PR/58054 CVS commit: src/lib/libm/src

["Taylor R Campbell" <riastradh%netbsd.org@localhost>]

The following reply was made to PR lib/58054; it has been noted by GNATS.

From: "Taylor R Campbell" <riastradh%netbsd.org@localhost>
To: gnats-bugs%gnats.NetBSD.org@localhost
Cc: 
Subject: PR/58054 CVS commit: src/lib/libm/src
Date: Sat, 4 May 2024 19:21:51 +0000

 Module Name:	src
 Committed By:	riastradh
 Date:		Sat May  4 19:21:51 UTC 2024
 
 Modified Files:
 	src/lib/libm/src: s_rintl.c
 
 Log Message:
 s_rintl.c: Reduce FreeBSD diff and fix on ld128 platforms.
 
 EXT_FRACBITS, the number of bits in the _binary encoding_ that stores
 the trailing significand field, is never 113.  In IEEE 754 binary128,
 it is 112, even though there are 113 bits of precision in the set of
 floating-point numbers -- the leading 1 bit is implicit in binary128.
 So ld128 platforms like aarch64 and sparc64 were skipping the real
 definition and just defining rintl as an alias for rint, which is
 wrong.
 
 In contrast, LDBL_MANT_DIG, the number of bits of precision in the set
 of floating-point numbers (p, in IEEE 754 parlance), is 113 in IEEE 754
 binary128.  This is also the constant used in FreeBSD libm anyway.  So
 let's just use that instead of trying to translate it to our private
 EXT_FRACBITS (not defined in FreeBSD) with a fencepos terror.  And
 delete the buggy rintl=rint alias.
 
 PR lib/58054
 
 
 To generate a diff of this commit:
 cvs rdiff -u -r1.6 -r1.7 src/lib/libm/src/s_rintl.c
 
 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.