Messages in this thread | | | Subject | Re: [PATCH] [RFC] [2.5 i386] GCC 3.1 -march support, PPRO_FENCE reduction, prefetch fixes and other CPU-related changes | From | Alan Cox <> | Date | 05 Aug 2002 01:02:12 +0100 |
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On Sun, 2002-08-04 at 21:43, Luca Barbieri wrote: > > When we use MMX/SSE we need the view to be consistent anyway so the > > various copying routines already handle this internally. > That's why sfence is not used unless CONFIG_X86_OOSTORE (and > CONFIG_X86_MMXEXT) is defined. > mfence and lfence instead replace the "lock; addl $0,0(%%esp)". Is this > wrong?
I'm trying to understand why you think they are needed at all. Except for code that specifically does non-temporal we don't need fences on an X86, and the code that uses non temporal stores has its own fences built in.
So as far as I can see the only cases we ever have to care about are
PPro - processor bug IDT Winchip - because we run it in oostore module not strict x86 mode
I don't see why you are generating extra fence instructions for other cases
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