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[ValueTracking] Fix crash in GetPointerBaseWithConstantOffset() 

Summary:
While walking defs of pointer operands we were assuming that the pointer
size would remain constant.  This is not true, because addresspacecast
instructions may cast the pointer to an address space with a different
pointer width.

This partial reverts r282612, which was a more conservative solution
to this problem.

Reviewers: reames, sanjoy, apilipenko

Subscribers: wdng, llvm-commits

Differential Revision: https://reviews.llvm.org/D24772

llvm-svn: 283557
This commit is contained in:
Tom Stellard 2016-10-07 14:23:29 +00:00
parent 88b9d66d4a
commit 17eb3413cd
3 changed files with 36 additions and 30 deletions
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19
llvm/lib/Analysis/ValueTracking.cpp
View File

@ -2855,21 +2855,22 @@ Value *llvm::GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset,
break;
if (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
APInt GEPOffset(BitWidth, 0);
// If one of the values we have visited is an addrspacecast, then
// the pointer type of this GEP may be different from the type
// of the Ptr parameter which was passed to this function. This
// means when we construct GEPOffset, we need to use the size
// of GEP's pointer type rather than the size of the original
// pointer type.
APInt GEPOffset(DL.getPointerTypeSizeInBits(Ptr->getType()), 0);
if (!GEP->accumulateConstantOffset(DL, GEPOffset))
break;
ByteOffset += GEPOffset;
ByteOffset += GEPOffset.getSExtValue();
Ptr = GEP->getPointerOperand();
} else if (Operator::getOpcode(Ptr) == Instruction::BitCast) {
} else if (Operator::getOpcode(Ptr) == Instruction::BitCast ||
Operator::getOpcode(Ptr) == Instruction::AddrSpaceCast) {
Ptr = cast<Operator>(Ptr)->getOperand(0);
} else if (AddrSpaceCastInst *ASCI = dyn_cast<AddrSpaceCastInst>(Ptr)) {
Value *SourcePtr = ASCI->getPointerOperand();
// Don't look through addrspace cast which changes pointer size
if (BitWidth != DL.getPointerTypeSizeInBits(SourcePtr->getType()))
break;
Ptr = SourcePtr;
} else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(Ptr)) {
if (GA->isInterposable())
break;

26
llvm/test/Analysis/ValueTracking/get-pointer-base-with-const-off.ll Normal file
View File

@ -0,0 +1,26 @@
; RUN: opt -gvn -S < %s | FileCheck %s
; Make sure we don't crash when analyzing an addrspacecast in
; GetPointerBaseWithConstantOffset()
target datalayout = "e-p:32:32-p4:64:64"
define i32 @addrspacecast-crash() {
; CHECK-LABEL: @addrspacecast-crash
; CHECK: %tmp = alloca [25 x i64]
; CHECK: %tmp1 = getelementptr inbounds [25 x i64], [25 x i64]* %tmp, i32 0, i32 0
; CHECK: %tmp2 = addrspacecast i64* %tmp1 to <8 x i64> addrspace(4)*
; CHECK: store <8 x i64> zeroinitializer, <8 x i64> addrspace(4)* %tmp2
; CHECK-NOT: load
bb:
%tmp = alloca [25 x i64]
%tmp1 = getelementptr inbounds [25 x i64], [25 x i64]* %tmp, i32 0, i32 0
%tmp2 = addrspacecast i64* %tmp1 to <8 x i64> addrspace(4)*
%tmp3 = getelementptr inbounds <8 x i64>, <8 x i64> addrspace(4)* %tmp2, i64 0
store <8 x i64> zeroinitializer, <8 x i64> addrspace(4)* %tmp3
%tmp4 = getelementptr inbounds [25 x i64], [25 x i64]* %tmp, i32 0, i32 0
%tmp5 = addrspacecast i64* %tmp4 to i32 addrspace(4)*
%tmp6 = getelementptr inbounds i32, i32 addrspace(4)* %tmp5, i64 10
%tmp7 = load i32, i32 addrspace(4)* %tmp6, align 4
ret i32 %tmp7
}

21
llvm/test/Transforms/GVN/addrspace-cast.ll
View File

@ -1,21 +0,0 @@
; RUN: opt < %s -gvn -S | FileCheck %s
target datalayout = "e-m:e-p:16:16-p1:32:16-i32:16-i64:16-n8:16"
; In cases where two address spaces do not have the same size pointer, the
; input for the addrspacecast should not be used as a substitute for itself
; when manipulating the pointer.
; Check that we don't hit the assert in this scenario
define i8 @test(i32 %V, i32* %P) {
; CHECK-LABEL: @test(
; CHECK: load
%P1 = getelementptr inbounds i32, i32* %P, i16 16
store i32 %V, i32* %P1
%P2 = addrspacecast i32* %P1 to i8 addrspace(1)*
%P3 = getelementptr i8, i8 addrspace(1)* %P2, i32 2
%A = load i8, i8 addrspace(1)* %P3
ret i8 %A
}