commit 69cbe8ea3c54b181a42612973ae25aada7bd8b6e (tree)
parent 888014c83724008194b4234d96dc3af3c86dc38a
Author: mihael <hi@mihaelm.com>
Date: Wed, 11 Mar 2026 18:51:39 +0100
`libzigc`: Implement `asin`
The changes were tested by running:
```
$ ./build/stage3/bin/zig build -p stage4 -Denable-llvm -Dno-lib
$ stage4/bin/zig build test-libc -Dlibc-test-path=<LIBC-TEST-PATH> -Dtest-filter=asin -fqemu -fwasmtime --summary line
Build Summary: 921/921 steps succeeded
```
Diffstat:
5 files changed, 5 insertions(+), 131 deletions(-)
diff --git a/lib/c/math.zig b/lib/c/math.zig
@@ -42,6 +42,7 @@ comptime {
if (builtin.target.isMuslLibC() or builtin.target.isWasiLibC()) {
symbol(&acos, "acos");
symbol(&acosf, "acosf");
+ symbol(&asin, "asin");
symbol(&atan, "atan");
symbol(&atanf, "atanf");
symbol(&atanl, "atanl");
@@ -73,6 +74,10 @@ fn acosf(x: f32) callconv(.c) f32 {
return math.acos(x);
}
+fn asin(x: f64) callconv(.c) f64 {
+ return math.asin(x);
+}
+
fn atan(x: f64) callconv(.c) f64 {
return math.atan(x);
}
diff --git a/lib/libc/musl/src/math/asin.c b/lib/libc/musl/src/math/asin.c
@@ -1,107 +0,0 @@
-/* origin: FreeBSD /usr/src/lib/msun/src/e_asin.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.
- * ====================================================
- */
-/* asin(x)
- * Method :
- * Since asin(x) = x + x^3/6 + x^5*3/40 + x^7*15/336 + ...
- * we approximate asin(x) on [0,0.5] by
- * asin(x) = x + x*x^2*R(x^2)
- * where
- * R(x^2) is a rational approximation of (asin(x)-x)/x^3
- * and its remez error is bounded by
- * |(asin(x)-x)/x^3 - R(x^2)| < 2^(-58.75)
- *
- * For x in [0.5,1]
- * asin(x) = pi/2-2*asin(sqrt((1-x)/2))
- * Let y = (1-x), z = y/2, s := sqrt(z), and pio2_hi+pio2_lo=pi/2;
- * then for x>0.98
- * asin(x) = pi/2 - 2*(s+s*z*R(z))
- * = pio2_hi - (2*(s+s*z*R(z)) - pio2_lo)
- * For x<=0.98, let pio4_hi = pio2_hi/2, then
- * f = hi part of s;
- * c = sqrt(z) - f = (z-f*f)/(s+f) ...f+c=sqrt(z)
- * and
- * asin(x) = pi/2 - 2*(s+s*z*R(z))
- * = pio4_hi+(pio4-2s)-(2s*z*R(z)-pio2_lo)
- * = pio4_hi+(pio4-2f)-(2s*z*R(z)-(pio2_lo+2c))
- *
- * Special cases:
- * if x is NaN, return x itself;
- * if |x|>1, return NaN with invalid signal.
- *
- */
-
-#include "libm.h"
-
-static const double
-pio2_hi = 1.57079632679489655800e+00, /* 0x3FF921FB, 0x54442D18 */
-pio2_lo = 6.12323399573676603587e-17, /* 0x3C91A626, 0x33145C07 */
-/* coefficients for R(x^2) */
-pS0 = 1.66666666666666657415e-01, /* 0x3FC55555, 0x55555555 */
-pS1 = -3.25565818622400915405e-01, /* 0xBFD4D612, 0x03EB6F7D */
-pS2 = 2.01212532134862925881e-01, /* 0x3FC9C155, 0x0E884455 */
-pS3 = -4.00555345006794114027e-02, /* 0xBFA48228, 0xB5688F3B */
-pS4 = 7.91534994289814532176e-04, /* 0x3F49EFE0, 0x7501B288 */
-pS5 = 3.47933107596021167570e-05, /* 0x3F023DE1, 0x0DFDF709 */
-qS1 = -2.40339491173441421878e+00, /* 0xC0033A27, 0x1C8A2D4B */
-qS2 = 2.02094576023350569471e+00, /* 0x40002AE5, 0x9C598AC8 */
-qS3 = -6.88283971605453293030e-01, /* 0xBFE6066C, 0x1B8D0159 */
-qS4 = 7.70381505559019352791e-02; /* 0x3FB3B8C5, 0xB12E9282 */
-
-static double R(double z)
-{
- double_t p, q;
- p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
- q = 1.0+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
- return p/q;
-}
-
-double asin(double x)
-{
- double z,r,s;
- uint32_t hx,ix;
-
- GET_HIGH_WORD(hx, x);
- ix = hx & 0x7fffffff;
- /* |x| >= 1 or nan */
- if (ix >= 0x3ff00000) {
- uint32_t lx;
- GET_LOW_WORD(lx, x);
- if ((ix-0x3ff00000 | lx) == 0)
- /* asin(1) = +-pi/2 with inexact */
- return x*pio2_hi + 0x1p-120f;
- return 0/(x-x);
- }
- /* |x| < 0.5 */
- if (ix < 0x3fe00000) {
- /* if 0x1p-1022 <= |x| < 0x1p-26, avoid raising underflow */
- if (ix < 0x3e500000 && ix >= 0x00100000)
- return x;
- return x + x*R(x*x);
- }
- /* 1 > |x| >= 0.5 */
- z = (1 - fabs(x))*0.5;
- s = sqrt(z);
- r = R(z);
- if (ix >= 0x3fef3333) { /* if |x| > 0.975 */
- x = pio2_hi-(2*(s+s*r)-pio2_lo);
- } else {
- double f,c;
- /* f+c = sqrt(z) */
- f = s;
- SET_LOW_WORD(f,0);
- c = (z-f*f)/(s+f);
- x = 0.5*pio2_hi - (2*s*r - (pio2_lo-2*c) - (0.5*pio2_hi-2*f));
- }
- if (hx >> 31)
- return -x;
- return x;
-}
diff --git a/lib/libc/musl/src/math/i386/asin.s b/lib/libc/musl/src/math/i386/asin.s
@@ -1,21 +0,0 @@
-.global asin
-.type asin,@function
-asin:
- fldl 4(%esp)
- mov 8(%esp),%eax
- add %eax,%eax
- cmp $0x00200000,%eax
- jb 1f
- fld %st(0)
- fld1
- fsub %st(0),%st(1)
- fadd %st(2)
- fmulp
- fsqrt
- fpatan
- fstpl 4(%esp)
- fldl 4(%esp)
- ret
- # subnormal x, return x with underflow
-1: fsts 4(%esp)
- ret
diff --git a/src/libs/musl.zig b/src/libs/musl.zig
@@ -801,7 +801,6 @@ const src_files = [_][]const u8{
"musl/src/math/acosl.c",
"musl/src/math/arm/fma.c",
"musl/src/math/arm/fmaf.c",
- "musl/src/math/asin.c",
"musl/src/math/asinf.c",
"musl/src/math/asinh.c",
"musl/src/math/asinhf.c",
@@ -849,7 +848,6 @@ const src_files = [_][]const u8{
"musl/src/math/i386/acosl.s",
"musl/src/math/i386/asinf.s",
"musl/src/math/i386/asinl.s",
- "musl/src/math/i386/asin.s",
"musl/src/math/i386/atan2f.s",
"musl/src/math/i386/atan2l.s",
"musl/src/math/i386/atan2.s",
diff --git a/src/libs/wasi_libc.zig b/src/libs/wasi_libc.zig
@@ -668,7 +668,6 @@ const libc_top_half_src_files = [_][]const u8{
"musl/src/math/acoshf.c",
"musl/src/math/acoshl.c",
"musl/src/math/acosl.c",
- "musl/src/math/asin.c",
"musl/src/math/asinf.c",
"musl/src/math/asinh.c",
"musl/src/math/asinhf.c",
