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fN::BITS constants for feature float_bits_const #151109

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Merged
rust-bors merged 1 commit into from
Feb 3, 2026
Merged

fN::BITS constants for feature float_bits_const #151109

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1 change: 1 addition & 0 deletions library/compiler-builtins/compiler-builtins/src/lib.rs
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Expand Up @@ -11,6 +11,7 @@
#![feature(repr_simd)]
#![feature(macro_metavar_expr_concat)]
#![feature(rustc_attrs)]
#![feature(float_bits_const)]
#![cfg_attr(f16_enabled, feature(f16))]
#![cfg_attr(f128_enabled, feature(f128))]
#![no_builtins]
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5 changes: 5 additions & 0 deletions library/core/src/num/f128.rs
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Expand Up @@ -145,6 +145,11 @@ impl f128 {
#[unstable(feature = "f128", issue = "116909")]
pub const RADIX: u32 = 2;

/// The size of this float type in bits.
// #[unstable(feature = "f128", issue = "116909")]
#[unstable(feature = "float_bits_const", issue = "151073")]
pub const BITS: u32 = 128;

/// Number of significant digits in base 2.
///
/// Note that the size of the mantissa in the bitwise representation is one
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5 changes: 5 additions & 0 deletions library/core/src/num/f16.rs
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Expand Up @@ -142,6 +142,11 @@ impl f16 {
#[unstable(feature = "f16", issue = "116909")]
pub const RADIX: u32 = 2;

/// The size of this float type in bits.
// #[unstable(feature = "f16", issue = "116909")]
#[unstable(feature = "float_bits_const", issue = "151073")]
pub const BITS: u32 = 16;

/// Number of significant digits in base 2.
///
/// Note that the size of the mantissa in the bitwise representation is one
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4 changes: 4 additions & 0 deletions library/core/src/num/f32.rs
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Expand Up @@ -390,6 +390,10 @@ impl f32 {
#[stable(feature = "assoc_int_consts", since = "1.43.0")]
pub const RADIX: u32 = 2;

/// The size of this float type in bits.
#[unstable(feature = "float_bits_const", issue = "151073")]
pub const BITS: u32 = 32;

/// Number of significant digits in base 2.
///
/// Note that the size of the mantissa in the bitwise representation is one
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4 changes: 4 additions & 0 deletions library/core/src/num/f64.rs
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Expand Up @@ -390,6 +390,10 @@ impl f64 {
#[stable(feature = "assoc_int_consts", since = "1.43.0")]
pub const RADIX: u32 = 2;

/// The size of this float type in bits.
#[unstable(feature = "float_bits_const", issue = "151073")]
pub const BITS: u32 = 64;

/// Number of significant digits in base 2.
///
/// Note that the size of the mantissa in the bitwise representation is one
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6 changes: 3 additions & 3 deletions src/tools/miri/tests/pass/float.rs
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Expand Up @@ -353,7 +353,7 @@ macro_rules! test_ftoi_itof {
assert_itof(i, f, msg);
}

let fbits = <$fty>::BITS;
let fbits = <$fty as Float>::BITS;
let fsig_bits = <$fty>::SIGNIFICAND_BITS;
let ibits = <$ity>::BITS;
let imax: $ity = <$ity>::MAX;
Expand Down Expand Up @@ -528,9 +528,9 @@ macro_rules! test_ftof {
assert!((<$f1>::NAN as $f2).is_nan(), "{} -> {} nan", stringify!($f1), stringify!($f2));

let min_sub_casted = <$f1>::from_bits(0x1) as $f2;
let min_neg_sub_casted = <$f1>::from_bits(0x1 | 1 << (<$f1>::BITS - 1)) as $f2;
let min_neg_sub_casted = <$f1>::from_bits(0x1 | 1 << (<$f1 as Float>::BITS - 1)) as $f2;

if <$f1>::BITS > <$f2>::BITS {
if <$f1 as Float>::BITS > <$f2 as Float>::BITS {
assert_feq(<$f1>::MAX as $f2, <$f2>::INFINITY, "max -> inf");
assert_feq(<$f1>::MIN as $f2, <$f2>::NEG_INFINITY, "max -> inf");
assert_biteq(min_sub_casted, f2zero, "min subnormal -> 0.0");
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2 changes: 1 addition & 1 deletion src/tools/test-float-parse/src/traits.rs
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Expand Up @@ -155,7 +155,7 @@ macro_rules! impl_float {
const BITS: u32 = <$ity>::BITS;
const MAN_BITS: u32 = Self::MANTISSA_DIGITS - 1;
const MAN_MASK: Self::Int = (Self::Int::ONE << Self::MAN_BITS) - Self::Int::ONE;
const SIGN_MASK: Self::Int = Self::Int::ONE << (Self::BITS-1);
const SIGN_MASK: Self::Int = Self::Int::ONE << (<Self as Float>::BITS-1);
fn from_bits(i: Self::Int) -> Self { Self::from_bits(i) }
fn to_bits(self) -> Self::Int { self.to_bits() }
fn constants() -> &'static Constants {
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