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share sqrt implemention across float types

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This commit is contained in:
Ralf Jung 2025-09-18 22:13:15 +02:00
parent f19b560fa9
commit 77f2d86554
2 changed files with 25 additions and 39 deletions
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52
src/tools/miri/src/intrinsics/math.rs
View file

@ -1,5 +1,5 @@
use rand::Rng;
use rustc_apfloat::{self, Float, Round};
use rustc_apfloat::{self, Float, FloatConvert, Round};
use rustc_middle::mir;
use rustc_middle::ty::{self, FloatTy};
@ -7,6 +7,20 @@ use self::helpers::{ToHost, ToSoft};
use super::check_intrinsic_arg_count;
use crate::*;
fn sqrt<'tcx, F: Float + FloatConvert<F> + Into<Scalar>>(
this: &mut MiriInterpCx<'tcx>,
args: &[OpTy<'tcx>],
dest: &MPlaceTy<'tcx>,
) -> InterpResult<'tcx> {
let [f] = check_intrinsic_arg_count(args)?;
let f = this.read_scalar(f)?;
let f: F = f.to_float()?;
// Sqrt is specified to be fully precise.
let res = math::sqrt(f);
let res = this.adjust_nan(res, &[f]);
this.write_scalar(res, dest)
}
impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
fn emulate_math_intrinsic(
@ -20,38 +34,10 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
match intrinsic_name {
// Operations we can do with soft-floats.
"sqrtf16" => {
let [f] = check_intrinsic_arg_count(args)?;
let f = this.read_scalar(f)?.to_f16()?;
// Sqrt is specified to be fully precise.
let res = math::sqrt(f);
let res = this.adjust_nan(res, &[f]);
this.write_scalar(res, dest)?;
}
"sqrtf32" => {
let [f] = check_intrinsic_arg_count(args)?;
let f = this.read_scalar(f)?.to_f32()?;
// Sqrt is specified to be fully precise.
let res = math::sqrt(f);
let res = this.adjust_nan(res, &[f]);
this.write_scalar(res, dest)?;
}
"sqrtf64" => {
let [f] = check_intrinsic_arg_count(args)?;
let f = this.read_scalar(f)?.to_f64()?;
// Sqrt is specified to be fully precise.
let res = math::sqrt(f);
let res = this.adjust_nan(res, &[f]);
this.write_scalar(res, dest)?;
}
"sqrtf128" => {
let [f] = check_intrinsic_arg_count(args)?;
let f = this.read_scalar(f)?.to_f128()?;
// Sqrt is specified to be fully precise.
let res = math::sqrt(f);
let res = this.adjust_nan(res, &[f]);
this.write_scalar(res, dest)?;
}
"sqrtf16" => sqrt::<rustc_apfloat::ieee::Half>(this, args, dest)?,
"sqrtf32" => sqrt::<rustc_apfloat::ieee::Single>(this, args, dest)?,
"sqrtf64" => sqrt::<rustc_apfloat::ieee::Double>(this, args, dest)?,
"sqrtf128" => sqrt::<rustc_apfloat::ieee::Quad>(this, args, dest)?,
"fmaf32" => {
let [a, b, c] = check_intrinsic_arg_count(args)?;

12
src/tools/miri/src/math.rs
View file

@ -2,7 +2,7 @@ use std::ops::Neg;
use std::{f32, f64};
use rand::Rng as _;
use rustc_apfloat::Float as _;
use rustc_apfloat::Float;
use rustc_apfloat::ieee::{DoubleS, IeeeFloat, Semantics, SingleS};
use rustc_middle::ty::{self, FloatTy, ScalarInt};
@ -317,19 +317,19 @@ where
}
}
pub(crate) fn sqrt<S: rustc_apfloat::ieee::Semantics>(x: IeeeFloat<S>) -> IeeeFloat<S> {
pub(crate) fn sqrt<F: Float>(x: F) -> F {
match x.category() {
// preserve zero sign
rustc_apfloat::Category::Zero => x,
// propagate NaN
rustc_apfloat::Category::NaN => x,
// sqrt of negative number is NaN
_ if x.is_negative() => IeeeFloat::NAN,
_ if x.is_negative() => F::NAN,
// sqrt(∞) = ∞
rustc_apfloat::Category::Infinity => IeeeFloat::INFINITY,
rustc_apfloat::Category::Infinity => F::INFINITY,
rustc_apfloat::Category::Normal => {
// Floating point precision, excluding the integer bit
let prec = i32::try_from(S::PRECISION).unwrap() - 1;
let prec = i32::try_from(F::PRECISION).unwrap() - 1;
// x = 2^(exp - prec) * mant
// where mant is an integer with prec+1 bits
@ -394,7 +394,7 @@ pub(crate) fn sqrt<S: rustc_apfloat::ieee::Semantics>(x: IeeeFloat<S>) -> IeeeFl
res = (res + 1) >> 1;
// Build resulting value with res as mantissa and exp/2 as exponent
IeeeFloat::from_u128(res).value.scalbn(exp / 2 - prec)
F::from_u128(res).value.scalbn(exp / 2 - prec)
}
}
}