Re: i386 code label alignment patch

[Jeffrey A Law <law at cygnus dot com>]

  In message <199805041430.KAA22226@jwlab.FEITH.COM>you write:
  > Hello,
  > 
  > This change implements the alignment of code labels following
  > the recommendations of the "Intel Architecture Optimization Manual".
  > This change seem to be worth about 33% speed increase in the simple
  > case of:
  > 
  >   main()
  >     {
  >     int a;
  >     int i;
  > 
  >     a = 0;
  >     for (i = 0; i < 1000000000; i++)
  >       a += i;
  > 
  >     return a;
  >     }
I like the idea.  However...

I don't think you can use an autoconf test like that -- what happens
for a cross or canadian cross build?  It doesn't look like you handle
those cases.  Then again, I'm not an autoconf guru, so I could be
missing something simple.

Maybe the way to go is make worst case assumptions in those cases.
Thoughts?

I also don't see why we need new output routines for
ASM_OUTPUT_LABEL_ALIGN_AFTER_BARRIER.  Isn't the desired alignment
for each label stored in LABEL_TO_ALIGNMENT?  Can you say more about
the motivation behind this aspect of the change

I also worry about the correctness of shorten_branches in the case
where the label is far away from the jump site and thus the alignment
directive has no effect.  This may cause problems since shorten_branches
no longer uses trivial algorithms that either only grow or only shrink.

jeff