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Rollup merge of #141521 - ruancomelli:const-float-rounding, r=RalfJung
Add `const` support for float rounding methods # Add `const` support for float rounding methods This PR makes the following float rounding methods `const`: - `f64::{floor, ceil, trunc, round, round_ties_even}` - and the corresponding methods for `f16`, `f32` and `f128` Tracking issue: #141555 ## Procedure I followed c09ed3e as closely as I could in making float methods `const`, and also received great guidance from https://internals.rust-lang.org/t/const-rounding-methods-in-float-types/22957/3?u=ruancomelli. ## Note This is my first code contribution to the Rust project, so please let me know if I missed anything - I'd be more than happy to revise and learn more. Thank you for taking the time to review it!
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‎compiler/rustc_const_eval/src/interpret/intrinsics.rs

Lines changed: 113 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -518,6 +518,103 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
518518
sym::fabsf64 => self.float_abs_intrinsic::<Double>(args, dest)?,
519519
sym::fabsf128 => self.float_abs_intrinsic::<Quad>(args, dest)?,
520520

521+
sym::floorf16 => self.float_round_intrinsic::<Half>(
522+
args,
523+
dest,
524+
rustc_apfloat::Round::TowardNegative,
525+
)?,
526+
sym::floorf32 => self.float_round_intrinsic::<Single>(
527+
args,
528+
dest,
529+
rustc_apfloat::Round::TowardNegative,
530+
)?,
531+
sym::floorf64 => self.float_round_intrinsic::<Double>(
532+
args,
533+
dest,
534+
rustc_apfloat::Round::TowardNegative,
535+
)?,
536+
sym::floorf128 => self.float_round_intrinsic::<Quad>(
537+
args,
538+
dest,
539+
rustc_apfloat::Round::TowardNegative,
540+
)?,
541+
542+
sym::ceilf16 => self.float_round_intrinsic::<Half>(
543+
args,
544+
dest,
545+
rustc_apfloat::Round::TowardPositive,
546+
)?,
547+
sym::ceilf32 => self.float_round_intrinsic::<Single>(
548+
args,
549+
dest,
550+
rustc_apfloat::Round::TowardPositive,
551+
)?,
552+
sym::ceilf64 => self.float_round_intrinsic::<Double>(
553+
args,
554+
dest,
555+
rustc_apfloat::Round::TowardPositive,
556+
)?,
557+
sym::ceilf128 => self.float_round_intrinsic::<Quad>(
558+
args,
559+
dest,
560+
rustc_apfloat::Round::TowardPositive,
561+
)?,
562+
563+
sym::truncf16 => {
564+
self.float_round_intrinsic::<Half>(args, dest, rustc_apfloat::Round::TowardZero)?
565+
}
566+
sym::truncf32 => {
567+
self.float_round_intrinsic::<Single>(args, dest, rustc_apfloat::Round::TowardZero)?
568+
}
569+
sym::truncf64 => {
570+
self.float_round_intrinsic::<Double>(args, dest, rustc_apfloat::Round::TowardZero)?
571+
}
572+
sym::truncf128 => {
573+
self.float_round_intrinsic::<Quad>(args, dest, rustc_apfloat::Round::TowardZero)?
574+
}
575+
576+
sym::roundf16 => self.float_round_intrinsic::<Half>(
577+
args,
578+
dest,
579+
rustc_apfloat::Round::NearestTiesToAway,
580+
)?,
581+
sym::roundf32 => self.float_round_intrinsic::<Single>(
582+
args,
583+
dest,
584+
rustc_apfloat::Round::NearestTiesToAway,
585+
)?,
586+
sym::roundf64 => self.float_round_intrinsic::<Double>(
587+
args,
588+
dest,
589+
rustc_apfloat::Round::NearestTiesToAway,
590+
)?,
591+
sym::roundf128 => self.float_round_intrinsic::<Quad>(
592+
args,
593+
dest,
594+
rustc_apfloat::Round::NearestTiesToAway,
595+
)?,
596+
597+
sym::round_ties_even_f16 => self.float_round_intrinsic::<Half>(
598+
args,
599+
dest,
600+
rustc_apfloat::Round::NearestTiesToEven,
601+
)?,
602+
sym::round_ties_even_f32 => self.float_round_intrinsic::<Single>(
603+
args,
604+
dest,
605+
rustc_apfloat::Round::NearestTiesToEven,
606+
)?,
607+
sym::round_ties_even_f64 => self.float_round_intrinsic::<Double>(
608+
args,
609+
dest,
610+
rustc_apfloat::Round::NearestTiesToEven,
611+
)?,
612+
sym::round_ties_even_f128 => self.float_round_intrinsic::<Quad>(
613+
args,
614+
dest,
615+
rustc_apfloat::Round::NearestTiesToEven,
616+
)?,
617+
521618
// Unsupported intrinsic: skip the return_to_block below.
522619
_ => return interp_ok(false),
523620
}
@@ -900,4 +997,20 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
900997
self.write_scalar(x.abs(), dest)?;
901998
interp_ok(())
902999
}
1000+
1001+
fn float_round_intrinsic<F>(
1002+
&mut self,
1003+
args: &[OpTy<'tcx, M::Provenance>],
1004+
dest: &PlaceTy<'tcx, M::Provenance>,
1005+
mode: rustc_apfloat::Round,
1006+
) -> InterpResult<'tcx, ()>
1007+
where
1008+
F: rustc_apfloat::Float + rustc_apfloat::FloatConvert<F> + Into<Scalar<M::Provenance>>,
1009+
{
1010+
let x: F = self.read_scalar(&args[0])?.to_float()?;
1011+
let res = x.round_to_integral(mode).value;
1012+
let res = self.adjust_nan(res, &[x]);
1013+
self.write_scalar(res, dest)?;
1014+
interp_ok(())
1015+
}
9031016
}

‎library/core/src/intrinsics/mod.rs

Lines changed: 20 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -2212,86 +2212,86 @@ pub unsafe fn fmuladdf128(a: f128, b: f128, c: f128) -> f128;
22122212
/// [`f16::floor`](../../std/primitive.f16.html#method.floor)
22132213
#[rustc_intrinsic]
22142214
#[rustc_nounwind]
2215-
pub unsafe fn floorf16(x: f16) -> f16;
2215+
pub const unsafe fn floorf16(x: f16) -> f16;
22162216
/// Returns the largest integer less than or equal to an `f32`.
22172217
///
22182218
/// The stabilized version of this intrinsic is
22192219
/// [`f32::floor`](../../std/primitive.f32.html#method.floor)
22202220
#[rustc_intrinsic]
22212221
#[rustc_nounwind]
2222-
pub unsafe fn floorf32(x: f32) -> f32;
2222+
pub const unsafe fn floorf32(x: f32) -> f32;
22232223
/// Returns the largest integer less than or equal to an `f64`.
22242224
///
22252225
/// The stabilized version of this intrinsic is
22262226
/// [`f64::floor`](../../std/primitive.f64.html#method.floor)
22272227
#[rustc_intrinsic]
22282228
#[rustc_nounwind]
2229-
pub unsafe fn floorf64(x: f64) -> f64;
2229+
pub const unsafe fn floorf64(x: f64) -> f64;
22302230
/// Returns the largest integer less than or equal to an `f128`.
22312231
///
22322232
/// The stabilized version of this intrinsic is
22332233
/// [`f128::floor`](../../std/primitive.f128.html#method.floor)
22342234
#[rustc_intrinsic]
22352235
#[rustc_nounwind]
2236-
pub unsafe fn floorf128(x: f128) -> f128;
2236+
pub const unsafe fn floorf128(x: f128) -> f128;
22372237

22382238
/// Returns the smallest integer greater than or equal to an `f16`.
22392239
///
22402240
/// The stabilized version of this intrinsic is
22412241
/// [`f16::ceil`](../../std/primitive.f16.html#method.ceil)
22422242
#[rustc_intrinsic]
22432243
#[rustc_nounwind]
2244-
pub unsafe fn ceilf16(x: f16) -> f16;
2244+
pub const unsafe fn ceilf16(x: f16) -> f16;
22452245
/// Returns the smallest integer greater than or equal to an `f32`.
22462246
///
22472247
/// The stabilized version of this intrinsic is
22482248
/// [`f32::ceil`](../../std/primitive.f32.html#method.ceil)
22492249
#[rustc_intrinsic]
22502250
#[rustc_nounwind]
2251-
pub unsafe fn ceilf32(x: f32) -> f32;
2251+
pub const unsafe fn ceilf32(x: f32) -> f32;
22522252
/// Returns the smallest integer greater than or equal to an `f64`.
22532253
///
22542254
/// The stabilized version of this intrinsic is
22552255
/// [`f64::ceil`](../../std/primitive.f64.html#method.ceil)
22562256
#[rustc_intrinsic]
22572257
#[rustc_nounwind]
2258-
pub unsafe fn ceilf64(x: f64) -> f64;
2258+
pub const unsafe fn ceilf64(x: f64) -> f64;
22592259
/// Returns the smallest integer greater than or equal to an `f128`.
22602260
///
22612261
/// The stabilized version of this intrinsic is
22622262
/// [`f128::ceil`](../../std/primitive.f128.html#method.ceil)
22632263
#[rustc_intrinsic]
22642264
#[rustc_nounwind]
2265-
pub unsafe fn ceilf128(x: f128) -> f128;
2265+
pub const unsafe fn ceilf128(x: f128) -> f128;
22662266

22672267
/// Returns the integer part of an `f16`.
22682268
///
22692269
/// The stabilized version of this intrinsic is
22702270
/// [`f16::trunc`](../../std/primitive.f16.html#method.trunc)
22712271
#[rustc_intrinsic]
22722272
#[rustc_nounwind]
2273-
pub unsafe fn truncf16(x: f16) -> f16;
2273+
pub const unsafe fn truncf16(x: f16) -> f16;
22742274
/// Returns the integer part of an `f32`.
22752275
///
22762276
/// The stabilized version of this intrinsic is
22772277
/// [`f32::trunc`](../../std/primitive.f32.html#method.trunc)
22782278
#[rustc_intrinsic]
22792279
#[rustc_nounwind]
2280-
pub unsafe fn truncf32(x: f32) -> f32;
2280+
pub const unsafe fn truncf32(x: f32) -> f32;
22812281
/// Returns the integer part of an `f64`.
22822282
///
22832283
/// The stabilized version of this intrinsic is
22842284
/// [`f64::trunc`](../../std/primitive.f64.html#method.trunc)
22852285
#[rustc_intrinsic]
22862286
#[rustc_nounwind]
2287-
pub unsafe fn truncf64(x: f64) -> f64;
2287+
pub const unsafe fn truncf64(x: f64) -> f64;
22882288
/// Returns the integer part of an `f128`.
22892289
///
22902290
/// The stabilized version of this intrinsic is
22912291
/// [`f128::trunc`](../../std/primitive.f128.html#method.trunc)
22922292
#[rustc_intrinsic]
22932293
#[rustc_nounwind]
2294-
pub unsafe fn truncf128(x: f128) -> f128;
2294+
pub const unsafe fn truncf128(x: f128) -> f128;
22952295

22962296
/// Returns the nearest integer to an `f16`. Rounds half-way cases to the number with an even
22972297
/// least significant digit.
@@ -2300,7 +2300,7 @@ pub unsafe fn truncf128(x: f128) -> f128;
23002300
/// [`f16::round_ties_even`](../../std/primitive.f16.html#method.round_ties_even)
23012301
#[rustc_intrinsic]
23022302
#[rustc_nounwind]
2303-
pub fn round_ties_even_f16(x: f16) -> f16;
2303+
pub const fn round_ties_even_f16(x: f16) -> f16;
23042304

23052305
/// Returns the nearest integer to an `f32`. Rounds half-way cases to the number with an even
23062306
/// least significant digit.
@@ -2309,7 +2309,7 @@ pub fn round_ties_even_f16(x: f16) -> f16;
23092309
/// [`f32::round_ties_even`](../../std/primitive.f32.html#method.round_ties_even)
23102310
#[rustc_intrinsic]
23112311
#[rustc_nounwind]
2312-
pub fn round_ties_even_f32(x: f32) -> f32;
2312+
pub const fn round_ties_even_f32(x: f32) -> f32;
23132313

23142314
/// Returns the nearest integer to an `f64`. Rounds half-way cases to the number with an even
23152315
/// least significant digit.
@@ -2318,7 +2318,7 @@ pub fn round_ties_even_f32(x: f32) -> f32;
23182318
/// [`f64::round_ties_even`](../../std/primitive.f64.html#method.round_ties_even)
23192319
#[rustc_intrinsic]
23202320
#[rustc_nounwind]
2321-
pub fn round_ties_even_f64(x: f64) -> f64;
2321+
pub const fn round_ties_even_f64(x: f64) -> f64;
23222322

23232323
/// Returns the nearest integer to an `f128`. Rounds half-way cases to the number with an even
23242324
/// least significant digit.
@@ -2327,36 +2327,36 @@ pub fn round_ties_even_f64(x: f64) -> f64;
23272327
/// [`f128::round_ties_even`](../../std/primitive.f128.html#method.round_ties_even)
23282328
#[rustc_intrinsic]
23292329
#[rustc_nounwind]
2330-
pub fn round_ties_even_f128(x: f128) -> f128;
2330+
pub const fn round_ties_even_f128(x: f128) -> f128;
23312331

23322332
/// Returns the nearest integer to an `f16`. Rounds half-way cases away from zero.
23332333
///
23342334
/// The stabilized version of this intrinsic is
23352335
/// [`f16::round`](../../std/primitive.f16.html#method.round)
23362336
#[rustc_intrinsic]
23372337
#[rustc_nounwind]
2338-
pub unsafe fn roundf16(x: f16) -> f16;
2338+
pub const unsafe fn roundf16(x: f16) -> f16;
23392339
/// Returns the nearest integer to an `f32`. Rounds half-way cases away from zero.
23402340
///
23412341
/// The stabilized version of this intrinsic is
23422342
/// [`f32::round`](../../std/primitive.f32.html#method.round)
23432343
#[rustc_intrinsic]
23442344
#[rustc_nounwind]
2345-
pub unsafe fn roundf32(x: f32) -> f32;
2345+
pub const unsafe fn roundf32(x: f32) -> f32;
23462346
/// Returns the nearest integer to an `f64`. Rounds half-way cases away from zero.
23472347
///
23482348
/// The stabilized version of this intrinsic is
23492349
/// [`f64::round`](../../std/primitive.f64.html#method.round)
23502350
#[rustc_intrinsic]
23512351
#[rustc_nounwind]
2352-
pub unsafe fn roundf64(x: f64) -> f64;
2352+
pub const unsafe fn roundf64(x: f64) -> f64;
23532353
/// Returns the nearest integer to an `f128`. Rounds half-way cases away from zero.
23542354
///
23552355
/// The stabilized version of this intrinsic is
23562356
/// [`f128::round`](../../std/primitive.f128.html#method.round)
23572357
#[rustc_intrinsic]
23582358
#[rustc_nounwind]
2359-
pub unsafe fn roundf128(x: f128) -> f128;
2359+
pub const unsafe fn roundf128(x: f128) -> f128;
23602360

23612361
/// Float addition that allows optimizations based on algebraic rules.
23622362
/// May assume inputs are finite.

‎library/core/src/num/f128.rs

Lines changed: 18 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -1447,8 +1447,10 @@ impl f128 {
14471447
#[inline]
14481448
#[rustc_allow_incoherent_impl]
14491449
#[unstable(feature = "f128", issue = "116909")]
1450+
#[rustc_const_unstable(feature = "f128", issue = "116909")]
1451+
// #[rustc_const_unstable(feature = "const_float_round_methods", issue = "141555")]
14501452
#[must_use = "method returns a new number and does not mutate the original value"]
1451-
pub fn floor(self) -> f128 {
1453+
pub const fn floor(self) -> f128 {
14521454
// SAFETY: intrinsic with no preconditions
14531455
unsafe { intrinsics::floorf128(self) }
14541456
}
@@ -1477,8 +1479,10 @@ impl f128 {
14771479
#[doc(alias = "ceiling")]
14781480
#[rustc_allow_incoherent_impl]
14791481
#[unstable(feature = "f128", issue = "116909")]
1482+
#[rustc_const_unstable(feature = "f128", issue = "116909")]
1483+
// #[rustc_const_unstable(feature = "const_float_round_methods", issue = "141555")]
14801484
#[must_use = "method returns a new number and does not mutate the original value"]
1481-
pub fn ceil(self) -> f128 {
1485+
pub const fn ceil(self) -> f128 {
14821486
// SAFETY: intrinsic with no preconditions
14831487
unsafe { intrinsics::ceilf128(self) }
14841488
}
@@ -1513,8 +1517,10 @@ impl f128 {
15131517
#[inline]
15141518
#[rustc_allow_incoherent_impl]
15151519
#[unstable(feature = "f128", issue = "116909")]
1520+
#[rustc_const_unstable(feature = "f128", issue = "116909")]
1521+
// #[rustc_const_unstable(feature = "const_float_round_methods", issue = "141555")]
15161522
#[must_use = "method returns a new number and does not mutate the original value"]
1517-
pub fn round(self) -> f128 {
1523+
pub const fn round(self) -> f128 {
15181524
// SAFETY: intrinsic with no preconditions
15191525
unsafe { intrinsics::roundf128(self) }
15201526
}
@@ -1547,8 +1553,10 @@ impl f128 {
15471553
#[inline]
15481554
#[rustc_allow_incoherent_impl]
15491555
#[unstable(feature = "f128", issue = "116909")]
1556+
#[rustc_const_unstable(feature = "f128", issue = "116909")]
1557+
// #[rustc_const_unstable(feature = "const_float_round_methods", issue = "141555")]
15501558
#[must_use = "method returns a new number and does not mutate the original value"]
1551-
pub fn round_ties_even(self) -> f128 {
1559+
pub const fn round_ties_even(self) -> f128 {
15521560
intrinsics::round_ties_even_f128(self)
15531561
}
15541562

@@ -1579,8 +1587,10 @@ impl f128 {
15791587
#[doc(alias = "truncate")]
15801588
#[rustc_allow_incoherent_impl]
15811589
#[unstable(feature = "f128", issue = "116909")]
1590+
#[rustc_const_unstable(feature = "f128", issue = "116909")]
1591+
// #[rustc_const_unstable(feature = "const_float_round_methods", issue = "141555")]
15821592
#[must_use = "method returns a new number and does not mutate the original value"]
1583-
pub fn trunc(self) -> f128 {
1593+
pub const fn trunc(self) -> f128 {
15841594
// SAFETY: intrinsic with no preconditions
15851595
unsafe { intrinsics::truncf128(self) }
15861596
}
@@ -1610,8 +1620,10 @@ impl f128 {
16101620
#[inline]
16111621
#[rustc_allow_incoherent_impl]
16121622
#[unstable(feature = "f128", issue = "116909")]
1623+
#[rustc_const_unstable(feature = "f128", issue = "116909")]
1624+
// #[rustc_const_unstable(feature = "const_float_round_methods", issue = "141555")]
16131625
#[must_use = "method returns a new number and does not mutate the original value"]
1614-
pub fn fract(self) -> f128 {
1626+
pub const fn fract(self) -> f128 {
16151627
self - self.trunc()
16161628
}
16171629

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