[lto] set alias info, poorly

Toon Moene toon@moene.indiv.nluug.nl
Mon Dec 10 19:55:00 GMT 2007

Kenneth Zadeck wrote:

> If you want to ask a question about two types, the first part of
> that check will to see if the types come from the same front end.  If
> they do, then this issue can be resolved by asking some language
> dependent code that will be located in the middle end of the compiler. 

Well, that will mean that it'll be a fascinating piece of "language 
dependent code [...] located in the middle end of the compiler".

The Fortran rules are basically:  If you don't *tell* the compiler 
(hence the front end) that two items alias, they don't.

I think this means that LTO *with* Fortran-sensible alias analysis will 
only work if the Fortran front end actually determines alias equivalence 
sets and passes that down to the middle end, which then (in this 
magically "language dependent code") has to do something intelligent 
with it ...

Hmmmm, magic ...

Toon Moene - e-mail: toon@moene.indiv.nluug.nl - phone: +31 346 214290
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands
At home: http://moene.indiv.nluug.nl/~toon/
GNU Fortran's path to Fortran 2003: http://gcc.gnu.org/wiki/Fortran2003

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