From 718da3d1f6976a1bf89f960519ddab1316637c9a Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Fri, 29 Jul 2016 18:48:27 +0000
Subject: [PATCH] [ConstantFolding] Handle bitcasts of undef fp vector elements

We used the wrong type for constructing a zero vector element which led
to type mismatches.

This fixes PR28771.

llvm-svn: 277197
---
 llvm/lib/Analysis/ConstantFolding.cpp    | 2 +-
 llvm/test/Transforms/InstCombine/cast.ll | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 60b94a9..39e422f 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -187,7 +187,7 @@ Constant *FoldBitCast(Constant *C, Type *DestTy, const DataLayout &DL) {
       for (unsigned j = 0; j != Ratio; ++j) {
         Constant *Src = C->getAggregateElement(SrcElt++);
         if (Src && isa<UndefValue>(Src))
-          Src = Constant::getNullValue(SrcEltTy);
+          Src = Constant::getNullValue(C->getType()->getVectorElementType());
         else
           Src = dyn_cast_or_null<ConstantInt>(Src);
         if (!Src)  // Reject constantexpr elements.
diff --git a/llvm/test/Transforms/InstCombine/cast.ll b/llvm/test/Transforms/InstCombine/cast.ll
index 46ae14c..c4990ea 100644
--- a/llvm/test/Transforms/InstCombine/cast.ll
+++ b/llvm/test/Transforms/InstCombine/cast.ll
@@ -1386,3 +1386,10 @@ define i32 @test89() {
 ; CHECK-NEXT:    ret i32 393216
   ret i32 bitcast (<2 x i16> <i16 6, i16 undef> to i32)
 }
+
+define <2 x i32> @test90() {
+; CHECK-LABEL: @test90(
+; CHECK: ret <2 x i32> <i32 0, i32 15360>
+  %tmp6 = bitcast <4 x half> <half undef, half undef, half undef, half 0xH3C00> to <2 x i32>
+  ret <2 x i32> %tmp6
+}
-- 
2.7.4