From 9835e2ae736235810b4ea1c162ca5e65c547e770 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sat, 18 May 2024 04:49:50 +0200
Subject: Merging upstream version 1.71.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 vendor/libm-0.1.4/src/math/log2.rs | 107 +++++++++++++++++++++++++++++++++++++
 1 file changed, 107 insertions(+)
 create mode 100644 vendor/libm-0.1.4/src/math/log2.rs

(limited to 'vendor/libm-0.1.4/src/math/log2.rs')

diff --git a/vendor/libm-0.1.4/src/math/log2.rs b/vendor/libm-0.1.4/src/math/log2.rs
new file mode 100644
index 000000000..a3d43e55c
--- /dev/null
+++ b/vendor/libm-0.1.4/src/math/log2.rs
@@ -0,0 +1,107 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/e_log2.c */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunSoft, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+/*
+ * Return the base 2 logarithm of x.  See log.c for most comments.
+ *
+ * Reduce x to 2^k (1+f) and calculate r = log(1+f) - f + f*f/2
+ * as in log.c, then combine and scale in extra precision:
+ *    log2(x) = (f - f*f/2 + r)/log(2) + k
+ */
+
+use core::f64;
+
+const IVLN2HI: f64 = 1.44269504072144627571e+00; /* 0x3ff71547, 0x65200000 */
+const IVLN2LO: f64 = 1.67517131648865118353e-10; /* 0x3de705fc, 0x2eefa200 */
+const LG1: f64 = 6.666666666666735130e-01; /* 3FE55555 55555593 */
+const LG2: f64 = 3.999999999940941908e-01; /* 3FD99999 9997FA04 */
+const LG3: f64 = 2.857142874366239149e-01; /* 3FD24924 94229359 */
+const LG4: f64 = 2.222219843214978396e-01; /* 3FCC71C5 1D8E78AF */
+const LG5: f64 = 1.818357216161805012e-01; /* 3FC74664 96CB03DE */
+const LG6: f64 = 1.531383769920937332e-01; /* 3FC39A09 D078C69F */
+const LG7: f64 = 1.479819860511658591e-01; /* 3FC2F112 DF3E5244 */
+
+#[inline]
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn log2(mut x: f64) -> f64 {
+    let x1p54 = f64::from_bits(0x4350000000000000); // 0x1p54 === 2 ^ 54
+
+    let mut ui: u64 = x.to_bits();
+    let hfsq: f64;
+    let f: f64;
+    let s: f64;
+    let z: f64;
+    let r: f64;
+    let mut w: f64;
+    let t1: f64;
+    let t2: f64;
+    let y: f64;
+    let mut hi: f64;
+    let lo: f64;
+    let mut val_hi: f64;
+    let mut val_lo: f64;
+    let mut hx: u32;
+    let mut k: i32;
+
+    hx = (ui >> 32) as u32;
+    k = 0;
+    if hx < 0x00100000 || (hx >> 31) > 0 {
+        if ui << 1 == 0 {
+            return -1. / (x * x); /* log(+-0)=-inf */
+        }
+        if (hx >> 31) > 0 {
+            return (x - x) / 0.0; /* log(-#) = NaN */
+        }
+        /* subnormal number, scale x up */
+        k -= 54;
+        x *= x1p54;
+        ui = x.to_bits();
+        hx = (ui >> 32) as u32;
+    } else if hx >= 0x7ff00000 {
+        return x;
+    } else if hx == 0x3ff00000 && ui << 32 == 0 {
+        return 0.;
+    }
+
+    /* reduce x into [sqrt(2)/2, sqrt(2)] */
+    hx += 0x3ff00000 - 0x3fe6a09e;
+    k += (hx >> 20) as i32 - 0x3ff;
+    hx = (hx & 0x000fffff) + 0x3fe6a09e;
+    ui = (hx as u64) << 32 | (ui & 0xffffffff);
+    x = f64::from_bits(ui);
+
+    f = x - 1.0;
+    hfsq = 0.5 * f * f;
+    s = f / (2.0 + f);
+    z = s * s;
+    w = z * z;
+    t1 = w * (LG2 + w * (LG4 + w * LG6));
+    t2 = z * (LG1 + w * (LG3 + w * (LG5 + w * LG7)));
+    r = t2 + t1;
+
+    /* hi+lo = f - hfsq + s*(hfsq+R) ~ log(1+f) */
+    hi = f - hfsq;
+    ui = hi.to_bits();
+    ui &= (-1i64 as u64) << 32;
+    hi = f64::from_bits(ui);
+    lo = f - hi - hfsq + s * (hfsq + r);
+
+    val_hi = hi * IVLN2HI;
+    val_lo = (lo + hi) * IVLN2LO + lo * IVLN2HI;
+
+    /* spadd(val_hi, val_lo, y), except for not using double_t: */
+    y = k.into();
+    w = y + val_hi;
+    val_lo += (y - w) + val_hi;
+    val_hi = w;
+
+    val_lo + val_hi
+}
-- 
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