InferAddressSpaces: Avoid assertion failure with replacing identical

cloned constexpr

Have cloneConstantExprWithNewAddressSpaces return nullptr when
returning initial ConstantExpr.

Reviewers: arsenm

Subscribers: jholewinski, wdng, llvm-commits

Differential Revision: https://reviews.llvm.org/D33995

llvm-svn: 304975

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp b/llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp
index 85a017e9bce..3c8fbd35bf8 100644
--- a/llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp
+++ b/llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp
@@ -500,6 +500,7 @@ static Value *cloneConstantExprWithNewAddressSpace(
   }
 
   // Computes the operands of the new constant expression.
+  bool IsNew = false;
   SmallVector<Constant *, 4> NewOperands;
   for (unsigned Index = 0; Index < CE->getNumOperands(); ++Index) {
     Constant *Operand = CE->getOperand(Index);
@@ -509,6 +510,7 @@ static Value *cloneConstantExprWithNewAddressSpace(
     // bitcast, and getelementptr) do not incur cycles in the data flow graph
     // and (2) this function is called on constant expressions in postorder.
     if (Value *NewOperand = ValueWithNewAddrSpace.lookup(Operand)) {
+      IsNew = true;
       NewOperands.push_back(cast<Constant>(NewOperand));
     } else {
       // Otherwise, reuses the old operand.
@@ -516,6 +518,11 @@ static Value *cloneConstantExprWithNewAddressSpace(
     }
   }
 
+  // If !IsNew, we will replace the Value with itself. However, replaced values
+  // are assumed to wrapped in a addrspace cast later so drop it now.
+  if (!IsNew)
+    return nullptr;
+
   if (CE->getOpcode() == Instruction::GetElementPtr) {
     // Needs to specify the source type while constructing a getelementptr
     // constant expression.