[RISCV] Optimize vfmv.s.f intrinisc with scalar 0.0 to vmv.s.x with x0.

[craig.topper]

Summary

We already do this for RISCVISD::VFMV_S_F_VL and the vfmv.v.f
intrinsic.

[kito-cheng]

LGTM :)

llvm/lib/Target/RISCV/RISCVInstrInfoVPseudos.td

foreach fvti = AllFloatVectors in {
 
   def : Pat<(fvti.Vector (int_riscv_vfmv_s_f (fvti.Vector fvti.RegClass:$rs1),
                          (fvti.Scalar fvti.ScalarRegClass:$rs2), VLOpFrag)),
             (!cast<Instruction>("PseudoVFMV_S_"#fvti.ScalarSuffix#"_" #
                                 fvti.LMul.MX)
              (fvti.Vector $rs1),
              (fvti.Scalar fvti.ScalarRegClass:$rs2),
              GPR:$vl, fvti.Log2SEW)>;
+
+  def : Pat<(fvti.Vector (int_riscv_vfmv_s_f (fvti.Vector fvti.RegClass:$rs1),
+                         (fvti.Scalar (fpimm0)), VLOpFrag)),
+            (!cast<Instruction>("PseudoVMV_S_X_" # fvti.LMul.MX)
+             (fvti.Vector $rs1), X0, GPR:$vl, fvti.Log2SEW)>;
 }
 } // Predicates = [HasVInstructionsAnyF]
 
 //===----------------------------------------------------------------------===//
 // 17.3. Vector Slide Instructions
 //===----------------------------------------------------------------------===//
 let Predicates = [HasVInstructions] in {
   defm : VPatTernaryV_VX_VI<"int_riscv_vslideup", "PseudoVSLIDEUP", AllIntegerVectors, uimm5>;

llvm/test/CodeGen/RISCV/rvv/vfmv.s.f.ll

 ; CHECK:       # %bb.0: # %entry
 ; CHECK-NEXT:    vsetvli zero, a0, e64, m8, tu, mu
 ; CHECK-NEXT:    vfmv.s.f v8, fa0
 ; CHECK-NEXT:    ret
 entry:
   %a = call <vscale x 8 x double> @llvm.riscv.vfmv.s.f.nxv8f64(<vscale x 8 x double> %0, double %1, iXLen %2)
   ret <vscale x 8 x double> %a
 }
+
+define <vscale x 1 x half> @intrinsic_vfmv.s.f_f_zero_nxv1f16(<vscale x 1 x half> %0, iXLen %1) nounwind {
+; CHECK-LABEL: intrinsic_vfmv.s.f_f_zero_nxv1f16:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e16, mf4, tu, mu
+; CHECK-NEXT:    vmv.s.x v8, zero
+; CHECK-NEXT:    ret
+entry:
+  %a = call <vscale x 1 x half> @llvm.riscv.vfmv.s.f.nxv1f16(<vscale x 1 x half> %0, half 0.0, iXLen %1)
+  ret <vscale x 1 x half> %a
+}
+
+define <vscale x 2 x half> @intrinsic_vfmv.s.f_f_zero_nxv2f16(<vscale x 2 x half> %0, iXLen %1) nounwind {
+; CHECK-LABEL: intrinsic_vfmv.s.f_f_zero_nxv2f16:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e16, mf2, tu, mu
+; CHECK-NEXT:    vmv.s.x v8, zero
+; CHECK-NEXT:    ret
+entry:
+  %a = call <vscale x 2 x half> @llvm.riscv.vfmv.s.f.nxv2f16(<vscale x 2 x half> %0, half 0.0, iXLen %1)
+  ret <vscale x 2 x half> %a
+}
+
+define <vscale x 4 x half> @intrinsic_vfmv.s.f_f_zero_nxv4f16(<vscale x 4 x half> %0, iXLen %1) nounwind {
+; CHECK-LABEL: intrinsic_vfmv.s.f_f_zero_nxv4f16:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e16, m1, tu, mu
+; CHECK-NEXT:    vmv.s.x v8, zero
+; CHECK-NEXT:    ret
+entry:
+  %a = call <vscale x 4 x half> @llvm.riscv.vfmv.s.f.nxv4f16(<vscale x 4 x half> %0, half 0.0, iXLen %1)
+  ret <vscale x 4 x half> %a
+}
+
+define <vscale x 8 x half> @intrinsic_vfmv.s.f_f_zero_nxv8f16(<vscale x 8 x half> %0, iXLen %1) nounwind {
+; CHECK-LABEL: intrinsic_vfmv.s.f_f_zero_nxv8f16:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e16, m2, tu, mu
+; CHECK-NEXT:    vmv.s.x v8, zero
+; CHECK-NEXT:    ret
+entry:
+  %a = call <vscale x 8 x half> @llvm.riscv.vfmv.s.f.nxv8f16(<vscale x 8 x half> %0, half 0.0, iXLen %1)
+  ret <vscale x 8 x half> %a
+}
+
+define <vscale x 16 x half> @intrinsic_vfmv.s.f_f_zero_nxv16f16(<vscale x 16 x half> %0, iXLen %1) nounwind {
+; CHECK-LABEL: intrinsic_vfmv.s.f_f_zero_nxv16f16:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e16, m4, tu, mu
+; CHECK-NEXT:    vmv.s.x v8, zero
+; CHECK-NEXT:    ret
+entry:
+  %a = call <vscale x 16 x half> @llvm.riscv.vfmv.s.f.nxv16f16(<vscale x 16 x half> %0, half 0.0, iXLen %1)
+  ret <vscale x 16 x half> %a
+}
+
+define <vscale x 32 x half> @intrinsic_vfmv.s.f_f_zero_nxv32f16(<vscale x 32 x half> %0, iXLen %1) nounwind {
+; CHECK-LABEL: intrinsic_vfmv.s.f_f_zero_nxv32f16:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e16, m8, tu, mu
+; CHECK-NEXT:    vmv.s.x v8, zero
+; CHECK-NEXT:    ret
+entry:
+  %a = call <vscale x 32 x half> @llvm.riscv.vfmv.s.f.nxv32f16(<vscale x 32 x half> %0, half 0.0, iXLen %1)
+  ret <vscale x 32 x half> %a
+}
+
+define <vscale x 1 x float> @intrinsic_vfmv.s.f_f_zero_nxv1f32(<vscale x 1 x float> %0, iXLen %1) nounwind {
+; CHECK-LABEL: intrinsic_vfmv.s.f_f_zero_nxv1f32:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e32, mf2, tu, mu
+; CHECK-NEXT:    vmv.s.x v8, zero
+; CHECK-NEXT:    ret
+entry:
+  %a = call <vscale x 1 x float> @llvm.riscv.vfmv.s.f.nxv1f32(<vscale x 1 x float> %0, float 0.0, iXLen %1)
+  ret <vscale x 1 x float> %a
+}
+
+define <vscale x 2 x float> @intrinsic_vfmv.s.f_f_zero_nxv2f32(<vscale x 2 x float> %0, iXLen %1) nounwind {
+; CHECK-LABEL: intrinsic_vfmv.s.f_f_zero_nxv2f32:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e32, m1, tu, mu
+; CHECK-NEXT:    vmv.s.x v8, zero
+; CHECK-NEXT:    ret
+entry:
+  %a = call <vscale x 2 x float> @llvm.riscv.vfmv.s.f.nxv2f32(<vscale x 2 x float> %0, float 0.0, iXLen %1)
+  ret <vscale x 2 x float> %a
+}
+
+define <vscale x 4 x float> @intrinsic_vfmv.s.f_f_zero_nxv4f32(<vscale x 4 x float> %0, iXLen %1) nounwind {
+; CHECK-LABEL: intrinsic_vfmv.s.f_f_zero_nxv4f32:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e32, m2, tu, mu
+; CHECK-NEXT:    vmv.s.x v8, zero
+; CHECK-NEXT:    ret
+entry:
+  %a = call <vscale x 4 x float> @llvm.riscv.vfmv.s.f.nxv4f32(<vscale x 4 x float> %0, float 0.0, iXLen %1)
+  ret <vscale x 4 x float> %a
+}
+
+define <vscale x 8 x float> @intrinsic_vfmv.s.f_f_zero_nxv8f32(<vscale x 8 x float> %0, iXLen %1) nounwind {
+; CHECK-LABEL: intrinsic_vfmv.s.f_f_zero_nxv8f32:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e32, m4, tu, mu
+; CHECK-NEXT:    vmv.s.x v8, zero
+; CHECK-NEXT:    ret
+entry:
+  %a = call <vscale x 8 x float> @llvm.riscv.vfmv.s.f.nxv8f32(<vscale x 8 x float> %0, float 0.0, iXLen %1)
+  ret <vscale x 8 x float> %a
+}
+
+define <vscale x 16 x float> @intrinsic_vfmv.s.f_f_zero_nxv16f32(<vscale x 16 x float> %0, iXLen %1) nounwind {
+; CHECK-LABEL: intrinsic_vfmv.s.f_f_zero_nxv16f32:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e32, m8, tu, mu
+; CHECK-NEXT:    vmv.s.x v8, zero
+; CHECK-NEXT:    ret
+entry:
+  %a = call <vscale x 16 x float> @llvm.riscv.vfmv.s.f.nxv16f32(<vscale x 16 x float> %0, float 0.0, iXLen %1)
+  ret <vscale x 16 x float> %a
+}
+
+define <vscale x 1 x double> @intrinsic_vfmv.s.f_f_zero_nxv1f64(<vscale x 1 x double> %0, iXLen %1) nounwind {
+; CHECK-LABEL: intrinsic_vfmv.s.f_f_zero_nxv1f64:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e64, m1, tu, mu
+; CHECK-NEXT:    vmv.s.x v8, zero
+; CHECK-NEXT:    ret
+entry:
+  %a = call <vscale x 1 x double> @llvm.riscv.vfmv.s.f.nxv1f64(<vscale x 1 x double> %0, double 0.0, iXLen %1)
+  ret <vscale x 1 x double> %a
+}
+
+define <vscale x 2 x double> @intrinsic_vfmv.s.f_f_zero_nxv2f64(<vscale x 2 x double> %0, iXLen %1) nounwind {
+; CHECK-LABEL: intrinsic_vfmv.s.f_f_zero_nxv2f64:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e64, m2, tu, mu
+; CHECK-NEXT:    vmv.s.x v8, zero
+; CHECK-NEXT:    ret
+entry:
+  %a = call <vscale x 2 x double> @llvm.riscv.vfmv.s.f.nxv2f64(<vscale x 2 x double> %0, double 0.0, iXLen %1)
+  ret <vscale x 2 x double> %a
+}
+
+define <vscale x 4 x double> @intrinsic_vfmv.s.f_f_zero_nxv4f64(<vscale x 4 x double> %0, iXLen %1) nounwind {
+; CHECK-LABEL: intrinsic_vfmv.s.f_f_zero_nxv4f64:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e64, m4, tu, mu
+; CHECK-NEXT:    vmv.s.x v8, zero
+; CHECK-NEXT:    ret
+entry:
+  %a = call <vscale x 4 x double> @llvm.riscv.vfmv.s.f.nxv4f64(<vscale x 4 x double> %0, double 0.0, iXLen %1)
+  ret <vscale x 4 x double> %a
+}
+
+define <vscale x 8 x double> @intrinsic_vfmv.s.f_f_zero_nxv8f64(<vscale x 8 x double> %0, iXLen %1) nounwind {
+; CHECK-LABEL: intrinsic_vfmv.s.f_f_zero_nxv8f64:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e64, m8, tu, mu
+; CHECK-NEXT:    vmv.s.x v8, zero
+; CHECK-NEXT:    ret
+entry:
+  %a = call <vscale x 8 x double> @llvm.riscv.vfmv.s.f.nxv8f64(<vscale x 8 x double> %0, double 0.0, iXLen %1)
+  ret <vscale x 8 x double> %a
+}