Refactor float rounding intrinsics a bit

Author: sayantn

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -1014,6 +1014,20 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         interp_ok(())
     }
 
+    fn float_round<F>(
+        &mut self,
+        x: Scalar<M::Provenance>,
+        mode: rustc_apfloat::Round,
+    ) -> InterpResult<'tcx, Scalar<M::Provenance>>
+    where
+        F: rustc_apfloat::Float + rustc_apfloat::FloatConvert<F> + Into<Scalar<M::Provenance>>,
+    {
+        let x: F = x.to_float()?;
+        let res = x.round_to_integral(mode).value;
+        let res = self.adjust_nan(res, &[x]);
+        interp_ok(res.into())
+    }
+
     fn float_round_intrinsic<F>(
         &mut self,
         args: &[OpTy<'tcx, M::Provenance>],
@@ -1023,9 +1037,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
     where
         F: rustc_apfloat::Float + rustc_apfloat::FloatConvert<F> + Into<Scalar<M::Provenance>>,
     {
-        let x: F = self.read_scalar(&args[0])?.to_float()?;
-        let res = x.round_to_integral(mode).value;
-        let res = self.adjust_nan(res, &[x]);
+        let res = self.float_round::<F>(self.read_scalar(&args[0])?, mode)?;
         self.write_scalar(res, dest)?;
         interp_ok(())
     }

compiler/rustc_const_eval/src/interpret/intrinsics/simd.rs

@@ -134,20 +134,11 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                                     intrinsic_name
                                 )
                             };
+                            let op = op.to_scalar();
                             match float_ty {
                                 FloatTy::F16 => unimplemented!("f16_f128"),
-                                FloatTy::F32 => {
-                                    let f = op.to_scalar().to_f32()?;
-                                    let res = f.round_to_integral(rounding).value;
-                                    let res = self.adjust_nan(res, &[f]);
-                                    Scalar::from_f32(res)
-                                }
-                                FloatTy::F64 => {
-                                    let f = op.to_scalar().to_f64()?;
-                                    let res = f.round_to_integral(rounding).value;
-                                    let res = self.adjust_nan(res, &[f]);
-                                    Scalar::from_f64(res)
-                                }
+                                FloatTy::F32 => self.float_round::<Single>(op, rounding)?,
+                                FloatTy::F64 => self.float_round::<Double>(op, rounding)?,
                                 FloatTy::F128 => unimplemented!("f16_f128"),
                             }
                         }