Date: Thu, 11 Sep 2014 16:11:23 +0200 From: Szabolcs Nagy <nsz@...t70.net> To: musl@...ts.openwall.com Subject: Re: [PATCH] Make musl math depend less on libgcc builtins * Sergey Dmitrouk <sdmitrouk@...esssoftek.com> [2014-09-11 16:22:53 +0300]: > Note that I'm performing tests in QEMU. vsqrt.f64 instruction returns > NAN for NAN input and doesn't raise any exceptions ($fpscr register is > unchanged). However I get INVALID exception after printing result with > musl implementation of printf(), glibc doesn't raise any exceptions in > printf(), but I'm not sure whether it's important, probably not. nan printf should not raise invalid exceptino in musl either musl checks for nan by if(y!=y) and my guess is that this is incorrectly done by a signaling comparision i checked on x86_64 and both clang and gcc get comparisions wrong in the other direction: they use quite comparisions when signaling is needed, eg http://goo.gl/GsdpZA (on a correct implementation ==, != are quiet, but <,>,<=,>= raise invalid if any of the operands are nan, on x86_64 the quiet instruction is ucomis* and the signaling one is comis* and both gcc-4.9 and clang-3.4 seem to use ucomis* for all relational operations, may be there is some compiler flag to make them behave..)
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