[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, 16 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index e1dd6d03550..6a83d43048c 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -1388,7 +1388,7 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
     // (result) is 256-bit but the source is 512-bit wide.
     // 128-bit was made Custom under AVX1.
     for (auto VT : { MVT::v32i8, MVT::v16i16, MVT::v8i32, MVT::v4i64,
-                     MVT::v8f32, MVT::v4f64 })
+                     MVT::v8f32, MVT::v4f64, MVT::v1i1 })
       setOperationAction(ISD::EXTRACT_SUBVECTOR, VT, Custom);
     for (auto VT : { MVT::v2i1, MVT::v4i1, MVT::v8i1,
                      MVT::v16i1, MVT::v32i1, MVT::v64i1 })
@@ -14532,6 +14532,21 @@ static SDValue LowerEXTRACT_SUBVECTOR(SDValue Op, const X86Subtarget &Subtarget,
   unsigned IdxVal = cast<ConstantSDNode>(Idx)->getZExtValue();
   MVT ResVT = Op.getSimpleValueType();
 
+  // When v1i1 is legal a scalarization of a vselect with a vXi1 Cond
+  // would result with: v1i1 = extract_subvector(vXi1, idx).
+  // Lower these into extract_vector_elt which is already selectable.
+  if (ResVT == MVT::v1i1) {
+    assert(Subtarget.hasAVX512() &&
+           "Boolean EXTRACT_SUBVECTOR requires AVX512");
+
+    MVT EltVT = ResVT.getVectorElementType();
+    const TargetLowering &TLI = DAG.getTargetLoweringInfo();
+    MVT LegalVT =
+        (TLI.getTypeToTransformTo(*DAG.getContext(), EltVT)).getSimpleVT();
+    SDValue Res = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, LegalVT, In, Idx);
+    return DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, ResVT, Res);
+  }
+
   assert((In.getSimpleValueType().is256BitVector() ||
           In.getSimpleValueType().is512BitVector()) &&
          "Can only extract from 256-bit or 512-bit vectors");