[llvm-commits] [llvm] r130426 - /llvm/trunk/lib/Transforms/Scalar/GVN.cpp

[Chris Lattner]

Author: lattner
Date: Thu Apr 28 15:02:57 2011
New Revision: 130426

URL: http://llvm.org/viewvc/llvm-project?rev=130426&view=rev
Log:
improve comment.

Modified:
    llvm/trunk/lib/Transforms/Scalar/GVN.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/GVN.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/GVN.cpp?rev=130426&r1=130425&r2=130426&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/GVN.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/GVN.cpp Thu Apr 28 15:02:57 2011
@@ -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;
   }