On 18 Jan 2007 07:51:51 -0800, Ian Lance Taylor <[EMAIL PROTECTED]> wrote:
Andrew Haley <[EMAIL PROTECTED]> writes:
> Ian Lance Taylor writes:
> > Abramo Bagnara <[EMAIL PROTECTED]> writes:
> >
> > > I'd like to know if gcc has implemented some generic way to help
> > > optimizer job by allowing programmers to specify assumptions (or
> > > constraints).
> >
> > The answer is no, there is nothing quite like you describe.
> >
> > But I think it would be a good idea.
>
> Something like this would greatly improve the code generation quality
> of gcj. There are a great many assertions that I could pass to VRP
> and the optimizers: this is invariant, this is less than that, and so
> on.
Well, internally, we do have ASSERT_EXPR. It would probably take a
little work to permit the frontends to generate it, but the optimizers
should understand it.
Providing a __builtin_assert () function is still one thing on my TODO, we can
derive proper ASSERT_EXPRs from it in VRP even in the -DNDEBUG case.
Of course if the asserts still end up in the source VRP already can derive
information from the IL of the assert code.
Richard.
