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Diffstat (limited to '')
| -rw-r--r-- | vendor/compiler_builtins/libm/src/math/sqrtf.rs | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/vendor/compiler_builtins/libm/src/math/sqrtf.rs b/vendor/compiler_builtins/libm/src/math/sqrtf.rs new file mode 100644 index 000000000..00b20e578 --- /dev/null +++ b/vendor/compiler_builtins/libm/src/math/sqrtf.rs @@ -0,0 +1,154 @@ +/* origin: FreeBSD /usr/src/lib/msun/src/e_sqrtf.c */ +/* + * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. + */ +/* + * ==================================================== + * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. + * + * Developed at SunPro, a Sun Microsystems, Inc. business. + * Permission to use, copy, modify, and distribute this + * software is freely granted, provided that this notice + * is preserved. + * ==================================================== + */ + +#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] +pub fn sqrtf(x: f32) -> f32 { + // On wasm32 we know that LLVM's intrinsic will compile to an optimized + // `f32.sqrt` native instruction, so we can leverage this for both code size + // and speed. + llvm_intrinsically_optimized! { + #[cfg(target_arch = "wasm32")] { + return if x < 0.0 { + ::core::f32::NAN + } else { + unsafe { ::core::intrinsics::sqrtf32(x) } + } + } + } + #[cfg(target_feature = "sse")] + { + // Note: This path is unlikely since LLVM will usually have already + // optimized sqrt calls into hardware instructions if sse is available, + // but if someone does end up here they'll apprected the speed increase. + #[cfg(target_arch = "x86")] + use core::arch::x86::*; + #[cfg(target_arch = "x86_64")] + use core::arch::x86_64::*; + unsafe { + let m = _mm_set_ss(x); + let m_sqrt = _mm_sqrt_ss(m); + _mm_cvtss_f32(m_sqrt) + } + } + #[cfg(not(target_feature = "sse"))] + { + const TINY: f32 = 1.0e-30; + + let mut z: f32; + let sign: i32 = 0x80000000u32 as i32; + let mut ix: i32; + let mut s: i32; + let mut q: i32; + let mut m: i32; + let mut t: i32; + let mut i: i32; + let mut r: u32; + + ix = x.to_bits() as i32; + + /* take care of Inf and NaN */ + if (ix as u32 & 0x7f800000) == 0x7f800000 { + return x * x + x; /* sqrt(NaN)=NaN, sqrt(+inf)=+inf, sqrt(-inf)=sNaN */ + } + + /* take care of zero */ + if ix <= 0 { + if (ix & !sign) == 0 { + return x; /* sqrt(+-0) = +-0 */ + } + if ix < 0 { + return (x - x) / (x - x); /* sqrt(-ve) = sNaN */ + } + } + + /* normalize x */ + m = ix >> 23; + if m == 0 { + /* subnormal x */ + i = 0; + while ix & 0x00800000 == 0 { + ix <<= 1; + i = i + 1; + } + m -= i - 1; + } + m -= 127; /* unbias exponent */ + ix = (ix & 0x007fffff) | 0x00800000; + if m & 1 == 1 { + /* odd m, double x to make it even */ + ix += ix; + } + m >>= 1; /* m = [m/2] */ + + /* generate sqrt(x) bit by bit */ + ix += ix; + q = 0; + s = 0; + r = 0x01000000; /* r = moving bit from right to left */ + + while r != 0 { + t = s + r as i32; + if t <= ix { + s = t + r as i32; + ix -= t; + q += r as i32; + } + ix += ix; + r >>= 1; + } + + /* use floating add to find out rounding direction */ + if ix != 0 { + z = 1.0 - TINY; /* raise inexact flag */ + if z >= 1.0 { + z = 1.0 + TINY; + if z > 1.0 { + q += 2; + } else { + q += q & 1; + } + } + } + + ix = (q >> 1) + 0x3f000000; + ix += m << 23; + f32::from_bits(ix as u32) + } +} + +// PowerPC tests are failing on LLVM 13: https://github.com/rust-lang/rust/issues/88520 +#[cfg(not(target_arch = "powerpc64"))] +#[cfg(test)] +mod tests { + use super::*; + use core::f32::*; + + #[test] + fn sanity_check() { + assert_eq!(sqrtf(100.0), 10.0); + assert_eq!(sqrtf(4.0), 2.0); + } + + /// The spec: https://en.cppreference.com/w/cpp/numeric/math/sqrt + #[test] + fn spec_tests() { + // Not Asserted: FE_INVALID exception is raised if argument is negative. + assert!(sqrtf(-1.0).is_nan()); + assert!(sqrtf(NAN).is_nan()); + for f in [0.0, -0.0, INFINITY].iter().copied() { + assert_eq!(sqrtf(f), f); + } + } +} |