[libcxx-commits] [libcxx] 66fa2f9 - [libc++] Refactor variant benchmarks (#174743)

[via libcxx-commits]

Author: Nikolas Klauser
Date: 2026-01-09T12:06:13+01:00
New Revision: 66fa2f9a14e522e238931e12a561e4359af44383

URL: https://github.com/llvm/llvm-project/commit/66fa2f9a14e522e238931e12a561e4359af44383
DIFF: https://github.com/llvm/llvm-project/commit/66fa2f9a14e522e238931e12a561e4359af44383.diff

LOG: [libc++] Refactor variant benchmarks (#174743)

The variant benchmarks are incredibly slow to compile and run currently.
This is due to them being incredibly exhaustive. This is usually a good
thing, but the exhaustiveness makes it prohibitive to actually run the
benchmarks. Even the new, incredibly reduced, set still requires almost
40 seconds to just compile on my system.

Added: 
    libcxx/test/benchmarks/variant.bench.cpp

Modified: 
    

Removed: 
    libcxx/test/benchmarks/VariantBenchmarks.h
    libcxx/test/benchmarks/variant_visit_1.bench.cpp
    libcxx/test/benchmarks/variant_visit_2.bench.cpp
    libcxx/test/benchmarks/variant_visit_3.bench.cpp


################################################################################
diff  --git a/libcxx/test/benchmarks/VariantBenchmarks.h b/libcxx/test/benchmarks/variant.bench.cpp
similarity index 62%
rename from libcxx/test/benchmarks/VariantBenchmarks.h
rename to libcxx/test/benchmarks/variant.bench.cpp
index bb0c714279150..e191aeeb00ae0 100644
--- a/libcxx/test/benchmarks/VariantBenchmarks.h
+++ b/libcxx/test/benchmarks/variant.bench.cpp
@@ -1,4 +1,3 @@
-// -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
@@ -7,21 +6,14 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef BENCHMARK_VARIANT_BENCHMARKS_H
-#define BENCHMARK_VARIANT_BENCHMARKS_H
+// UNSUPPORTED: c++03, c++11, c++14, c++17
 
 #include <array>
-#include <cstddef>
-#include <tuple>
-#include <type_traits>
 #include <variant>
 
 #include "benchmark/benchmark.h"
-
 #include "GenerateInput.h"
 
-namespace VariantBenchmarks {
-
 template <std::size_t I>
 struct S {
   static constexpr size_t v = I;
@@ -50,6 +42,14 @@ static void BM_Visit(benchmark::State& state) {
   }
 }
 
-} // namespace VariantBenchmarks
-
-#endif // BENCHMARK_VARIANT_BENCHMARKS_H
+BENCHMARK(BM_Visit<1, 1>)->Name("std::variant<1-alt>::visit() (1 variant)");
+BENCHMARK(BM_Visit<1, 8>)->Name("std::variant<8-alts>::visit() (1 variant)");
+BENCHMARK(BM_Visit<1, 100>)->Name("std::variant<100-alts>::visit() (1 variant)");
+BENCHMARK(BM_Visit<2, 1>)->Name("std::variant<1-alt>::visit() (2 variants)");
+BENCHMARK(BM_Visit<2, 8>)->Name("std::variant<8-alts>::visit() (2 variants)");
+BENCHMARK(BM_Visit<2, 50>)->Name("std::variant<50-alts>::visit() (2 variants)");
+BENCHMARK(BM_Visit<3, 1>)->Name("std::variant<1-alt>::visit() (3 variants)");
+BENCHMARK(BM_Visit<3, 8>)->Name("std::variant<8-alts>::visit() (3 variants)");
+BENCHMARK(BM_Visit<3, 20>)->Name("std::variant<20-alts>::visit() (3 variants)");
+
+BENCHMARK_MAIN();

diff  --git a/libcxx/test/benchmarks/variant_visit_1.bench.cpp b/libcxx/test/benchmarks/variant_visit_1.bench.cpp
deleted file mode 100644
index f1b702530bed3..0000000000000
--- a/libcxx/test/benchmarks/variant_visit_1.bench.cpp
+++ /dev/null
@@ -1,37 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-// UNSUPPORTED: c++03, c++11, c++14, c++17
-
-#include "benchmark/benchmark.h"
-
-#include "VariantBenchmarks.h"
-
-using namespace VariantBenchmarks;
-
-BENCHMARK(BM_Visit<1, 1>);
-BENCHMARK(BM_Visit<1, 2>);
-BENCHMARK(BM_Visit<1, 3>);
-BENCHMARK(BM_Visit<1, 4>);
-BENCHMARK(BM_Visit<1, 5>);
-BENCHMARK(BM_Visit<1, 6>);
-BENCHMARK(BM_Visit<1, 7>);
-BENCHMARK(BM_Visit<1, 8>);
-BENCHMARK(BM_Visit<1, 9>);
-BENCHMARK(BM_Visit<1, 10>);
-BENCHMARK(BM_Visit<1, 20>);
-BENCHMARK(BM_Visit<1, 30>);
-BENCHMARK(BM_Visit<1, 40>);
-BENCHMARK(BM_Visit<1, 50>);
-BENCHMARK(BM_Visit<1, 60>);
-BENCHMARK(BM_Visit<1, 70>);
-BENCHMARK(BM_Visit<1, 80>);
-BENCHMARK(BM_Visit<1, 90>);
-BENCHMARK(BM_Visit<1, 100>);
-
-BENCHMARK_MAIN();

diff  --git a/libcxx/test/benchmarks/variant_visit_2.bench.cpp b/libcxx/test/benchmarks/variant_visit_2.bench.cpp
deleted file mode 100644
index 7dd8d02b358be..0000000000000
--- a/libcxx/test/benchmarks/variant_visit_2.bench.cpp
+++ /dev/null
@@ -1,32 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-// UNSUPPORTED: c++03, c++11, c++14, c++17
-
-#include "benchmark/benchmark.h"
-
-#include "VariantBenchmarks.h"
-
-using namespace VariantBenchmarks;
-
-BENCHMARK(BM_Visit<2, 1>);
-BENCHMARK(BM_Visit<2, 2>);
-BENCHMARK(BM_Visit<2, 3>);
-BENCHMARK(BM_Visit<2, 4>);
-BENCHMARK(BM_Visit<2, 5>);
-BENCHMARK(BM_Visit<2, 6>);
-BENCHMARK(BM_Visit<2, 7>);
-BENCHMARK(BM_Visit<2, 8>);
-BENCHMARK(BM_Visit<2, 9>);
-BENCHMARK(BM_Visit<2, 10>);
-BENCHMARK(BM_Visit<2, 20>);
-BENCHMARK(BM_Visit<2, 30>);
-BENCHMARK(BM_Visit<2, 40>);
-BENCHMARK(BM_Visit<2, 50>);
-
-BENCHMARK_MAIN();

diff  --git a/libcxx/test/benchmarks/variant_visit_3.bench.cpp b/libcxx/test/benchmarks/variant_visit_3.bench.cpp
deleted file mode 100644
index 0fe42b0d8e009..0000000000000
--- a/libcxx/test/benchmarks/variant_visit_3.bench.cpp
+++ /dev/null
@@ -1,30 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-// UNSUPPORTED: c++03, c++11, c++14, c++17
-
-#include "benchmark/benchmark.h"
-
-#include "VariantBenchmarks.h"
-
-using namespace VariantBenchmarks;
-
-BENCHMARK(BM_Visit<3, 1>);
-BENCHMARK(BM_Visit<3, 2>);
-BENCHMARK(BM_Visit<3, 3>);
-BENCHMARK(BM_Visit<3, 4>);
-BENCHMARK(BM_Visit<3, 5>);
-BENCHMARK(BM_Visit<3, 6>);
-BENCHMARK(BM_Visit<3, 7>);
-BENCHMARK(BM_Visit<3, 8>);
-BENCHMARK(BM_Visit<3, 9>);
-BENCHMARK(BM_Visit<3, 10>);
-BENCHMARK(BM_Visit<3, 15>);
-BENCHMARK(BM_Visit<3, 20>);
-
-BENCHMARK_MAIN();