[RS4GC] Fix rematerialization of bitcast of bitcast.

Summary:
Previously, only the outer (last) bitcast was rematerialized, resulting in a
use of the unrelocated inner (first) bitcast after the statepoint.  See the
test case for an example.

Reviewers: igor-laevsky, reames

Subscribers: reames, alex, llvm-commits, sanjoy

Differential Revision: http://reviews.llvm.org/D15789

llvm-svn: 256520

1 files changed, 2 insertions, 6 deletions

diff --git a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
index a077ba01a92..a9dc8d8eec0 100644
--- a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
+++ b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
@@ -2101,16 +2101,12 @@ static bool findRematerializableChainToBasePointer(
   }
 
   if (CastInst *CI = dyn_cast<CastInst>(CurrentValue)) {
-    Value *Def = CI->stripPointerCasts();
-
-    // This two checks are basically similar. First one is here for the
-    // consistency with findBasePointers logic.
-    assert(!isa<CastInst>(Def) && "not a pointer cast found");
     if (!CI->isNoopCast(CI->getModule()->getDataLayout()))
       return false;
 
     ChainToBase.push_back(CI);
-    return findRematerializableChainToBasePointer(ChainToBase, Def, BaseValue);
+    return findRematerializableChainToBasePointer(ChainToBase,
+                                                  CI->getOperand(0), BaseValue);
   }
 
   // Not supported instruction in the chain