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Re: Great example of why "everything is a tree" sucks
- From: "Joseph S. Myers" <joseph at codesourcery dot com>
- To: Jakub Jelinek <jakub at redhat dot com>
- Cc: Jeff Law <law at redhat dot com>, Steven Bosscher <stevenb dot gcc at gmail dot com>, Richard Biener <richard dot guenther at gmail dot com>, Diego Novillo <dnovillo at google dot com>, GCC <gcc at gcc dot gnu dot org>
- Date: Wed, 13 Nov 2013 16:58:41 +0000
- Subject: Re: Great example of why "everything is a tree" sucks
- Authentication-results: sourceware.org; auth=none
- References: <528288B3 dot 8010109 at redhat dot com> <20131112203509 dot GC27813 at tucnak dot zalov dot cz> <CAD_=9DQRZy92RCJEopO=XHMj9+eDHQ0MW1g__ZaFNNrWQW=QNg at mail dot gmail dot com> <CAFiYyc38jGfAaWwo5OWTxmQnNeP9=f5McGrW_3HCNJotvbBtKQ at mail dot gmail dot com> <CABu31nOpcf1EivKXYy-i4Czm84aSv+hOYhrSPpefzNVTjjNW0Q at mail dot gmail dot com> <Pine dot LNX dot 4 dot 64 dot 1311131544060 dot 24404 at digraph dot polyomino dot org dot uk> <5283A72F dot 1030300 at redhat dot com> <Pine dot LNX dot 4 dot 64 dot 1311131641270 dot 24404 at digraph dot polyomino dot org dot uk> <20131113165002 dot GR27813 at tucnak dot zalov dot cz>
On Wed, 13 Nov 2013, Jakub Jelinek wrote:
> Note, in many cases, removing optimizations from fold-const.c leads to
> regressions on code assuming something is folded (especially in
> initializers). Sure, that is all typically undocumented GNU extensions,
> but we had several such problems in the past already.
That's what I said about distinguishing (c), (d) and (e) from (b), with
distribution rebuilds as a way of testing whether there is an issue with
removing some particular optimizations.
(In the static initializer case there's the option of the front end
generating GIMPLE code for the initializer and telling the middle end that
it should (ped)warn if it ends up being optimized to a constant, error if
it doesn't. But I rather hope that isn't needed.)
--
Joseph S. Myers
joseph@codesourcery.com