Pessimization from reduce-all-givs and move-all-movables

[Jan Hubicka]

> Jerry Quinn wrote:
> 
> >Without -fmove-all-movables -freduce-all-givs, performance improves to
> >1048 Kpos/sec, a 7% difference.
> 
> This wouldn't surprise me.  Between when I introduced those flags (in 
> 1997) and now we gathered quite some information on them.  It turns out 
> they're mostly useful for Fortran code (subroutines) with rank-n dummy 
> arguments where n>1.  Because this situation is so common in Fortran 
> code, these options are enabled by default when invoking g77.
> 
> For all other types of code it's a loss, especially on targets with very 
> few integer registers, like the Intel x86 line and derivatives.
> 
> Hope this helps [I can make the above reasoning more precise if you're 
> interested],
Perhaps it would make sense to add this into manual instead of call for
testcases...

Honza
> 
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