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Iteration counts should be
uint64_t
globally. (#817)
This is a shameless rip-off of #646 I did promise to look into why that proposed PR was producing so much worse assembly, and so i finally did. The reason is - that diff changes `size_t` (unsigned) to `int64_t` (signed). There is this nice little `assert`: https://github.com/google/benchmark/blob/7a1c37028359ca9d386d719a6ad527743cf1b753/include/benchmark/benchmark.h#L744 It ensures that we didn't magically decide to advance our iterator when we should have finished benchmarking. When `cached_` was unsigned, the `assert` was `cached_ UGT 0`. But we only ever get to that `assert` if `cached_ NE 0`, and naturally if `cached_` is not `0`, then it is bigger than `0`, so the `assert` is tautological, and gets folded away. But now that `cached_` became signed, the assert became `cached_ SGT 0`. And we still only know that `cached_ NE 0`, so the assert can't be optimized out, or at least it doesn't currently. Regardless of whether or not that is a bug in itself, that particular diff would have regressed the normal 64-bit systems, by halving the maximal iteration space (since we go from unsigned counter to signed one, of the same bit-width), which seems like a bug. And just so it happens, fixing *this* bug, fixes the other bug. This produces fully (bit-by-bit) identical state_assembly_test.s The filecheck change is actually needed regardless of this patch, else this test does not pass for me even without this diff.
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