authorgravatar for hahv@msn.comHuang Zhichao <hahv@msn.com> 2026-05-22 14:07:54+08:00
committergravatar for andrew@ziglang.orgAndrew Kelley <andrew@ziglang.org> 2026-05-31 09:21:02+02:00
log9f0a38ac815d4d38a3afec6628827f79fdf43b98
treebdc327508057d946facf9e6b672ffb50884e8157
parentcbc62662046c321bbdbb9315a3658ee50234033f

libzigc: log1p, log1pf

9 files changed, 25 insertions(+), 277 deletions(-)

lib/c/math.zig+10
......@@ -72,6 +72,8 @@ comptime {
7272 symbol(&finitef, "finitef");
7373 symbol(&frexp, "frexp");
7474 symbol(&hypot, "hypot");
75 symbol(&log1p, "log1p");
76 symbol(&log1pf, "log1pf");
7577 symbol(&lrint, "lrint");
7678 symbol(&lrintf, "lrintf");
7779 symbol(&modf, "modf");
......@@ -256,6 +258,14 @@ fn isnanl(x: c_longdouble) callconv(.c) c_int {
256258 return @intFromBool(math.isNan(x));
257259}
258260
261fn log1p(x: f64) callconv(.c) f64 {
262 return math.log1p(x);
263}
264
265fn log1pf(x: f32) callconv(.c) f32 {
266 return math.log1p(x);
267}
268
259269fn lrint(x: f64) callconv(.c) c_long {
260270 return @trunc(rint(x));
261271}
lib/libc/musl/src/math/i386/log1p.s deleted-25
......@@ -1,25 +0,0 @@
1.global log1p
2.type log1p,@function
3log1p:
4 mov 8(%esp),%eax
5 fldln2
6 and $0x7fffffff,%eax
7 fldl 4(%esp)
8 cmp $0x3fd28f00,%eax
9 ja 1f
10 cmp $0x00100000,%eax
11 jb 2f
12 fyl2xp1
13 fstpl 4(%esp)
14 fldl 4(%esp)
15 ret
161: fld1
17 faddp
18 fyl2x
19 fstpl 4(%esp)
20 fldl 4(%esp)
21 ret
22 # subnormal x, return x with underflow
232: fsts 4(%esp)
24 fstp %st(1)
25 ret
lib/libc/musl/src/math/i386/log1pf.s deleted-26
......@@ -1,26 +0,0 @@
1.global log1pf
2.type log1pf,@function
3log1pf:
4 mov 4(%esp),%eax
5 fldln2
6 and $0x7fffffff,%eax
7 flds 4(%esp)
8 cmp $0x3e940000,%eax
9 ja 1f
10 cmp $0x00800000,%eax
11 jb 2f
12 fyl2xp1
13 fstps 4(%esp)
14 flds 4(%esp)
15 ret
161: fld1
17 faddp
18 fyl2x
19 fstps 4(%esp)
20 flds 4(%esp)
21 ret
22 # subnormal x, return x with underflow
232: fxch
24 fmul %st(1)
25 fstps 4(%esp)
26 ret
lib/libc/musl/src/math/log1p.c deleted-122
......@@ -1,122 +0,0 @@
1/* origin: FreeBSD /usr/src/lib/msun/src/s_log1p.c */
2/*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 *
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
9 * is preserved.
10 * ====================================================
11 */
12/* double log1p(double x)
13 * Return the natural logarithm of 1+x.
14 *
15 * Method :
16 * 1. Argument Reduction: find k and f such that
17 * 1+x = 2^k * (1+f),
18 * where sqrt(2)/2 < 1+f < sqrt(2) .
19 *
20 * Note. If k=0, then f=x is exact. However, if k!=0, then f
21 * may not be representable exactly. In that case, a correction
22 * term is need. Let u=1+x rounded. Let c = (1+x)-u, then
23 * log(1+x) - log(u) ~ c/u. Thus, we proceed to compute log(u),
24 * and add back the correction term c/u.
25 * (Note: when x > 2**53, one can simply return log(x))
26 *
27 * 2. Approximation of log(1+f): See log.c
28 *
29 * 3. Finally, log1p(x) = k*ln2 + log(1+f) + c/u. See log.c
30 *
31 * Special cases:
32 * log1p(x) is NaN with signal if x < -1 (including -INF) ;
33 * log1p(+INF) is +INF; log1p(-1) is -INF with signal;
34 * log1p(NaN) is that NaN with no signal.
35 *
36 * Accuracy:
37 * according to an error analysis, the error is always less than
38 * 1 ulp (unit in the last place).
39 *
40 * Constants:
41 * The hexadecimal values are the intended ones for the following
42 * constants. The decimal values may be used, provided that the
43 * compiler will convert from decimal to binary accurately enough
44 * to produce the hexadecimal values shown.
45 *
46 * Note: Assuming log() return accurate answer, the following
47 * algorithm can be used to compute log1p(x) to within a few ULP:
48 *
49 * u = 1+x;
50 * if(u==1.0) return x ; else
51 * return log(u)*(x/(u-1.0));
52 *
53 * See HP-15C Advanced Functions Handbook, p.193.
54 */
55
56#include "libm.h"
57
58static const double
59ln2_hi = 6.93147180369123816490e-01, /* 3fe62e42 fee00000 */
60ln2_lo = 1.90821492927058770002e-10, /* 3dea39ef 35793c76 */
61Lg1 = 6.666666666666735130e-01, /* 3FE55555 55555593 */
62Lg2 = 3.999999999940941908e-01, /* 3FD99999 9997FA04 */
63Lg3 = 2.857142874366239149e-01, /* 3FD24924 94229359 */
64Lg4 = 2.222219843214978396e-01, /* 3FCC71C5 1D8E78AF */
65Lg5 = 1.818357216161805012e-01, /* 3FC74664 96CB03DE */
66Lg6 = 1.531383769920937332e-01, /* 3FC39A09 D078C69F */
67Lg7 = 1.479819860511658591e-01; /* 3FC2F112 DF3E5244 */
68
69double log1p(double x)
70{
71 union {double f; uint64_t i;} u = {x};
72 double_t hfsq,f,c,s,z,R,w,t1,t2,dk;
73 uint32_t hx,hu;
74 int k;
75
76 hx = u.i>>32;
77 k = 1;
78 if (hx < 0x3fda827a || hx>>31) { /* 1+x < sqrt(2)+ */
79 if (hx >= 0xbff00000) { /* x <= -1.0 */
80 if (x == -1)
81 return x/0.0; /* log1p(-1) = -inf */
82 return (x-x)/0.0; /* log1p(x<-1) = NaN */
83 }
84 if (hx<<1 < 0x3ca00000<<1) { /* |x| < 2**-53 */
85 /* underflow if subnormal */
86 if ((hx&0x7ff00000) == 0)
87 FORCE_EVAL((float)x);
88 return x;
89 }
90 if (hx <= 0xbfd2bec4) { /* sqrt(2)/2- <= 1+x < sqrt(2)+ */
91 k = 0;
92 c = 0;
93 f = x;
94 }
95 } else if (hx >= 0x7ff00000)
96 return x;
97 if (k) {
98 u.f = 1 + x;
99 hu = u.i>>32;
100 hu += 0x3ff00000 - 0x3fe6a09e;
101 k = (int)(hu>>20) - 0x3ff;
102 /* correction term ~ log(1+x)-log(u), avoid underflow in c/u */
103 if (k < 54) {
104 c = k >= 2 ? 1-(u.f-x) : x-(u.f-1);
105 c /= u.f;
106 } else
107 c = 0;
108 /* reduce u into [sqrt(2)/2, sqrt(2)] */
109 hu = (hu&0x000fffff) + 0x3fe6a09e;
110 u.i = (uint64_t)hu<<32 | (u.i&0xffffffff);
111 f = u.f - 1;
112 }
113 hfsq = 0.5*f*f;
114 s = f/(2.0+f);
115 z = s*s;
116 w = z*z;
117 t1 = w*(Lg2+w*(Lg4+w*Lg6));
118 t2 = z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7)));
119 R = t2 + t1;
120 dk = k;
121 return s*(hfsq+R) + (dk*ln2_lo+c) - hfsq + f + dk*ln2_hi;
122}
lib/libc/musl/src/math/log1pf.c deleted-77
......@@ -1,77 +0,0 @@
1/* origin: FreeBSD /usr/src/lib/msun/src/s_log1pf.c */
2/*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 *
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
9 * is preserved.
10 * ====================================================
11 */
12
13#include "libm.h"
14
15static const float
16ln2_hi = 6.9313812256e-01, /* 0x3f317180 */
17ln2_lo = 9.0580006145e-06, /* 0x3717f7d1 */
18/* |(log(1+s)-log(1-s))/s - Lg(s)| < 2**-34.24 (~[-4.95e-11, 4.97e-11]). */
19Lg1 = 0xaaaaaa.0p-24, /* 0.66666662693 */
20Lg2 = 0xccce13.0p-25, /* 0.40000972152 */
21Lg3 = 0x91e9ee.0p-25, /* 0.28498786688 */
22Lg4 = 0xf89e26.0p-26; /* 0.24279078841 */
23
24float log1pf(float x)
25{
26 union {float f; uint32_t i;} u = {x};
27 float_t hfsq,f,c,s,z,R,w,t1,t2,dk;
28 uint32_t ix,iu;
29 int k;
30
31 ix = u.i;
32 k = 1;
33 if (ix < 0x3ed413d0 || ix>>31) { /* 1+x < sqrt(2)+ */
34 if (ix >= 0xbf800000) { /* x <= -1.0 */
35 if (x == -1)
36 return x/0.0f; /* log1p(-1)=+inf */
37 return (x-x)/0.0f; /* log1p(x<-1)=NaN */
38 }
39 if (ix<<1 < 0x33800000<<1) { /* |x| < 2**-24 */
40 /* underflow if subnormal */
41 if ((ix&0x7f800000) == 0)
42 FORCE_EVAL(x*x);
43 return x;
44 }
45 if (ix <= 0xbe95f619) { /* sqrt(2)/2- <= 1+x < sqrt(2)+ */
46 k = 0;
47 c = 0;
48 f = x;
49 }
50 } else if (ix >= 0x7f800000)
51 return x;
52 if (k) {
53 u.f = 1 + x;
54 iu = u.i;
55 iu += 0x3f800000 - 0x3f3504f3;
56 k = (int)(iu>>23) - 0x7f;
57 /* correction term ~ log(1+x)-log(u), avoid underflow in c/u */
58 if (k < 25) {
59 c = k >= 2 ? 1-(u.f-x) : x-(u.f-1);
60 c /= u.f;
61 } else
62 c = 0;
63 /* reduce u into [sqrt(2)/2, sqrt(2)] */
64 iu = (iu&0x007fffff) + 0x3f3504f3;
65 u.i = iu;
66 f = u.f - 1;
67 }
68 s = f/(2.0f + f);
69 z = s*s;
70 w = z*z;
71 t1= w*(Lg2+w*Lg4);
72 t2= z*(Lg1+w*Lg3);
73 R = t2 + t1;
74 hfsq = 0.5f*f*f;
75 dk = k;
76 return s*(hfsq+R) + (dk*ln2_lo+c) - hfsq + f + dk*ln2_hi;
77}
lib/std/math/log1p.zig+13-19
......@@ -43,17 +43,14 @@ fn log1p_32(x: f32) f32 {
4343
4444 // 1 + x < sqrt(2)+
4545 if (ix < 0x3ED413D0 or ix >> 31 != 0) {
46 // x <= -1.0
47 if (ix >= 0xBF800000) {
46 // x = -1.0
47 if (ix == 0xBF800000)
4848 // log1p(-1) = -inf
49 if (x == -1.0) {
50 return -math.inf(f32);
51 }
49 return x / 0.0;
50 // x < -1.0
51 if (ix > 0xBF800000)
5252 // log1p(x < -1) = nan
53 else {
54 return math.nan(f32);
55 }
56 }
53 return (x - x) / 0.0;
5754 // |x| < 2^(-24)
5855 if ((ix << 1) < (0x33800000 << 1)) {
5956 // underflow if subnormal
......@@ -122,21 +119,18 @@ fn log1p_64(x: f64) f64 {
122119
123120 // 1 + x < sqrt(2)
124121 if (hx < 0x3FDA827A or hx >> 31 != 0) {
125 // x <= -1.0
126 if (hx >= 0xBFF00000) {
122 // x = -1.0
123 if (ix == 0xBFF0000000000000)
127124 // log1p(-1) = -inf
128 if (x == -1.0) {
129 return -math.inf(f64);
130 }
125 return x / 0.0;
126 // x < -1.0
127 if (hx >= 0xBFF00000)
131128 // log1p(x < -1) = nan
132 else {
133 return math.nan(f64);
134 }
135 }
129 return (x - x) / 0.0;
136130 // |x| < 2^(-53)
137131 if ((hx << 1) < (0x3CA00000 << 1)) {
138132 if ((hx & 0x7FF00000) == 0) {
139 math.raiseUnderflow();
133 mem.doNotOptimizeAway(@as(f32, @floatCast(x)));
140134 }
141135 return x;
142136 }
src/libs/musl.zig-4
......@@ -845,9 +845,7 @@ const src_files = [_][]const u8{
845845 "musl/src/math/i386/llrintf.c",
846846 "musl/src/math/i386/llrintl.c",
847847 "musl/src/math/i386/log10l.s",
848 "musl/src/math/i386/log1pf.s",
849848 "musl/src/math/i386/log1pl.s",
850 "musl/src/math/i386/log1p.s",
851849 "musl/src/math/i386/log2l.s",
852850 "musl/src/math/i386/logl.s",
853851 "musl/src/math/i386/remainder.c",
......@@ -887,8 +885,6 @@ const src_files = [_][]const u8{
887885 "musl/src/math/llroundf.c",
888886 "musl/src/math/llroundl.c",
889887 "musl/src/math/log10l.c",
890 "musl/src/math/log1p.c",
891 "musl/src/math/log1pf.c",
892888 "musl/src/math/log1pl.c",
893889 "musl/src/math/log2l.c",
894890 "musl/src/math/logb.c",
src/libs/wasi_libc.zig-2
......@@ -719,8 +719,6 @@ const libc_top_half_src_files = [_][]const u8{
719719 "musl/src/math/llroundf.c",
720720 "musl/src/math/llroundl.c",
721721 "musl/src/math/log10l.c",
722 "musl/src/math/log1p.c",
723 "musl/src/math/log1pf.c",
724722 "musl/src/math/log1pl.c",
725723 "musl/src/math/log2l.c",
726724 "musl/src/math/logb.c",
test/libc.zig+2-2
......@@ -252,8 +252,8 @@ pub fn addCases(cases: *tests.LibcContext) void {
252252 cases.addLibcTestCase("math/log10.c", true, .{});
253253 cases.addLibcTestCase("math/log10f.c", true, .{});
254254 cases.addLibcTestCase("math/log10l.c", true, .{});
255 // cases.addLibcTestCase("math/log1p.c", true, .{});
256 // cases.addLibcTestCase("math/log1pf.c", true, .{});
255 cases.addLibcTestCase("math/log1p.c", true, .{});
256 cases.addLibcTestCase("math/log1pf.c", true, .{});
257257 // cases.addLibcTestCase("math/log1pl.c", true, .{});
258258 cases.addLibcTestCase("math/log2.c", true, .{});
259259 cases.addLibcTestCase("math/log2f.c", true, .{});