From 0381c21d2ddc182aebfef25c6500d781ddb428fe Mon Sep 17 00:00:00 2001
From: Eli Friedman <eli.friedman@gmail.com>
Date: Wed, 20 Jul 2011 18:14:33 +0000
Subject: [PATCH] PR10421: Fix a straightforward bug in the widening logic for
 CONCAT_VECTORS.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135595 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp | 10 +++++-----
 test/CodeGen/X86/widen_shuffle-1.ll              |  8 ++++++++
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp b/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
index 85a169261aa..c8454bf28ee 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -1661,6 +1661,7 @@ SDValue DAGTypeLegalizer::WidenVecRes_CONCAT_VECTORS(SDNode *N) {
   EVT WidenVT = TLI.getTypeToTransformTo(*DAG.getContext(), N->getValueType(0));
   DebugLoc dl = N->getDebugLoc();
   unsigned WidenNumElts = WidenVT.getVectorNumElements();
+  unsigned NumInElts = InVT.getVectorNumElements();
   unsigned NumOperands = N->getNumOperands();
 
   bool InputWidened = false; // Indicates we need to widen the input.
@@ -1686,17 +1687,17 @@ SDValue DAGTypeLegalizer::WidenVecRes_CONCAT_VECTORS(SDNode *N) {
         if (N->getOperand(i).getOpcode() != ISD::UNDEF)
           break;
 
-      if (i > NumOperands)
+      if (i == NumOperands)
         // Everything but the first operand is an UNDEF so just return the
         // widened first operand.
         return GetWidenedVector(N->getOperand(0));
 
       if (NumOperands == 2) {
         // Replace concat of two operands with a shuffle.
-        SmallVector<int, 16> MaskOps(WidenNumElts);
-        for (unsigned i=0; i < WidenNumElts/2; ++i) {
+        SmallVector<int, 16> MaskOps(WidenNumElts, -1);
+        for (unsigned i = 0; i < NumInElts; ++i) {
           MaskOps[i] = i;
-          MaskOps[i+WidenNumElts/2] = i+WidenNumElts;
+          MaskOps[i + NumInElts] = i + WidenNumElts;
         }
         return DAG.getVectorShuffle(WidenVT, dl,
                                     GetWidenedVector(N->getOperand(0)),
@@ -1708,7 +1709,6 @@ SDValue DAGTypeLegalizer::WidenVecRes_CONCAT_VECTORS(SDNode *N) {
 
   // Fall back to use extracts and build vector.
   EVT EltVT = WidenVT.getVectorElementType();
-  unsigned NumInElts = InVT.getVectorNumElements();
   SmallVector<SDValue, 16> Ops(WidenNumElts);
   unsigned Idx = 0;
   for (unsigned i=0; i < NumOperands; ++i) {
diff --git a/test/CodeGen/X86/widen_shuffle-1.ll b/test/CodeGen/X86/widen_shuffle-1.ll
index 034c42c758b..8e951b77ca6 100644
--- a/test/CodeGen/X86/widen_shuffle-1.ll
+++ b/test/CodeGen/X86/widen_shuffle-1.ll
@@ -30,6 +30,7 @@ entry:
 ; opA with opB, the DAG will produce new operations with opA.
 define void @shuf3(<4 x float> %tmp10, <4 x float> %vecinit15, <4 x float>* %dst) nounwind {
 entry:
+; CHECK: shuf3:
 ; CHECK: pshufd
   %shuffle.i.i.i12 = shufflevector <4 x float> %tmp10, <4 x float> %vecinit15, <4 x i32> <i32 0, i32 1, i32 4, i32 5>
   %tmp25.i.i = shufflevector <4 x float> %shuffle.i.i.i12, <4 x float> undef, <3 x i32> <i32 0, i32 1, i32 2> 
@@ -46,3 +47,10 @@ entry:
   ret void
 }
 
+; PR10421: make sure we correctly handle extreme widening with CONCAT_VECTORS
+define <8 x i8> @shuf4(<4 x i8> %a, <4 x i8> %b) nounwind readnone {
+; CHECK: shuf4:
+; CHECK: punpckldq
+  %vshuf = shufflevector <4 x i8> %a, <4 x i8> %b, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  ret <8 x i8> %vshuf
+}
-- 
2.34.1