Index: lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp	(revision 201645)
+++ lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp	(working copy)
@@ -299,6 +299,17 @@
 
     Type *SrcPTy = SrcTy->getElementType();
 
+    // XXX note that we might end up with a bogus cast: if the original
+    // cast in 'load (cast P)' is between "foo addrspace1 **" and "foo
+    // addrspace2 **", then we cannot re-express the two operations as
+    // 'cast (load P)' because that would be casting a "foo addrspace1 *"
+    // to "foo addrspace2 *".  While nothing is really wrong about that
+    // cast, llvm forbids it even in internally-generated operations.
+    if (SrcPTy->isPointerTy() && DestPTy->isPointerTy() &&
+         cast<PointerType>(DestPTy)->getAddressSpace() !=
+         cast<PointerType>(SrcPTy)->getAddressSpace())
+      return 0;
+
     if (DestPTy->isIntegerTy() || DestPTy->isPointerTy() ||
          DestPTy->isVectorTy()) {
       // If the source is an array, the code below will not succeed.  Check to
@@ -510,6 +521,12 @@
       IC.getDataLayout()->getTypeSizeInBits(DestPTy))
     return 0;
 
+  // XXX this is similar to the issue in InstCombineLoadCast
+  if (SrcPTy->isPointerTy() && DestPTy->isPointerTy() &&
+       cast<PointerType>(DestPTy)->getAddressSpace() !=
+       cast<PointerType>(SrcPTy)->getAddressSpace())
+    return 0;
+
   // Okay, we are casting from one integer or pointer type to another of
   // the same size.  Instead of casting the pointer before
   // the store, cast the value to be stored.