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IR: Don't constant fold GEP bitcasts between different address spaces

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PR15262 reported a bug where the following instruction:

  i8 getelementptr inbounds i8* bitcast ([4 x i8] addrspace(12)* @buf to i8*),
                                i32 2

was getting folded into:

  addrspace(12)* getelementptr inbounds ([4 x i8] addrspace(12)* @buf, i32 0,
                                        i32 2)

This caused instcombine to crash because the original instruction and
the folded instruction have different types.  The issue was fixed by
disallowing bitcasts between different address spaces to be folded away.

llvm-svn: 176156
This commit is contained in:
Meador Inge 2013-02-27 02:26:42 +00:00
parent 894d0f9fc3
commit c24a74205b
2 changed files with 42 additions and 13 deletions
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35
lib/IR/ConstantFold.cpp
View File

@ -1971,21 +1971,30 @@ static Constant *ConstantFoldGetElementPtrImpl(Constant *C,
}
}
// Implement folding of:
// i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*),
// i64 0, i64 0)
// To: i32* getelementptr ([3 x i32]* %X, i64 0, i64 0)
// Attempt to fold casts to the same type away. For example, folding:
//
// i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*),
// i64 0, i64 0)
// into:
//
// i32* getelementptr ([3 x i32]* %X, i64 0, i64 0)
//
// Don't fold if the cast is changing address spaces.
if (CE->isCast() && Idxs.size() > 1 && Idx0->isNullValue()) {
if (PointerType *SPT =
dyn_cast<PointerType>(CE->getOperand(0)->getType()))
if (ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
if (ArrayType *CAT =
dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
if (CAT->getElementType() == SAT->getElementType())
return
ConstantExpr::getGetElementPtr((Constant*)CE->getOperand(0),
Idxs, inBounds);
PointerType *SrcPtrTy =
dyn_cast<PointerType>(CE->getOperand(0)->getType());
PointerType *DstPtrTy = dyn_cast<PointerType>(CE->getType());
if (SrcPtrTy && DstPtrTy) {
ArrayType *SrcArrayTy =
dyn_cast<ArrayType>(SrcPtrTy->getElementType());
ArrayType *DstArrayTy =
dyn_cast<ArrayType>(DstPtrTy->getElementType());
if (SrcArrayTy && DstArrayTy
&& SrcArrayTy->getElementType() == DstArrayTy->getElementType()
&& SrcPtrTy->getAddressSpace() == DstPtrTy->getAddressSpace())
return ConstantExpr::getGetElementPtr((Constant*)CE->getOperand(0),
Idxs, inBounds);
}
}
}

20
test/Other/constant-fold-gep.ll
View File

@ -447,4 +447,24 @@ define i32* @fZ() nounwind {
ret i32* %t
}
; PR15262 - Check GEP folding with casts between address spaces.
@p0 = global [4 x i8] zeroinitializer, align 1
@p12 = addrspace(12) global [4 x i8] zeroinitializer, align 1
define i8* @different_addrspace() nounwind noinline {
; OPT: different_addrspace
%p = getelementptr inbounds i8* bitcast ([4 x i8] addrspace(12)* @p12 to i8*),
i32 2
ret i8* %p
; OPT: ret i8* getelementptr (i8* bitcast ([4 x i8] addrspace(12)* @p12 to i8*), i32 2)
}
define i8* @same_addrspace() nounwind noinline {
; OPT: same_addrspace
%p = getelementptr inbounds i8* bitcast ([4 x i8] * @p0 to i8*), i32 2
ret i8* %p
; OPT: ret i8* getelementptr inbounds ([4 x i8]* @p0, i32 0, i32 2)
}
; CHECK: attributes #0 = { nounwind }