1 files changed, 57 insertions, 0 deletions
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 5d40e89fae0..de18adb110d 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -17540,6 +17540,57 @@ static SDValue LowerI64IntToFP_AVX512DQ(SDValue Op, SelectionDAG &DAG,
                      DAG.getIntPtrConstant(0, dl));
 }
 
+static bool useVectorCast(unsigned Opcode, MVT FromVT, MVT ToVT,
+                          const X86Subtarget &Subtarget) {
+  switch (Opcode) {
+    case ISD::SINT_TO_FP:
+      // TODO: Handle wider types with AVX/AVX512.
+      if (!Subtarget.hasSSE2() || FromVT != MVT::v4i32)
+        return false;
+      // CVTDQ2PS or (V)CVTDQ2PD
+      return ToVT == MVT::v4f32 || (Subtarget.hasAVX() && ToVT == MVT::v4f64);
+
+    case ISD::UINT_TO_FP:
+      // TODO: Handle wider types and i64 elements.
+      if (!Subtarget.hasAVX512() || FromVT != MVT::v4i32)
+        return false;
+      // VCVTUDQ2PS or VCVTUDQ2PD
+      return ToVT == MVT::v4f32 || ToVT == MVT::v4f64;
+
+    default:
+      return false;
+  }
+}
+
+/// Given a scalar cast operation that is extracted from a vector, try to
+/// vectorize the cast op followed by extraction. This will avoid an expensive
+/// round-trip between XMM and GPR.
+static SDValue vectorizeExtractedCast(SDValue Cast, SelectionDAG &DAG,
+                                      const X86Subtarget &Subtarget) {
+  // TODO: The limitation for extracting from the 0-element is not required,
+  // but if we extract from some other element, it will require shuffling to
+  // get the result into the right place.
+  // TODO: This could be enhanced to handle smaller integer types by peeking
+  // through an extend.
+  SDValue Extract = Cast.getOperand(0);
+  MVT DestVT = Cast.getSimpleValueType();
+  if (Extract.getOpcode() != ISD::EXTRACT_VECTOR_ELT ||
+      !isNullConstant(Extract.getOperand(1)))
+    return SDValue();
+
+  SDValue VecOp = Extract.getOperand(0);
+  MVT FromVT = VecOp.getSimpleValueType();
+  MVT ToVT = MVT::getVectorVT(DestVT, FromVT.getVectorNumElements());
+  if (!useVectorCast(Cast.getOpcode(), FromVT, ToVT, Subtarget))
+    return SDValue();
+
+  // cast (extract V, Y) --> extract (cast V), Y
+  SDLoc DL(Cast);
+  SDValue VCast = DAG.getNode(Cast.getOpcode(), DL, ToVT, VecOp);
+  return DAG.getNode(ISD::EXTRACT_VECTOR_ELT, DL, DestVT, VCast,
+                     Extract.getOperand(1));
+}
+
 SDValue X86TargetLowering::LowerSINT_TO_FP(SDValue Op,
                                            SelectionDAG &DAG) const {
   SDValue Src = Op.getOperand(0);
@@ -17547,6 +17598,9 @@ SDValue X86TargetLowering::LowerSINT_TO_FP(SDValue Op,
   MVT VT = Op.getSimpleValueType();
   SDLoc dl(Op);
 
+  if (SDValue Extract = vectorizeExtractedCast(Op, DAG, Subtarget))
+    return Extract;
+
   if (SrcVT.isVector()) {
     if (SrcVT == MVT::v2i32 && VT == MVT::v2f64) {
       return DAG.getNode(X86ISD::CVTSI2P, dl, VT,
@@ -17909,6 +17963,9 @@ SDValue X86TargetLowering::LowerUINT_TO_FP(SDValue Op,
   if (Op.getSimpleValueType().isVector())
     return lowerUINT_TO_FP_vec(Op, DAG, Subtarget);
 
+  if (SDValue Extract = vectorizeExtractedCast(Op, DAG, Subtarget))
+    return Extract;
+
   MVT SrcVT = N0.getSimpleValueType();
   MVT DstVT = Op.getSimpleValueType();