Fix InstCombine address space assert

Workaround bug where the InstCombine pass was asserting on the IR added in lit
test, where we have a bitcast instruction after a GEP from an addrspace cast.

The second bitcast in the test was getting combined into
`bitcast <16 x i32>* %0 to <16 x i32> addrspace(3)*`, which looks like it should
be an addrspace cast instruction instead. Otherwise if control flow is allowed
to continue as it is now we create a GEP instruction
`<badref> = getelementptr inbounds <16 x i32>, <16 x i32>* %0, i32 0`. However
because the type of this instruction doesn't match the address space we hit an
assert when replacing the bitcast with that GEP.

```
void llvm::Value::doRAUW(llvm::Value*, bool): Assertion `New->getType() == getType() && "replaceAllUses of value with new value of different type!"' failed.
```

Differential Revision: https://reviews.llvm.org/D50058

llvm-svn: 338395

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
index e8ea7396a96..fd59c3a7c0c 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -2243,6 +2243,12 @@ Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
     Type *DstElTy = DstPTy->getElementType();
     Type *SrcElTy = SrcPTy->getElementType();
 
+    // Casting pointers between the same type, but with different address spaces
+    // is an addrspace cast rather than a bitcast.
+    if ((DstElTy == SrcElTy) &&
+        (DstPTy->getAddressSpace() != SrcPTy->getAddressSpace()))
+      return new AddrSpaceCastInst(Src, DestTy);
+
     // If we are casting a alloca to a pointer to a type of the same
     // size, rewrite the allocation instruction to allocate the "right" type.
     // There is no need to modify malloc calls because it is their bitcast that