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.
llvm-svn: 104185
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 347024f..0ea46af 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -6024,6 +6024,10 @@
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)) {