On 1/30/2012 3:29 AM, Julian Seward wrote: > I would have thought that FSAVE/FRSTOR in 64 bit mode is essentially > useless, and the fact that we've not so far needed to implement them > kind of supports that suspicion. Reason is that they don't save or > restore the XMM registers. The x86-64 bit ELF ABI requires floating point > values to be in the XMM registers; hence FSAVE/FRSTOR don't succeed in > correctly saving and restoring the CPU's floating point state. What you > need for that is FXSAVE and FXRSTOR, and they are indeed implemented.
I couldn't find an ELF ABI requirement that floating point values *must* be in XMM regs versus MMX regs. The difference I could find is that MMX registers are not saved across calls -- but saving and restoring might still be useful if you are doing MMX computations ... Anyway, HotSpot uses them :-) ... They may not be interesting for *OS* use though ... Does this seem right? Regards -- Eliot ------------------------------------------------------------------------------ Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 _______________________________________________ Valgrind-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/valgrind-users
