From c82751dd6761e3db62668b6b1cfddd4f659855b6 Mon Sep 17 00:00:00 2001
From: Eli Friedman <eli.friedman@gmail.com>
Date: Thu, 15 Sep 2011 01:14:29 +0000
Subject: Make demanded-elt simplification for shufflevector slightly stronger.
  Spotted by inspection.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139768 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'lib')

diff --git a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index 66f39be17b..81929bc623 100644
--- a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -962,6 +962,9 @@ Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
       unsigned MaskVal = Shuffle->getMaskValue(i);
       if (MaskVal == -1u) {
         UndefElts.setBit(i);
+      } else if (!DemandedElts[i]) {
+        NewUndefElts = true;
+        UndefElts.setBit(i);
       } else if (MaskVal < LHSVWidth) {
         if (UndefElts4[MaskVal]) {
           NewUndefElts = true;
-- 
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