https://bugs.gentoo.org/922877 https://github.com/google/benchmark/pull/1753 From cdd4a6d48077a78d07e3b7f165383f6d5052108c Mon Sep 17 00:00:00 2001 From: Sam James Date: Fri, 2 Feb 2024 21:38:11 -0500 Subject: [PATCH 1/3] CycleClock: Add support for Alpha architecture As documented, the real cycle counter is unsafe to use here, because it is a 32-bit integer which wraps every ~4s. Use gettimeofday instead, which has a limitation of a low-precision real-time-clock (~1ms), but no wrapping. Passes test suite. Signed-off-by: Sam James --- src/cycleclock.h | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/src/cycleclock.h b/src/cycleclock.h index 931bba146..eff563e7f 100644 --- a/src/cycleclock.h +++ b/src/cycleclock.h @@ -218,6 +218,15 @@ inline BENCHMARK_ALWAYS_INLINE int64_t Now() { uint64_t pcycle; asm volatile("%0 = C15:14" : "=r"(pcycle)); return static_cast(pcycle); +#elif defined(__alpha__) + // Alpha has a cycle counter, the PCC register, but it is an unsigned 32-bit + // integer and thus wraps every ~4s, making using it for tick counts + // unreliable beyond this time range. The real-time clock is low-precision, + // roughtly ~1ms, but it is the only option that can reasonable count + // indefinitely. + struct timeval tv; + gettimeofday(&tv, nullptr); + return static_cast(tv.tv_sec) * 1000000 + tv.tv_usec; #else // The soft failover to a generic implementation is automatic only for ARM. // For other platforms the developer is expected to make an attempt to create From b1bec2fa5aed335b5be78720a9812cf27baf9df6 Mon Sep 17 00:00:00 2001 From: Sam James Date: Fri, 2 Feb 2024 21:46:06 -0500 Subject: [PATCH 2/3] sysinfo: support parsing /proc/cpuinfo on Alpha And also, bail out if unable to parse /proc/cpuinfo. This will preemptively alert users on platforms that need custom code for parsing /proc/cpuinfo. Signed-off-by: Sam James --- src/sysinfo.cc | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/src/sysinfo.cc b/src/sysinfo.cc index 04d64dc5b..786bb1b41 100644 --- a/src/sysinfo.cc +++ b/src/sysinfo.cc @@ -513,7 +513,11 @@ int GetNumCPUs() { std::cerr << "failed to open /proc/cpuinfo\n"; return -1; } +#if defined(__alpha__) + const std::string Key = "cpus detected"; +#else const std::string Key = "processor"; +#endif std::string ln; while (std::getline(f, ln)) { if (ln.empty()) continue; From 17f2f35e1ce650b4f8596a5c5df6a050588136c5 Mon Sep 17 00:00:00 2001 From: Sam James Date: Fri, 2 Feb 2024 21:49:24 -0500 Subject: [PATCH 3/3] tabular_test: add a missing DoNotOptimize call Signed-off-by: Sam James --- test/user_counters_tabular_test.cc | 3 +++ 1 file changed, 3 insertions(+) diff --git a/test/user_counters_tabular_test.cc b/test/user_counters_tabular_test.cc index 3e8fb1bf0..ffd3c0992 100644 --- a/test/user_counters_tabular_test.cc +++ b/test/user_counters_tabular_test.cc @@ -63,6 +63,9 @@ ADD_CASES(TC_CSVOut, {{"%csv_header," void BM_Counters_Tabular(benchmark::State& state) { for (auto _ : state) { + // This test requires a non-zero CPU time to avoid divide-by-zero + auto iterations = state.iterations(); + benchmark::DoNotOptimize(iterations); } namespace bm = benchmark; state.counters.insert({