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Re: PATCH: Fix ll/sc for mips (take 3)
On Mon, Feb 04, 2002 at 05:28:57PM -0800, H . J . Lu wrote:
> On Mon, Feb 04, 2002 at 04:46:07PM +0000, Dominic Sweetman wrote:
> >
> > H . J . Lu (hjl@lucon.org) writes:
> >
> > > I can change glibc not to use branch-likely without using nop. But it
> > > may require one or two instructions outside of the loop. Should I do
> > > it given what we know now?
> >
> > I would not recommend using "branch likely" in assembler coding, if
> > that's what you're asking.
> >
>
> Here is a patch to remove branch likely. But I couldn't find a way
> not to fill the delay slot with nop. BTW, is that safe to remove
> ".set noreorder"?
You mean, if there is nothing which can be put there? Yes, it's safe.
> --- libc/linuxthreads/sysdeps/mips/pspinlock.c.llsc Mon Feb 4 13:45:01 2002
> +++ libc/linuxthreads/sysdeps/mips/pspinlock.c Mon Feb 4 17:09:02 2002
> @@ -40,7 +40,7 @@ __pthread_spin_lock (pthread_spinlock_t
> "bnez %1,1b\n\t"
> " li %2,1\n\t"
> "sc %2,%0\n\t"
> - "beqzl %2,1b\n\t"
> + "beqz %2,1b\n\t"
> " ll %1,%3\n\t"
> ".set pop"
> : "=m" (*lock), "=&r" (tmp1), "=&r" (tmp2)
Is that really what you meant to do? The ll is now in the delay slot
of the beqz.
> --- libc/linuxthreads/sysdeps/mips/pt-machine.h.llsc Mon Feb 4 13:45:01 2002
> +++ libc/linuxthreads/sysdeps/mips/pt-machine.h Mon Feb 4 17:09:36 2002
> @@ -66,7 +66,7 @@ __compare_and_swap (long int *p, long in
> " move %0,$0\n\t"
> "move %0,%4\n\t"
> "sc %0,%2\n\t"
> - "beqzl %0,1b\n\t"
> + "beqz %0,1b\n\t"
> " ll %1,%5\n\t"
> ".set pop\n"
> "2:\n\t"
Ditto.
> @@ -89,7 +89,7 @@ compare_and_swap (volatile long int *p,
> " move %0,$0\n\t"
> "move %0,%4\n\t"
> "sc %0,%2\n\t"
> - "beqzl %0,1b\n\t"
> + "beqz %0,1b\n\t"
> " ll %1,%5\n\t"
> ".set pop\n"
> "2:\n\t"
Ditto.
--
Daniel Jacobowitz Carnegie Mellon University
MontaVista Software Debian GNU/Linux Developer