Hello! > 0. Gradual underflow control is implemented as "not supported by the > processor" (its SUPPORT > function returns false, and the GET and SET procedures abort if you call > them). That’s explicitly > allowed by the standard, so it’s not actually “missing". We can improve on > this in the future, if > people can help.
Please look at libgcc/config/i386/crtfastmath.c for how to set MXCSR_FTZ from mxcsr. You already have all necessary bits in place, the function is basically only: + if (has_sse()) + { + unsigned int cw_sse; + + __asm__ __volatile__ ("%vstmxcsr\t%0" : "=m" (cw_sse)); + cw_sse |= MXCSR_DAZ; + __asm__ __volatile__ ("%vldmxcsr\t%0" : : "m" (cw_sse)); + } Please note, that FTZ applies only to SSE math. x87 and (IIRC) soft-FP don't handle this setting. Uros.