Re: [patch] smp-2.3.30-A1, mb(), wmb(), rmb()

Jamie Lokier (lkd@tantalophile.demon.co.uk)
Fri, 26 Nov 1999 12:53:51 +0100

Jes Sorensen wrote:
> Linus> which instead of using a read-modify-write cycle and a long
> Linus> immediate just uses a single write-cycle. It makes gcc allocate
> Linus> a word on the stack, and sometimes that might be unnecessary,
> Linus> but it should be smaller and faster. You might want to check
> Linus> out code generation..
>
> This can actually become a bit expensive if you use mb() a lot in your
> code, ie. if you use __raw_writel() etc.

GCC still doesn't reuse stack slots for non-overlapping variables?
(Quick test later) You're right. GCC 2.95.1 uses different slots.

This should work:

asm volatile ("movl %%ebp,-4(%%esp)" : : : "memory");

-- Jamie

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