From: Eli Friedman <eli.friedman@gmail.com>
Date: Thu, 15 Sep 2011 01:14:29 +0000 (+0000)
Subject: Make demanded-elt simplification for shufflevector slightly stronger.  Spotted by... 
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=c82751dd6761e3db62668b6b1cfddd4f659855b6;p=oota-llvm.git

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
---

diff --git a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index 66f39be17b3..81929bc6230 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;
diff --git a/test/Transforms/InstCombine/vec_demanded_elts.ll b/test/Transforms/InstCombine/vec_demanded_elts.ll
index e0188fe91ae..cc63371eded 100644
--- a/test/Transforms/InstCombine/vec_demanded_elts.ll
+++ b/test/Transforms/InstCombine/vec_demanded_elts.ll
@@ -152,3 +152,14 @@ entry:
 	ret <4 x i32> %0
 }
 declare <4 x i32> @llvm.x86.sse41.pmovzxwd(<8 x i16>) nounwind readnone
+
+define <4 x float> @dead_shuffle_elt(<4 x float> %x, <2 x float> %y) nounwind {
+entry:
+; CHECK: define <4 x float> @dead_shuffle_elt
+; CHECK: shufflevector <2 x float> %y, <2 x float> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
+  %shuffle.i = shufflevector <2 x float> %y, <2 x float> %y, <4 x i32> <i32 0, i32 1, i32 0, i32 1>
+  %shuffle9.i = shufflevector <4 x float> %x, <4 x float> %shuffle.i, <4 x i32> <i32 4, i32 5, i32 2, i32 3>
+  ret <4 x float> %shuffle9.i
+}
+
+