https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108922
--- Comment #8 from Jan Kratochvil <jkratochvil at azul dot com> --- (In reply to Andrew Pinski from comment #2) > So the simple test is run the full GCC bootstrap/test with all languages and > check if the testcase fails or not. I suspect it will. It does not. Tested on Fedora 36 x86-64. I did test only a revert of: https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=93ba85fdd253b4b9cf2b9e54e8e5969b1a3db098 The revert makes it 13x faster. But the produced code still falls back to calling glibc fmod() as shown in the disassembly in Comment 0. If I use the "fprem" instruction directly it gets 15x faster - but I did not figure out some (easy) way for me how to patch GCC to no longer produce the call to fmod() at all and produce only the "fprem" instruction. (In reply to Alexander Monakov from comment #4) > Plus, Glibc does use fprem/fprem1 for fmodl/remainderl on x86_64, It is true replacing fmod() with fmodl() makes it 5x faster (but only 5x). There is still some infinity check and I haven't found any real justification in glibc sources for it: 28 if (__builtin_expect (isinf (x) || y == 0.0L, 0) 29 && _LIB_VERSION != _IEEE_ && !isnan (y) && !isnan (x)) 30 /* fmod(+-Inf,y) or fmod(x,0) */ 31 return __kernel_standard_l (x, y, 227); > The ieee_2.f90 testcase attempts to change rounding mode. It 2014 it > probably just was "miscompiled". The testsuite run did include "gfortran.dg/ieee/ieee_2.f90" and it has no regression.
