>> Unfortunately the assessment that there are only "small changes" or >> "unimportant differences" is plain wrong. [...]
The 64-bit approximation was done to make the initial VEX implementation of x87 floating point easier. Simulating x87 FP even without having to do 80-bit arithmetic was a major PITA, and the 64-bit approximation scheme seemed a reasonable tradeoff for portable software. It would be possible, at some effort, to do proper 80-bit arithmetic. What it would take is a few new IR primops (Iop_AddF80 etc), hacking the front ends to produce those, and having the instruction selectors generate the right code. Oh, and producing a bunch of test cases to verify it all. Although the inner standards-compliant engineer in me is more sympathetic to the current implementation's bias in favour of portable (non-80-bit) code, I can see that having x87 FP be 80 bit precise would sometimes be helpful. Even then it's not simple. The x87 control word has a bit-pair that controls the default x87 FP precision. Currently V ignores all attempts to change it, and just does its thing at 64 bits. If 80-bit arithmetic becomes supported, and V ignores attempts to change the precision away from 80 bits, will we have people complaining that the default precision can't be changed away from 80 bit? J ------------------------------------------------------------------------------ Symantec Endpoint Protection 12 positioned as A LEADER in The Forrester Wave(TM): Endpoint Security, Q1 2013 and "remains a good choice" in the endpoint security space. For insight on selecting the right partner to tackle endpoint security challenges, access the full report. http://p.sf.net/sfu/symantec-dev2dev _______________________________________________ Valgrind-users mailing list Valgrind-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/valgrind-users
