diff options
Diffstat (limited to 'library/compiler-builtins/libm/src/math/sqrt.rs')
| -rw-r--r-- | library/compiler-builtins/libm/src/math/sqrt.rs | 235 |
1 files changed, 127 insertions, 108 deletions
diff --git a/library/compiler-builtins/libm/src/math/sqrt.rs b/library/compiler-builtins/libm/src/math/sqrt.rs index 58cf00ed888..31afe33566b 100644 --- a/library/compiler-builtins/libm/src/math/sqrt.rs +++ b/library/compiler-builtins/libm/src/math/sqrt.rs @@ -77,9 +77,6 @@ */ use core::f64; -use core::num::Wrapping; - -const TINY: f64 = 1.0e-300; #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] pub fn sqrt(x: f64) -> f64 { @@ -95,128 +92,150 @@ pub fn sqrt(x: f64) -> f64 { } } } - let mut z: f64; - let sign: Wrapping<u32> = Wrapping(0x80000000); - let mut ix0: i32; - let mut s0: i32; - let mut q: i32; - let mut m: i32; - let mut t: i32; - let mut i: i32; - let mut r: Wrapping<u32>; - let mut t1: Wrapping<u32>; - let mut s1: Wrapping<u32>; - let mut ix1: Wrapping<u32>; - let mut q1: Wrapping<u32>; + #[cfg(target_feature = "sse2")] + { + // Note: This path is unlikely since LLVM will usually have already + // optimized sqrt calls into hardware instructions if sse2 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_sd(x); + let m_sqrt = _mm_sqrt_pd(m); + _mm_cvtsd_f64(m_sqrt) + } + } + #[cfg(not(target_feature = "sse2"))] + { + use core::num::Wrapping; - ix0 = (x.to_bits() >> 32) as i32; - ix1 = Wrapping(x.to_bits() as u32); + const TINY: f64 = 1.0e-300; - /* take care of Inf and NaN */ - if (ix0 & 0x7ff00000) == 0x7ff00000 { - return x * x + x; /* sqrt(NaN)=NaN, sqrt(+inf)=+inf, sqrt(-inf)=sNaN */ - } - /* take care of zero */ - if ix0 <= 0 { - if ((ix0 & !(sign.0 as i32)) | ix1.0 as i32) == 0 { - return x; /* sqrt(+-0) = +-0 */ + let mut z: f64; + let sign: Wrapping<u32> = Wrapping(0x80000000); + let mut ix0: i32; + let mut s0: i32; + let mut q: i32; + let mut m: i32; + let mut t: i32; + let mut i: i32; + let mut r: Wrapping<u32>; + let mut t1: Wrapping<u32>; + let mut s1: Wrapping<u32>; + let mut ix1: Wrapping<u32>; + let mut q1: Wrapping<u32>; + + ix0 = (x.to_bits() >> 32) as i32; + ix1 = Wrapping(x.to_bits() as u32); + + /* take care of Inf and NaN */ + if (ix0 & 0x7ff00000) == 0x7ff00000 { + return x * x + x; /* sqrt(NaN)=NaN, sqrt(+inf)=+inf, sqrt(-inf)=sNaN */ } - if ix0 < 0 { - return (x - x) / (x - x); /* sqrt(-ve) = sNaN */ + /* take care of zero */ + if ix0 <= 0 { + if ((ix0 & !(sign.0 as i32)) | ix1.0 as i32) == 0 { + return x; /* sqrt(+-0) = +-0 */ + } + if ix0 < 0 { + return (x - x) / (x - x); /* sqrt(-ve) = sNaN */ + } } - } - /* normalize x */ - m = ix0 >> 20; - if m == 0 { - /* subnormal x */ - while ix0 == 0 { - m -= 21; - ix0 |= (ix1 >> 11).0 as i32; - ix1 <<= 21; + /* normalize x */ + m = ix0 >> 20; + if m == 0 { + /* subnormal x */ + while ix0 == 0 { + m -= 21; + ix0 |= (ix1 >> 11).0 as i32; + ix1 <<= 21; + } + i = 0; + while (ix0 & 0x00100000) == 0 { + i += 1; + ix0 <<= 1; + } + m -= i - 1; + ix0 |= (ix1 >> (32 - i) as usize).0 as i32; + ix1 = ix1 << i as usize; } - i = 0; - while (ix0 & 0x00100000) == 0 { - i += 1; - ix0 <<= 1; + m -= 1023; /* unbias exponent */ + ix0 = (ix0 & 0x000fffff) | 0x00100000; + if (m & 1) == 1 { + /* odd m, double x to make it even */ + ix0 += ix0 + ((ix1 & sign) >> 31).0 as i32; + ix1 += ix1; } - m -= i - 1; - ix0 |= (ix1 >> (32 - i) as usize).0 as i32; - ix1 = ix1 << i as usize; - } - m -= 1023; /* unbias exponent */ - ix0 = (ix0 & 0x000fffff) | 0x00100000; - if (m & 1) == 1 { - /* odd m, double x to make it even */ - ix0 += ix0 + ((ix1 & sign) >> 31).0 as i32; - ix1 += ix1; - } - m >>= 1; /* m = [m/2] */ - - /* generate sqrt(x) bit by bit */ - ix0 += ix0 + ((ix1 & sign) >> 31).0 as i32; - ix1 += ix1; - q = 0; /* [q,q1] = sqrt(x) */ - q1 = Wrapping(0); - s0 = 0; - s1 = Wrapping(0); - r = Wrapping(0x00200000); /* r = moving bit from right to left */ + m >>= 1; /* m = [m/2] */ - while r != Wrapping(0) { - t = s0 + r.0 as i32; - if t <= ix0 { - s0 = t + r.0 as i32; - ix0 -= t; - q += r.0 as i32; - } + /* generate sqrt(x) bit by bit */ ix0 += ix0 + ((ix1 & sign) >> 31).0 as i32; ix1 += ix1; - r >>= 1; - } + q = 0; /* [q,q1] = sqrt(x) */ + q1 = Wrapping(0); + s0 = 0; + s1 = Wrapping(0); + r = Wrapping(0x00200000); /* r = moving bit from right to left */ - r = sign; - while r != Wrapping(0) { - t1 = s1 + r; - t = s0; - if t < ix0 || (t == ix0 && t1 <= ix1) { - s1 = t1 + r; - if (t1 & sign) == sign && (s1 & sign) == Wrapping(0) { - s0 += 1; + while r != Wrapping(0) { + t = s0 + r.0 as i32; + if t <= ix0 { + s0 = t + r.0 as i32; + ix0 -= t; + q += r.0 as i32; } - ix0 -= t; - if ix1 < t1 { - ix0 -= 1; + ix0 += ix0 + ((ix1 & sign) >> 31).0 as i32; + ix1 += ix1; + r >>= 1; + } + + r = sign; + while r != Wrapping(0) { + t1 = s1 + r; + t = s0; + if t < ix0 || (t == ix0 && t1 <= ix1) { + s1 = t1 + r; + if (t1 & sign) == sign && (s1 & sign) == Wrapping(0) { + s0 += 1; + } + ix0 -= t; + if ix1 < t1 { + ix0 -= 1; + } + ix1 -= t1; + q1 += r; } - ix1 -= t1; - q1 += r; + ix0 += ix0 + ((ix1 & sign) >> 31).0 as i32; + ix1 += ix1; + r >>= 1; } - ix0 += ix0 + ((ix1 & sign) >> 31).0 as i32; - ix1 += ix1; - r >>= 1; - } - /* use floating add to find out rounding direction */ - if (ix0 as u32 | ix1.0) != 0 { - z = 1.0 - TINY; /* raise inexact flag */ - if z >= 1.0 { - z = 1.0 + TINY; - if q1.0 == 0xffffffff { - q1 = Wrapping(0); - q += 1; - } else if z > 1.0 { - if q1.0 == 0xfffffffe { + /* use floating add to find out rounding direction */ + if (ix0 as u32 | ix1.0) != 0 { + z = 1.0 - TINY; /* raise inexact flag */ + if z >= 1.0 { + z = 1.0 + TINY; + if q1.0 == 0xffffffff { + q1 = Wrapping(0); q += 1; + } else if z > 1.0 { + if q1.0 == 0xfffffffe { + q += 1; + } + q1 += Wrapping(2); + } else { + q1 += q1 & Wrapping(1); } - q1 += Wrapping(2); - } else { - q1 += q1 & Wrapping(1); } } + ix0 = (q >> 1) + 0x3fe00000; + ix1 = q1 >> 1; + if (q & 1) == 1 { + ix1 |= sign; + } + ix0 += m << 20; + f64::from_bits((ix0 as u64) << 32 | ix1.0 as u64) } - ix0 = (q >> 1) + 0x3fe00000; - ix1 = q1 >> 1; - if (q & 1) == 1 { - ix1 |= sign; - } - ix0 += m << 20; - f64::from_bits((ix0 as u64) << 32 | ix1.0 as u64) } |