commit 187db7b950e57e2f1f10b57e7ee2a7f38e8965c0
author Dan Gohman <gohman@apple.com> Mon Apr 28 18:47:17 2008 +0000
committer Dan Gohman <gohman@apple.com> Mon Apr 28 18:47:17 2008 +0000
tree 0b398091f5d11a6465ea8db71d647a7d6896b182
parent ebc3a3a3b2adb3bf5a1dae0c0e6572be79375efd

Evan pointed out that folding sext to zext may not be correct
if the zext is not legal.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50368 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index dc59006..28f32d3 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2888,7 +2888,8 @@
   }
   
   // fold (sext x) -> (zext x) if the sign bit is known zero.
-  if (DAG.SignBitIsZero(N0))
+  if ((!AfterLegalize || TLI.isOperationLegal(ISD::ZERO_EXTEND, VT)) &&
+      DAG.SignBitIsZero(N0))
     return DAG.getNode(ISD::ZERO_EXTEND, VT, N0);
   
   return SDOperand();