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InstCombine optimizes gep(bitcast(x)) even when the bitcasts casts away address

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space info. We crash with an assert in this case. This change checks that the
address space of the bitcasted pointer is the same as the gep ptr.

llvm-svn: 128884
This commit is contained in:
Nadav Rotem 2011-04-05 14:29:52 +00:00
parent b6e583dc5f
commit 8bb81fc184
2 changed files with 27 additions and 8 deletions
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19
lib/Transforms/InstCombine/InstructionCombining.cpp
View File

@ -849,22 +849,23 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
GetElementPtrInst::Create(Src->getOperand(0), Indices.begin(),
Indices.end(), GEP.getName());
}
// Handle gep(bitcast x) and gep(gep x, 0, 0, 0).
Value *StrippedPtr = PtrOp->stripPointerCasts();
if (StrippedPtr != PtrOp) {
const PointerType *StrippedPtrTy =cast<PointerType>(StrippedPtr->getType());
const PointerType *StrippedPtrTy =cast<PointerType>(StrippedPtr->getType());
if (StrippedPtr != PtrOp &&
StrippedPtrTy->getAddressSpace() == GEP.getPointerAddressSpace()) {
bool HasZeroPointerIndex = false;
if (ConstantInt *C = dyn_cast<ConstantInt>(GEP.getOperand(1)))
HasZeroPointerIndex = C->isZero();
// Transform: GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ...
// into : GEP [10 x i8]* X, i32 0, ...
//
// Likewise, transform: GEP (bitcast i8* X to [0 x i8]*), i32 0, ...
// into : GEP i8* X, ...
//
//
// This occurs when the program declares an array extern like "int X[];"
if (HasZeroPointerIndex) {
const PointerType *CPTy = cast<PointerType>(PtrOp->getType());
@ -975,7 +976,7 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
}
}
}
/// See if we can simplify:
/// X = bitcast A* to B*
/// Y = gep X, <...constant indices...>
@ -983,12 +984,14 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
/// analysis of unions. If "A" is also a bitcast, wait for A/X to be merged.
if (BitCastInst *BCI = dyn_cast<BitCastInst>(PtrOp)) {
if (TD &&
!isa<BitCastInst>(BCI->getOperand(0)) && GEP.hasAllConstantIndices()) {
!isa<BitCastInst>(BCI->getOperand(0)) && GEP.hasAllConstantIndices() &&
StrippedPtrTy->getAddressSpace() == GEP.getPointerAddressSpace()) {
// Determine how much the GEP moves the pointer. We are guaranteed to get
// a constant back from EmitGEPOffset.
ConstantInt *OffsetV = cast<ConstantInt>(EmitGEPOffset(&GEP));
int64_t Offset = OffsetV->getSExtValue();
// If this GEP instruction doesn't move the pointer, just replace the GEP
// with a bitcast of the real input to the dest type.
if (Offset == 0) {

16
test/Transforms/InstCombine/gep-addrspace.ll Normal file
View File

@ -0,0 +1,16 @@
; RUN: opt < %s -instcombine -S
%myStruct = type { float, [3 x float], [4 x float], i32 }
; make sure that we are not crashing when creating an illegal type
define void @func(%myStruct addrspace(1)* nocapture %p) nounwind {
ST:
%A = getelementptr inbounds %myStruct addrspace(1)* %p, i64 0
%B = bitcast %myStruct addrspace(1)* %A to %myStruct*
%C = getelementptr inbounds %myStruct* %B, i32 0, i32 1
%D = getelementptr inbounds [3 x float]* %C, i32 0, i32 2
%E = load float* %D, align 4
%F = fsub float %E, undef
ret void
}