Date: Fri, 15 Mar 2019 05:50:37 +1100 From: Peter Jeremy <peter@rulingia.com> To: Steve Kargl <sgk@troutmask.apl.washington.edu> Cc: John Baldwin <jhb@freebsd.org>, freebsd-toolchain@freebsd.org, freebsd-current@freebsd.org Subject: Re: Optimization bug with floating-point? Message-ID: <20190314185037.GI87064@server.rulingia.com> In-Reply-To: <20190314063007.GA41995@troutmask.apl.washington.edu> References: <20190313024506.GA31746@troutmask.apl.washington.edu> <20190313151635.GA34757@troutmask.apl.washington.edu> <e290b68f-7a1d-2456-4a0c-9f7dfd303f55@FreeBSD.org> <20190313164039.GA35340@troutmask.apl.washington.edu> <e638e0bf-b8d0-9bd1-d034-8acc6eef872c@FreeBSD.org> <20190313212455.GA37717@troutmask.apl.washington.edu> <20190314063007.GA41995@troutmask.apl.washington.edu>
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--ABTtc+pdwF7KHXCz Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2019-Mar-13 23:30:07 -0700, Steve Kargl <sgk@troutmask.apl.washington.ed= u> wrote: >AFAICT, all libm float routines need to be modified to conditional >include ieeefp.h and call fpsetprec(FP_PD). This will work around >issues is FP and libm. FreeBSD needs to issue an erratum about=20 >the numerical issues with clang. I vaguely recall looking into the x87 initialisation a long time ago and STR that the startup code (either crtX or in the kernel) does a fninit() to set the precision. I don't recall exactly where. IMO, calling fpsetprec() in every libm float function is overkill. It should be enough to fpsetprec() before main() and add a note in the man pages that libm is built to use the default FPU configuration and changing the configuration (precision or rounding) may result in larger errors. --=20 Peter Jeremy --ABTtc+pdwF7KHXCz Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQKTBAEBCgB9FiEE7rKYbDBnHnTmXCJ+FqWXoOSiCzQFAlyKon1fFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldEVF QjI5ODZDMzA2NzFFNzRFNjVDMjI3RTE2QTU5N0EwRTRBMjBCMzQACgkQFqWXoOSi CzRz9Q/+OjrikP4PpHTymluNc8n4nsbSy40WblYJX2mCk85Rn3F8y0IPYAPk8x6U GlyulPEvgdom2WwuWJ4EhyEqH2pGQzFHSoc3sLiF8XRNlLH/IX0CkFhv2CWGTD0R oCHb1Q5Gs0RdbKKIbrHJTCCQeuYNwPiLExZfxZ2nwpxMOhTAuMSVBTlG00E3a2OF 3APRz+f/cL72+1mt8PV9bIEg4R0xaGzpxf8t9/V9/Ljnzh/Wd/nNhI9NrOoUJ8Df i1/gHcg4SUiMaZBIdU4WpPo2dhy2PJx3w6wl5M6CKd+6VUmX041M+xkDqa6mepvc UdsJkfJ3Kfj7iZ0UYGWw56QR2yTlbNyB73enGbQEUv6fbUgVeAlcKoVS+JWE6t8y en3VC8JcsdlbmRUkJCFlDufJMD6v+wtN7fe/wAedut5gp5j/wlWFzNYhb+2UBBJp FCaE7zgkILXJY58tae2kTOe00zNYg1SlAyHIk4XZt1qlZ99wjAmbD/Fo+YSVR7wL xsgCJ8ZDUqiV8ny2TospBYdoCuqGTgEu5tJw3l5HAyX86RVLMVFDj94PvdrkdvtO v6y68hnIeCO6f5bnQ/AzWFhtWHx8QxB7MCGDnNPM3XVhXFQLs+GtSg9o4V6yt27p Itss96uin2NlCVgAC0lsFz+ZO2VR/UWu0slzsopgDTn+zonbOdE= =M9/i -----END PGP SIGNATURE----- --ABTtc+pdwF7KHXCz--
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