gcc-2.7 creates faster code than pgcc-1.1.1

[H.J. Lu]

> 
> 
>   In message < 199903050001.BAA00973@mira.isdn.cs.tu-berlin.de >you write:
>   > > -  if ((TARGET_ZERO_EXTEND_WITH_AND || REGNO (operands[0]) == 0)
>   > > +  if ((TARGET_ZERO_EXTEND_WITH_AND || (0 & REGNO (operands[0]) == 0))
>   > 
>   > It's late, so I'm probably going to say stupid things, but ...
>   > 
>   > Isn't (0 & REGNO (operands[0]) == 0) always 0? Why isn't the condition
>   > just deleted?
> Disabling the code like that is actually the wrong thing to do for certain
> processor variants.
> 
> I need to dust off my changes to this code which do the right thing when
> optimizing for size, PPro, Pent and older x86 variants.
> 
> It's not as simple as just deleting the test like that.
> 

Just keep in mind that this small change speeds up gzip by 10-20% on
PPro, P/II and maybe P/III. It may be true also for 386. According
to TARGET_ZERO_EXTEND_WITH_AND, only 486 and Pentium seems to prefer
"and".

BTW, FWIW, "movzbl" has 3 bytes and "addl" has 5 bytes. So "movzbl" is
smaller and faster on 386, PPro, P/II and P/III.


-- 
H.J. Lu (hjl@gnu.org)