From b7e230d999deec5c90ee51a7c2bbc6ee5be0a914 Mon Sep 17 00:00:00 2001
From: Nadav Rotem <nadav.rotem@intel.com>
Date: Sat, 14 Jul 2012 21:30:27 +0000
Subject: [PATCH] Add a dagcombine optimization to convert concat_vectors of
 undefs into a single undef. The unoptimized concat_vectors isd prevented the
 canonicalization of the vector_shuffle node.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160221 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 11 +++++++++++
 test/CodeGen/X86/2012-07-10-shufnorm.ll  | 17 +++++++++++++++++
 2 files changed, 28 insertions(+)
 create mode 100644 test/CodeGen/X86/2012-07-10-shufnorm.ll

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index e2c7dec40c7..1e87d5184f2 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7816,6 +7816,17 @@ SDValue DAGCombiner::visitCONCAT_VECTORS(SDNode *N) {
   if (N->getNumOperands() == 1)
     return N->getOperand(0);
 
+  // Check if all of the operands are undefs.
+  bool AllUndef = true;
+  for (unsigned i = 0; i < N->getNumOperands(); ++i)
+    if (N->getOperand(i).getOpcode() != ISD::UNDEF) {
+      AllUndef = false;
+      break;
+    }
+
+  if (AllUndef)
+    return DAG.getUNDEF(N->getValueType(0));
+
   return SDValue();
 }
 
diff --git a/test/CodeGen/X86/2012-07-10-shufnorm.ll b/test/CodeGen/X86/2012-07-10-shufnorm.ll
new file mode 100644
index 00000000000..e39df58877f
--- /dev/null
+++ b/test/CodeGen/X86/2012-07-10-shufnorm.ll
@@ -0,0 +1,17 @@
+; RUN: llc < %s -march=x86 -mcpu=corei7 -mattr=+avx | FileCheck %s
+
+; CHECK: ocl
+define void @ocl() {
+entry:
+  %vext = shufflevector <2 x double> zeroinitializer, <2 x double> undef, <8 x i32> <i32 0, i32 1, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef>
+  %vecinit = shufflevector <8 x double> %vext, <8 x double> undef, <8 x i32> <i32 0, i32 1, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef>
+  %vecinit1 = insertelement <8 x double> %vecinit, double undef, i32 2
+  %vecinit3 = insertelement <8 x double> %vecinit1, double undef, i32 3
+  %vecinit5 = insertelement <8 x double> %vecinit3, double 0.000000e+00, i32 4
+  %vecinit9 = shufflevector <8 x double> %vecinit5, <8 x double> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 8, i32 9, i32 10>
+  store <8 x double> %vecinit9, <8 x double>* undef
+  ret void
+; CHECK: vxorps
+; CHECK: ret
+}
+
-- 
2.34.1