improve comment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130426 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp
index abd7689..efecb97 100644
--- a/lib/Transforms/Scalar/GVN.cpp
+++ b/lib/Transforms/Scalar/GVN.cpp
@@ -969,8 +969,13 @@
NewLoadSize*8-SrcVal->getType()->getPrimitiveSizeInBits());
RV = Builder.CreateTrunc(RV, SrcVal->getType());
SrcVal->replaceAllUsesWith(RV);
+
+ // We would like to use gvn.markInstructionForDeletion here, but we can't
+ // because the load is already memoized into the leader map table that GVN
+ // tracks. It is potentially possible to remove the load from the table,
+ // but then there all of the operations based on it would need to be
+ // rehashed. Just leave the dead load around.
gvn.getMemDep().removeInstruction(SrcVal);
- //gvn.markInstructionForDeletion(SrcVal);
SrcVal = NewLoad;
}