mips: omit initialization of $gp and stack allocation when possible

[Alexandre Oliva]

On Apr  1, 2003, Alexandre Oliva <aoliva@redhat.com> wrote:

> On Mar 24, 2003, Alexandre Oliva <aoliva@redhat.com> wrote:
>> This patch improves the code generated by GCC on mips for functions
>> that don't need $gp to be set.  It also documents a number of things
>> that formerly went unexplained about stack allocation and $gp slot
>> assignment, and cleans up some gunk that had piled up with the
>> confusion of ABIs in the mips back-end.  This was tested on
>> mips64-linux-gnu and mips-sgi-irix6.5.

> There was a bug in the patch, that might cause it to recover the stack
> space reserved for $gp even when no such space was allocated, causing
> the frame size to potentially go negative.  Oops.  Thanks to Richard
> Sandiford for spotting it.  This revised patch fixes it.  It was
> tested on mips64-linux-gnu (also building a 32-bit kernel, which
> happened to trigger the bug) and mips-sgi-irix6.5.  Ok to install?

This is an updated version of the patch, such that it applies cleanly
after the merged from mips-rewrite-branch.  No changes other than
patch context.  Tested by bootstrapping on mips-sgi-irix6.5 with
native as and ld, and mips-sgi-irix6.5o32 with GNU as (for some reason
the native as didn't seem to like some %got expressions introduced
with the rewrite when assembling for -32).

Ok to install?

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-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                 aoliva@{redhat.com, gcc.gnu.org}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist                Professional serial bug killer