#include "InstCombine.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/Loads.h"
-#include "llvm/DataLayout.h"
-#include "llvm/IntrinsicInst.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/Support/CommandLine.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
+/// Hidden option to stress test load slicing, i.e., when this option
+/// is enabled, load slicing bypasses most of its profitability guards.
+/// It will also generate, uncanonalized form of slicing.
+static cl::opt<bool>
+StressLoadSlicing("instcombine-stress-load-slicing", cl::Hidden,
+ cl::desc("Bypass the profitability model of load "
+ "slicing"),
+ cl::init(false));
+
STATISTIC(NumDeadStore, "Number of dead stores eliminated");
STATISTIC(NumGlobalCopies, "Number of allocas copied from constant global");
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, ToDelete,
- IsOffset || !GEP->hasAllZeroIndices()))
+ if (!isOnlyCopiedFromConstantGlobal(
+ GEP, TheCopy, ToDelete, IsOffset || !GEP->hasAllZeroIndices()))
return false;
continue;
}
// Ensure that the alloca array size argument has type intptr_t, so that
// any casting is exposed early.
if (TD) {
- Type *IntPtrTy = TD->getIntPtrType(AI.getContext());
+ Type *IntPtrTy = TD->getIntPtrType(AI.getType());
if (AI.getArraySize()->getType() != IntPtrTy) {
Value *V = Builder->CreateIntCast(AI.getArraySize(),
IntPtrTy, false);
// Convert: alloca Ty, C - where C is a constant != 1 into: alloca [C x Ty], 1
if (AI.isArrayAllocation()) { // Check C != 1
if (const ConstantInt *C = dyn_cast<ConstantInt>(AI.getArraySize())) {
- Type *NewTy =
+ Type *NewTy =
ArrayType::get(AI.getAllocatedType(), C->getZExtValue());
AllocaInst *New = Builder->CreateAlloca(NewTy, 0, AI.getName());
New->setAlignment(AI.getAlignment());
// Now that I is pointing to the first non-allocation-inst in the block,
// insert our getelementptr instruction...
//
- Value *NullIdx =Constant::getNullValue(Type::getInt32Ty(AI.getContext()));
- Value *Idx[2];
- Idx[0] = NullIdx;
- Idx[1] = NullIdx;
+ Type *IdxTy = TD
+ ? TD->getIntPtrType(AI.getType())
+ : Type::getInt64Ty(AI.getContext());
+ Value *NullIdx = Constant::getNullValue(IdxTy);
+ Value *Idx[2] = { NullIdx, NullIdx };
Instruction *GEP =
- GetElementPtrInst::CreateInBounds(New, Idx, New->getName()+".sub");
+ GetElementPtrInst::CreateInBounds(New, Idx, New->getName() + ".sub");
InsertNewInstBefore(GEP, *It);
// Now make everything use the getelementptr instead of the original
Type *SrcPTy = SrcTy->getElementType();
- if (DestPTy->isIntegerTy() || DestPTy->isPointerTy() ||
+ if (DestPTy->isIntegerTy() || DestPTy->isPointerTy() ||
DestPTy->isVectorTy()) {
// If the source is an array, the code below will not succeed. Check to
// see if a trivial 'gep P, 0, 0' will help matters. Only do this for
if (ArrayType *ASrcTy = dyn_cast<ArrayType>(SrcPTy))
if (Constant *CSrc = dyn_cast<Constant>(CastOp))
if (ASrcTy->getNumElements() != 0) {
- Value *Idxs[2];
- Idxs[0] = Constant::getNullValue(Type::getInt32Ty(LI.getContext()));
- Idxs[1] = Idxs[0];
+ Type *IdxTy = TD
+ ? TD->getIntPtrType(SrcTy)
+ : Type::getInt64Ty(SrcTy->getContext());
+ Value *Idx = Constant::getNullValue(IdxTy);
+ Value *Idxs[2] = { Idx, Idx };
CastOp = ConstantExpr::getGetElementPtr(CSrc, Idxs);
SrcTy = cast<PointerType>(CastOp->getType());
SrcPTy = SrcTy->getElementType();
}
if (IC.getDataLayout() &&
- (SrcPTy->isIntegerTy() || SrcPTy->isPointerTy() ||
+ (SrcPTy->isIntegerTy() || SrcPTy->isPointerTy() ||
SrcPTy->isVectorTy()) &&
// Do not allow turning this into a load of an integer, which is then
// casted to a pointer, this pessimizes pointer analysis a lot.
// Okay, we are casting from one integer or pointer type to another of
// the same size. Instead of casting the pointer before the load, cast
// the result of the loaded value.
- LoadInst *NewLoad =
+ LoadInst *NewLoad =
IC.Builder->CreateLoad(CastOp, LI.isVolatile(), CI->getName());
NewLoad->setAlignment(LI.getAlignment());
NewLoad->setAtomic(LI.getOrdering(), LI.getSynchScope());
return 0;
}
+namespace {
+ /// \brief Helper structure used to slice a load in smaller loads.
+ struct LoadedSlice {
+ // The last instruction that represent the slice. This should be a
+ // truncate instruction.
+ Instruction *Inst;
+ // The original load instruction.
+ LoadInst *Origin;
+ // The right shift amount in bits from the original load.
+ unsigned Shift;
+
+ LoadedSlice(Instruction *Inst = NULL, LoadInst *Origin = NULL,
+ unsigned Shift = 0)
+ : Inst(Inst), Origin(Origin), Shift(Shift) {}
+
+ LoadedSlice(const LoadedSlice& LS) : Inst(LS.Inst), Origin(LS.Origin),
+ Shift(LS.Shift) {}
+
+ /// \brief Get the bits used in a chunk of bits \p BitWidth large.
+ /// \return Result is \p BitWidth and has used bits set to 1 and
+ /// not used bits set to 0.
+ APInt getUsedBits() const {
+ // Reproduce the trunc(lshr) sequence:
+ // - Start from the truncated value.
+ // - Zero extend to the desired bit width.
+ // - Shift left.
+ assert(Origin && "No original load to compare against.");
+ unsigned BitWidth = Origin->getType()->getPrimitiveSizeInBits();
+ assert(Inst && "This slice is not bound to an instruction");
+ assert(Inst->getType()->getPrimitiveSizeInBits() <= BitWidth &&
+ "Extracted slice is smaller than the whole type!");
+ APInt UsedBits(Inst->getType()->getPrimitiveSizeInBits(), 0);
+ UsedBits.setAllBits();
+ UsedBits = UsedBits.zext(BitWidth);
+ UsedBits <<= Shift;
+ return UsedBits;
+ }
+
+ /// \brief Get the size of the slice to be loaded in bytes.
+ unsigned getLoadedSize() const {
+ unsigned SliceSize = getUsedBits().countPopulation();
+ assert(!(SliceSize & 0x7) && "Size is not a multiple of a byte.");
+ return SliceSize / 8;
+ }
+
+ /// \brief Get the offset in bytes of this slice in the original chunk of
+ /// bits, whose layout is defined by \p IsBigEndian.
+ uint64_t getOffsetFromBase(bool IsBigEndian) const {
+ assert(!(Shift & 0x7) && "Shifts not aligned on Bytes are not support.");
+ uint64_t Offset = Shift / 8;
+ unsigned TySizeInBytes = Origin->getType()->getPrimitiveSizeInBits() / 8;
+ assert(!(Origin->getType()->getPrimitiveSizeInBits() & 0x7) &&
+ "The size of the original loaded type is not a multiple of a"
+ " byte.");
+ // If Offset is bigger than TySizeInBytes, it means we are loading all
+ // zeros. This should have been optimized before in the process.
+ assert(TySizeInBytes > Offset &&
+ "Invalid shift amount for given loaded size");
+ if (IsBigEndian)
+ Offset = TySizeInBytes - Offset - getLoadedSize();
+ return Offset;
+ }
+
+ /// \brief Generate the sequence of instructions to load the slice
+ /// represented by this object and redirect the uses of this slice to
+ /// this new sequence of instructions.
+ /// \pre this->Inst && this->Origin are valid Instructions.
+ /// \return The last instruction of the sequence used to load the slice.
+ Instruction *loadSlice(InstCombiner::BuilderTy &Builder,
+ bool IsBigEndian) const {
+ assert(Inst && Origin && "Unable to replace a non-existing slice.");
+ Value *BaseAddr = Origin->getOperand(0);
+ unsigned Alignment = Origin->getAlignment();
+ Builder.SetInsertPoint(Origin);
+ // Assume we are looking at a chunk of bytes.
+ // BaseAddr = (i8*)BaseAddr.
+ BaseAddr = Builder.CreateBitCast(BaseAddr, Builder.getInt8PtrTy(),
+ "raw_cast");
+ // Get the offset in that chunk of bytes w.r.t. the endianess.
+ uint64_t Offset = getOffsetFromBase(IsBigEndian);
+ if (Offset) {
+ APInt APOffset(64, Offset);
+ // BaseAddr = BaseAddr + Offset.
+ BaseAddr = Builder.CreateInBoundsGEP(BaseAddr, Builder.getInt(APOffset),
+ "raw_idx");
+ }
+
+ // Create the type of the loaded slice according to its size.
+ Type *SliceType =
+ Type::getIntNTy(Origin->getContext(), getLoadedSize() * 8);
+
+ // Bit cast the raw pointer to the pointer type of the slice.
+ BaseAddr = Builder.CreateBitCast(BaseAddr, SliceType->getPointerTo(),
+ "cast");
+
+ // Compute the new alignment.
+ if (Offset != 0)
+ Alignment = MinAlign(Alignment, Alignment + Offset);
+
+ // Create the load for the slice.
+ Instruction *LastInst = Builder.CreateAlignedLoad(BaseAddr, Alignment,
+ Inst->getName()+".val");
+ // If the final type is not the same as the loaded type, this means that
+ // we have to pad with zero. Create a zero extend for that.
+ Type * FinalType = Inst->getType();
+ if (SliceType != FinalType)
+ LastInst = cast<Instruction>(Builder.CreateZExt(LastInst, FinalType));
+
+ // Update the IR to reflect the new access to the slice.
+ Inst->replaceAllUsesWith(LastInst);
+
+ return LastInst;
+ }
+
+ /// \brief Check if it would be profitable to expand this slice as an
+ /// independant load.
+ bool isProfitable() const {
+ // Slicing is assumed to be profitable iff the chains leads to arithmetic
+ // operations.
+ SmallVector<const Instruction *, 8> Uses;
+ Uses.push_back(Inst);
+ do {
+ const Instruction *Use = Uses.pop_back_val();
+ for (Value::const_use_iterator UseIt = Use->use_begin(),
+ UseItEnd = Use->use_end(); UseIt != UseItEnd; ++UseIt) {
+ const Instruction *UseOfUse = cast<Instruction>(*UseIt);
+ // Consider these instructions as arithmetic operations.
+ if (isa<BinaryOperator>(UseOfUse) ||
+ isa<CastInst>(UseOfUse) ||
+ isa<PHINode>(UseOfUse) ||
+ isa<GetElementPtrInst>(UseOfUse))
+ return true;
+ // No need to check if the Use has already been checked as we do not
+ // insert any PHINode.
+ Uses.push_back(UseOfUse);
+ }
+ } while (!Uses.empty());
+ DEBUG(dbgs() << "IC: Not a profitable slice " << *Inst << '\n');
+ return false;
+ }
+ };
+}
+
+/// \brief Check the profitability of all involved LoadedSlice.
+/// Unless StressLoadSlicing is specified, this also returns false
+/// when slicing is not in the canonical form.
+/// The canonical form of sliced load is (1) two loads,
+/// which are (2) next to each other in memory.
+///
+/// FIXME: We may want to allow more slices to be created but
+/// this means other passes should know how to deal with all those
+/// slices.
+/// FIXME: We may want to split loads to different types, e.g.,
+/// int vs. float.
+static bool
+isSlicingProfitable(const SmallVectorImpl<LoadedSlice> &LoadedSlices,
+ const APInt &UsedBits) {
+ unsigned NbOfSlices = LoadedSlices.size();
+ // Check (1).
+ if (!StressLoadSlicing && NbOfSlices != 2)
+ return false;
+
+ // Check (2).
+ if (!StressLoadSlicing && !UsedBits.isAllOnesValue()) {
+ // Get rid of the unused bits on the right.
+ APInt MemoryLayout = UsedBits.lshr(UsedBits.countTrailingZeros());
+ // Get rid of the unused bits on the left.
+ if (MemoryLayout.countLeadingZeros())
+ MemoryLayout = MemoryLayout.trunc(MemoryLayout.getActiveBits());
+ // Check that the chunk of memory is completely used.
+ if (!MemoryLayout.isAllOnesValue())
+ return false;
+ }
+
+ unsigned NbOfProfitableSlices = 0;
+ for (unsigned CurrSlice = 0; CurrSlice < NbOfSlices; ++CurrSlice) {
+ if (LoadedSlices[CurrSlice].isProfitable())
+ ++NbOfProfitableSlices;
+ else if (!StressLoadSlicing)
+ return false;
+ }
+ // In Stress mode, we may have 0 profitable slice.
+ // Check that here.
+ // In non-Stress mode, all the slices are profitable at this point.
+ return NbOfProfitableSlices > 0;
+}
+
+/// \brief If the given load, \p LI, is used only by trunc or trunc(lshr)
+/// operations, split it in the various pieces being extracted.
+///
+/// This sort of thing is introduced by SROA.
+/// This slicing takes care not to insert overlapping loads.
+/// \pre LI is a simple load (i.e., not an atomic or volatile load).
+static Instruction *sliceUpLoadInst(LoadInst &LI,
+ InstCombiner::BuilderTy &Builder,
+ DataLayout &TD) {
+ assert(LI.isSimple() && "We are trying to transform a non-simple load!");
+
+ // FIXME: If we want to support floating point and vector types, we should
+ // support bitcast and extract/insert element instructions.
+ Type *LITy = LI.getType();
+ if (!LITy->isIntegerTy()) return 0;
+
+ // Keep track of already used bits to detect overlapping values.
+ // In that case, we will just abort the transformation.
+ APInt UsedBits(LITy->getPrimitiveSizeInBits(), 0);
+
+ SmallVector<LoadedSlice, 4> LoadedSlices;
+
+ // Check if this load is used as several smaller chunks of bits.
+ // Basically, look for uses in trunc or trunc(lshr) and record a new chain
+ // of computation for each trunc.
+ for (Value::use_iterator UI = LI.use_begin(), UIEnd = LI.use_end();
+ UI != UIEnd; ++UI) {
+ Instruction *User = cast<Instruction>(*UI);
+ unsigned Shift = 0;
+
+ // Check if this is a trunc(lshr).
+ if (User->getOpcode() == Instruction::LShr && User->hasOneUse() &&
+ isa<ConstantInt>(User->getOperand(1))) {
+ Shift = cast<ConstantInt>(User->getOperand(1))->getZExtValue();
+ User = User->use_back();
+ }
+
+ // At this point, User is a TruncInst, iff we encountered, trunc or
+ // trunc(lshr).
+ if (!isa<TruncInst>(User))
+ return 0;
+
+ // The width of the type must be a power of 2 and greater than 8-bits.
+ // Otherwise the load cannot be represented in LLVM IR.
+ // Moreover, if we shifted with a non 8-bits multiple, the slice
+ // will be accross several bytes. We do not support that.
+ unsigned Width = User->getType()->getPrimitiveSizeInBits();
+ if (Width < 8 || !isPowerOf2_32(Width) || (Shift & 0x7))
+ return 0;
+
+ // Build the slice for this chain of computations.
+ LoadedSlice LS(User, &LI, Shift);
+ APInt CurrentUsedBits = LS.getUsedBits();
+
+ // Check if this slice overlaps with another.
+ if ((CurrentUsedBits & UsedBits) != 0)
+ return 0;
+ // Update the bits used globally.
+ UsedBits |= CurrentUsedBits;
+
+ // Record the slice.
+ LoadedSlices.push_back(LS);
+ }
+
+ // Abort slicing if it does not seem to be profitable.
+ if (!isSlicingProfitable(LoadedSlices, UsedBits))
+ return 0;
+
+ // Rewrite each chain to use an independent load.
+ // By construction, each chain can be represented by a unique load.
+ bool IsBigEndian = TD.isBigEndian();
+ for (SmallVectorImpl<LoadedSlice>::const_iterator LSIt = LoadedSlices.begin(),
+ LSItEnd = LoadedSlices.end(); LSIt != LSItEnd; ++LSIt) {
+ Instruction *SliceInst = LSIt->loadSlice(Builder, IsBigEndian);
+ (void)SliceInst;
+ DEBUG(dbgs() << "IC: Replacing " << *LSIt->Inst << "\n"
+ " with " << *SliceInst << '\n');
+ }
+ return 0; // Don't do anything with LI.
+}
+
Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
Value *Op = LI.getOperand(0);
// None of the following transforms are legal for volatile/atomic loads.
// FIXME: Some of it is okay for atomic loads; needs refactoring.
if (!LI.isSimple()) return 0;
-
+
// Do really simple store-to-load forwarding and load CSE, to catch cases
// where there are several consecutive memory accesses to the same location,
// separated by a few arithmetic operations.
Constant::getNullValue(Op->getType()), &LI);
return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
}
- }
+ }
// load null/undef -> unreachable
// TODO: Consider a target hook for valid address spaces for this xform.
if (CE->isCast())
if (Instruction *Res = InstCombineLoadCast(*this, LI, TD))
return Res;
-
+
if (Op->hasOneUse()) {
// Change select and PHI nodes to select values instead of addresses: this
// helps alias analysis out a lot, allows many others simplifications, and
}
}
}
+
+ // Try to split a load in smaller non-overlapping loads to expose independant
+ // chain of computations and get rid of trunc/lshr sequence of code.
+ // The data layout is required for that operation, as code generation will
+ // change with respect to endianess.
+ if (TD)
+ return sliceUpLoadInst(LI, *Builder, *TD);
return 0;
}
Type *DestPTy = cast<PointerType>(CI->getType())->getElementType();
PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType());
if (SrcTy == 0) return 0;
-
+
Type *SrcPTy = SrcTy->getElementType();
if (!DestPTy->isIntegerTy() && !DestPTy->isPointerTy())
return 0;
-
+
/// NewGEPIndices - If SrcPTy is an aggregate type, we can emit a "noop gep"
/// to its first element. This allows us to handle things like:
/// store i32 xxx, (bitcast {foo*, float}* %P to i32*)
/// on 32-bit hosts.
SmallVector<Value*, 4> NewGEPIndices;
-
+
// If the source is an array, the code below will not succeed. Check to
// see if a trivial 'gep P, 0, 0' will help matters. Only do this for
// constants.
// Index through pointer.
Constant *Zero = Constant::getNullValue(Type::getInt32Ty(SI.getContext()));
NewGEPIndices.push_back(Zero);
-
+
while (1) {
if (StructType *STy = dyn_cast<StructType>(SrcPTy)) {
if (!STy->getNumElements()) /* Struct can be empty {} */
break;
}
}
-
+
SrcTy = PointerType::get(SrcPTy, SrcTy->getAddressSpace());
}
if (!SrcPTy->isIntegerTy() && !SrcPTy->isPointerTy())
return 0;
-
+
// If the pointers point into different address spaces or if they point to
// values with different sizes, we can't do the transformation.
if (!IC.getDataLayout() ||
- SrcTy->getAddressSpace() !=
+ SrcTy->getAddressSpace() !=
cast<PointerType>(CI->getType())->getAddressSpace() ||
IC.getDataLayout()->getTypeSizeInBits(SrcPTy) !=
IC.getDataLayout()->getTypeSizeInBits(DestPTy))
return 0;
// Okay, we are casting from one integer or pointer type to another of
- // the same size. Instead of casting the pointer before
+ // the same size. Instead of casting the pointer before
// the store, cast the value to be stored.
Value *NewCast;
Value *SIOp0 = SI.getOperand(0);
if (SIOp0->getType()->isPointerTy())
opcode = Instruction::PtrToInt;
}
-
+
// SIOp0 is a pointer to aggregate and this is a store to the first field,
// emit a GEP to index into its first field.
if (!NewGEPIndices.empty())
CastOp = IC.Builder->CreateInBoundsGEP(CastOp, NewGEPIndices);
-
+
NewCast = IC.Builder->CreateCast(opcode, SIOp0, CastDstTy,
SIOp0->getName()+".c");
SI.setOperand(0, NewCast);
static bool equivalentAddressValues(Value *A, Value *B) {
// Test if the values are trivially equivalent.
if (A == B) return true;
-
+
// Test if the values come form identical arithmetic instructions.
// This uses isIdenticalToWhenDefined instead of isIdenticalTo because
// its only used to compare two uses within the same basic block, which
if (Instruction *BI = dyn_cast<Instruction>(B))
if (cast<Instruction>(A)->isIdenticalToWhenDefined(BI))
return true;
-
+
// Otherwise they may not be equivalent.
return false;
}
// If the RHS is an alloca with a single use, zapify the store, making the
// alloca dead.
if (Ptr->hasOneUse()) {
- if (isa<AllocaInst>(Ptr))
+ if (isa<AllocaInst>(Ptr))
return EraseInstFromFunction(SI);
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr)) {
if (isa<AllocaInst>(GEP->getOperand(0))) {
(isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())) {
ScanInsts++;
continue;
- }
-
+ }
+
if (StoreInst *PrevSI = dyn_cast<StoreInst>(BBI)) {
// Prev store isn't volatile, and stores to the same location?
if (PrevSI->isSimple() && equivalentAddressValues(PrevSI->getOperand(1),
}
break;
}
-
+
// If this is a load, we have to stop. However, if the loaded value is from
// the pointer we're loading and is producing the pointer we're storing,
// then *this* store is dead (X = load P; store X -> P).
if (LI == Val && equivalentAddressValues(LI->getOperand(0), Ptr) &&
LI->isSimple())
return EraseInstFromFunction(SI);
-
+
// Otherwise, this is a load from some other location. Stores before it
// may not be dead.
break;
}
-
+
// Don't skip over loads or things that can modify memory.
if (BBI->mayWriteToMemory() || BBI->mayReadFromMemory())
break;
if (Instruction *Res = InstCombineStoreToCast(*this, SI))
return Res;
-
+
// If this store is the last instruction in the basic block (possibly
// excepting debug info instructions), and if the block ends with an
// unconditional branch, try to move it to the successor block.
- BBI = &SI;
+ BBI = &SI;
do {
++BBI;
} while (isa<DbgInfoIntrinsic>(BBI) ||
if (BI->isUnconditional())
if (SimplifyStoreAtEndOfBlock(SI))
return 0; // xform done!
-
+
return 0;
}
///
bool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) {
BasicBlock *StoreBB = SI.getParent();
-
+
// Check to see if the successor block has exactly two incoming edges. If
// so, see if the other predecessor contains a store to the same location.
// if so, insert a PHI node (if needed) and move the stores down.
BasicBlock *DestBB = StoreBB->getTerminator()->getSuccessor(0);
-
+
// Determine whether Dest has exactly two predecessors and, if so, compute
// the other predecessor.
pred_iterator PI = pred_begin(DestBB);
if (++PI == pred_end(DestBB))
return false;
-
+
P = *PI;
if (P != StoreBB) {
if (OtherBB)
BranchInst *OtherBr = dyn_cast<BranchInst>(BBI);
if (!OtherBr || BBI == OtherBB->begin())
return false;
-
+
// If the other block ends in an unconditional branch, check for the 'if then
// else' case. there is an instruction before the branch.
StoreInst *OtherStore = 0;
} else {
// Otherwise, the other block ended with a conditional branch. If one of the
// destinations is StoreBB, then we have the if/then case.
- if (OtherBr->getSuccessor(0) != StoreBB &&
+ if (OtherBr->getSuccessor(0) != StoreBB &&
OtherBr->getSuccessor(1) != StoreBB)
return false;
-
+
// Okay, we know that OtherBr now goes to Dest and StoreBB, so this is an
// if/then triangle. See if there is a store to the same ptr as SI that
// lives in OtherBB.
BBI == OtherBB->begin())
return false;
}
-
+
// In order to eliminate the store in OtherBr, we have to
// make sure nothing reads or overwrites the stored value in
// StoreBB.
return false;
}
}
-
+
// Insert a PHI node now if we need it.
Value *MergedVal = OtherStore->getOperand(0);
if (MergedVal != SI.getOperand(0)) {
PN->addIncoming(OtherStore->getOperand(0), OtherBB);
MergedVal = InsertNewInstBefore(PN, DestBB->front());
}
-
+
// Advance to a place where it is safe to insert the new store and
// insert it.
BBI = DestBB->getFirstInsertionPt();
SI.getOrdering(),
SI.getSynchScope());
InsertNewInstBefore(NewSI, *BBI);
- NewSI->setDebugLoc(OtherStore->getDebugLoc());
+ NewSI->setDebugLoc(OtherStore->getDebugLoc());
// If the two stores had the same TBAA tag, preserve it.
- if (MDNode *TBAATag1 = SI.getMetadata(LLVMContext::MD_tbaa))
- if (MDNode *TBAATag2 = OtherStore->getMetadata(LLVMContext::MD_tbaa))
- if (TBAATag1 == TBAATag2)
- NewSI->setMetadata(LLVMContext::MD_tbaa, TBAATag1);
+ if (MDNode *TBAATag = SI.getMetadata(LLVMContext::MD_tbaa))
+ if ((TBAATag = MDNode::getMostGenericTBAA(TBAATag,
+ OtherStore->getMetadata(LLVMContext::MD_tbaa))))
+ NewSI->setMetadata(LLVMContext::MD_tbaa, TBAATag);
+
-
// Nuke the old stores.
EraseInstFromFunction(SI);
EraseInstFromFunction(*OtherStore);