From 7e0e166d1783671e555eff26b9932012fadea691 Mon Sep 17 00:00:00 2001
From: Nick Lewycky <nicholas@mxc.ca>
Date: Fri, 28 Sep 2012 09:33:53 +0000
Subject: [PATCH] Surprisingly, we missed a trivial case here. Fix that!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164814 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/InstCombine/InstCombineSelect.cpp | 4 ++++
 test/Transforms/InstCombine/vec_shuffle.ll       | 8 ++++++++
 2 files changed, 12 insertions(+)

diff --git a/lib/Transforms/InstCombine/InstCombineSelect.cpp b/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 70483ceb062..0ba7340e642 100644
--- a/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -930,6 +930,10 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
       Value *V = Builder->CreateShuffleVector(TrueVal, FalseVal, MaskVal);
       return ReplaceInstUsesWith(SI, V);
     }
+
+    if (isa<ConstantAggregateZero>(CondVal)) {
+      return ReplaceInstUsesWith(SI, FalseVal);
+    }
   }
 
   return 0;
diff --git a/test/Transforms/InstCombine/vec_shuffle.ll b/test/Transforms/InstCombine/vec_shuffle.ll
index a7f9fcfbe0f..14f532195d7 100644
--- a/test/Transforms/InstCombine/vec_shuffle.ll
+++ b/test/Transforms/InstCombine/vec_shuffle.ll
@@ -188,3 +188,11 @@ define <4 x i16> @test13d(<4 x i16> %lhs, <4 x i16> %rhs) {
            <4 x i16> %lhs, <4 x i16> %rhs
   ret <4 x i16> %A
 }
+
+define <4 x i16> @test13e(<4 x i16> %lhs, <4 x i16> %rhs) {
+; CHECK: @test13e
+; CHECK-NEXT: ret <4 x i16> %rhs
+  %A = select <4 x i1> <i1 false, i1 false, i1 false, i1 false>,
+           <4 x i16> %lhs, <4 x i16> %rhs
+  ret <4 x i16> %A
+}