[AArch64] Allow FP16 vector fixed point converts

This extends performFpToIntCombine to work on FP16 vectors as well as
the f32 and f64 vectors it already supported.

Differential Revision: https://reviews.llvm.org/D113297

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -13395,7 +13395,8 @@ static SDValue performFpToIntCombine(SDNode *N, SelectionDAG &DAG,
 
   MVT FloatTy = Op.getSimpleValueType().getVectorElementType();
   uint32_t FloatBits = FloatTy.getSizeInBits();
-  if (FloatBits != 32 && FloatBits != 64)
+  if (FloatBits != 32 && FloatBits != 64 &&
+      (FloatBits != 16 || !Subtarget->hasFullFP16()))
     return SDValue();
 
   MVT IntTy = N->getSimpleValueType(0).getVectorElementType();
@@ -13414,25 +13415,10 @@ static SDValue performFpToIntCombine(SDNode *N, SelectionDAG &DAG,
   if (C == -1 || C == 0 || C > Bits)
     return SDValue();
 
-  MVT ResTy;
-  unsigned NumLanes = Op.getValueType().getVectorNumElements();
-  switch (NumLanes) {
-  default:
-    return SDValue();
-  case 2:
-    ResTy = FloatBits == 32 ? MVT::v2i32 : MVT::v2i64;
-    break;
-  case 4:
-    ResTy = FloatBits == 32 ? MVT::v4i32 : MVT::v4i64;
-    break;
-  }
-
-  if (ResTy == MVT::v4i64 && DCI.isBeforeLegalizeOps())
+  EVT ResTy = Op.getValueType().changeVectorElementTypeToInteger();
+  if (!DAG.getTargetLoweringInfo().isTypeLegal(ResTy))
     return SDValue();
 
-  assert((ResTy != MVT::v4i64 || DCI.isBeforeLegalizeOps()) &&
-         "Illegal vector type after legalization");
-
   if (N->getOpcode() == ISD::FP_TO_SINT_SAT ||
       N->getOpcode() == ISD::FP_TO_UINT_SAT) {
     EVT SatVT = cast<VTSDNode>(N->getOperand(1))->getVT();

llvm/test/CodeGen/AArch64/fcvt_combine.ll

@@ -228,9 +228,7 @@ define <8 x i16> @test_v8f16(<8 x half> %in) {
 ;
 ; CHECK-FP16-LABEL: test_v8f16:
 ; CHECK-FP16:       // %bb.0:
-; CHECK-FP16-NEXT:    movi v1.8h, #68, lsl #8
-; CHECK-FP16-NEXT:    fmul v0.8h, v0.8h, v1.8h
-; CHECK-FP16-NEXT:    fcvtzs v0.8h, v0.8h
+; CHECK-FP16-NEXT:    fcvtzs v0.8h, v0.8h, #2
 ; CHECK-FP16-NEXT:    ret
   %scale = fmul <8 x half> %in, <half 4.0, half 4.0, half 4.0, half 4.0, half 4.0, half 4.0, half 4.0, half 4.0>
   %val = fptosi <8 x half> %scale to <8 x i16>
@@ -251,9 +249,7 @@ define <4 x i16> @test_v4f16(<4 x half> %in) {
 ;
 ; CHECK-FP16-LABEL: test_v4f16:
 ; CHECK-FP16:       // %bb.0:
-; CHECK-FP16-NEXT:    movi v1.4h, #68, lsl #8
-; CHECK-FP16-NEXT:    fmul v0.4h, v0.4h, v1.4h
-; CHECK-FP16-NEXT:    fcvtzu v0.4h, v0.4h
+; CHECK-FP16-NEXT:    fcvtzu v0.4h, v0.4h, #2
 ; CHECK-FP16-NEXT:    ret
   %scale = fmul <4 x half> %in, <half 4.0, half 4.0, half 4.0, half 4.0>
   %val = fptoui <4 x half> %scale to <4 x i16>
@@ -580,9 +576,7 @@ define <8 x i16> @test_v8f16_sat(<8 x half> %in) {
 ;
 ; CHECK-FP16-LABEL: test_v8f16_sat:
 ; CHECK-FP16:       // %bb.0:
-; CHECK-FP16-NEXT:    movi v1.8h, #68, lsl #8
-; CHECK-FP16-NEXT:    fmul v0.8h, v0.8h, v1.8h
-; CHECK-FP16-NEXT:    fcvtzs v0.8h, v0.8h
+; CHECK-FP16-NEXT:    fcvtzs v0.8h, v0.8h, #2
 ; CHECK-FP16-NEXT:    ret
   %mul.i = fmul <8 x half> %in, <half 4.0, half 4.0, half 4.0, half 4.0, half 4.0, half 4.0, half 4.0, half 4.0>
   %val = call <8 x i16> @llvm.fptosi.sat.v8i16.v8f16(<8 x half> %mul.i)
@@ -603,9 +597,7 @@ define <4 x i16> @test_v4f16_sat(<4 x half> %in) {
 ;
 ; CHECK-FP16-LABEL: test_v4f16_sat:
 ; CHECK-FP16:       // %bb.0:
-; CHECK-FP16-NEXT:    movi v1.4h, #68, lsl #8
-; CHECK-FP16-NEXT:    fmul v0.4h, v0.4h, v1.4h
-; CHECK-FP16-NEXT:    fcvtzu v0.4h, v0.4h
+; CHECK-FP16-NEXT:    fcvtzu v0.4h, v0.4h, #2
 ; CHECK-FP16-NEXT:    ret
   %mul.i = fmul <4 x half> %in, <half 4.0, half 4.0, half 4.0, half 4.0>
   %val = call <4 x i16> @llvm.fptoui.sat.v4i16.v4f16(<4 x half> %mul.i)