From: Bob Wilson <bob.wilson@apple.com>
Date: Wed, 19 May 2010 23:42:58 +0000 (+0000)
Subject: Optimize away insertelement of an undef value.  This shows up in
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=492fd454ca3aa3d45e76c4f42b602e934cf519b1;p=oota-llvm.git

Optimize away insertelement of an undef value.  This shows up in
test/Codegen/ARM/reg_sequence.ll but it doesn't affect the generated code
because the coalescer cleans it up.  Radar 7998853.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@104185 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 347024f0ae4..0ea46af2acf 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -6024,6 +6024,10 @@ SDValue DAGCombiner::visitINSERT_VECTOR_ELT(SDNode *N) {
   SDValue InVal = N->getOperand(1);
   SDValue EltNo = N->getOperand(2);
 
+  // If the inserted element is an UNDEF, just use the input vector.
+  if (InVal.getOpcode() == ISD::UNDEF)
+    return InVec;
+
   // If the invec is a BUILD_VECTOR and if EltNo is a constant, build a new
   // vector with the inserted element.
   if (InVec.getOpcode() == ISD::BUILD_VECTOR && isa<ConstantSDNode>(EltNo)) {