Date: Fri, 18 Dec 2020 09:13:10 -0800 From: Fangrui Song <i@...kray.me> To: musl@...ts.openwall.com, Rich Felker <dalias@...c.org>, "joao@...rdrivepizza.com" <joao@...rdrivepizza.com> Subject: Re: -frounding-math breaking src/math/acosf.c On Mon, Oct 12, 2020 at 2:40 AM Szabolcs Nagy <nsz@...t70.net> wrote: > > * Rich Felker <dalias@...c.org> [2020-10-09 19:10:00 -0400]: > > > On Sat, Oct 10, 2020 at 12:16:13AM +0200, joao@...rdrivepizza.com wrote: > > > Hi, > > > > > > I just noticed that the upstream LLVM is no longer capable of > > > compiling musl 1.2.0 (and possibly more recent versions too) when > > > -frounding-math is in use. I bisected the LLVM commit to > > > https://reviews.llvm.org/D87822, and pointed the problem there. > > > > > > Just reporting in case someone else also has issues with this. > > > > > > Best, > > > Joao. > > > > Thanks. This probably needs to be reported as aa bug against LLVM (or > > clang?) rather than just a comment on the review so that it's tracked > > as such. It seems they've erroneously made it treat static > > initializers as non-constant-expressions rather than evaluating them > > statically in the default rounding mode per the spec. > > const expressions should work as described in > > http://port70.net/~nsz/c/c11/n1570.html#F.8.4 clang main has fixed (https://reviews.llvm.org/D89360) the regression of https://reviews.llvm.org/D87822 > but it seems clang handles literals that don't > need conversion: > > float x = 0.1f; // works > float y = 0.1; // fails > > we may want to fix this anyway in musl to always > use the right type of literal (then it's clear > that there is no double rounding).
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