[RFC] Meta-description for tree and gimple folding

[Marc Glisse]

On Mon, 3 Mar 2014, Richard Biener wrote:

>> How do you handle a
>> transformation that currently tries to recursively fold something else and
>> does the main transformation only if that simplified?
>
> And doesn't do the other folding (because it's not in the IL literally?)?
> Similar to the cst without overflow case, by writing custom C code
> and allowing that to signal failure.

Note that for this kind of simplification, it can be inconvenient to have 
canonicalization included with the "real" simplifications. Imagine I am 
looking at (x?3:5)+y. If 3+y "simplifies" to y+3 and 5+y "simplifies" to 
y+5, then it looks worth it to replace the expression with x?y+3:(y+5).

Would there be a convenient way to separate them, so it can tell me that 
3+y should be replaced with y+3 but that it is not a simplification?

-- 
Marc Glisse