Messages in this thread |  | | Date | Sat, 17 Nov 2001 12:42:35 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: i386 flags register clober in inline assembly |
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On Sat, 17 Nov 2001, Jan Hubicka wrote: > > Actually the main dificulty I see is storing cc0 to variable. CC0 is hard > register and pretty strange one - you can't move it, you can't spill.
Well, you _can_ spill it, but you need to use "pushfl/popfl" to spill/restore.
Also, if you're clever you don't spill cc0 itself, but the _comparison_, ie if you need to spill in
asm(.. "=cc" (cc0)) if (cc0 > 0)
a sufficiently clever spill-engine would spill not eflags, but instead spill "cc0 > 0", which it can do with the "seq" expansions..
gcc already does know about "store-flag" instructions, although I certainly agree that the _patterns_ of usage may end up being very different than existing conditional comparisons..
Linus
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