Optimizations Enabled by -ffast-Math

Re:Optimizations Enabled by -ffast-Math by throwawaylinux on Wednesday October 20, 2021 @05:33AM (#28928645)

This test can not be optimized to always true:

    if (count > 0)
        total += unit_price(volume, count);

Are you confusing it with the opposite scenario:

    total += unit_price(volume, count);
    if (count == 0)
        printf("oops\n");

That test might be optimized out because divide by zero is undefined behavior.

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Re:Optimizations Enabled by -ffast-Math by colejohnson66 on Wednesday October 20, 2021 @06:56AM (#28929216)

I probably am confusing them. I don’t program in C or C++, so I’m not aware of all the “gotchas”, and can easily confuse them (as shown here). Not to mention that compilers have been getting more aggressive in optimizing undefined behavior.

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