diff --git a/test/bench_internal/CMakeLists.txt b/test/bench_internal/CMakeLists.txt
index 4174d9b6c5..9f35353672 100644
--- a/test/bench_internal/CMakeLists.txt
+++ b/test/bench_internal/CMakeLists.txt
@@ -6,6 +6,7 @@ add_executable(fizzy-bench-internal)
 
 target_sources(fizzy-bench-internal PRIVATE
     bench_internal.cpp
+    execute_benchmarks.cpp
     experimental.cpp
     parser_benchmarks.cpp
     parser_noinline.cpp
diff --git a/test/bench_internal/execute_benchmarks.cpp b/test/bench_internal/execute_benchmarks.cpp
new file mode 100644
index 0000000000..81eda67ad1
--- /dev/null
+++ b/test/bench_internal/execute_benchmarks.cpp
@@ -0,0 +1,80 @@
+// Fizzy: A fast WebAssembly interpreter
+// Copyright 2020 The Fizzy Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+#include "span.hpp"
+#include <benchmark/benchmark.h>
+#include <memory>
+#include <vector>
+
+namespace
+{
+[[gnu::noinline]] auto init_locals_1(fizzy::span<const uint64_t> args, uint32_t local_count)
+{
+    std::vector<uint64_t> locals;
+    locals.reserve(args.size() + local_count);
+    std::copy_n(args.begin(), args.size(), std::back_inserter(locals));
+    locals.resize(locals.size() + local_count);
+    return locals;
+}
+
+[[gnu::noinline]] auto init_locals_2(fizzy::span<const uint64_t> args, uint32_t local_count)
+{
+    std::vector<uint64_t> locals(args.size() + local_count);
+    std::copy_n(args.begin(), args.size(), locals.begin());
+    return locals;
+}
+
+[[gnu::noinline]] auto init_locals_3(fizzy::span<const uint64_t> args, uint32_t local_count)
+{
+    std::vector<uint64_t> locals(args.size() + local_count);
+    __builtin_memcpy(locals.data(), args.data(), args.size());
+    return locals;
+}
+
+[[gnu::noinline]] auto init_locals_4(fizzy::span<const uint64_t> args, uint32_t local_count)
+{
+    auto locals = std::make_unique<uint64_t[]>(args.size() + local_count);
+    std::copy_n(args.begin(), args.size(), &locals[0]);
+    std::fill_n(&locals[args.size()], local_count, 0);
+    return locals;
+}
+
+[[gnu::noinline]] auto init_locals_5(fizzy::span<const uint64_t> args, uint32_t local_count)
+{
+    auto locals = std::make_unique<uint64_t[]>(args.size() + local_count);
+    __builtin_memcpy(locals.get(), args.data(), args.size());
+    __builtin_memset(locals.get() + args.size(), 0, local_count);
+    return locals;
+}
+}  // namespace
+
+template <typename T, T Fn(fizzy::span<const uint64_t>, uint32_t)>
+static void init_locals(benchmark::State& state)
+{
+    const auto num_args = static_cast<size_t>(state.range(0));
+    const auto num_locals = static_cast<uint32_t>(state.range(1));
+
+    const std::vector<uint64_t> args(num_args, 0xa49);
+    benchmark::ClobberMemory();
+
+    for ([[maybe_unused]] auto _ : state)
+    {
+        const auto locals = Fn(args, num_locals);
+        benchmark::DoNotOptimize(locals);
+    }
+}
+#define ARGS            \
+    Args({0, 0})        \
+        ->Args({2, 4})  \
+        ->Args({2, 38}) \
+        ->Args({3, 4})  \
+        ->Args({3, 8})  \
+        ->Args({3, 13}) \
+        ->Args({5, 30}) \
+        ->Args({10, 100})
+BENCHMARK_TEMPLATE(init_locals, std::vector<uint64_t>, init_locals_1)->ARGS;
+BENCHMARK_TEMPLATE(init_locals, std::vector<uint64_t>, init_locals_2)->ARGS;
+BENCHMARK_TEMPLATE(init_locals, std::vector<uint64_t>, init_locals_3)->ARGS;
+BENCHMARK_TEMPLATE(init_locals, std::unique_ptr<uint64_t[]>, init_locals_4)->ARGS;
+BENCHMARK_TEMPLATE(init_locals, std::unique_ptr<uint64_t[]>, init_locals_5)->ARGS;