Re: GCC optimizes integer overflow: bug or feature?

[Robert Dewar]

Andrew Pinski wrote:

> I don't have the number of times this shows up or how much it helps but
> it does help out on being able to vectorize this loop.

Just to be clear, when I ask for quantitative data, it is precisely
data about "how much it helps". It is always easy enough to show
cases where the optimization does help the code.

> All of these do show up in real code, and since loops are now more
> important to optimize than anything else, well knowing the number of
> iterations is very important.

Using "very" is usually a substitute for actual data, and that appears
to be the case here. What would make me confident that this optimization
is worth while is a message that says"

This test (hopefully one from a realistic example, or at least from a
real benchmark suite, and not just cooked up for demonstration) runs
in X seconds with the optimization and X+Y seconds without on bla
architecture.

That does not seem too much to ask :-)
> Thanks,
> Andrew Pinski