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Rename EXP_MAX to EXP_SAT

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`EXP_MAX` sounds like it would be the maximum value representable by
that float type's exponent, rather than the maximum unsigned value of
its bits. Clarify this by renaming to `EXP_SAT`, the "saturated"
exponent representation.
This commit is contained in:
Trevor Gross 2025-01-31 12:31:35 +00:00 • committed by Trevor Gross
parent 7d674145ae
commit 8db5ff73e6
3 changed files with 15 additions and 12 deletions
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2
library/compiler-builtins/libm/src/math/generic/fmod.rs
View file

@ -13,7 +13,7 @@ pub fn fmod<F: Float>(x: F, y: F) -> F {
let mut ey = y.exp().signed();
let sx = ix & F::SIGN_MASK;
if iy << 1 == zero || y.is_nan() || ex == F::EXP_MAX as i32 {
if iy << 1 == zero || y.is_nan() || ex == F::EXP_SAT as i32 {
return (x * y) / (x * y);
}

4
library/compiler-builtins/libm/src/math/generic/sqrt.rs
View file

@ -68,7 +68,7 @@ where
(Exp::NoShift(()), special_case)
} else {
let top = u32::cast_from(ix >> F::SIG_BITS);
let special_case = top.wrapping_sub(1) >= F::EXP_MAX - 1;
let special_case = top.wrapping_sub(1) >= F::EXP_SAT - 1;
(Exp::Shifted(top), special_case)
};
@ -119,7 +119,7 @@ where
if even {
m_u2 >>= 1;
}
e = (e.wrapping_add(F::EXP_MAX >> 1)) >> 1;
e = (e.wrapping_add(F::EXP_SAT >> 1)) >> 1;
(m_u2, Exp::Shifted(e))
}
Exp::NoShift(()) => {

21
library/compiler-builtins/libm/src/math/support/float_traits.rs
View file

@ -48,11 +48,14 @@ pub trait Float:
/// The bitwidth of the exponent
const EXP_BITS: u32 = Self::BITS - Self::SIG_BITS - 1;
/// The saturated value of the exponent (infinite representation), in the rightmost postiion.
const EXP_MAX: u32 = (1 << Self::EXP_BITS) - 1;
/// The saturated (maximum bitpattern) value of the exponent, i.e. the infinite
/// representation.
///
/// This shifted fully right, use `EXP_MASK` for the shifted value.
const EXP_SAT: u32 = (1 << Self::EXP_BITS) - 1;
/// The exponent bias value
const EXP_BIAS: u32 = Self::EXP_MAX >> 1;
const EXP_BIAS: u32 = Self::EXP_SAT >> 1;
/// A mask for the sign bit
const SIGN_MASK: Self::Int;
@ -109,7 +112,7 @@ pub trait Float:
/// Returns the exponent, not adjusting for bias, not accounting for subnormals or zero.
fn exp(self) -> u32 {
u32::cast_from(self.to_bits() >> Self::SIG_BITS) & Self::EXP_MAX
u32::cast_from(self.to_bits() >> Self::SIG_BITS) & Self::EXP_SAT
}
/// Extract the exponent and adjust it for bias, not accounting for subnormals or zero.
@ -135,7 +138,7 @@ pub trait Float:
let sign = if negative { Self::Int::ONE } else { Self::Int::ZERO };
Self::from_bits(
(sign << (Self::BITS - 1))
| (Self::Int::cast_from(exponent & Self::EXP_MAX) << Self::SIG_BITS)
| (Self::Int::cast_from(exponent & Self::EXP_SAT) << Self::SIG_BITS)
| (significand & Self::SIG_MASK),
)
}
@ -267,7 +270,7 @@ mod tests {
#[cfg(f16_enabled)]
fn check_f16() {
// Constants
assert_eq!(f16::EXP_MAX, 0b11111);
assert_eq!(f16::EXP_SAT, 0b11111);
assert_eq!(f16::EXP_BIAS, 15);
// `exp_unbiased`
@ -289,7 +292,7 @@ mod tests {
#[test]
fn check_f32() {
// Constants
assert_eq!(f32::EXP_MAX, 0b11111111);
assert_eq!(f32::EXP_SAT, 0b11111111);
assert_eq!(f32::EXP_BIAS, 127);
// `exp_unbiased`
@ -312,7 +315,7 @@ mod tests {
#[test]
fn check_f64() {
// Constants
assert_eq!(f64::EXP_MAX, 0b11111111111);
assert_eq!(f64::EXP_SAT, 0b11111111111);
assert_eq!(f64::EXP_BIAS, 1023);
// `exp_unbiased`
@ -336,7 +339,7 @@ mod tests {
#[cfg(f128_enabled)]
fn check_f128() {
// Constants
assert_eq!(f128::EXP_MAX, 0b111111111111111);
assert_eq!(f128::EXP_SAT, 0b111111111111111);
assert_eq!(f128::EXP_BIAS, 16383);
// `exp_unbiased`