cppgc: Fix empty benchmark on Windows

Keep idiomatic state loop but rely on USE() to avoid
warning about unused variables.

Bug: v8:11687
Change-Id: Icde295723c5d389d827280f70a65776866d4e7a9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2850645
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74200}

test/benchmarks/cpp/BUILD.gn

@@ -9,7 +9,7 @@ group("gn_all") {
 
   deps = []
 
-  if (v8_enable_google_benchmark && !is_win) {
+  if (v8_enable_google_benchmark) {
     deps += [
       ":empty_benchmark",
       "cppgc:gn_all",
@@ -17,7 +17,7 @@ group("gn_all") {
   }
 }
 
-if (v8_enable_google_benchmark && !is_win) {
+if (v8_enable_google_benchmark) {
   v8_executable("empty_benchmark") {
     testonly = true
 

test/benchmarks/cpp/DEPS

@@ -1,3 +1,4 @@
 include_rules = [
+  "+src/base",
   "+third_party/google_benchmark/src/include/benchmark/benchmark.h",
 ]

test/benchmarks/cpp/cppgc/BUILD.gn

@@ -9,12 +9,12 @@ group("gn_all") {
 
   deps = []
 
-  if (v8_enable_google_benchmark && !is_win) {
+  if (v8_enable_google_benchmark) {
     deps += [ ":cppgc_basic_benchmarks" ]
   }
 }
 
-if (v8_enable_google_benchmark && !is_win) {
+if (v8_enable_google_benchmark) {
   v8_source_set("cppgc_benchmark_support") {
     testonly = true
 

test/benchmarks/cpp/cppgc/DEPS

@@ -1,5 +1,6 @@
 include_rules = [
   "+include/cppgc",
+  "+src/base",
   "+src/heap/cppgc",
   "+test/unittests/heap/cppgc",
   "+third_party/google_benchmark/src/include/benchmark/benchmark.h",

test/benchmarks/cpp/cppgc/allocation_perf.cc

@@ -5,6 +5,7 @@
 #include "include/cppgc/allocation.h"
 #include "include/cppgc/garbage-collected.h"
 #include "include/cppgc/heap-consistency.h"
+#include "src/base/macros.h"
 #include "src/heap/cppgc/globals.h"
 #include "src/heap/cppgc/heap.h"
 #include "test/benchmarks/cpp/cppgc/utils.h"
@@ -24,6 +25,7 @@ class TinyObject final : public cppgc::GarbageCollected<TinyObject> {
 BENCHMARK_F(Allocate, Tiny)(benchmark::State& st) {
   subtle::NoGarbageCollectionScope no_gc(*Heap::From(&heap()));
   for (auto _ : st) {
+    USE(_);
     benchmark::DoNotOptimize(
         cppgc::MakeGarbageCollected<TinyObject>(heap().GetAllocationHandle()));
   }
@@ -39,6 +41,7 @@ class LargeObject final : public GarbageCollected<LargeObject> {
 BENCHMARK_F(Allocate, Large)(benchmark::State& st) {
   subtle::NoGarbageCollectionScope no_gc(*Heap::From(&heap()));
   for (auto _ : st) {
+    USE(_);
     benchmark::DoNotOptimize(
         cppgc::MakeGarbageCollected<LargeObject>(heap().GetAllocationHandle()));
   }

test/benchmarks/cpp/cppgc/trace_perf.cc

@@ -5,6 +5,7 @@
 #include "include/cppgc/allocation.h"
 #include "include/cppgc/garbage-collected.h"
 #include "include/cppgc/persistent.h"
+#include "src/base/macros.h"
 #include "src/heap/cppgc/globals.h"
 #include "src/heap/cppgc/heap.h"
 #include "test/benchmarks/cpp/cppgc/utils.h"
@@ -65,6 +66,7 @@ BENCHMARK_F(Trace, Static)(benchmark::State& st) {
                                         heap().GetAllocationHandle())));
   VisitorBase visitor;
   for (auto _ : st) {
+    USE(_);
     DispatchTrace(&visitor, holder->base_ref);
   }
 }
@@ -75,6 +77,7 @@ BENCHMARK_F(Trace, Dynamic)(benchmark::State& st) {
                                         heap().GetAllocationHandle())));
   VisitorBase visitor;
   for (auto _ : st) {
+    USE(_);
     DispatchTrace(&visitor, holder->mixin_ref);
   }
 }

test/benchmarks/cpp/empty.cc

@@ -2,11 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "src/base/macros.h"
 #include "third_party/google_benchmark/src/include/benchmark/benchmark.h"
 
 static void BM_Empty(benchmark::State& state) {
   for (auto _ : state) {
+    USE(_);
   }
 }
-// Register the function as a benchmark
+
+// Register the function as a benchmark. The empty benchmark ensures that the
+// framework compiles and links as expected.
 BENCHMARK(BM_Empty);