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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:02:58 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:02:58 +0000
commit698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch)
tree173a775858bd501c378080a10dca74132f05bc50 /vendor/compiler_builtins/libm/src/math/logf.rs
parentInitial commit. (diff)
downloadrustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.tar.xz
rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.zip
Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'vendor/compiler_builtins/libm/src/math/logf.rs')
-rw-r--r--vendor/compiler_builtins/libm/src/math/logf.rs65
1 files changed, 65 insertions, 0 deletions
diff --git a/vendor/compiler_builtins/libm/src/math/logf.rs b/vendor/compiler_builtins/libm/src/math/logf.rs
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+/* origin: FreeBSD /usr/src/lib/msun/src/e_logf.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.
+ * ====================================================
+ */
+
+const LN2_HI: f32 = 6.9313812256e-01; /* 0x3f317180 */
+const LN2_LO: f32 = 9.0580006145e-06; /* 0x3717f7d1 */
+/* |(log(1+s)-log(1-s))/s - Lg(s)| < 2**-34.24 (~[-4.95e-11, 4.97e-11]). */
+const LG1: f32 = 0.66666662693; /* 0xaaaaaa.0p-24*/
+const LG2: f32 = 0.40000972152; /* 0xccce13.0p-25 */
+const LG3: f32 = 0.28498786688; /* 0x91e9ee.0p-25 */
+const LG4: f32 = 0.24279078841; /* 0xf89e26.0p-26 */
+
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn logf(mut x: f32) -> f32 {
+ let x1p25 = f32::from_bits(0x4c000000); // 0x1p25f === 2 ^ 25
+
+ let mut ix = x.to_bits();
+ let mut k = 0i32;
+
+ if (ix < 0x00800000) || ((ix >> 31) != 0) {
+ /* x < 2**-126 */
+ if ix << 1 == 0 {
+ return -1. / (x * x); /* log(+-0)=-inf */
+ }
+ if (ix >> 31) != 0 {
+ return (x - x) / 0.; /* log(-#) = NaN */
+ }
+ /* subnormal number, scale up x */
+ k -= 25;
+ x *= x1p25;
+ ix = x.to_bits();
+ } else if ix >= 0x7f800000 {
+ return x;
+ } else if ix == 0x3f800000 {
+ return 0.;
+ }
+
+ /* reduce x into [sqrt(2)/2, sqrt(2)] */
+ ix += 0x3f800000 - 0x3f3504f3;
+ k += ((ix >> 23) as i32) - 0x7f;
+ ix = (ix & 0x007fffff) + 0x3f3504f3;
+ x = f32::from_bits(ix);
+
+ let f = x - 1.;
+ let s = f / (2. + f);
+ let z = s * s;
+ let w = z * z;
+ let t1 = w * (LG2 + w * LG4);
+ let t2 = z * (LG1 + w * LG3);
+ let r = t2 + t1;
+ let hfsq = 0.5 * f * f;
+ let dk = k as f32;
+ s * (hfsq + r) + dk * LN2_LO - hfsq + f + dk * LN2_HI
+}