[InstCombine] fix crash due to ignored addrspacecast

Summary:
Part of the InstCombine code for simplifying GEPs looks through
addrspacecasts. However, this was done by updating a variable
also used by the next transformation, for marking GEPs as
inbounds. This led to replacing a GEP with a similar instruction
in a different addrspace, which caused an assertion failure in RAUW.

This caused julia issue https://github.com/JuliaLang/julia/issues/27055

Patch by Jeff Bezanson <jeff@juliacomputing.com>

Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D46722

llvm-svn: 332302

1 files changed, 3 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 2549257bc97..e0a9ec21621 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1937,16 +1937,17 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
   // addrspacecast between types is canonicalized as a bitcast, then an
   // addrspacecast. To take advantage of the below bitcast + struct GEP, look
   // through the addrspacecast.
+  Value *ASCStrippedPtrOp = PtrOp;
   if (auto *ASC = dyn_cast<AddrSpaceCastInst>(PtrOp)) {
     //   X = bitcast A addrspace(1)* to B addrspace(1)*
     //   Y = addrspacecast A addrspace(1)* to B addrspace(2)*
     //   Z = gep Y, <...constant indices...>
     // Into an addrspacecasted GEP of the struct.
     if (auto *BC = dyn_cast<BitCastInst>(ASC->getOperand(0)))
-      PtrOp = BC;
+      ASCStrippedPtrOp = BC;
   }
 
-  if (auto *BCI = dyn_cast<BitCastInst>(PtrOp)) {
+  if (auto *BCI = dyn_cast<BitCastInst>(ASCStrippedPtrOp)) {
     Value *SrcOp = BCI->getOperand(0);
     PointerType *SrcType = cast<PointerType>(BCI->getSrcTy());
     Type *SrcEltType = SrcType->getElementType();