In the following program, with gcc-5.3 doit() is significantly faster than doit2() in 64-bit Linux:

================================================================
#include <stdint.h>

int
doit(int64_t index, int64_t nitems)
{
    return index < 0 || index >= nitems;
}

int
doit2(int64_t index, int64_t nitems)
{
    return (uint64_t)index >= (uint64_t)nitems;
}

int
main(void)
{
    int count, i;

    for (i = 0; i < 1000000000; i++) {
        count += doit(832921, i);
    }

    return count;
}
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