DAGLegalize: add last-ditch type-legalization for VSELECT.

When LLVM sees something like (v1iN (vselect v1i1, v1iN, v1iN)) it can
decide that the result is OK (v1i64 is legal on AArch64, for example)
but it still need scalarising because of that v1i1. There was no code
to do this though.

AArch64 and ARM64 have DAG combines to produce efficient code and
prevent that occuring in *most* such situations, but there are edge
cases that they miss. This adds a legalization to cope with that.

llvm-svn: 205626

2 files changed, 16 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h b/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h
index 947ea10fd70..835d34f004f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h
@@ -540,6 +540,7 @@ private:
   SDValue ScalarizeVecOp_UnaryOp(SDNode *N);
   SDValue ScalarizeVecOp_CONCAT_VECTORS(SDNode *N);
   SDValue ScalarizeVecOp_EXTRACT_VECTOR_ELT(SDNode *N);
+  SDValue ScalarizeVecOp_VSELECT(SDNode *N);
   SDValue ScalarizeVecOp_STORE(StoreSDNode *N, unsigned OpNo);
   SDValue ScalarizeVecOp_FP_ROUND(SDNode *N, unsigned OpNo);
 
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
index 04de324eabf..3c7f111a33e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -394,6 +394,9 @@ bool DAGTypeLegalizer::ScalarizeVectorOperand(SDNode *N, unsigned OpNo) {
     case ISD::EXTRACT_VECTOR_ELT:
       Res = ScalarizeVecOp_EXTRACT_VECTOR_ELT(N);
       break;
+    case ISD::VSELECT:
+      Res = ScalarizeVecOp_VSELECT(N);
+      break;
     case ISD::STORE:
       Res = ScalarizeVecOp_STORE(cast<StoreSDNode>(N), OpNo);
       break;
@@ -462,6 +465,18 @@ SDValue DAGTypeLegalizer::ScalarizeVecOp_EXTRACT_VECTOR_ELT(SDNode *N) {
   return Res;
 }
 
+
+/// ScalarizeVecOp_VSELECT - If the input condition is a vector that needs to be
+/// scalarized, it must be <1 x i1>, so just convert to a normal ISD::SELECT
+/// (still with vector output type since that was acceptable if we got here).
+SDValue DAGTypeLegalizer::ScalarizeVecOp_VSELECT(SDNode *N) {
+  SDValue ScalarCond = GetScalarizedVector(N->getOperand(0));
+  EVT VT = N->getValueType(0);
+
+  return DAG.getNode(ISD::SELECT, SDLoc(N), VT, ScalarCond, N->getOperand(1),
+                     N->getOperand(2));
+}
+
 /// ScalarizeVecOp_STORE - If the value to store is a vector that needs to be
 /// scalarized, it must be <1 x ty>.  Just store the element.
 SDValue DAGTypeLegalizer::ScalarizeVecOp_STORE(StoreSDNode *N, unsigned OpNo){