--- /dev/null
+/* Correctly-rounded half-revolution arc-cosine function for binary32 value.
+
+Copyright (c) 2022-2025 Alexei Sibidanov.
+
+The original version of this file was copied from the CORE-MATH
+project (file src/binary32/acospi/acospif.c, revision 1a6a9ab).
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+*/
+
+#include <math.h>
+#include <stdint.h>
+#include <libm-alias-float.h>
+#include "math_config.h"
+
+float
+__acospif (float x)
+{
+ float ax = fabsf (x);
+ double az = ax;
+ double z = x;
+ uint32_t t = asuint (x);
+ int e = (t >> 23) & 0xff;
+ if (__glibc_unlikely (e >= 127))
+ {
+ if (x == 1.0f)
+ return 0.0f;
+ if (x == -1.0f)
+ return 1.0f;
+ if (e == 0xff && (t << 9))
+ return x + x; /* nan */
+ return __math_edomf ((x - x) / (x - x)); /* nan */
+ }
+ int s = 146 - e;
+ int i = 0;
+ if (__glibc_likely (s < 32))
+ i = ((t & (~0u >> 9)) | 1 << 23) >> s;
+ static const double ch[][8] = {
+ { 0x1.45f306dc9c882p-2, 0x1.b2995e7b7dc2fp-5, 0x1.8723a1cf50c7ep-6,
+ 0x1.d1a4591d16a29p-7, 0x1.3ce3aa68ddaeep-7, 0x1.d3182ab0cc1bfp-8,
+ 0x1.62b379a8b88e3p-8, 0x1.6811411fcfec2p-8 },
+ { 0x1.ffffffffd3cd9p-2, -0x1.17cc1b3355fd5p-4, 0x1.d067a1e8d5a99p-6,
+ -0x1.08e16fb09314ap-6, 0x1.5eed43d42dcb2p-7, -0x1.f58baca7acc71p-8,
+ 0x1.5dab64e2dcf15p-8, -0x1.59270e30797acp-9 },
+ { 0x1.fffffff7c4622p-2, -0x1.17cc149ded3a2p-4, 0x1.d0654d4cb2c1ap-6,
+ -0x1.08c3ba713d33ap-6, 0x1.5d2053481079cp-7, -0x1.e485ebc545e7ep-8,
+ 0x1.303baca167dddp-8, -0x1.dee8d16d06b38p-10 },
+ { 0x1.ffffffa749848p-2, -0x1.17cbe7155935p-4, 0x1.d05a312269adfp-6,
+ -0x1.0862b3ee617d7p-6, 0x1.5920708db2a73p-7, -0x1.cb0463b3862c3p-8,
+ 0x1.02b82478f95d7p-8, -0x1.52a7b8579e729p-10 },
+ { 0x1.fffffe1f92bb5p-2, -0x1.17cb3e74c64e3p-4, 0x1.d03af67311cbfp-6,
+ -0x1.079441cbfc7ap-6, 0x1.52b4287805a61p-7, -0x1.ac3286d604a98p-8,
+ 0x1.b2f1210d9701bp-9, -0x1.e740ddc25afd6p-11 },
+ { 0x1.fffff92beb6e2p-2, -0x1.17c986fe9518bp-4, 0x1.cff98167c9a5ep-6,
+ -0x1.0638b591eae52p-6, 0x1.4a0803828959ep-7, -0x1.8adeca229f11dp-8,
+ 0x1.6b9a7ba05dfcep-9, -0x1.640521a43b2dp-11 },
+ { 0x1.ffffeccee5bfcp-2, -0x1.17c5f1753f5eap-4, 0x1.cf874e4fe258fp-6,
+ -0x1.043e6cf77b256p-6, 0x1.3f7db42227d92p-7, -0x1.691a6fa2a2882p-8,
+ 0x1.2f6543162bc61p-9, -0x1.07d5da05822b6p-11 },
+ { 0x1.ffffd2f64431dp-2, -0x1.17bf8208c10c1p-4, 0x1.ced7487cdb124p-6,
+ -0x1.01a0d30932905p-6, 0x1.3388f99b254dap-7, -0x1.4844e245c65bdp-8,
+ 0x1.fa777150197c6p-10, -0x1.8c1ecf16a05c8p-12 },
+ { 0x1.ffffa36d1712ep-2, -0x1.17b523971bd4ep-4, 0x1.cddee26de2deep-6,
+ -0x1.fccb00abaaabcp-7, 0x1.269afc3622342p-7, -0x1.2933152686752p-8,
+ 0x1.a76d4956cc9a3p-10, -0x1.2ce7d6dc651cep-12 },
+ { 0x1.ffff5402ab3a1p-2, -0x1.17a5ba85da77ap-4, 0x1.cc96894e05c02p-6,
+ -0x1.f532143cb832ep-7, 0x1.19180b660ff09p-7, -0x1.0c57417a78b3cp-8,
+ 0x1.62e26cbd7bb1ep-10, -0x1.ce28d33fe1df3p-13 },
+ { 0x1.fffed8d639751p-2, -0x1.1790349f3ae76p-4, 0x1.caf9a4fd1b398p-6,
+ -0x1.ec986b111342ep-7, 0x1.0b53c3ad4baa4p-7, -0x1.e3c2282eeace4p-9,
+ 0x1.2a55369f55bbep-10, -0x1.667fe48c396e8p-13 },
+ { 0x1.fffe24b714161p-2, -0x1.177394fbcb719p-4, 0x1.c90652d920ebdp-6,
+ -0x1.e3239197bddf1p-7, 0x1.fb2188525b025p-8, -0x1.b3aadd451afc7p-9,
+ 0x1.f74020f31fdabp-11, -0x1.18b0cb246768dp-13 },
+ { 0x1.fffd298bec9e2p-2, -0x1.174efbfd34648p-4, 0x1.c6bcfe48ea92bp-6,
+ -0x1.d8f9f2a16157cp-7, 0x1.e0044f56c8864p-8, -0x1.883e2347fe76cp-9,
+ 0x1.a9f0e3c1b7af5p-11, -0x1.bb5acc0e60825p-14 },
+ { 0x1.fffbd8b784c4dp-2, -0x1.1721abdd3722ep-4, 0x1.c41fee756d4bp-6,
+ -0x1.ce40bccf8065fp-7, 0x1.c59b684b70ef9p-8, -0x1.6133d027996b3p-9,
+ 0x1.69cad01106397p-11, -0x1.60f8e45494156p-14 },
+ { 0x1.fffa23749cf88p-2, -0x1.16eb0a8285c06p-4, 0x1.c132d762e1b0dp-6,
+ -0x1.c31a959398f4ep-7, 0x1.ac1c5b46bc8ap-8, -0x1.3e34f1abe51dcp-9,
+ 0x1.346738737c0b9p-11, -0x1.1b227a3f5c75p-14 },
+ { 0x1.fff7fb25bb407p-2, -0x1.16aaa14d7564p-4, 0x1.bdfa75fca5ff2p-6,
+ -0x1.b7a6e260d079cp-7, 0x1.93ab06911033cp-8, -0x1.1ee5560967fd5p-9,
+ 0x1.07d31060838bfp-11, -0x1.c96f33a283115p-15 },
+ };
+ const double *c = ch[i];
+ double z2 = z * z;
+ double z4 = z2 * z2;
+ if (__glibc_unlikely (i == 0))
+ {
+ double c0 = c[0] + z2 * c[1];
+ double c2 = c[2] + z2 * c[3];
+ double c4 = c[4] + z2 * c[5];
+ double c6 = c[6] + z2 * c[7];
+ c0 += c2 * z4;
+ c4 += c6 * z4;
+ /* For |x| <= 0x1.0fd288p-127, c0 += c4*(z4*z4) would raise a spurious
+ underflow exception, we use an FMA instead, where c4 * z4 does not
+ underflow. */
+ c0 = fma (c4 * z4, z4, c0);
+ return 0.5 - z * c0;
+ }
+ else
+ {
+ double f = sqrt (1 - az);
+ double c0 = c[0] + az * c[1];
+ double c2 = c[2] + az * c[3];
+ double c4 = c[4] + az * c[5];
+ double c6 = c[6] + az * c[7];
+ c0 += c2 * z2;
+ c4 += c6 * z2;
+ c0 += c4 * z4;
+ static const double o[] = { 0, 1 };
+ double r = o[t >> 31] + c0 * copysign (f, x);
+ return r;
+ }
+}
+libm_alias_float (__acospi, acospi)
projects / thirdparty / glibc.git / commitdiff
