[PATCH][RFC] Re-structure tree_ssa_useless_type_conversion_1 to work towards a middle-end type system

[Michael Matz]

Hi,

On Wed, 20 Jun 2007, Eric Botcazou wrote:

> > !      2) tree_ssa_useless_type_conversion_1 is not communtative.
> > ! 	From a < b does not follow a > b.
> > !
> > !      3) Conversions are useless only if with the resulting type
> > ! 	can be used in a subset of the operations the original type
> > ! 	can be applied to.  For example casts to void* are useless,
> > ! 	casts from void* not.  Casts to const T* are useless, casts
> > ! 	from const T* to T* not.
> 
> My understanding is that it's a relation, not an operation, so the 
> proper term for 2 would be "symmetric".

Correct.

> For the sake of completeness, 
> you could also add that it's reflexive: a < a holds.
> 
> Which would suggest to find a better symbol than '<' for it. :-)

a <# p ?  ;-)


Ciao,
Michael.