[PATCH][RFC] Optimize more with PAREN_EXPR

[Paolo Bonzini]

> The question is how sophisticated you want to be.  For example
> 
>  (a + b + c) and (a + b) + c
> 
> could have ((a + b) + c) as "same" operand?

Yes.  I'd call the function strictest_association or something like 
that, and it would assume that operand_equal_p (op0, op1, OPF_NO_PAREN).

> Of course you'd need to touch a whole lot of existing uses of
> operand_equal_p to get a benefit.  I'll see to cover the easy
> cases.

You can do it on a case-by-case basis.

Paolo