Re: [PATCH] Fix optimization regression in constant folder

[Mark Mitchell <mark@codesourcery.com>]

Michael Matz wrote:

> It was my understanding during this whole thread, that this sizetype with 
> the funny guarantees only can come out of the Ada frontend (and therefore 
> needs to be dealt with in the middle end), and should never be produced by 
> the other languages, in particular not C or C++.  I realize that this 
> currently is not the case (i.e. C/C++ do produce TYPE_IS_SIZETYPE types) 
> and my understanding was that this actually is a bug.

I don't think that's true.  My understanding was that sizetype was the
type that internal expressions for sizes (such as those stored in
DECL_SIZE) should have.

It's true that this is a different type from size_t, the user-visible
type.  The latter is just a typedef for some unsigned integral type, and
might be wider than sizetype, and might not have other special
properties of sizetype, whatever those might be.

Now, perhaps it would be possible to eliminate the special sizetype
stuff, and just use the size_t type throughout the compiler.  But, if we
don't do that, then I think C/C++ should continue to use sizetype for
DECL_SIZE, etc.

-- 
Mark Mitchell
CodeSourcery
mark@codesourcery.com
(650) 331-3385 x713