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f92903cc53
This is a shameless rip-off of https://github.com/google/benchmark/pull/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`:
7a1c370283/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.
137 lines
3.7 KiB
C++
137 lines
3.7 KiB
C++
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#include "benchmark/benchmark.h"
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#define BASIC_BENCHMARK_TEST(x) BENCHMARK(x)->Arg(8)->Arg(512)->Arg(8192)
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void BM_empty(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(state.iterations());
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}
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}
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BENCHMARK(BM_empty);
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BENCHMARK(BM_empty)->ThreadPerCpu();
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void BM_spin_empty(benchmark::State& state) {
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for (auto _ : state) {
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for (int x = 0; x < state.range(0); ++x) {
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benchmark::DoNotOptimize(x);
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}
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}
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}
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BASIC_BENCHMARK_TEST(BM_spin_empty);
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BASIC_BENCHMARK_TEST(BM_spin_empty)->ThreadPerCpu();
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void BM_spin_pause_before(benchmark::State& state) {
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for (int i = 0; i < state.range(0); ++i) {
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benchmark::DoNotOptimize(i);
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}
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for (auto _ : state) {
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for (int i = 0; i < state.range(0); ++i) {
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benchmark::DoNotOptimize(i);
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}
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}
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}
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BASIC_BENCHMARK_TEST(BM_spin_pause_before);
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BASIC_BENCHMARK_TEST(BM_spin_pause_before)->ThreadPerCpu();
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void BM_spin_pause_during(benchmark::State& state) {
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for (auto _ : state) {
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state.PauseTiming();
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for (int i = 0; i < state.range(0); ++i) {
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benchmark::DoNotOptimize(i);
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}
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state.ResumeTiming();
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for (int i = 0; i < state.range(0); ++i) {
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benchmark::DoNotOptimize(i);
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}
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}
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}
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BASIC_BENCHMARK_TEST(BM_spin_pause_during);
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BASIC_BENCHMARK_TEST(BM_spin_pause_during)->ThreadPerCpu();
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void BM_pause_during(benchmark::State& state) {
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for (auto _ : state) {
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state.PauseTiming();
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state.ResumeTiming();
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}
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}
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BENCHMARK(BM_pause_during);
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BENCHMARK(BM_pause_during)->ThreadPerCpu();
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BENCHMARK(BM_pause_during)->UseRealTime();
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BENCHMARK(BM_pause_during)->UseRealTime()->ThreadPerCpu();
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void BM_spin_pause_after(benchmark::State& state) {
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for (auto _ : state) {
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for (int i = 0; i < state.range(0); ++i) {
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benchmark::DoNotOptimize(i);
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}
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}
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for (int i = 0; i < state.range(0); ++i) {
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benchmark::DoNotOptimize(i);
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}
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}
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BASIC_BENCHMARK_TEST(BM_spin_pause_after);
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BASIC_BENCHMARK_TEST(BM_spin_pause_after)->ThreadPerCpu();
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void BM_spin_pause_before_and_after(benchmark::State& state) {
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for (int i = 0; i < state.range(0); ++i) {
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benchmark::DoNotOptimize(i);
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}
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for (auto _ : state) {
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for (int i = 0; i < state.range(0); ++i) {
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benchmark::DoNotOptimize(i);
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}
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}
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for (int i = 0; i < state.range(0); ++i) {
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benchmark::DoNotOptimize(i);
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}
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}
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BASIC_BENCHMARK_TEST(BM_spin_pause_before_and_after);
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BASIC_BENCHMARK_TEST(BM_spin_pause_before_and_after)->ThreadPerCpu();
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void BM_empty_stop_start(benchmark::State& state) {
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for (auto _ : state) {
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}
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}
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BENCHMARK(BM_empty_stop_start);
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BENCHMARK(BM_empty_stop_start)->ThreadPerCpu();
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void BM_KeepRunning(benchmark::State& state) {
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benchmark::IterationCount iter_count = 0;
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assert(iter_count == state.iterations());
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while (state.KeepRunning()) {
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++iter_count;
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}
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assert(iter_count == state.iterations());
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}
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BENCHMARK(BM_KeepRunning);
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void BM_KeepRunningBatch(benchmark::State& state) {
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// Choose a prime batch size to avoid evenly dividing max_iterations.
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const benchmark::IterationCount batch_size = 101;
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benchmark::IterationCount iter_count = 0;
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while (state.KeepRunningBatch(batch_size)) {
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iter_count += batch_size;
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}
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assert(state.iterations() == iter_count);
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}
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BENCHMARK(BM_KeepRunningBatch);
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void BM_RangedFor(benchmark::State& state) {
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benchmark::IterationCount iter_count = 0;
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for (auto _ : state) {
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++iter_count;
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}
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assert(iter_count == state.max_iterations);
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}
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BENCHMARK(BM_RangedFor);
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// Ensure that StateIterator provides all the necessary typedefs required to
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// instantiate std::iterator_traits.
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static_assert(std::is_same<
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typename std::iterator_traits<benchmark::State::StateIterator>::value_type,
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typename benchmark::State::StateIterator::value_type>::value, "");
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BENCHMARK_MAIN();
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