[SelectionDAG] When scalarizing vselect, don't assert on

a legal cond operand.

When scalarizing the result of a vselect, the legalizer currently expects
to already have scalarized the operands. While this is true for the true/false
operands (which have the same type as the result), it is not case for the
condition operand. On X86 AVX512, v1i1 is legal - this leads to operations such
as '< N x type> vselect < N x i1> < N x type> < N x type>' where < N x type > is
illegal to hit an assertion during the scalarization.

The handling is similar to r205625.
This also exposes the fact that (v1i1 extract_subvector) should be legal
and selectable on AVX512 - We do this by custom lowering to vector_extract_elt.
This still leaves us in some cases with redundant dag nodes which will be
combined in a separate soon to come patch.

This fixes pr33349.

Differential revision: https://reviews.llvm.org/D36511

llvm-svn: 310552

1 files changed, 15 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
index dc844fe9086..748e7422514 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -302,7 +302,21 @@ SDValue DAGTypeLegalizer::ScalarizeVecRes_SCALAR_TO_VECTOR(SDNode *N) {
 }
 
 SDValue DAGTypeLegalizer::ScalarizeVecRes_VSELECT(SDNode *N) {
-  SDValue Cond = GetScalarizedVector(N->getOperand(0));
+  SDValue Cond = N->getOperand(0);
+  EVT OpVT = Cond.getValueType();
+  SDLoc DL(N);
+  // The vselect result and true/value operands needs scalarizing, but it's
+  // not a given that the Cond does. For instance, in AVX512 v1i1 is legal.
+  // See the similar logic in ScalarizeVecRes_VSETCC
+  if (getTypeAction(OpVT) == TargetLowering::TypeScalarizeVector) {
+    Cond = GetScalarizedVector(Cond);
+  } else {
+    EVT VT = OpVT.getVectorElementType();
+    Cond = DAG.getNode(
+        ISD::EXTRACT_VECTOR_ELT, DL, VT, Cond,
+        DAG.getConstant(0, DL, TLI.getVectorIdxTy(DAG.getDataLayout())));
+  }
+
   SDValue LHS = GetScalarizedVector(N->getOperand(1));
   TargetLowering::BooleanContent ScalarBool =
       TLI.getBooleanContents(false, false);