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Fix part 3/2 of PR3290, making instcombine zap (gep(bitcast)) when possible.
llvm-svn: 61980
This commit is contained in:
Chris Lattner
parent
4166afffa7
commit
5ce930d116
@ -7695,6 +7695,66 @@ Instruction *InstCombiner::commonCastTransforms(CastInst &CI) {
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return 0;
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}
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/// FindElementAtOffset - Given a type and a constant offset, determine whether
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/// or not there is a sequence of GEP indices into the type that will land us at
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/// the specified offset. If so, fill them into NewIndices and return true,
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/// otherwise return false.
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static bool FindElementAtOffset(const Type *Ty, int64_t Offset,
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SmallVectorImpl<Value*> &NewIndices,
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const TargetData *TD) {
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if (!Ty->isSized()) return false;
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// Start with the index over the outer type. Note that the type size
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// might be zero (even if the offset isn't zero) if the indexed type
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// is something like [0 x {int, int}]
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const Type *IntPtrTy = TD->getIntPtrType();
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int64_t FirstIdx = 0;
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if (int64_t TySize = TD->getABITypeSize(Ty)) {
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FirstIdx = Offset/TySize;
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Offset %= TySize;
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// Handle silly modulus not returning values values [0..TySize).
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if (Offset < 0) {
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--FirstIdx;
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Offset += TySize;
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assert(Offset >= 0);
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}
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assert((uint64_t)Offset < (uint64_t)TySize && "Out of range offset");
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}
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NewIndices.push_back(ConstantInt::get(IntPtrTy, FirstIdx));
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// Index into the types. If we fail, set OrigBase to null.
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while (Offset) {
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if (const StructType *STy = dyn_cast<StructType>(Ty)) {
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const StructLayout *SL = TD->getStructLayout(STy);
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if (Offset >= (int64_t)SL->getSizeInBytes()) {
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// We can't index into this, bail out.
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return false;
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}
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unsigned Elt = SL->getElementContainingOffset(Offset);
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NewIndices.push_back(ConstantInt::get(Type::Int32Ty, Elt));
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Offset -= SL->getElementOffset(Elt);
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Ty = STy->getElementType(Elt);
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} else if (isa<ArrayType>(Ty) || isa<VectorType>(Ty)) {
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const SequentialType *STy = cast<SequentialType>(Ty);
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if (uint64_t EltSize = TD->getABITypeSize(STy->getElementType())) {
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NewIndices.push_back(ConstantInt::get(IntPtrTy,Offset/EltSize));
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Offset %= EltSize;
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} else {
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NewIndices.push_back(ConstantInt::get(IntPtrTy, 0));
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}
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Ty = STy->getElementType();
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} else {
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// Otherwise, we can't index into this, bail out.
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return false;
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}
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}
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return true;
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}
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/// @brief Implement the transforms for cast of pointer (bitcast/ptrtoint)
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Instruction *InstCombiner::commonPointerCastTransforms(CastInst &CI) {
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Value *Src = CI.getOperand(0);
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@ -7725,74 +7785,21 @@ Instruction *InstCombiner::commonPointerCastTransforms(CastInst &CI) {
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Value *OrigBase = cast<BitCastInst>(GEP->getOperand(0))->getOperand(0);
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const Type *GEPIdxTy =
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cast<PointerType>(OrigBase->getType())->getElementType();
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if (GEPIdxTy->isSized()) {
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SmallVector<Value*, 8> NewIndices;
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SmallVector<Value*, 8> NewIndices;
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if (FindElementAtOffset(GEPIdxTy, Offset, NewIndices, TD)) {
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// If we were able to index down into an element, create the GEP
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// and bitcast the result. This eliminates one bitcast, potentially
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// two.
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Instruction *NGEP = GetElementPtrInst::Create(OrigBase,
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NewIndices.begin(),
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NewIndices.end(), "");
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InsertNewInstBefore(NGEP, CI);
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NGEP->takeName(GEP);
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// Start with the index over the outer type. Note that the type size
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// might be zero (even if the offset isn't zero) if the indexed type
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// is something like [0 x {int, int}]
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const Type *IntPtrTy = TD->getIntPtrType();
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int64_t FirstIdx = 0;
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if (int64_t TySize = TD->getABITypeSize(GEPIdxTy)) {
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FirstIdx = Offset/TySize;
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Offset %= TySize;
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// Handle silly modulus not returning values values [0..TySize).
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if (Offset < 0) {
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--FirstIdx;
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Offset += TySize;
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assert(Offset >= 0);
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}
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assert((uint64_t)Offset < (uint64_t)TySize &&"Out of range offset");
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}
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NewIndices.push_back(ConstantInt::get(IntPtrTy, FirstIdx));
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// Index into the types. If we fail, set OrigBase to null.
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while (Offset) {
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if (const StructType *STy = dyn_cast<StructType>(GEPIdxTy)) {
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const StructLayout *SL = TD->getStructLayout(STy);
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if (Offset < (int64_t)SL->getSizeInBytes()) {
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unsigned Elt = SL->getElementContainingOffset(Offset);
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NewIndices.push_back(ConstantInt::get(Type::Int32Ty, Elt));
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Offset -= SL->getElementOffset(Elt);
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GEPIdxTy = STy->getElementType(Elt);
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} else {
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// Otherwise, we can't index into this, bail out.
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Offset = 0;
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OrigBase = 0;
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}
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} else if (isa<ArrayType>(GEPIdxTy) || isa<VectorType>(GEPIdxTy)) {
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const SequentialType *STy = cast<SequentialType>(GEPIdxTy);
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if (uint64_t EltSize = TD->getABITypeSize(STy->getElementType())){
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NewIndices.push_back(ConstantInt::get(IntPtrTy,Offset/EltSize));
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Offset %= EltSize;
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} else {
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NewIndices.push_back(ConstantInt::get(IntPtrTy, 0));
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}
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GEPIdxTy = STy->getElementType();
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} else {
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// Otherwise, we can't index into this, bail out.
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Offset = 0;
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OrigBase = 0;
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}
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}
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if (OrigBase) {
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// If we were able to index down into an element, create the GEP
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// and bitcast the result. This eliminates one bitcast, potentially
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// two.
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Instruction *NGEP = GetElementPtrInst::Create(OrigBase,
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NewIndices.begin(),
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NewIndices.end(), "");
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InsertNewInstBefore(NGEP, CI);
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NGEP->takeName(GEP);
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if (isa<BitCastInst>(CI))
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return new BitCastInst(NGEP, CI.getType());
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assert(isa<PtrToIntInst>(CI));
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return new PtrToIntInst(NGEP, CI.getType());
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}
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if (isa<BitCastInst>(CI))
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return new BitCastInst(NGEP, CI.getType());
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assert(isa<PtrToIntInst>(CI));
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return new PtrToIntInst(NGEP, CI.getType());
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}
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}
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}
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@ -10675,24 +10682,52 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
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}
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}
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/// See if we can simplify:
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/// X = bitcast A to B*
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/// Y = gep X, <...constant indices...>
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/// into a gep of the original struct. This is important for SROA and alias
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/// analysis of unions. If "A" is also a bitcast, wait for A/X to be merged.
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if (BitCastInst *BCI = dyn_cast<BitCastInst>(PtrOp)) {
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// If this GEP instruction doesn't move the pointer, just replace the GEP
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// with a bitcast of the real input to the dest type.
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if (GEP.hasAllZeroIndices()) {
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// If the bitcast is of an allocation, and the allocation will be
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// converted to match the type of the cast, don't touch this.
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if (isa<AllocationInst>(BCI->getOperand(0))) {
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// See if the bitcast simplifies, if so, don't nuke this GEP yet.
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if (Instruction *I = visitBitCast(*BCI)) {
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if (I != BCI) {
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I->takeName(BCI);
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BCI->getParent()->getInstList().insert(BCI, I);
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ReplaceInstUsesWith(*BCI, I);
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if (!isa<BitCastInst>(BCI->getOperand(0)) && GEP.hasAllConstantIndices()) {
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// Determine how much the GEP moves the pointer. We are guaranteed to get
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// a constant back from EmitGEPOffset.
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ConstantInt *OffsetV = cast<ConstantInt>(EmitGEPOffset(&GEP, GEP, *this));
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int64_t Offset = OffsetV->getSExtValue();
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// If this GEP instruction doesn't move the pointer, just replace the GEP
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// with a bitcast of the real input to the dest type.
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if (Offset == 0) {
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// If the bitcast is of an allocation, and the allocation will be
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// converted to match the type of the cast, don't touch this.
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if (isa<AllocationInst>(BCI->getOperand(0))) {
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// See if the bitcast simplifies, if so, don't nuke this GEP yet.
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if (Instruction *I = visitBitCast(*BCI)) {
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if (I != BCI) {
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I->takeName(BCI);
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BCI->getParent()->getInstList().insert(BCI, I);
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ReplaceInstUsesWith(*BCI, I);
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}
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return &GEP;
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}
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return &GEP;
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}
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return new BitCastInst(BCI->getOperand(0), GEP.getType());
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}
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// Otherwise, if the offset is non-zero, we need to find out if there is a
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// field at Offset in 'A's type. If so, we can pull the cast through the
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// GEP.
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SmallVector<Value*, 8> NewIndices;
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const Type *InTy =
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cast<PointerType>(BCI->getOperand(0)->getType())->getElementType();
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if (FindElementAtOffset(InTy, Offset, NewIndices, TD)) {
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Instruction *NGEP =
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GetElementPtrInst::Create(BCI->getOperand(0), NewIndices.begin(),
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NewIndices.end());
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if (NGEP->getType() == GEP.getType()) return NGEP;
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InsertNewInstBefore(NGEP, GEP);
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NGEP->takeName(&GEP);
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return new BitCastInst(NGEP, GEP.getType());
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}
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return new BitCastInst(BCI->getOperand(0), GEP.getType());
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}
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}
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@ -17,3 +17,14 @@ define i8* @test(i8* %v) {
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%G = load i8** %F ; <i8*> [#uses=1]
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ret i8* %G
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}
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; PR3290
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%struct.Key = type { { i32, i32 } }
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%struct.anon = type <{ i8, [3 x i8], i32 }>
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define i32 *@test2(%struct.Key *%A) {
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%B = bitcast %struct.Key* %A to %struct.anon*
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%C = getelementptr %struct.anon* %B, i32 0, i32 2
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ret i32 *%C
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}
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