Re: MIPS assembler branch relaxations

[Daniel Jacobowitz <drow at mvista dot com>]

On Sat, Sep 14, 2002 at 05:21:32PM -0400, Paul Koning wrote:
> >>>>> "Daniel" == Daniel Jacobowitz <drow@mvista.com> writes:
> 
>  Daniel> On Sat, Sep 14, 2002 at 02:59:45AM -0300, Alexandre Oliva
>  Daniel> wrote:
>  >> This patch arranges for the MIPS assembler to turn out-of-range
>  >> branches into jumps.  No regressions are introduced in the
>  >> binutils testsuites for a mips-linux build.  Details on how it is
>  >> done are in comments in the beginning of the patch.  Ok to
>  >> install?
> 
>  Daniel> A couple of thoughts:
> 
>  Daniel> + beql reg1, reg2, 1f + nop + beqzl $0, 2f + nop + 1: j[al]
>  Daniel> label + delay slot (executed only if branch taken) + 2:
> 
>  Daniel> Why beqzl?  Admittedly, I don't know much about MIPS
>  Daniel> hardware, but I'd think that just "b" would probably be
>  Daniel> faster, since that's the normal unconditional branch.
> 
> Not only that, but MIPS64 explicitly deprecates all flavors of "branch
> likely" which is why gcc has a way to avoid generating them.  So the
> assembler should either have the same conditional stuff, or avoid them
> entirely.  

That's not a problem here - Alex's patch only generated branch-likely
in response to existing branch-likely in the source.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer