On Nov 21 2013, Uros Bizjak wrote:
Indeed, 387/SSE has flush-to-zero modes. But other APIs do not (glibc,
SysV, AIX). I'm perfectly willing to add it, especially to 387/SSE, if
given a bit of help (someone to write the assembly code).
Just set FTZ bit in mxcsr. Please see
libgcc/config/i386/crtfastmath.c, this mode is used when -ffast-math
is used.
Does that work for all of Intel's zoo of floating-point mechanisms?
Even if gfortran doesn't use all of them, it is important to at least
know which it works for and which it does not. My understanding of
the architecture is that all of x87, MMX, SSE and AVX are potentially
different in this respect :-(
Regards,
Nick Maclaren.
