A question about integer promotion in GCC

[Joseph S. Myers]

On Mon, 6 Sep 2004, Nathan Sidwell wrote:

> IMO when to tackle this is after the next release branches, and the
> way to do is implement fe-fold-constant-expr (tree, flags) first, and then
> make a fold-const optimizer pass from the remnants.

That seems a plausible approach.  (With the interface for folding true 
constants then getting adapted so it can pass overflow information back 
other than by TREE_OVERFLOW etc., with a view to removing those overflow 
flags from constants.)  Splitting fold that way, with the subsequent pass 
running just before gimplification, should be straightforward.  (I don't 
know what performance impact there might be, though gains from smaller 
footprint while parsing the whole file before optimising any of it are 
possible.)  The hard bit would be creating a fold parse for GIMPLE that 
does everything fold currently does.

-- 
Joseph S. Myers               http://www.srcf.ucam.org/~jsm28/gcc/
  http://www.srcf.ucam.org/~jsm28/gcc/#c90status - status of C90 for GCC 3.5
    jsm@polyomino.org.uk (personal mail)
    jsm28@gcc.gnu.org (Bugzilla assignments and CCs)