diff options
| -rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 15 | ||||
| -rw-r--r-- | test/CodeGen/X86/2010-09-17-SideEffectsInChain.ll | 8 |
2 files changed, 17 insertions, 6 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index c9c4d91e97..91e370b271 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -7030,8 +7030,19 @@ bool DAGCombiner::isAlias(SDValue Ptr1, int64_t Size1, if (Base1 == Base2 || (GV1 && (GV1 == GV2)) || (CV1 && (CV1 == CV2))) return !((Offset1 + Size1) <= Offset2 || (Offset2 + Size2) <= Offset1); - // If we know what the bases are, and they aren't identical, then we know they - // cannot alias. + // It is possible for different frame indices to alias each other, mostly + // when tail call optimization reuses return address slots for arguments. + // To catch this case, look up the actual index of frame indices to compute + // the real alias relationship. + if (isFrameIndex1 && isFrameIndex2) { + MachineFrameInfo *MFI = DAG.getMachineFunction().getFrameInfo(); + Offset1 += MFI->getObjectOffset(cast<FrameIndexSDNode>(Base1)->getIndex()); + Offset2 += MFI->getObjectOffset(cast<FrameIndexSDNode>(Base2)->getIndex()); + return !((Offset1 + Size1) <= Offset2 || (Offset2 + Size2) <= Offset1); + } + + // Otherwise, if we know what the bases are, and they aren't identical, then + // we know they cannot alias. if ((isFrameIndex1 || CV1 || GV1) && (isFrameIndex2 || CV2 || GV2)) return false; diff --git a/test/CodeGen/X86/2010-09-17-SideEffectsInChain.ll b/test/CodeGen/X86/2010-09-17-SideEffectsInChain.ll index 35434ffafa..8fe0309421 100644 --- a/test/CodeGen/X86/2010-09-17-SideEffectsInChain.ll +++ b/test/CodeGen/X86/2010-09-17-SideEffectsInChain.ll @@ -19,8 +19,8 @@ entry: } ; CHECK: movq ___stack_chk_guard@GOTPCREL(%rip), %rax -; CHECK: movb (%rsp), %dl -; CHECK-NEXT: movb 30(%rsp), %sil -; CHECK: movb %dl, (%rsp) -; CHECK-NEXT: movb %sil, 30(%rsp) +; CHECK: movb 30(%rsp), %dl +; CHECK: movb (%rsp), %sil +; CHECK: movb %sil, (%rsp) +; CHECK: movb %dl, 30(%rsp) ; CHECK: callq ___stack_chk_fail |