[llvm] r258646 - [SelectionDAG] Generalised the CONCAT_VECTORS creation to support BUILD_VECTOR and UNDEF folding.

[Simon Pilgrim via llvm-commits]

Author: rksimon
Date: Sat Jan 23 16:27:54 2016
New Revision: 258646

URL: http://llvm.org/viewvc/llvm-project?rev=258646&view=rev
Log:
[SelectionDAG] Generalised the CONCAT_VECTORS creation to support BUILD_VECTOR and UNDEF folding.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
    llvm/trunk/test/CodeGen/X86/avx-cast.ll

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp?rev=258646&r1=258645&r2=258646&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp Sat Jan 23 16:27:54 2016
@@ -2844,18 +2844,20 @@ static SDValue FoldCONCAT_VECTORS(SDLoc
                   [](SDValue Op) { return Op.isUndef(); }))
     return DAG.getUNDEF(VT);
 
-  // A CONCAT_VECTOR with all operands BUILD_VECTOR can be simplified
-  // to one big BUILD_VECTOR.
-  // FIXME: Add support for UNDEF and SCALAR_TO_VECTOR as well.
-  if (!std::all_of(Ops.begin(), Ops.end(), [](SDValue Op) {
-        return Op.getOpcode() == ISD::BUILD_VECTOR;
-      }))
-    return SDValue();
-
+  // A CONCAT_VECTOR with all UNDEF/BUILD_VECTOR operands can be
+  // simplified to one big BUILD_VECTOR.
+  // FIXME: Add support for SCALAR_TO_VECTOR as well.
   EVT SVT = VT.getScalarType();
   SmallVector<SDValue, 16> Elts;
-  for (SDValue Op : Ops)
-    Elts.append(Op->op_begin(), Op->op_end());
+  for (SDValue Op : Ops) {
+    EVT OpVT = Op.getValueType();
+    if (Op.isUndef())
+      Elts.append(OpVT.getVectorNumElements(), DAG.getUNDEF(SVT));
+    else if (Op.getOpcode() == ISD::BUILD_VECTOR)
+      Elts.append(Op->op_begin(), Op->op_end());
+    else
+      return SDValue();
+  }
 
   // BUILD_VECTOR requires all inputs to be of the same type, find the
   // maximum type and extend them all.

Modified: llvm/trunk/test/CodeGen/X86/avx-cast.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/avx-cast.ll?rev=258646&r1=258645&r2=258646&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/avx-cast.ll (original)
+++ llvm/trunk/test/CodeGen/X86/avx-cast.ll Sat Jan 23 16:27:54 2016
@@ -31,8 +31,8 @@ define <4 x double> @castB(<2 x double>
 define <4 x i64> @castC(<2 x i64> %m) nounwind uwtable readnone ssp {
 ; AVX1-LABEL: castC:
 ; AVX1:       ## BB#0:
-; AVX1-NEXT:    vxorps %ymm1, %ymm1, %ymm1
-; AVX1-NEXT:    vblendps {{.*#+}} ymm0 = ymm0[0,1,2,3],ymm1[4,5,6,7]
+; AVX1-NEXT:    vxorpd %ymm1, %ymm1, %ymm1
+; AVX1-NEXT:    vblendpd {{.*#+}} ymm0 = ymm0[0,1],ymm1[2,3]
 ; AVX1-NEXT:    retq
 ;
 ; AVX2-LABEL: castC: