[ConstantFold] Delay fetching pointer element type

Don't do this while stipping pointer casts, instead fetch it at
the end. This improves compatibility with opaque pointers for the
case where the base object is not opaque.

1 files changed, 6 insertions, 8 deletions

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index ceed375..1c6709c 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -867,8 +867,7 @@ Constant *CastGEPIndices(Type *SrcElemTy, ArrayRef<Constant *> Ops,
 }
 
 /// Strip the pointer casts, but preserve the address space information.
-Constant *StripPtrCastKeepAS(Constant *Ptr, Type *&ElemTy,
-                             bool ForLoadOperand) {
+Constant *StripPtrCastKeepAS(Constant *Ptr, bool ForLoadOperand) {
   assert(Ptr->getType()->isPointerTy() && "Not a pointer type");
   auto *OldPtrTy = cast<PointerType>(Ptr->getType());
   Ptr = cast<Constant>(Ptr->stripPointerCasts());
@@ -881,8 +880,6 @@ Constant *StripPtrCastKeepAS(Constant *Ptr, Type *&ElemTy,
 
   auto *NewPtrTy = cast<PointerType>(Ptr->getType());
 
-  ElemTy = NewPtrTy->getPointerElementType();
-
   // Preserve the address space number of the pointer.
   if (NewPtrTy->getAddressSpace() != OldPtrTy->getAddressSpace()) {
     Ptr = ConstantExpr::getPointerCast(
@@ -942,7 +939,7 @@ Constant *SymbolicallyEvaluateGEP(const GEPOperator *GEP,
             DL.getIndexedOffsetInType(
                 SrcElemTy,
                 makeArrayRef((Value * const *)Ops.data() + 1, Ops.size() - 1)));
-  Ptr = StripPtrCastKeepAS(Ptr, SrcElemTy, ForLoadOperand);
+  Ptr = StripPtrCastKeepAS(Ptr, ForLoadOperand);
 
   // If this is a GEP of a GEP, fold it all into a single GEP.
   while (auto *GEP = dyn_cast<GEPOperator>(Ptr)) {
@@ -964,7 +961,7 @@ Constant *SymbolicallyEvaluateGEP(const GEPOperator *GEP,
     Ptr = cast<Constant>(GEP->getOperand(0));
     SrcElemTy = GEP->getSourceElementType();
     Offset += APInt(BitWidth, DL.getIndexedOffsetInType(SrcElemTy, NestedOps));
-    Ptr = StripPtrCastKeepAS(Ptr, SrcElemTy, ForLoadOperand);
+    Ptr = StripPtrCastKeepAS(Ptr, ForLoadOperand);
   }
 
   // If the base value for this address is a literal integer value, fold the
@@ -988,8 +985,9 @@ Constant *SymbolicallyEvaluateGEP(const GEPOperator *GEP,
   // we eliminate over-indexing of the notional static type array bounds.
   // This makes it easy to determine if the getelementptr is "inbounds".
   // Also, this helps GlobalOpt do SROA on GlobalVariables.
-  Type *Ty = PTy;
   SmallVector<Constant *, 32> NewIdxs;
+  Type *Ty = PTy;
+  SrcElemTy = PTy->getElementType();
 
   do {
     if (!Ty->isStructTy()) {
@@ -1074,7 +1072,7 @@ Constant *SymbolicallyEvaluateGEP(const GEPOperator *GEP,
 
   // If we ended up indexing a member with a type that doesn't match
   // the type of what the original indices indexed, add a cast.
-  if (Ty != ResElemTy)
+  if (C->getType() != ResTy)
     C = FoldBitCast(C, ResTy, DL);
 
   return C;