Preserving 'nonnull' metadata in SimplifyCFG

When we hoist two loads above an if, we can preserve the nonnull metadata.  We could also do the same for sinking them, but we appear to not handle metadata at all in that case.

Thanks to Hal for the review.

Differential Revision: http://reviews.llvm.org/D5910



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220392 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Utils/SimplifyCFG.cpp

@@ -1061,7 +1061,8 @@ static bool HoistThenElseCodeToIf(BranchInst *BI, const DataLayout *DL) {
       LLVMContext::MD_tbaa,
       LLVMContext::MD_range,
       LLVMContext::MD_fpmath,
-      LLVMContext::MD_invariant_load
+      LLVMContext::MD_invariant_load,
+      LLVMContext::MD_nonnull
     };
     combineMetadata(I1, I2, KnownIDs);
     I2->eraseFromParent();
@@ -1311,6 +1312,8 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
     if (!I2->use_empty())
       I2->replaceAllUsesWith(I1);
     I1->intersectOptionalDataWith(I2);
+    // TODO: Use combineMetadata here to preserve what metadata we can
+    // (analogous to the hoisting case above).
     I2->eraseFromParent();
 
     if (UpdateRE1)