[X86] AVX512 fallback for floating-point scalar selects

Summary:
In the case where of 'select i1 , f32, f32' or select i1, f64, f64 prefer lowering to masked-moves over branches.

Fixes pr30561

Reviewers: igorb, aymanmus, delena

Differential Revision: https://reviews.llvm.org/D25310

llvm-svn: 285196

2 files changed, 13 insertions, 12 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 8880d1f6cb2..5f1bf7096fa 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -16149,6 +16149,11 @@ SDValue X86TargetLowering::LowerSELECT(SDValue Op, SelectionDAG &DAG) const {
     }
   }
 
+  // AVX512 fallback is to lower selects of scalar floats to masked moves.
+  if (Cond.getValueType() == MVT::i1 && (VT == MVT::f64 || VT == MVT::f32) &&
+      Subtarget.hasAVX512())
+    return DAG.getNode(X86ISD::SELECTS, DL, VT, Cond, Op1, Op2);
+
   if (VT.isVector() && VT.getVectorElementType() == MVT::i1) {
     SDValue Op1Scalar;
     if (ISD::isBuildVectorOfConstantSDNodes(Op1.getNode()))
diff --git a/llvm/test/CodeGen/X86/avx512-select.ll b/llvm/test/CodeGen/X86/avx512-select.ll
index aedb69db2d6..4a3695fab18 100644
--- a/llvm/test/CodeGen/X86/avx512-select.ll
+++ b/llvm/test/CodeGen/X86/avx512-select.ll
@@ -159,27 +159,23 @@ define i64 @pr30249() {
   ret i64 %v
 }
 
-define double @pr30561_f64(double %a, double %b, i1 %c) {
+define double @pr30561_f64(double %b, double %a, i1 %c) {
 ; CHECK-LABEL: pr30561_f64:
 ; CHECK:       ## BB#0:
-; CHECK-NEXT:    testb $1, %dil
-; CHECK-NEXT:    jne LBB11_2
-; CHECK-NEXT:  ## BB#1:
-; CHECK-NEXT:    vmovaps %xmm1, %xmm0
-; CHECK-NEXT:  LBB11_2:
+; CHECK-NEXT:    andl $1, %edi
+; CHECK-NEXT:    kmovw %edi, %k1
+; CHECK-NEXT:    vmovsd %xmm1, %xmm0, %xmm0 {%k1}
 ; CHECK-NEXT:    retq
   %cond = select i1 %c, double %a, double %b
   ret double %cond
 }
 
-define float @pr30561_f32(float %a, float %b, i1 %c) {
+define float @pr30561_f32(float %b, float %a, i1 %c) {
 ; CHECK-LABEL: pr30561_f32:
 ; CHECK:       ## BB#0:
-; CHECK-NEXT:    testb $1, %dil
-; CHECK-NEXT:    jne LBB12_2
-; CHECK-NEXT:  ## BB#1:
-; CHECK-NEXT:    vmovaps %xmm1, %xmm0
-; CHECK-NEXT:  LBB12_2:
+; CHECK-NEXT:    andl $1, %edi
+; CHECK-NEXT:    kmovw %edi, %k1
+; CHECK-NEXT:    vmovss %xmm1, %xmm0, %xmm0 {%k1}
 ; CHECK-NEXT:    retq
   %cond = select i1 %c, float %a, float %b
   ret float %cond