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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