|
}
|
|
} else {
|
|
ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
|
|
ElementAllocas.reserve(AT->getNumElements());
|
|
Type *ElTy = AT->getElementType();
|
|
for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
|
|
AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
|
|
AI->getName() + "." + Twine(i), AI);
|
|
ElementAllocas.push_back(NA);
|
|
WorkList.push_back(NA); // Add to worklist for recursive processing
|
|
}
|
|
}
|
|
|
|
// Now that we have created the new alloca instructions, rewrite all the
|
|
// uses of the old alloca.
|
|
RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
|
|
|
|
// Now erase any instructions that were made dead while rewriting the alloca.
|
|
DeleteDeadInstructions();
|
|
AI->eraseFromParent();
|
|
|
|
++NumReplaced;
|
|
}
|
|
|
|
/// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
|
|
/// recursively including all their operands that become trivially dead.
|
|
void SROA::DeleteDeadInstructions() {
|
|
while (!DeadInsts.empty()) {
|
|
Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
|
|
|
|
for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
|
|
if (Instruction *U = dyn_cast<Instruction>(*OI)) {
|
|
// Zero out the operand and see if it becomes trivially dead.
|
|
// (But, don't add allocas to the dead instruction list -- they are
|
|
// already on the worklist and will be deleted separately.)
|
|
*OI = 0;
|
|
if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
|
|
DeadInsts.push_back(U);
|
|
}
|
|
|
|
I->eraseFromParent();
|
|
}
|
|
}
|
|
|
|
/// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
|
|
/// performing scalar replacement of alloca AI. The results are flagged in
|
|
/// the Info parameter. Offset indicates the position within AI that is
|
|
/// referenced by this instruction.
|
|
void SROA::isSafeForScalarRepl(Instruction *I, uint64_t Offset,
|
|
AllocaInfo &Info) {
|
|
for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
|
|
Instruction *User = cast<Instruction>(*UI);
|
|
|
|
if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
|
|
isSafeForScalarRepl(BC, Offset, Info);
|
|
} else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
|
|
uint64_t GEPOffset = Offset;
|
|
isSafeGEP(GEPI, GEPOffset, Info);
|
|
if (!Info.isUnsafe)
|
|
isSafeForScalarRepl(GEPI, GEPOffset, Info);
|
|
} else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
|
|
ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
|
|
if (Length == 0)
|
|
return MarkUnsafe(Info, User);
|
|
isSafeMemAccess(Offset, Length->getZExtValue(), 0,
|
|
UI.getOperandNo() == 0, Info, MI,
|
|
true /*AllowWholeAccess*/);
|
|
} else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
|
|
if (!LI->isSimple())
|
|
return MarkUnsafe(Info, User);
|
|
Type *LIType = LI->getType();
|
|
isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType),
|
|
LIType, false, Info, LI, true /*AllowWholeAccess*/);
|
|
Info.hasALoadOrStore = true;
|
|
|
|
} else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
|
|
// Store is ok if storing INTO the pointer, not storing the pointer
|
|
if (!SI->isSimple() || SI->getOperand(0) == I)
|
|
return MarkUnsafe(Info, User);
|
|
|
|
Type *SIType = SI->getOperand(0)->getType();
|
|
isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType),
|
|
SIType, true, Info, SI, true /*AllowWholeAccess*/);
|
|
Info.hasALoadOrStore = true;
|
|
} else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
|
|
if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
|
|
II->getIntrinsicID() != Intrinsic::lifetime_end)
|
|
return MarkUnsafe(Info, User);
|
|
} else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
|
|
isSafePHISelectUseForScalarRepl(User, Offset, Info);
|
|
} else {
|
|
return MarkUnsafe(Info, User);
|
|
}
|
|
if (Info.isUnsafe) return;
|
|
}
|
|
}
|
|
|
|
|
|
/// isSafePHIUseForScalarRepl - If we see a PHI node or select using a pointer
|
|
/// derived from the alloca, we can often still split the alloca into elements.
|
|
/// This is useful if we have a large alloca where one element is phi'd
|
|
/// together somewhere: we can SRoA and promote all the other elements even if
|
|
/// we end up not being able to promote this one.
|
|
///
|
|
/// All we require is that the uses of the PHI do not index into other parts of
|
|
/// the alloca. The most important use case for this is single load and stores
|
|
/// that are PHI'd together, which can happen due to code sinking.
|
|
void SROA::isSafePHISelectUseForScalarRepl(Instruction *I, uint64_t Offset,
|
|
AllocaInfo &Info) {
|
|
// If we've already checked this PHI, don't do it again.
|
|
if (PHINode *PN = dyn_cast<PHINode>(I))
|
|
if (!Info.CheckedPHIs.insert(PN))
|
|
return;
|
|
|
|
for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
|
|
Instruction *User = cast<Instruction>(*UI);
|
|
|
|
if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
|
|
isSafePHISelectUseForScalarRepl(BC, Offset, Info);
|
|
} else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
|
|
// Only allow "bitcast" GEPs for simplicity. We could generalize this,
|
|
// but would have to prove that we're staying inside of an element being
|
|
// promoted.
|
|
if (!GEPI->hasAllZeroIndices())
|
|
return MarkUnsafe(Info, User);
|
|
isSafePHISelectUseForScalarRepl(GEPI, Offset, Info);
|
|
} else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
|
|
if (!LI->isSimple())
|
|
return MarkUnsafe(Info, User);
|
|
Type *LIType = LI->getType();
|
|
isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType),
|
|
LIType, false, Info, LI, false /*AllowWholeAccess*/);
|
|
Info.hasALoadOrStore = true;
|
|
|
|
} else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
|
|
// Store is ok if storing INTO the pointer, not storing the pointer
|
|
if (!SI->isSimple() || SI->getOperand(0) == I)
|
|
return MarkUnsafe(Info, User);
|
|
|
|
Type *SIType = SI->getOperand(0)->getType();
|
|
isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType),
|
|
SIType, true, Info, SI, false /*AllowWholeAccess*/);
|
|
Info.hasALoadOrStore = true;
|
|
} else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
|
|
isSafePHISelectUseForScalarRepl(User, Offset, Info);
|
|
} else {
|
|
return MarkUnsafe(Info, User);
|
|
}
|
|
if (Info.isUnsafe) return;
|
|
}
|
|
}
|
|
|
|
/// isSafeGEP - Check if a GEP instruction can be handled for scalar
|
|
/// replacement. It is safe when all the indices are constant, in-bounds
|
|
/// references, and when the resulting offset corresponds to an element within
|
|
/// the alloca type. The results are flagged in the Info parameter. Upon
|
|
/// return, Offset is adjusted as specified by the GEP indices.
|
|
void SROA::isSafeGEP(GetElementPtrInst *GEPI,
|
|
uint64_t &Offset, AllocaInfo &Info) {
|
|
gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
|
|
if (GEPIt == E)
|
|
return;
|
|
|
|
// Walk through the GEP type indices, checking the types that this indexes
|
|
// into.
|
|
for (; GEPIt != E; ++GEPIt) {
|
|
// Ignore struct elements, no extra checking needed for these.
|
|
if ((*GEPIt)->isStructTy())
|
|
continue;
|
|
|
|
ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
|
|
if (!IdxVal)
|
|
return MarkUnsafe(Info, GEPI);
|
|
}
|
|
|
|
// Compute the offset due to this GEP and check if the alloca has a
|
|
// component element at that offset.
|
|
SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
|
|
Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), Indices);
|
|
if (!TypeHasComponent(Info.AI->getAllocatedType(), Offset, 0))
|
|
MarkUnsafe(Info, GEPI);
|
|
}
|
|
|
|
/// isHomogeneousAggregate - Check if type T is a struct or array containing
|
|
/// elements of the same type (which is always true for arrays). If so,
|
|
/// return true with NumElts and EltTy set to the number of elements and the
|
|
/// element type, respectively.
|
|
static bool isHomogeneousAggregate(Type *T, unsigned &NumElts,
|
|
Type *&EltTy) {
|
|
if (ArrayType *AT = dyn_cast<ArrayType>(T)) {
|
|
NumElts = AT->getNumElements();
|
|
EltTy = (NumElts == 0 ? 0 : AT->getElementType());
|
|
return true;
|
|
}
|
|
if (StructType *ST = dyn_cast<StructType>(T)) {
|
|
NumElts = ST->getNumContainedTypes();
|
|
EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0));
|
|
for (unsigned n = 1; n < NumElts; ++n) {
|
|
if (ST->getContainedType(n) != EltTy)
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// isCompatibleAggregate - Check if T1 and T2 are either the same type or are
|
|
/// "homogeneous" aggregates with the same element type and number of elements.
|
|
static bool isCompatibleAggregate(Type *T1, Type *T2) {
|
|
if (T1 == T2)
|
|
return true;
|
|
|
|
unsigned NumElts1, NumElts2;
|
|
Type *EltTy1, *EltTy2;
|
|
if (isHomogeneousAggregate(T1, NumElts1, EltTy1) &&
|
|
isHomogeneousAggregate(T2, NumElts2, EltTy2) &&
|
|
NumElts1 == NumElts2 &&
|
|
EltTy1 == EltTy2)
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
|
|
/// alloca or has an offset and size that corresponds to a component element
|
|
/// within it. The offset checked here may have been formed from a GEP with a
|
|
/// pointer bitcasted to a different type.
|
|
///
|
|
/// If AllowWholeAccess is true, then this allows uses of the entire alloca as a
|
|
/// unit. If false, it only allows accesses known to be in a single element.
|
|
void SROA::isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
|
|
Type *MemOpType, bool isStore,
|
|
AllocaInfo &Info, Instruction *TheAccess,
|
|
bool AllowWholeAccess) {
|
|
// Check if this is a load/store of the entire alloca.
|
|
if (Offset == 0 && AllowWholeAccess &&
|
|
MemSize == TD->getTypeAllocSize(Info.AI->getAllocatedType())) {
|
|
// This can be safe for MemIntrinsics (where MemOpType is 0) and integer
|
|
// loads/stores (which are essentially the same as the MemIntrinsics with
|
|
// regard to copying padding between elements). But, if an alloca is
|
|
// flagged as both a source and destination of such operations, we'll need
|
|
// to check later for padding between elements.
|
|
if (!MemOpType || MemOpType->isIntegerTy()) {
|
|
if (isStore)
|
|
Info.isMemCpyDst = true;
|
|
else
|
|
Info.isMemCpySrc = true;
|
|
return;
|
|
}
|
|
// This is also safe for references using a type that is compatible with
|
|
// the type of the alloca, so that loads/stores can be rewritten using
|
|
// insertvalue/extractvalue.
|
|
if (isCompatibleAggregate(MemOpType, Info.AI->getAllocatedType())) {
|
|
Info.hasSubelementAccess = true;
|
|
return;
|
|
}
|
|
}
|
|
// Check if the offset/size correspond to a component within the alloca type.
|
|
Type *T = Info.AI->getAllocatedType();
|
|
if (TypeHasComponent(T, Offset, MemSize)) {
|
|
Info.hasSubelementAccess = true;
|
|
return;
|
|
}
|
|
|
|
return MarkUnsafe(Info, TheAccess);
|
|
}
|
|
|
|
/// TypeHasComponent - Return true if T has a component type with the
|
|
/// specified offset and size. If Size is zero, do not check the size.
|
|
bool SROA::TypeHasComponent(Type *T, uint64_t Offset, uint64_t Size) {
|
|
Type *EltTy;
|
|
uint64_t EltSize;
|
|
if (StructType *ST = dyn_cast<StructType>(T)) {
|
|
const StructLayout *Layout = TD->getStructLayout(ST);
|
|
unsigned EltIdx = Layout->getElementContainingOffset(Offset);
|
|
EltTy = ST->getContainedType(EltIdx);
|
|
EltSize = TD->getTypeAllocSize(EltTy);
|
|
Offset -= Layout->getElementOffset(EltIdx);
|
|
} else if (ArrayType *AT = dyn_cast<ArrayType>(T)) {
|
|
EltTy = AT->getElementType();
|
|
EltSize = TD->getTypeAllocSize(EltTy);
|
|
if (Offset >= AT->getNumElements() * EltSize)
|
|
return false;
|
|
Offset %= EltSize;
|
|
} else {
|
|
return false;
|
|
}
|
|
if (Offset == 0 && (Size == 0 || EltSize == Size))
|
|
return true;
|
|
// Check if the component spans multiple elements.
|
|
if (Offset + Size > EltSize)
|
|
return false;
|
|
return TypeHasComponent(EltTy, Offset, Size);
|
|
}
|
|
|
|
/// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
|
|
/// the instruction I, which references it, to use the separate elements.
|
|
/// Offset indicates the position within AI that is referenced by this
|
|
/// instruction.
|
|
void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
|
|
SmallVector<AllocaInst*, 32> &NewElts) {
|
|
for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E;) {
|
|
Use &TheUse = UI.getUse();
|
|
Instruction *User = cast<Instruction>(*UI++);
|
|
|
|
if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
|
|
RewriteBitCast(BC, AI, Offset, NewElts);
|
|
continue;
|
|
}
|
|
|
|
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
|
|
RewriteGEP(GEPI, AI, Offset, NewElts);
|
|
continue;
|
|
}
|
|
|
|
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
|
|
ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
|
|
uint64_t MemSize = Length->getZExtValue();
|
|
if (Offset == 0 &&
|
|
MemSize == TD->getTypeAllocSize(AI->getAllocatedType()))
|
|
RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
|
|
// Otherwise the intrinsic can only touch a single element and the
|
|
// address operand will be updated, so nothing else needs to be done.
|
|
continue;
|
|
}
|
|
|
|
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
|
|
if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
|
|
II->getIntrinsicID() == Intrinsic::lifetime_end) {
|
|
RewriteLifetimeIntrinsic(II, AI, Offset, NewElts);
|
|
}
|
|
continue;
|
|
}
|
|
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
|
|
Type *LIType = LI->getType();
|
|
|
|
if (isCompatibleAggregate(LIType, AI->getAllocatedType())) {
|
|
// Replace:
|
|
// %res = load { i32, i32 }* %alloc
|
|
// with:
|
|
// %load.0 = load i32* %alloc.0
|
|
// %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
|
|
// %load.1 = load i32* %alloc.1
|
|
// %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
|
|
// (Also works for arrays instead of structs)
|
|
Value *Insert = UndefValue::get(LIType);
|
|
IRBuilder<> Builder(LI);
|
|
for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
|
|
Value *Load = Builder.CreateLoad(NewElts[i], "load");
|
|
Insert = Builder.CreateInsertValue(Insert, Load, i, "insert");
|
|
}
|
|
LI->replaceAllUsesWith(Insert);
|
|
DeadInsts.push_back(LI);
|
|
} else if (LIType->isIntegerTy() &&
|
|
TD->getTypeAllocSize(LIType) ==
|
|
TD->getTypeAllocSize(AI->getAllocatedType())) {
|
|
// If this is a load of the entire alloca to an integer, rewrite it.
|
|
RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
|
|
}
|
|
continue;
|
|
}
|
|
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
|
|
Value *Val = SI->getOperand(0);
|
|
Type *SIType = Val->getType();
|
|
if (isCompatibleAggregate(SIType, AI->getAllocatedType())) {
|
|
// Replace:
|
|
// store { i32, i32 } %val, { i32, i32 }* %alloc
|
|
// with:
|
|
// %val.0 = extractvalue { i32, i32 } %val, 0
|
|
// store i32 %val.0, i32* %alloc.0
|
|
// %val.1 = extractvalue { i32, i32 } %val, 1
|
|
// store i32 %val.1, i32* %alloc.1
|
|
// (Also works for arrays instead of structs)
|
|
IRBuilder<> Builder(SI);
|
|
for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
|
|
Value *Extract = Builder.CreateExtractValue(Val, i, Val->getName());
|
|
Builder.CreateStore(Extract, NewElts[i]);
|
|
}
|
|
DeadInsts.push_back(SI);
|
|
} else if (SIType->isIntegerTy() &&
|
|
TD->getTypeAllocSize(SIType) ==
|
|
TD->getTypeAllocSize(AI->getAllocatedType())) {
|
|
// If this is a store of the entire alloca from an integer, rewrite it.
|
|
RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
|
|
}
|
|
continue;
|
|
}
|
|
|
|
if (isa<SelectInst>(User) || isa<PHINode>(User)) {
|
|
// If we have a PHI user of the alloca itself (as opposed to a GEP or
|
|
// bitcast) we have to rewrite it. GEP and bitcast uses will be RAUW'd to
|
|
// the new pointer.
|
|
if (!isa<AllocaInst>(I)) continue;
|
|
|
|
assert(Offset == 0 && NewElts[0] &&
|
|
"Direct alloca use should have a zero offset");
|
|
|
|
// If we have a use of the alloca, we know the derived uses will be
|
|
// utilizing just the first element of the scalarized result. Insert a
|
|
// bitcast of the first alloca before the user as required.
|
|
AllocaInst *NewAI = NewElts[0];
|
|
BitCastInst *BCI = new BitCastInst(NewAI, AI->getType(), "", NewAI);
|
|
NewAI->moveBefore(BCI);
|
|
TheUse = BCI;
|
|
continue;
|
|
}
|
|
}
|
|
}
|
|
|
|
/// RewriteBitCast - Update a bitcast reference to the alloca being replaced
|
|
/// and recursively continue updating all of its uses.
|
|
void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
|
|
SmallVector<AllocaInst*, 32> &NewElts) {
|
|
RewriteForScalarRepl(BC, AI, Offset, NewElts);
|
|
if (BC->getOperand(0) != AI)
|
|
return;
|
|
|
|
// The bitcast references the original alloca. Replace its uses with
|
|
// references to the alloca containing offset zero (which is normally at
|
|
// index zero, but might not be in cases involving structs with elements
|
|
// of size zero).
|
|
Type *T = AI->getAllocatedType();
|
|
uint64_t EltOffset = 0;
|
|
Type *IdxTy;
|
|
uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
|
|
Instruction *Val = NewElts[Idx];
|
|
if (Val->getType() != BC->getDestTy()) {
|
|
Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
|
|
Val->takeName(BC);
|
|
}
|
|
BC->replaceAllUsesWith(Val);
|
|
DeadInsts.push_back(BC);
|
|
}
|
|
|
|
/// FindElementAndOffset - Return the index of the element containing Offset
|
|
/// within the specified type, which must be either a struct or an array.
|
|
/// Sets T to the type of the element and Offset to the offset within that
|
|
/// element. IdxTy is set to the type of the index result to be used in a
|
|
/// GEP instruction.
|
|
uint64_t SROA::FindElementAndOffset(Type *&T, uint64_t &Offset,
|
|
Type *&IdxTy) {
|
|
uint64_t Idx = 0;
|
|
if (StructType *ST = dyn_cast<StructType>(T)) {
|
|
const StructLayout *Layout = TD->getStructLayout(ST);
|
|
Idx = Layout->getElementContainingOffset(Offset);
|
|
T = ST->getContainedType(Idx);
|
|
Offset -= Layout->getElementOffset(Idx);
|
|
IdxTy = Type::getInt32Ty(T->getContext());
|
|
return Idx;
|
|
}
|
|
ArrayType *AT = cast<ArrayType>(T);
|
|
T = AT->getElementType();
|
|
uint64_t EltSize = TD->getTypeAllocSize(T);
|
|
Idx = Offset / EltSize;
|
|
Offset -= Idx * EltSize;
|
|
IdxTy = Type::getInt64Ty(T->getContext());
|
|
return Idx;
|
|
}
|
|
|
|
/// RewriteGEP - Check if this GEP instruction moves the pointer across
|
|
/// elements of the alloca that are being split apart, and if so, rewrite
|
|
/// the GEP to be relative to the new element.
|
|
void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
|
|
SmallVector<AllocaInst*, 32> &NewElts) {
|
|
uint64_t OldOffset = Offset;
|
|
SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
|
|
Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), Indices);
|
|
|
|
RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
|
|
|
|
Type *T = AI->getAllocatedType();
|
|
Type *IdxTy;
|
|
uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy);
|
|
if (GEPI->getOperand(0) == AI)
|
|
OldIdx = ~0ULL; // Force the GEP to be rewritten.
|
|
|
|
T = AI->getAllocatedType();
|
|
uint64_t EltOffset = Offset;
|
|
uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
|
|
|
|
// If this GEP does not move the pointer across elements of the alloca
|
|
// being split, then it does not needs to be rewritten.
|
|
if (Idx == OldIdx)
|
|
return;
|
|
|
|
Type *i32Ty = Type::getInt32Ty(AI->getContext());
|
|
SmallVector<Value*, 8> NewArgs;
|
|
NewArgs.push_back(Constant::getNullValue(i32Ty));
|
|
while (EltOffset != 0) {
|
|
uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy);
|
|
NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
|
|
}
|
|
Instruction *Val = NewElts[Idx];
|
|
if (NewArgs.size() > 1) {
|
|
Val = GetElementPtrInst::CreateInBounds(Val, NewArgs, "", GEPI);
|
|
Val->takeName(GEPI);
|
|
}
|
|
if (Val->getType() != GEPI->getType())
|
|
Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI);
|
|
GEPI->replaceAllUsesWith(Val);
|
|
DeadInsts.push_back(GEPI);
|
|
}
|
|
|
|
/// RewriteLifetimeIntrinsic - II is a lifetime.start/lifetime.end. Rewrite it
|
|
/// to mark the lifetime of the scalarized memory.
|
|
void SROA::RewriteLifetimeIntrinsic(IntrinsicInst *II, AllocaInst *AI,
|
|
uint64_t Offset,
|
|
SmallVector<AllocaInst*, 32> &NewElts) {
|
|
ConstantInt *OldSize = cast<ConstantInt>(II->getArgOperand(0));
|
|
// Put matching lifetime markers on everything from Offset up to
|
|
// Offset+OldSize.
|
|
Type *AIType = AI->getAllocatedType();
|
|
uint64_t NewOffset = Offset;
|
|
Type *IdxTy;
|
|
uint64_t Idx = FindElementAndOffset(AIType, NewOffset, IdxTy);
|
|
|
|
IRBuilder<> Builder(II);
|
|
uint64_t Size = OldSize->getLimitedValue();
|
|
|
|
if (NewOffset) {
|
|
// Splice the first element and index 'NewOffset' bytes in. SROA will
|
|
// split the alloca again later.
|
|
Value *V = Builder.CreateBitCast(NewElts[Idx], Builder.getInt8PtrTy());
|
|
V = Builder.CreateGEP(V, Builder.getInt64(NewOffset));
|
|
|
|
IdxTy = NewElts[Idx]->getAllocatedType();
|
|
uint64_t EltSize = TD->getTypeAllocSize(IdxTy) - NewOffset;
|
|
if (EltSize > Size) {
|
|
EltSize = Size;
|
|
Size = 0;
|
|
} else {
|
|
Size -= EltSize;
|
|
}
|
|
if (II->getIntrinsicID() == Intrinsic::lifetime_start)
|
|
Builder.CreateLifetimeStart(V, Builder.getInt64(EltSize));
|
|
else
|
|
Builder.CreateLifetimeEnd(V, Builder.getInt64(EltSize));
|
|
++Idx;
|
|
}
|
|
|
|
for (; Idx != NewElts.size() && Size; ++Idx) {
|
|
IdxTy = NewElts[Idx]->getAllocatedType();
|
|
uint64_t EltSize = TD->getTypeAllocSize(IdxTy);
|
|
if (EltSize > Size) {
|
|
EltSize = Size;
|
|
Size = 0;
|
|
} else {
|
|
Size -= EltSize;
|
|
}
|
|
if (II->getIntrinsicID() == Intrinsic::lifetime_start)
|
|
Builder.CreateLifetimeStart(NewElts[Idx],
|
|
Builder.getInt64(EltSize));
|
|
else
|
|
Builder.CreateLifetimeEnd(NewElts[Idx],
|
|
Builder.getInt64(EltSize));
|
|
}
|
|
DeadInsts.push_back(II);
|
|
}
|
|
|
|
/// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
|
|
/// Rewrite it to copy or set the elements of the scalarized memory.
|
|
void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
|
|
AllocaInst *AI,
|
|
SmallVector<AllocaInst*, 32> &NewElts) {
|
|
// If this is a memcpy/memmove, construct the other pointer as the
|
|
// appropriate type. The "Other" pointer is the pointer that goes to memory
|
|
// that doesn't have anything to do with the alloca that we are promoting. For
|
|
// memset, this Value* stays null.
|
|
Value *OtherPtr = 0;
|
|
unsigned MemAlignment = MI->getAlignment();
|
|
if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
|
|
if (Inst == MTI->getRawDest())
|
|
OtherPtr = MTI->getRawSource();
|
|
else {
|
|
assert(Inst == MTI->getRawSource());
|
|
OtherPtr = MTI->getRawDest();
|
|
}
|
|
}
|
|
|
|
// If there is an other pointer, we want to convert it to the same pointer
|
|
// type as AI has, so we can GEP through it safely.
|
|
if (OtherPtr) {
|
|
unsigned AddrSpace =
|
|
cast<PointerType>(OtherPtr->getType())->getAddressSpace();
|
|
|
|
// Remove bitcasts and all-zero GEPs from OtherPtr. This is an
|
|
// optimization, but it's also required to detect the corner case where
|
|
// both pointer operands are referencing the same memory, and where
|
|
// OtherPtr may be a bitcast or GEP that currently being rewritten. (This
|
|
// function is only called for mem intrinsics that access the whole
|
|
// aggregate, so non-zero GEPs are not an issue here.)
|
|
OtherPtr = OtherPtr->stripPointerCasts();
|
|
|
|
// Copying the alloca to itself is a no-op: just delete it.
|
|
if (OtherPtr == AI || OtherPtr == NewElts[0]) {
|
|
// This code will run twice for a no-op memcpy -- once for each operand.
|
|
// Put only one reference to MI on the DeadInsts list.
|
|
for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(),
|
|
E = DeadInsts.end(); I != E; ++I)
|
|
if (*I == MI) return;
|
|
DeadInsts.push_back(MI);
|
|
return;
|
|
}
|
|
|
|
// If the pointer is not the right type, insert a bitcast to the right
|
|
// type.
|
|
Type *NewTy =
|
|
PointerType::get(AI->getType()->getElementType(), AddrSpace);
|
|
|
|
if (OtherPtr->getType() != NewTy)
|
|
OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI);
|
|
}
|
|
|
|
// Process each element of the aggregate.
|
|
bool SROADest = MI->getRawDest() == Inst;
|
|
|
|
Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
|
|
|
|
for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
|
|
// If this is a memcpy/memmove, emit a GEP of the other element address.
|
|
Value *OtherElt = 0;
|
|
unsigned OtherEltAlign = MemAlignment;
|
|
|
|
if (OtherPtr) {
|
|
Value *Idx[2] = { Zero,
|
|
ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
|
|
OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx,
|
|
OtherPtr->getName()+"."+Twine(i),
|
|
MI);
|
|
uint64_t EltOffset;
|
|
PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
|
|
Type *OtherTy = OtherPtrTy->getElementType();
|
|
if (StructType *ST = dyn_cast<StructType>(OtherTy)) {
|
|
EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
|
|
} else {
|
|
Type *EltTy = cast<SequentialType>(OtherTy)->getElementType();
|
|
EltOffset = TD->getTypeAllocSize(EltTy)*i;
|
|
}
|
|
|
|
// The alignment of the other pointer is the guaranteed alignment of the
|
|
// element, which is affected by both the known alignment of the whole
|
|
// mem intrinsic and the alignment of the element. If the alignment of
|
|
// the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
|
|
// known alignment is just 4 bytes.
|
|
OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
|
|
}
|
|
|
|
Value *EltPtr = NewElts[i];
|
|
Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
|
|
|
|
// If we got down to a scalar, insert a load or store as appropriate.
|
|
if (EltTy->isSingleValueType()) {
|
|
if (isa<MemTransferInst>(MI)) {
|
|
if (SROADest) {
|
|
// From Other to Alloca.
|
|
Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
|
|
new StoreInst(Elt, EltPtr, MI);
|
|
} else {
|
|
// From Alloca to Other.
|
|
Value *Elt = new LoadInst(EltPtr, "tmp", MI);
|
|
new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
|
|
}
|
|
continue;
|
|
}
|
|
assert(isa<MemSetInst>(MI));
|
|
|
|
// If the stored element is zero (common case), just store a null
|
|
// constant.
|
|
Constant *StoreVal;
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) {
|
|
if (CI->isZero()) {
|
|
StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
|
|
} else {
|
|
// If EltTy is a vector type, get the element type.
|
|
Type *ValTy = EltTy->getScalarType();
|
|
|
|
// Construct an integer with the right value.
|
|
unsigned EltSize = TD->getTypeSizeInBits(ValTy);
|
|
APInt OneVal(EltSize, CI->getZExtValue());
|
|
APInt TotalVal(OneVal);
|
|
// Set each byte.
|
|
for (unsigned i = 0; 8*i < EltSize; ++i) {
|
|
TotalVal = TotalVal.shl(8);
|
|
TotalVal |= OneVal;
|
|
}
|
|
|
|
// Convert the integer value to the appropriate type.
|
|
StoreVal = ConstantInt::get(CI->getContext(), TotalVal);
|
|
if (ValTy->isPointerTy())
|
|
StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
|
|
else if (ValTy->isFloatingPointTy())
|
|
StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
|
|
assert(StoreVal->getType() == ValTy && "Type mismatch!");
|
|
|
|
// If the requested value was a vector constant, create it.
|
|
if (EltTy->isVectorTy()) {
|
|
unsigned NumElts = cast<VectorType>(EltTy)->getNumElements();
|
|
StoreVal = ConstantVector::getSplat(NumElts, StoreVal);
|
|
}
|
|
}
|
|
new StoreInst(StoreVal, EltPtr, MI);
|
|
continue;
|
|
}
|
|
// Otherwise, if we're storing a byte variable, use a memset call for
|
|
// this element.
|
|
}
|
|
|
|
unsigned EltSize = TD->getTypeAllocSize(EltTy);
|
|
if (!EltSize)
|
|
continue;
|
|
|
|
IRBuilder<> Builder(MI);
|
|
|
|
// Finally, insert the meminst for this element.
|
|
if (isa<MemSetInst>(MI)) {
|
|
Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize,
|
|
MI->isVolatile());
|
|
} else {
|
|
assert(isa<MemTransferInst>(MI));
|
|
Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr
|
|
Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr
|
|
|
|
if (isa<MemCpyInst>(MI))
|
|
Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile());
|
|
else
|
|
Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile());
|
|
}
|
|
}
|
|
DeadInsts.push_back(MI);
|
|
}
|
|
|
|
/// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
|
|
/// overwrites the entire allocation. Extract out the pieces of the stored
|
|
/// integer and store them individually.
|
|
void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
|
|
SmallVector<AllocaInst*, 32> &NewElts){
|
|
// Extract each element out of the integer according to its structure offset
|
|
// and store the element value to the individual alloca.
|
|
Value *SrcVal = SI->getOperand(0);
|
|
Type *AllocaEltTy = AI->getAllocatedType();
|
|
uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
|
|
|
|
IRBuilder<> Builder(SI);
|
|
|
|
// Handle tail padding by extending the operand
|
|
if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
|
|
SrcVal = Builder.CreateZExt(SrcVal,
|
|
IntegerType::get(SI->getContext(), AllocaSizeBits));
|
|
|
|
DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
|
|
<< '\n');
|
|
|
|
// There are two forms here: AI could be an array or struct. Both cases
|
|
// have different ways to compute the element offset.
|
|
if (StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
|
|
const StructLayout *Layout = TD->getStructLayout(EltSTy);
|
|
|
|
for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
|
|
// Get the number of bits to shift SrcVal to get the value.
|
|
Type *FieldTy = EltSTy->getElementType(i);
|
|
uint64_t Shift = Layout->getElementOffsetInBits(i);
|
|
|
|
if (TD->isBigEndian())
|
|
Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
|
|
|
|
Value *EltVal = SrcVal;
|
|
if (Shift) {
|
|
Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
|
|
EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
|
|
}
|
|
|
|
// Truncate down to an integer of the right size.
|
|
uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
|
|
|
|
// Ignore zero sized fields like {}, they obviously contain no data.
|
|
if (FieldSizeBits == 0) continue;
|
|
|
|
if (FieldSizeBits != AllocaSizeBits)
|
|
EltVal = Builder.CreateTrunc(EltVal,
|
|
IntegerType::get(SI->getContext(), FieldSizeBits));
|
|
Value *DestField = NewElts[i];
|
|
if (EltVal->getType() == FieldTy) {
|
|
// Storing to an integer field of this size, just do it.
|
|
} else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) {
|
|
// Bitcast to the right element type (for fp/vector values).
|
|
EltVal = Builder.CreateBitCast(EltVal, FieldTy);
|
|
} else {
|
|
// Otherwise, bitcast the dest pointer (for aggregates).
|
|
DestField = Builder.CreateBitCast(DestField,
|
|
PointerType::getUnqual(EltVal->getType()));
|
|
}
|
|
new StoreInst(EltVal, DestField, SI);
|
|
}
|
|
|
|
} else {
|
|
ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
|
|
Type *ArrayEltTy = ATy->getElementType();
|
|
uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
|
|
uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
|
|
|
|
uint64_t Shift;
|
|
|
|
if (TD->isBigEndian())
|
|
Shift = AllocaSizeBits-ElementOffset;
|
|
else
|
|
Shift = 0;
|
|
|
|
for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
|
|
// Ignore zero sized fields like {}, they obviously contain no data.
|
|
if (ElementSizeBits == 0) continue;
|
|
|
|
Value *EltVal = SrcVal;
|
|
if (Shift) {
|
|
Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
|
|
EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
|
|
}
|
|
|
|
// Truncate down to an integer of the right size.
|
|
if (ElementSizeBits != AllocaSizeBits)
|
|
EltVal = Builder.CreateTrunc(EltVal,
|
|
IntegerType::get(SI->getContext(),
|
|
ElementSizeBits));
|
|
Value *DestField = NewElts[i];
|
|
if (EltVal->getType() == ArrayEltTy) {
|
|
// Storing to an integer field of this size, just do it.
|
|
} else if (ArrayEltTy->isFloatingPointTy() ||
|
|
ArrayEltTy->isVectorTy()) {
|
|
// Bitcast to the right element type (for fp/vector values).
|
|
EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy);
|
|
} else {
|
|
// Otherwise, bitcast the dest pointer (for aggregates).
|
|
DestField = Builder.CreateBitCast(DestField,
|
|
PointerType::getUnqual(EltVal->getType()));
|
|
}
|
|
new StoreInst(EltVal, DestField, SI);
|
|
|
|
if (TD->isBigEndian())
|
|
Shift -= ElementOffset;
|
|
else
|
|
Shift += ElementOffset;
|
|
}
|
|
}
|
|
|
|
DeadInsts.push_back(SI);
|
|
}
|
|
|
|
/// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
|
|
/// an integer. Load the individual pieces to form the aggregate value.
|
|
void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
|
|
SmallVector<AllocaInst*, 32> &NewElts) {
|
|
// Extract each element out of the NewElts according to its structure offset
|
|
// and form the result value.
|
|
Type *AllocaEltTy = AI->getAllocatedType();
|
|
uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
|
|
|
|
DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
|
|
<< '\n');
|
|
|
|
// There are two forms here: AI could be an array or struct. Both cases
|
|
// have different ways to compute the element offset.
|
|
const StructLayout *Layout = 0;
|
|
uint64_t ArrayEltBitOffset = 0;
|
|
if (StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
|
|
Layout = TD->getStructLayout(EltSTy);
|
|
} else {
|
|
Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
|
|
ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
|
|
}
|
|
|
|
Value *ResultVal =
|
|
Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
|
|
|
|
for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
|
|
// Load the value from the alloca. If the NewElt is an aggregate, cast
|
|
// the pointer to an integer of the same size before doing the load.
|
|
Value *SrcField = NewElts[i];
|
|
Type *FieldTy =
|
|
cast<PointerType>(SrcField->getType())->getElementType();
|
|
uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
|
|
|
|
// Ignore zero sized fields like {}, they obviously contain no data.
|
|
if (FieldSizeBits == 0) continue;
|
|
|
|
IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
|
|
FieldSizeBits);
|
|
if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() &&
|
|
!FieldTy->isVectorTy())
|
|
SrcField = new BitCastInst(SrcField,
|
|
PointerType::getUnqual(FieldIntTy),
|
|
"", LI);
|
|
SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
|
|
|
|
// If SrcField is a fp or vector of the right size but that isn't an
|
|
// integer type, bitcast to an integer so we can shift it.
|
|
if (SrcField->getType() != FieldIntTy)
|
|
SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
|
|
|
|
// Zero extend the field to be the same size as the final alloca so that
|
|
// we can shift and insert it.
|
|
if (SrcField->getType() != ResultVal->getType())
|
|
SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
|
|
|
|
// Determine the number of bits to shift SrcField.
|
|
uint64_t Shift;
|
|
if (Layout) // Struct case.
|
|
Shift = Layout->getElementOffsetInBits(i);
|
|
else // Array case.
|
|
Shift = i*ArrayEltBitOffset;
|
|
|
|
if (TD->isBigEndian())
|
|
Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
|
|
|
|
if (Shift) {
|
|
Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
|
|
SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
|
|
}
|
|
|
|
// Don't create an 'or x, 0' on the first iteration.
|
|
if (!isa<Constant>(ResultVal) ||
|
|
!cast<Constant>(ResultVal)->isNullValue())
|
|
ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
|
|
else
|
|
ResultVal = SrcField;
|
|
}
|
|
|
|
// Handle tail padding by truncating the result
|
|
if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
|
|
ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
|
|
|
|
LI->replaceAllUsesWith(ResultVal);
|
|
DeadInsts.push_back(LI);
|
|
}
|
|
|
|
/// HasPadding - Return true if the specified type has any structure or
|
|
/// alignment padding in between the elements that would be split apart
|
|
/// by SROA; return false otherwise.
|
|
static bool HasPadding(Type *Ty, const TargetData &TD) {
|
|
if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
|
|
Ty = ATy->getElementType();
|
|
return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
|
|
}
|
|
|
|
// SROA currently handles only Arrays and Structs.
|
|
StructType *STy = cast<StructType>(Ty);
|
|
const StructLayout *SL = TD.getStructLayout(STy);
|
|
unsigned PrevFieldBitOffset = 0;
|
|
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
|
|
unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
|
|
|
|
// Check to see if there is any padding between this element and the
|
|
// previous one.
|
|
if (i) {
|
|
unsigned PrevFieldEnd =
|
|
PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
|
|
if (PrevFieldEnd < FieldBitOffset)
|
|
return true;
|
|
}
|
|
PrevFieldBitOffset = FieldBitOffset;
|
|
}
|
|
// Check for tail padding.
|
|
if (unsigned EltCount = STy->getNumElements()) {
|
|
unsigned PrevFieldEnd = PrevFieldBitOffset +
|
|
TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
|
|
if (PrevFieldEnd < SL->getSizeInBits())
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
|
|
/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
|
|
/// or 1 if safe after canonicalization has been performed.
|
|
bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
|
|
// Loop over the use list of the alloca. We can only transform it if all of
|
|
// the users are safe to transform.
|
|
AllocaInfo Info(AI);
|
|
|
|
isSafeForScalarRepl(AI, 0, Info);
|
|
if (Info.isUnsafe) {
|
|
DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
|
|
return false;
|
|
}
|
|
|
|
// Okay, we know all the users are promotable. If the aggregate is a memcpy
|
|
// source and destination, we have to be careful. In particular, the memcpy
|
|
// could be moving around elements that live in structure padding of the LLVM
|
|
// types, but may actually be used. In these cases, we refuse to promote the
|
|
// struct.
|
|
if (Info.isMemCpySrc && Info.isMemCpyDst &&
|
|
HasPadding(AI->getAllocatedType(), *TD))
|
|
return false;
|
|
|
|
// If the alloca never has an access to just *part* of it, but is accessed
|
|
// via loads and stores, then we should use ConvertToScalarInfo to promote
|
|
// the alloca instead of promoting each piece at a time and inserting fission
|
|
// and fusion code.
|
|
if (!Info.hasSubelementAccess && Info.hasALoadOrStore) {
|
|
// If the struct/array just has one element, use basic SRoA.
|
|
if (StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
|
|
if (ST->getNumElements() > 1) return false;
|
|
} else {
|
|
if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1)
|
|
return false;
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
|
|
|
|
/// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
|
|
/// some part of a constant global variable. This intentionally only accepts
|
|
/// constant expressions because we don't can't rewrite arbitrary instructions.
|
|
static bool PointsToConstantGlobal(Value *V) {
|
|
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
|
|
return GV->isConstant();
|
|
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
|
|
if (CE->getOpcode() == Instruction::BitCast ||
|
|
CE->getOpcode() == Instruction::GetElementPtr)
|
|
return PointsToConstantGlobal(CE->getOperand(0));
|
|
return false;
|
|
}
|
|
|
|
/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
|
|
/// pointer to an alloca. Ignore any reads of the pointer, return false if we
|
|
/// see any stores or other unknown uses. If we see pointer arithmetic, keep
|
|
/// track of whether it moves the pointer (with isOffset) but otherwise traverse
|
|
/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
|
|
/// the alloca, and if the source pointer is a pointer to a constant global, we
|
|
/// can optimize this.
|
|
static bool
|
|
isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
|
|
bool isOffset,
|
|
SmallVector<Instruction *, 4> &LifetimeMarkers) {
|
|
// We track lifetime intrinsics as we encounter them. If we decide to go
|
|
// ahead and replace the value with the global, this lets the caller quickly
|
|
// eliminate the markers.
|
|
|
|
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
|
|
User *U = cast<Instruction>(*UI);
|
|
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
|
|
// Ignore non-volatile loads, they are always ok.
|
|
if (!LI->isSimple()) return false;
|
|
continue;
|
|
}
|
|
|
|
if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
|
|
// If uses of the bitcast are ok, we are ok.
|
|
if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset,
|
|
LifetimeMarkers))
|
|
return false;
|
|
continue;
|
|
}
|
|
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
|
|
// If the GEP has all zero indices, it doesn't offset the pointer. If it
|
|
// doesn't, it does.
|
|
if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
|
|
isOffset || !GEP->hasAllZeroIndices(),
|
|
LifetimeMarkers))
|
|
return false;
|
|
continue;
|
|
}
|
|
|
|
if (CallSite CS = U) {
|
|
// If this is the function being called then we treat it like a load and
|
|
// ignore it.
|
|
if (CS.isCallee(UI))
|
|
continue;
|
|
|
|
// If this is a readonly/readnone call site, then we know it is just a
|
|
// load (but one that potentially returns the value itself), so we can
|
|
// ignore it if we know that the value isn't captured.
|
|
unsigned ArgNo = CS.getArgumentNo(UI);
|
|
if (CS.onlyReadsMemory() &&
|
|
(CS.getInstruction()->use_empty() || CS.doesNotCapture(ArgNo)))
|
|
continue;
|
|
|
|
// If this is being passed as a byval argument, the caller is making a
|
|
// copy, so it is only a read of the alloca.
|
|
if (CS.isByValArgument(ArgNo))
|
|
continue;
|
|
}
|
|
|
|
// Lifetime intrinsics can be handled by the caller.
|
|
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U)) {
|
|
if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
|
|
II->getIntrinsicID() == Intrinsic::lifetime_end) {
|
|
assert(II->use_empty() && "Lifetime markers have no result to use!");
|
|
LifetimeMarkers.push_back(II);
|
|
continue;
|
|
}
|
|
}
|
|
|
|
// If this is isn't our memcpy/memmove, reject it as something we can't
|
|
// handle.
|
|
MemTransferInst *MI = dyn_cast<MemTransferInst>(U);
|
|
if (MI == 0)
|
|
return false;
|
|
|
|
// If the transfer is using the alloca as a source of the transfer, then
|
|
// ignore it since it is a load (unless the transfer is volatile).
|
|
if (UI.getOperandNo() == 1) {
|
|
if (MI->isVolatile()) return false;
|
|
continue;
|
|
}
|
|
|
|
// If we already have seen a copy, reject the second one.
|
|
if (TheCopy) return false;
|
|
|
|
// If the pointer has been offset from the start of the alloca, we can't
|
|
// safely handle this.
|
|
if (isOffset) return false;
|
|
|
|
// If the memintrinsic isn't using the alloca as the dest, reject it.
|
|
if (UI.getOperandNo() != 0) return false;
|
|
|
|
// If the source of the memcpy/move is not a constant global, reject it.
|
|
if (!PointsToConstantGlobal(MI->getSource()))
|
|
return false;
|
|
|
|
// Otherwise, the transform is safe. Remember the copy instruction.
|
|
TheCopy = MI;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
|
|
/// modified by a copy from a constant global. If we can prove this, we can
|
|
/// replace any uses of the alloca with uses of the global directly.
|
|
MemTransferInst *
|
|
SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI,
|
|
SmallVector<Instruction*, 4> &ToDelete) {
|
|
MemTransferInst *TheCopy = 0;
|
|
if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false, ToDelete))
|
|
return TheCopy;
|
|
return 0;
|
|
}
|