Re: GCC-How does the coding style affect the insv pattern recognization?

[Jeff Law <law at redhat dot com>]

On 01/18/10 03:39, fanqifei wrote:
> 2010/1/18 Adam Nemet<adambnemet@gmail.com>:
>    
> > Sorry for jumping in late.  See make_file_assigment in combine.c.
> >
> > The problem usually is that:
> >
> >   (set A (ior (and B C1) OTHER))
> >
> > can only be turned into a bit-insertion if A and B happen to be the same
> > pseudos.
> >
> > Adam
> >
> >      
> Thank you, Adam.  The problem is that before combine pass the
> statement is expressed in 6 insns. The insns can't be combined into
> the expected pattern (set A (ior (and B C1) OTHER)). Otherwise,
> make_field_assignment can do the job of simplifying the SET insn.
>    
It is sometimes possible to create intermediate patterns to allow the 
combiner to see a larger window of insns.  Obviously if you create these 
intermediate patterns you should split them if they survive beyond the 
combiner phase.

jeff