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Message-ID: <20151121215438.GI23362@port70.net>
Date: Sat, 21 Nov 2015 22:54:38 +0100
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: for information, gcc-4.2.3 miscompiles musl math
* Rich Felker <dalias@...c.org> [2015-11-21 15:15:51 -0500]:
> I just tested with 4.2.1 binaries from Aboriginal Linux and (1) was
> able to reproduce the bug, and (2) made it go away with your patch.
> Not only did the bogus out-of-range result go away; the new result is
> a bit-exact match for modern gcc.
>
> Conceptually, it seems to me that for code that explicitly uses
> float_t and double_t in expressions and only converts down to float or
> double with stores, -ffloat-store should be just as good (albeit
> overly pessimizing) as -fexcess-precision=standard. So IMO this looks
> like a really good solution, and might come in handy as hardening
> against mistakes in new compilers too. IIRC firm used to do this wrong
> and I would not be at all surprised if pcc gets it wrong.
>
i did the changes where i think it was necessary
(hypot has asm implementation on i386 though).
(in most cases the code already uses float_t, double_t
where this would matter.)
View attachment "0001-math-make-ffloat-store-work-on-i386.patch" of type "text/x-diff" (2259 bytes)
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