[RISCV][llvm] Remove custom legalization of fixed-length vector SPLAT_VECTOR (llvm#172870)

BUILD_VECTOR is combined to SPLAT_VECTOR if operation action of
SPLAT_VECTOR is not Expand. However we already have custom handle of
BUILD_VECTOR for fixed-length vector which has explicit constant VL
instead of making it VLMAX if lowered through SPLAT_VECTOR.

Author: 4vtomat

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -91,10 +91,9 @@ static cl::opt<bool>
 static const unsigned ZvfbfaVPOps[] = {
     ISD::VP_FNEG, ISD::VP_FABS, ISD::VP_FCOPYSIGN};
 static const unsigned ZvfbfaOps[] = {
-    ISD::FNEG,    ISD::FABS,        ISD::FCOPYSIGN,   ISD::SPLAT_VECTOR,
-    ISD::FADD,    ISD::FSUB,        ISD::FMUL,        ISD::FMINNUM,
-    ISD::FMAXNUM, ISD::FMINIMUMNUM, ISD::FMAXIMUMNUM, ISD::FMINIMUM,
-    ISD::FMAXIMUM};
+    ISD::FNEG,        ISD::FABS,        ISD::FCOPYSIGN, ISD::FADD,
+    ISD::FSUB,        ISD::FMUL,        ISD::FMINNUM,   ISD::FMAXNUM,
+    ISD::FMINIMUMNUM, ISD::FMAXIMUMNUM, ISD::FMINIMUM,  ISD::FMAXIMUM};
 
 RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
                                          const RISCVSubtarget &STI)
@@ -4547,7 +4546,8 @@ static SDValue lowerBUILD_VECTOR(SDValue Op, SelectionDAG &DAG,
   // Proper support for f16 requires Zvfh. bf16 always requires special
   // handling. We need to cast the scalar to integer and create an integer
   // build_vector.
-  if ((EltVT == MVT::f16 && !Subtarget.hasStdExtZvfh()) || EltVT == MVT::bf16) {
+  if ((EltVT == MVT::f16 && !Subtarget.hasStdExtZvfh()) ||
+      (EltVT == MVT::bf16 && !Subtarget.hasVInstructionsBF16())) {
     MVT IVT = VT.changeVectorElementType(MVT::i16);
     SmallVector<SDValue, 16> NewOps(Op.getNumOperands());
     for (const auto &[I, U] : enumerate(Op->ops())) {

llvm/test/CodeGen/RISCV/rvv/fixed-vectors-fp-splat-bf16.ll

@@ -23,7 +23,7 @@ define <8 x bfloat> @splat_v8bf16(ptr %x, bfloat %y) {
 ;
 ; ZVFBFA-LABEL: splat_v8bf16:
 ; ZVFBFA:       # %bb.0:
-; ZVFBFA-NEXT:    vsetvli a0, zero, e16alt, m1, ta, ma
+; ZVFBFA-NEXT:    vsetivli zero, 8, e16alt, m1, ta, ma
 ; ZVFBFA-NEXT:    vfmv.v.f v8, fa0
 ; ZVFBFA-NEXT:    ret
   %a = insertelement <8 x bfloat> poison, bfloat %y, i32 0
@@ -48,7 +48,7 @@ define <16 x bfloat> @splat_16bf16(ptr %x, bfloat %y) {
 ;
 ; ZVFBFA-LABEL: splat_16bf16:
 ; ZVFBFA:       # %bb.0:
-; ZVFBFA-NEXT:    vsetvli a0, zero, e16alt, m2, ta, ma
+; ZVFBFA-NEXT:    vsetivli zero, 16, e16alt, m2, ta, ma
 ; ZVFBFA-NEXT:    vfmv.v.f v8, fa0
 ; ZVFBFA-NEXT:    ret
   %a = insertelement <16 x bfloat> poison, bfloat %y, i32 0
@@ -75,7 +75,8 @@ define <64 x bfloat> @splat_64bf16(ptr %x, bfloat %y) {
 ;
 ; ZVFBFA-LABEL: splat_64bf16:
 ; ZVFBFA:       # %bb.0:
-; ZVFBFA-NEXT:    vsetvli a0, zero, e16alt, m8, ta, ma
+; ZVFBFA-NEXT:    li a0, 64
+; ZVFBFA-NEXT:    vsetvli zero, a0, e16alt, m8, ta, ma
 ; ZVFBFA-NEXT:    vfmv.v.f v8, fa0
 ; ZVFBFA-NEXT:    ret
   %a = insertelement <64 x bfloat> poison, bfloat %y, i32 0
@@ -98,7 +99,7 @@ define <8 x bfloat> @splat_zero_v8bf16(ptr %x) {
 ;
 ; ZVFBFA-LABEL: splat_zero_v8bf16:
 ; ZVFBFA:       # %bb.0:
-; ZVFBFA-NEXT:    vsetvli a0, zero, e16, m1, ta, ma
+; ZVFBFA-NEXT:    vsetivli zero, 8, e16, m1, ta, ma
 ; ZVFBFA-NEXT:    vmv.v.i v8, 0
 ; ZVFBFA-NEXT:    ret
   ret <8 x bfloat> splat (bfloat 0.0)
@@ -119,7 +120,7 @@ define <16 x bfloat> @splat_zero_16bf16(ptr %x) {
 ;
 ; ZVFBFA-LABEL: splat_zero_16bf16:
 ; ZVFBFA:       # %bb.0:
-; ZVFBFA-NEXT:    vsetvli a0, zero, e16, m2, ta, ma
+; ZVFBFA-NEXT:    vsetivli zero, 16, e16, m2, ta, ma
 ; ZVFBFA-NEXT:    vmv.v.i v8, 0
 ; ZVFBFA-NEXT:    ret
   ret <16 x bfloat> splat (bfloat 0.0)
@@ -143,7 +144,7 @@ define <8 x bfloat> @splat_negzero_v8bf16(ptr %x) {
 ; ZVFBFA-LABEL: splat_negzero_v8bf16:
 ; ZVFBFA:       # %bb.0:
 ; ZVFBFA-NEXT:    lui a0, 1048568
-; ZVFBFA-NEXT:    vsetvli a1, zero, e16, m1, ta, ma
+; ZVFBFA-NEXT:    vsetivli zero, 8, e16, m1, ta, ma
 ; ZVFBFA-NEXT:    vmv.v.x v8, a0
 ; ZVFBFA-NEXT:    ret
   ret <8 x bfloat> splat (bfloat -0.0)
@@ -167,7 +168,7 @@ define <16 x bfloat> @splat_negzero_16bf16(ptr %x) {
 ; ZVFBFA-LABEL: splat_negzero_16bf16:
 ; ZVFBFA:       # %bb.0:
 ; ZVFBFA-NEXT:    lui a0, 1048568
-; ZVFBFA-NEXT:    vsetvli a1, zero, e16, m2, ta, ma
+; ZVFBFA-NEXT:    vsetivli zero, 16, e16, m2, ta, ma
 ; ZVFBFA-NEXT:    vmv.v.x v8, a0
 ; ZVFBFA-NEXT:    ret
   ret <16 x bfloat> splat (bfloat -0.0)