Date: Thu, 07 May 2026 22:36:22 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 295089] [libm] implementation of rsqrt, rsqrtf, and rsqrtl. Message-ID: <bug-295089-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=295089 Bug ID: 295089 Summary: [libm] implementation of rsqrt, rsqrtf, and rsqrtl. Product: Base System Version: CURRENT Hardware: Any OS: Any Status: New Severity: Affects Only Me Priority: --- Component: bin Assignee: bugs@FreeBSD.org Reporter: kargl@FreeBSD.org Created attachment 270500 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=270500&action=edit Patch with libm changes The attached diff implements the inverse square root function, i.e, rsqrt(x) = 1 / sqrt(x). Exhaustive testing of the float version suggests that it is correctly rounded in round-to-nearest for all test values in the range [0x1p-127,0x1p126] except for 127 values. Exhaustive testing of rsqrt and rsqrtl cannot be done, but 1100M values of x for rsqrt and 400M values for rsqrtl were tested. All tested values were correctly rounded. I do not have access to LD128 (i.e., IEEE 128-bit floating point) hardware, so the implementation of rsqrtl() is untested. The following is a summary of changes to source code. * lib/msun/Makefile: . Add s_rsqrt.c and s_rsqrtf.c to COMMON_SRCS. . For non-53-bit long double targets, add s_rsqrtl.c to COMMON_SRCS. . Add MLINKS for rsqrt.3, rsqrtf.3, and rsqrtl.3 to sqrt.3. * lib/msun/Symbol.map: . Add rsqrt, rsqrtf, and rsqrtl to the Symbol map for shared libm.so. * lib/msun/man/sqrt.3: . Update the sqrt.3 manual page to include information for rsqrt[fl]. . Note, these function come from ISO C23 (and IEEE-754 2008). * lib/msun/src/math.h: . Add prototypes for new functions. * lib/msun/src/math_private.h: . Add _SPLIT, _FAST2SUM, _SLOW2SUM, _XADD, _MUL, and _XMUL macros to perform type-type arthimetic (i.e., float-float). * src/s_rsqrt.c: . New file with the implementation of 'double rsqrt(double)'. . For 53-bit long double targets, add a weak reference for rsqrtl. * src/s_rsqrtf.c: . New file with the implementation of 'float rsqrt(float)'. * src/s_rsqrtl.c . New file with the implementation of 'long double rsqrt(long double)'. Note, the LD80 version uses bit twiddling and LD128 version is a straight C language implementation. The LD128 is untested due to lack of hardware. -- You are receiving this mail because: You are the assignee for the bug.home | help
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