SSA usage question

[Diego Novillo]

On Mon, 2004-06-07 at 11:22, Richard Kenner wrote:
>     So, you want a reference like 'a[3]' to show up as 'a[3,v,x]' where 'v'
>     is TYPE_MIN_VALUE and 'x' is TYPE_SIZE_UNIT?  Would 'v' and 'x' be set
>     sometime before the reference?
> 
> I missed your last question.
> 
> By "set", do you mean when they get set into the ARRAY_REF or do you
> mean when the value is assigned to them during execution?
> 
Assigned to.  ie, something like:

x = ...
v = ...
... = a[3,x,v]


Either.  If 'v' and 'x' are compile time constants, then I would expect
something like:

> For the former, they'll get set during gimplification.  And that's also
> related to the answer to the latter: gimplification will generate the
> assignment of those variable to whatever expression they need to have.
>
OK, then things should work.  How will this added information affect the
optimizers?  Isn't this information about TYPE_MIN_VALUE and
TYPE_SIZE_UNIT already expressed in the TREE_TYPE of the ARRAY_REF?  Why
are these attributes replicated in every ARRAY_REF?  These things can
change from reference to reference?  That is, given the array 'a' above,
will every reference to 'a' use a potentially different 'x' and 'v'?


Diego.