[gcmole] Simplify gcmole directives and add tests

This prepares work for speeding up gcmole infrastructure by adding
more checks and testing.

- Add a presubmit check that verifies gcmole directives in gn files.
- Simplify gcmole directives in gn files. Drop all but the
  architecture property as the others were unused. Simplify regular
  expressions.
- Fix some gcmole directives (fly by - only on untested
  architectures).
- Add a python test for the changed function in gcmole.py. There's
  no other testing yet and this starts somewhere. The test simulates
  real BUILD.gn files via checked-in test data.

Bug: v8:12660
Change-Id: I9ca3152b2c3b806de5d4509c152283b36294950d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4020268
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Alexander Schulze <alexschulze@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#84239}

BUILD.gn

@@ -2454,57 +2454,57 @@ v8_source_set("v8_initializers") {
 
   if (v8_current_cpu == "x86") {
     sources += [
-      ### gcmole(arch:ia32) ###
+      ### gcmole(ia32) ###
       "src/builtins/ia32/builtins-ia32.cc",
     ]
   } else if (v8_current_cpu == "x64") {
     sources += [
-      ### gcmole(arch:x64) ###
+      ### gcmole(x64) ###
       "src/builtins/x64/builtins-x64.cc",
     ]
   } else if (v8_current_cpu == "arm") {
     sources += [
-      ### gcmole(arch:arm) ###
+      ### gcmole(arm) ###
       "src/builtins/arm/builtins-arm.cc",
     ]
   } else if (v8_current_cpu == "arm64") {
     sources += [
-      ### gcmole(arch:arm64) ###
+      ### gcmole(arm64) ###
       "src/builtins/arm64/builtins-arm64.cc",
     ]
   } else if (v8_current_cpu == "mips64" || v8_current_cpu == "mips64el") {
     sources += [
-      ### gcmole(arch:mips64el) ###
+      ### gcmole(mips64el) ###
       "src/builtins/mips64/builtins-mips64.cc",
     ]
   } else if (v8_current_cpu == "loong64") {
     sources += [
-      ### gcmole(arch:loong64) ###
+      ### gcmole(loong64) ###
       "src/builtins/loong64/builtins-loong64.cc",
     ]
   } else if (v8_current_cpu == "ppc") {
     sources += [
-      ### gcmole(arch:ppc) ###
+      ### gcmole(ppc) ###
       "src/builtins/ppc/builtins-ppc.cc",
     ]
   } else if (v8_current_cpu == "ppc64") {
     sources += [
-      ### gcmole(arch:ppc64) ###
+      ### gcmole(ppc64) ###
       "src/builtins/ppc/builtins-ppc.cc",
     ]
   } else if (v8_current_cpu == "s390" || v8_current_cpu == "s390x") {
     sources += [
-      ### gcmole(arch:s390) ###
+      ### gcmole(s390) ###
       "src/builtins/s390/builtins-s390.cc",
     ]
   } else if (v8_current_cpu == "riscv64") {
     sources += [
-      ### gcmole(arch:riscv64) ###
+      ### gcmole(riscv64) ###
       "src/builtins/riscv/builtins-riscv.cc",
     ]
   } else if (v8_current_cpu == "riscv32") {
     sources += [
-      ### gcmole(arch:riscv32) ###
+      ### gcmole(riscv32) ###
       "src/builtins/riscv/builtins-riscv.cc",
     ]
   }
@@ -3758,7 +3758,8 @@ v8_header_set("v8_internal_headers") {
   }
 
   if (v8_current_cpu == "x86") {
-    sources += [  ### gcmole(arch:ia32) ###
+    sources += [
+      ### gcmole(ia32) ###
       "src/baseline/ia32/baseline-assembler-ia32-inl.h",
       "src/baseline/ia32/baseline-compiler-ia32-inl.h",
       "src/codegen/ia32/assembler-ia32-inl.h",
@@ -3776,7 +3777,8 @@ v8_header_set("v8_internal_headers") {
       "src/wasm/baseline/ia32/liftoff-assembler-ia32.h",
     ]
   } else if (v8_current_cpu == "x64") {
-    sources += [  ### gcmole(arch:x64) ###
+    sources += [
+      ### gcmole(x64) ###
       "src/baseline/x64/baseline-assembler-x64-inl.h",
       "src/baseline/x64/baseline-compiler-x64-inl.h",
       "src/codegen/shared-ia32-x64/macro-assembler-shared-ia32-x64.h",
@@ -3812,7 +3814,8 @@ v8_header_set("v8_internal_headers") {
       }
     }
   } else if (v8_current_cpu == "arm") {
-    sources += [  ### gcmole(arch:arm) ###
+    sources += [
+      ### gcmole(arm) ###
       "src/baseline/arm/baseline-assembler-arm-inl.h",
       "src/baseline/arm/baseline-compiler-arm-inl.h",
       "src/codegen/arm/assembler-arm-inl.h",
@@ -3830,7 +3833,8 @@ v8_header_set("v8_internal_headers") {
       "src/wasm/baseline/arm/liftoff-assembler-arm.h",
     ]
   } else if (v8_current_cpu == "arm64") {
-    sources += [  ### gcmole(arch:arm64) ###
+    sources += [
+      ### gcmole(arm64) ###
       "src/baseline/arm64/baseline-assembler-arm64-inl.h",
       "src/baseline/arm64/baseline-compiler-arm64-inl.h",
       "src/codegen/arm64/assembler-arm64-inl.h",
@@ -3872,7 +3876,8 @@ v8_header_set("v8_internal_headers") {
       sources += [ "src/diagnostics/unwinding-info-win64.h" ]
     }
   } else if (v8_current_cpu == "mips64" || v8_current_cpu == "mips64el") {
-    sources += [  ### gcmole(arch:mips64el) ###
+    sources += [
+      ### gcmole(mips64el) ###
       "src/baseline/mips64/baseline-assembler-mips64-inl.h",
       "src/baseline/mips64/baseline-compiler-mips64-inl.h",
       "src/codegen/mips64/assembler-mips64-inl.h",
@@ -3888,7 +3893,8 @@ v8_header_set("v8_internal_headers") {
       "src/wasm/baseline/mips64/liftoff-assembler-mips64.h",
     ]
   } else if (v8_current_cpu == "loong64") {
-    sources += [  ### gcmole(arch:loong64) ###
+    sources += [
+      ### gcmole(loong64) ###
       "src/baseline/loong64/baseline-assembler-loong64-inl.h",
       "src/baseline/loong64/baseline-compiler-loong64-inl.h",
       "src/codegen/loong64/assembler-loong64-inl.h",
@@ -3904,7 +3910,8 @@ v8_header_set("v8_internal_headers") {
       "src/wasm/baseline/loong64/liftoff-assembler-loong64.h",
     ]
   } else if (v8_current_cpu == "ppc") {
-    sources += [  ### gcmole(arch:ppc) ###
+    sources += [
+      ### gcmole(ppc) ###
       "src/codegen/ppc/assembler-ppc-inl.h",
       "src/codegen/ppc/assembler-ppc.h",
       "src/codegen/ppc/constants-ppc.h",
@@ -3920,7 +3927,8 @@ v8_header_set("v8_internal_headers") {
       "src/wasm/baseline/ppc/liftoff-assembler-ppc.h",
     ]
   } else if (v8_current_cpu == "ppc64") {
-    sources += [  ### gcmole(arch:ppc64) ###
+    sources += [
+      ### gcmole(ppc64) ###
       "src/baseline/ppc/baseline-assembler-ppc-inl.h",
       "src/baseline/ppc/baseline-compiler-ppc-inl.h",
       "src/codegen/ppc/assembler-ppc-inl.h",
@@ -3938,7 +3946,8 @@ v8_header_set("v8_internal_headers") {
       "src/wasm/baseline/ppc/liftoff-assembler-ppc.h",
     ]
   } else if (v8_current_cpu == "s390" || v8_current_cpu == "s390x") {
-    sources += [  ### gcmole(arch:s390) ###
+    sources += [
+      ### gcmole(s390) ###
       "src/baseline/s390/baseline-assembler-s390-inl.h",
       "src/baseline/s390/baseline-compiler-s390-inl.h",
       "src/codegen/s390/assembler-s390-inl.h",
@@ -3956,7 +3965,8 @@ v8_header_set("v8_internal_headers") {
       "src/wasm/baseline/s390/liftoff-assembler-s390.h",
     ]
   } else if (v8_current_cpu == "riscv64") {
-    sources += [  ### gcmole(arch:riscv64) ###
+    sources += [
+      ### gcmole(riscv64) ###
       "src/baseline/riscv/baseline-assembler-riscv-inl.h",
       "src/baseline/riscv/baseline-compiler-riscv-inl.h",
       "src/codegen/riscv/assembler-riscv-inl.h",
@@ -3995,7 +4005,8 @@ v8_header_set("v8_internal_headers") {
       "src/wasm/baseline/riscv64/liftoff-assembler-riscv64.h",
     ]
   } else if (v8_current_cpu == "riscv32") {
-    sources += [  ### gcmole(arch:riscv32) ###
+    sources += [
+      ### gcmole(riscv32) ###
       "src/baseline/riscv/baseline-assembler-riscv-inl.h",
       "src/baseline/riscv/baseline-compiler-riscv-inl.h",
       "src/codegen/riscv/assembler-riscv.h",
@@ -4771,7 +4782,8 @@ v8_source_set("v8_base_without_compiler") {
   }
 
   if (v8_enable_webassembly) {
-    sources += [  ### gcmole(all) ###
+    sources += [
+      ### gcmole(all) ###
       "src/asmjs/asm-js.cc",
       "src/asmjs/asm-parser.cc",
       "src/asmjs/asm-scanner.cc",
@@ -4853,7 +4865,8 @@ v8_source_set("v8_base_without_compiler") {
   }
 
   if (v8_current_cpu == "x86") {
-    sources += [  ### gcmole(arch:ia32) ###
+    sources += [
+      ### gcmole(ia32) ###
       "src/codegen/ia32/assembler-ia32.cc",
       "src/codegen/ia32/cpu-ia32.cc",
       "src/codegen/ia32/macro-assembler-ia32.cc",
@@ -4868,7 +4881,8 @@ v8_source_set("v8_base_without_compiler") {
       "src/regexp/ia32/regexp-macro-assembler-ia32.cc",
     ]
   } else if (v8_current_cpu == "x64") {
-    sources += [  ### gcmole(arch:x64) ###
+    sources += [
+      ### gcmole(x64) ###
       "src/codegen/shared-ia32-x64/macro-assembler-shared-ia32-x64.cc",
       "src/codegen/x64/assembler-x64.cc",
       "src/codegen/x64/cpu-x64.cc",
@@ -4906,7 +4920,8 @@ v8_source_set("v8_base_without_compiler") {
       }
     }
   } else if (v8_current_cpu == "arm") {
-    sources += [  ### gcmole(arch:arm) ###
+    sources += [
+      ### gcmole(arm) ###
       "src/codegen/arm/assembler-arm.cc",
       "src/codegen/arm/constants-arm.cc",
       "src/codegen/arm/cpu-arm.cc",
@@ -4924,7 +4939,8 @@ v8_source_set("v8_base_without_compiler") {
       "src/regexp/arm/regexp-macro-assembler-arm.cc",
     ]
   } else if (v8_current_cpu == "arm64") {
-    sources += [  ### gcmole(arch:arm64) ###
+    sources += [
+      ### gcmole(arm64) ###
       "src/codegen/arm64/assembler-arm64.cc",
       "src/codegen/arm64/cpu-arm64.cc",
       "src/codegen/arm64/decoder-arm64.cc",
@@ -4971,7 +4987,8 @@ v8_source_set("v8_base_without_compiler") {
       sources += [ "src/diagnostics/unwinding-info-win64.cc" ]
     }
   } else if (v8_current_cpu == "mips64" || v8_current_cpu == "mips64el") {
-    sources += [  ### gcmole(arch:mips64el) ###
+    sources += [
+      ### gcmole(mips64el) ###
       "src/codegen/mips64/assembler-mips64.cc",
       "src/codegen/mips64/constants-mips64.cc",
       "src/codegen/mips64/cpu-mips64.cc",
@@ -4988,7 +5005,8 @@ v8_source_set("v8_base_without_compiler") {
       "src/regexp/mips64/regexp-macro-assembler-mips64.cc",
     ]
   } else if (v8_current_cpu == "loong64") {
-    sources += [  ### gcmole(arch:loong64) ###
+    sources += [
+      ### gcmole(loong64) ###
       "src/codegen/loong64/assembler-loong64.cc",
       "src/codegen/loong64/constants-loong64.cc",
       "src/codegen/loong64/cpu-loong64.cc",
@@ -5005,7 +5023,8 @@ v8_source_set("v8_base_without_compiler") {
       "src/regexp/loong64/regexp-macro-assembler-loong64.cc",
     ]
   } else if (v8_current_cpu == "ppc") {
-    sources += [  ### gcmole(arch:ppc) ###
+    sources += [
+      ### gcmole(ppc) ###
       "src/codegen/ppc/assembler-ppc.cc",
       "src/codegen/ppc/constants-ppc.cc",
       "src/codegen/ppc/cpu-ppc.cc",
@@ -5023,7 +5042,8 @@ v8_source_set("v8_base_without_compiler") {
       "src/regexp/ppc/regexp-macro-assembler-ppc.cc",
     ]
   } else if (v8_current_cpu == "ppc64") {
-    sources += [  ### gcmole(arch:ppc64) ###
+    sources += [
+      ### gcmole(ppc64) ###
       "src/codegen/ppc/assembler-ppc.cc",
       "src/codegen/ppc/constants-ppc.cc",
       "src/codegen/ppc/cpu-ppc.cc",
@@ -5041,7 +5061,8 @@ v8_source_set("v8_base_without_compiler") {
       "src/regexp/ppc/regexp-macro-assembler-ppc.cc",
     ]
   } else if (v8_current_cpu == "s390" || v8_current_cpu == "s390x") {
-    sources += [  ### gcmole(arch:s390) ###
+    sources += [
+      ### gcmole(s390) ###
       "src/codegen/s390/assembler-s390.cc",
       "src/codegen/s390/constants-s390.cc",
       "src/codegen/s390/cpu-s390.cc",
@@ -5059,7 +5080,8 @@ v8_source_set("v8_base_without_compiler") {
       "src/regexp/s390/regexp-macro-assembler-s390.cc",
     ]
   } else if (v8_current_cpu == "riscv64") {
-    sources += [  ### gcmole(arch:riscv64) ###
+    sources += [
+      ### gcmole(riscv64) ###
       "src/codegen/riscv/assembler-riscv.cc",
       "src/codegen/riscv/base-assembler-riscv.cc",
       "src/codegen/riscv/base-constants-riscv.cc",
@@ -5085,7 +5107,8 @@ v8_source_set("v8_base_without_compiler") {
       "src/regexp/riscv/regexp-macro-assembler-riscv.cc",
     ]
   } else if (v8_current_cpu == "riscv32") {
-    sources += [  ### gcmole(arch:riscv32) ###
+    sources += [
+      ### gcmole(riscv32) ###
       "src/codegen/riscv/assembler-riscv.cc",
       "src/codegen/riscv/base-assembler-riscv.cc",
       "src/codegen/riscv/base-constants-riscv.cc",

PRESUBMIT.py

@@ -85,6 +85,7 @@ def _V8PresubmitChecks(input_api, output_api):
   sys.path.append(input_api.os_path.join(
         input_api.PresubmitLocalPath(), 'tools'))
   from v8_presubmit import CppLintProcessor
+  from v8_presubmit import GCMoleProcessor
   from v8_presubmit import JSLintProcessor
   from v8_presubmit import TorqueLintProcessor
   from v8_presubmit import SourceProcessor
@@ -126,6 +127,9 @@ def _V8PresubmitChecks(input_api, output_api):
   if not StatusFilesProcessor().RunOnFiles(
       input_api.AffectedFiles(include_deletes=True)):
     results.append(output_api.PresubmitError("Status file check failed"))
+  if not GCMoleProcessor().RunOnFiles(
+      input_api.AffectedFiles(include_deletes=False)):
+    results.append(output_api.PresubmitError("GCMole pattern check failed"))
   results.extend(input_api.canned_checks.CheckAuthorizedAuthor(
       input_api, output_api, bot_allowlist=[
         'v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com'

test/cctest/BUILD.gn

@@ -207,7 +207,8 @@ v8_source_set("cctest_sources") {
   ]
 
   if (v8_current_cpu == "arm") {
-    sources += [  ### gcmole(arch:arm) ###
+    sources += [
+      ### gcmole(arm) ###
       "assembler-helper-arm.cc",
       "assembler-helper-arm.h",
       "test-assembler-arm.cc",
@@ -215,7 +216,8 @@ v8_source_set("cctest_sources") {
       "test-sync-primitives-arm.cc",
     ]
   } else if (v8_current_cpu == "arm64") {
-    sources += [  ### gcmole(arch:arm64) ###
+    sources += [
+      ### gcmole(arm64) ###
       "test-assembler-arm64.cc",
       "test-fuzz-arm64.cc",
       "test-javascript-arm64.cc",
@@ -228,48 +230,60 @@ v8_source_set("cctest_sources") {
       sources += [ "test-stack-unwinding-win64.cc" ]
     }
   } else if (v8_current_cpu == "x86") {
-    sources += [  ### gcmole(arch:ia32) ###
+    sources += [
+      ### gcmole(ia32) ###
       "test-assembler-ia32.cc",
       "test-log-stack-tracer.cc",
     ]
   } else if (v8_current_cpu == "mips64") {
-    sources += [  ### gcmole(arch:mips64) ###
+    sources += [
+      ### gcmole(mips64) ###
       "test-assembler-mips64.cc",
       "test-macro-assembler-mips64.cc",
     ]
   } else if (v8_current_cpu == "mips64el") {
-    sources += [  ### gcmole(arch:mips64el) ###
+    sources += [
+      ### gcmole(mips64el) ###
       "test-assembler-mips64.cc",
       "test-macro-assembler-mips64.cc",
     ]
   } else if (v8_current_cpu == "x64") {
     sources += [
-      ### gcmole(arch:x64) ###
+      ### gcmole(x64) ###
       "test-log-stack-tracer.cc",
     ]
     if (is_win) {
       sources += [ "test-stack-unwinding-win64.cc" ]
     }
   } else if (v8_current_cpu == "ppc" || v8_current_cpu == "ppc64") {
-    sources += [ "test-assembler-ppc.cc" ]  ### gcmole(arch:ppc) ###
+    sources += [
+      ### gcmole(ppc) ###
+      "test-assembler-ppc.cc",
+    ]
   } else if (v8_current_cpu == "s390" || v8_current_cpu == "s390x") {
-    sources += [ "test-assembler-s390.cc" ]  ### gcmole(arch:s390) ###
+    sources += [
+      ### gcmole(s390) ###
+      "test-assembler-s390.cc",
+    ]
   } else if (v8_current_cpu == "riscv64") {
-    sources += [  ### gcmole(arch:riscv64) ###
+    sources += [
+      ### gcmole(riscv64) ###
       "test-assembler-riscv64.cc",
       "test-helper-riscv64.cc",
       "test-macro-assembler-riscv64.cc",
       "test-simple-riscv64.cc",
     ]
   } else if (v8_current_cpu == "riscv32") {
-    sources += [  ### gcmole(arch:riscv32) ###
+    sources += [
+      ### gcmole(riscv32) ###
       "test-assembler-riscv32.cc",
       "test-helper-riscv32.cc",
       "test-macro-assembler-riscv32.cc",
       "test-simple-riscv32.cc",
     ]
   } else if (v8_current_cpu == "loong64") {
-    sources += [  ### gcmole(arch:loong64) ###
+    sources += [
+      ### gcmole(loong64) ###
       "test-assembler-loong64.cc",
       "test-macro-assembler-loong64.cc",
     ]

tools/gcmole/PRESUBMIT.py

@@ -0,0 +1,32 @@
+# Copyright 2022 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+USE_PYTHON3 = True
+
+
+def _RunTests(input_api, output_api):
+  return input_api.RunTests(
+      input_api.canned_checks.GetUnitTestsInDirectory(
+          input_api,
+          output_api,
+          '.',
+          files_to_check=[r'.+_test\.py$'],
+          run_on_python2=False))
+
+
+def _CommonChecks(input_api, output_api):
+  """Checks common to both upload and commit."""
+  checks = [
+      _RunTests,
+  ]
+
+  return sum([check(input_api, output_api) for check in checks], [])
+
+
+def CheckChangeOnCommit(input_api, output_api):
+  return _CommonChecks(input_api, output_api)
+
+
+def CheckChangeOnUpload(input_api, output_api):
+  return _CommonChecks(input_api, output_api)

tools/gcmole/gcmole.py

@@ -222,58 +222,42 @@ def invoke_clang_plugin_for_each_file(filenames, plugin, plugin_args, options):
 # -----------------------------------------------------------------------------
 
 
-def parse_gn_file(options, for_test):
+def build_file_list(options, for_test):
+  """Calculates the list of source files to be checked with gcmole.
+
+  The list comprises all files from marked source sections in the
+  listed BUILD.gn files. All files preceeded by the following comment and
+  until the end of the source section are used:
+  ### gcmole(arch) ###
+  Where arch can either be all (all architectures) or one of the supported V8
+  architectures.
+
+  The structure of these directives is also checked by presubmit via:
+  tools/v8_presubmit.py::GCMoleProcessor.
+
+  Returns: List of file paths (of type Path).
+  """
   if for_test:
-    return {"all": [options.v8_root_dir / "tools/gcmole/gcmole-test.cc"]}
+    return [options.v8_root_dir / "tools/gcmole/gcmole-test.cc"]
-  result = {}
+  result = []
   gn_files = [
       ("BUILD.gn", re.compile('"([^"]*?\.cc)"'), ""),
       ("test/cctest/BUILD.gn", re.compile('"(test-[^"]*?\.cc)"'),
        Path("test/cctest/")),
   ]
-  for filename, pattern, prefix in gn_files:
+  gn_re = re.compile(f"### gcmole\((all|{options.v8_target_cpu})\) ###(.*?)\]",
+                     re.MULTILINE | re.DOTALL)
+  for filename, file_pattern, prefix in gn_files:
     path = options.v8_root_dir / filename
     with open(path) as gn_file:
       gn = gn_file.read()
-      for condition, sources in re.findall("### gcmole\((.*?)\) ###(.*?)\]", gn,
+      for _, sources in gn_re.findall(gn):
-                                           re.MULTILINE | re.DOTALL):
+        for file in file_pattern.findall(sources):
-        if condition not in result:
+          result.append(options.v8_root_dir / prefix / file)
-          result[condition] = []
-        for file in pattern.findall(sources):
-          result[condition].append(options.v8_root_dir / prefix / file)
 
   return result
 
 
-def evaluate_condition(cond, props):
-  if cond == "all":
-    return True
-
-  m = re.match("(\w+):(\w+)", cond)
-  if m is None:
-    fatal("failed to parse condition: {}", cond)
-  p, v = m.groups()
-  if p not in props:
-    fatal("undefined configuration property: {}", p)
-
-  return props[p] == v
-
-
-def build_file_list(options, for_test):
-  sources = parse_gn_file(options, for_test)
-  props = {
-      "os": "linux",
-      "arch": options.v8_target_cpu,
-      "mode": "debug",
-      "simulator": ""
-  }
-  ret = []
-  for condition, files in list(sources.items()):
-    if evaluate_condition(condition, props):
-      ret += files
-  return ret
-
-
 # -----------------------------------------------------------------------------
 # GCSuspects Generation
 

tools/gcmole/gcmole_test.py

@@ -0,0 +1,64 @@
+#!/usr/bin/env python3
+# Copyright 2022 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+from pathlib import Path
+
+import collections
+import os
+import unittest
+
+import gcmole
+
+TESTDATA_PATH = os.path.join(
+    os.path.dirname(os.path.abspath(__file__)), 'testdata', 'v8')
+
+Options = collections.namedtuple('Options', ['v8_root_dir', 'v8_target_cpu'])
+
+
+def abs_test_file(f):
+  return Path(os.path.join(TESTDATA_PATH, f))
+
+
+class FilesTest(unittest.TestCase):
+
+  def testFileList_for_testing(self):
+    options = Options(Path(TESTDATA_PATH), 'x64')
+    self.assertEqual(
+        gcmole.build_file_list(options, True),
+        list(map(abs_test_file, ['tools/gcmole/gcmole-test.cc'])))
+
+  def testFileList_x64(self):
+    options = Options(Path(TESTDATA_PATH), 'x64')
+    expected = [
+        'file1.cc',
+        'file2.cc',
+        'x64/file1.cc',
+        'x64/file2.cc',
+        'file3.cc',
+        'file4.cc',
+        'test/cctest/test-x64-file1.cc',
+        'test/cctest/test-x64-file2.cc',
+    ]
+    self.assertEqual(
+        gcmole.build_file_list(options, False),
+        list(map(abs_test_file, expected)))
+
+  def testFileList_arm(self):
+    options = Options(Path(TESTDATA_PATH), 'arm')
+    expected = [
+        'file1.cc',
+        'file2.cc',
+        'file3.cc',
+        'file4.cc',
+        'arm/file1.cc',
+        'arm/file2.cc',
+    ]
+    self.assertEqual(
+        gcmole.build_file_list(options, False),
+        list(map(abs_test_file, expected)))
+
+
+if __name__ == '__main__':
+  unittest.main()

tools/gcmole/testdata/v8/BUILD.gn

@@ -0,0 +1,35 @@
+# Copyright 2022 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Test data for gcmole.
+
+some_sources = [
+  ### gcmole(all) ###
+  "file1.cc",
+  "file1.h",
+  "file2.cc",
+]
+
+other_sources = [
+  ### gcmole(x64) ###
+  "x64/file1.cc",
+  "x64/file1.h",
+  "x64/file2.cc",
+]
+
+yet_more_sources = [
+  ### gcmole(all) ###
+  "file3.cc",
+
+  # Some other comment.
+  "file4.cc",
+  "file4.h",
+]
+
+the_last_sources = [
+  ### gcmole(arm) ###
+  "arm/file1.cc",
+  "arm/file1.h",
+  "arm/file2.cc",
+]

tools/gcmole/testdata/v8/test/cctest/BUILD.gn

@@ -0,0 +1,12 @@
+# Copyright 2022 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Test data for gcmole.
+
+some_sources = [
+  ### gcmole(x64) ###
+  "foo-x64-file1.cc",
+  "test-x64-file1.cc",
+  "test-x64-file2.cc",
+]

tools/v8_presubmit.py

@@ -719,6 +719,45 @@ class StatusFilesProcessor(SourceFileProcessor):
     return status_files
 
 
+class GCMoleProcessor(SourceFileProcessor):
+  """Check relevant BUILD.gn files for correct gcmole file pattern.
+
+  The pattern must match the algorithm used in:
+  tools/gcmole/gcmole.py::build_file_list()
+  """
+  gcmole_re = re.compile('### gcmole(.*)')
+  arch_re = re.compile('\((.+)\) ###')
+
+  def IsRelevant(self, name):
+    return True
+
+  def GetPathsToSearch(self):
+    # TODO(https://crbug.com/v8/12660): These should be directories according
+    # to the API, but in order to find the toplevel BUILD.gn, we'd need to walk
+    # the entire project.
+    return ['BUILD.gn', 'test/cctest/BUILD.gn']
+
+  def ProcessFiles(self, files):
+    success = True
+    for path in files:
+      with open(path) as f:
+        gn_file_text = f.read()
+      for suffix in self.gcmole_re.findall(gn_file_text):
+        arch_match = self.arch_re.match(suffix)
+        if not arch_match:
+          print(f'{path}: Malformed gcmole suffix: {suffix}')
+          success = False
+          continue
+        arch = arch_match.group(1)
+        if arch not in [
+            'all', 'ia32', 'x64', 'arm', 'arm64', 's390', 'ppc', 'ppc64',
+            'mips64', 'mips64el', 'riscv32', 'riscv64', 'loong64'
+        ]:
+          print(f'{path}: Unknown architecture for gcmole: {arch}')
+          success = False
+    return success
+
+
 def CheckDeps(workspace):
   checkdeps_py = join(workspace, 'buildtools', 'checkdeps', 'checkdeps.py')
   return subprocess.call([sys.executable, checkdeps_py, workspace]) == 0
@@ -792,6 +831,8 @@ def Main():
   success &= StatusFilesProcessor().RunOnPath(workspace)
   print("Running python tests...")
   success &= PyTests(workspace)
+  print("Running gcmole pattern check...")
+  success &= GCMoleProcessor().RunOnPath(workspace)
   if success:
     return 0
   else: