Re: GCC optimizes integer overflow: bug or feature?

[Andrew Haley]

Robert Dewar writes:
 > Brooks Moses wrote:
 > 
 > > Now, if your argument is that following the LIA-1 standard will
 > > prevent optimizations that could otherwise be made if one
 > > followed only the C standard, that's a reasonable argument, but
 > > it should not be couched as if it implies that preventing the
 > > optimizations would not be following the C standard.
 > 
 > I continue to suspect that the gains from this optimization are minimal
 > to non-existent in practice. Given the requirements in LIA-1, I would
 > think that taking advantage of overflow being undefined is only 
 > acceptable

That's an interesting use of the passive voice.  Acceptable to whom?

 > if there is very clear quantitative data showing that this indeed
 > is a significant optimization.

We've already defined `-fwrapv' for people who need nonstandard
arithmetic.  I don't see that this is any different from the
interminable strict-aliasing discussion.

Andrew.