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On 02/22/2015 05:40 AM, Mike Frysinger wrote: > On 19 Feb 2015 21:45, Jiri Gaisler wrote: >> On 02/17/2015 10:05 AM, Mike Frysinger wrote: >>> On 17 Feb 2015 08:44, Jiri Gaisler wrote: >>>> * float.c (get_accex) access FPU control and status words on x64 >>> >>> shouldn't you gut this file and use <fenv.h> instead for a portable method ? >>> http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/fenv.h.html >>> >>> at the very least, you could cut over to <fpu_control.h> ... >> >> I will switch to fenv.h, but this will produce less accurate results >> on Intel hardware. double on SPARC V8 has 53-bit mantissa while Intel has >> both 53- and 64-bit, and 64-bit is default. To get accurate SPARC V8 FPU >> operations, the Intel FPU should be switched to 53-bit, but the fenv.h >> does not have an API for this. I guess we will have to live with that ... > > if you wanted to keep a little inline asm to just that particular bit twiddle, > that should be fine. Can't be bothered, I like the idea of dropping the assembly fully. > > normally the sims are functional ... but i guess this part of the simulator is > relying on the inaccuracies of floating point to trade for speed ? > -mike Yes, instead of emulating the FPU (soft-float libs) we use the host FPU directly. Works fine when the host is standard IEEE-754 compatible, but can lead to minor discrepancies when the host has extended precision (like Intel/AMD). If somebody really cares, he can run sis on a non-x86 box (SPARC, ARM or PowerPC). Jiri.
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