[infra] Add coverage builder configurations

Bug: chromium:1265931
Change-Id: Ic051ff5e86c8abbc269009a281c5a135bc405c36
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3779684
Reviewed-by: Alexander Schulze <alexschulze@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/main@{#84200}

DEPS

@@ -30,8 +30,15 @@ vars = {
 
   'checkout_instrumented_libraries': False,
   'checkout_ittapi': False,
+
+  # Fetch the prebuilt binaries for llvm-cov and llvm-profdata. Needed to
+  # process the raw profiles produced by instrumented targets (built with
+  # the gn arg 'use_clang_coverage').
+  'checkout_clang_coverage_tools': False,
+
   # Fetch clang-tidy into the same bin/ directory as our clang binary.
   'checkout_clang_tidy': False,
+
   'chromium_url': 'https://chromium.googlesource.com',
   'android_url': 'https://android.googlesource.com',
   'download_gcmole': False,
@@ -557,6 +564,14 @@ hooks = [
     'condition': 'host_os != "aix"',
     'action': ['python3', 'tools/clang/scripts/update.py'],
   },
+  {
+    # This is supposed to support the same set of platforms as 'clang' above.
+    'name': 'clang_coverage',
+    'pattern': '.',
+    'condition': 'checkout_clang_coverage_tools',
+    'action': ['python3', 'tools/clang/scripts/update.py',
+               '--package=coverage_tools'],
+  },
   {
     'name': 'clang_tidy',
     'pattern': '.',

infra/mb/mb_config.pyl

@@ -111,6 +111,7 @@
       'V8 Linux64 - arm64 - sim - heap sandbox - debug - builder': 'debug_x64_heap_sandbox_arm64_sim',
       'V8 Linux64 - arm64 - sim - no pointer compression - builder':
           'release_simulate_arm64_no_pointer_compression',
+      'V8 Linux64 - coverage': 'release_x64_coverage',
       'V8 Linux64 - cppgc-non-default - debug - builder': 'debug_x64_non_default_cppgc',
       'V8 Linux64 - debug - perfetto - builder': 'debug_x64_perfetto',
       'V8 Linux64 - disable runtime call stats - builder': 'release_x64_disable_runtime_call_stats',
@@ -225,6 +226,7 @@
           'release_simulate_arm64_no_pointer_compression',
       'v8_linux64_cppgc_non_default_compile_dbg': 'debug_x64_non_default_cppgc',
       'v8_linux64_compile_dbg': 'debug_x64_trybot',
+      'v8_linux64_coverage': 'release_x64_coverage',
       'v8_linux64_no_sandbox_compile_dbg': 'debug_x64_no_sandbox',
       'v8_linux64_dict_tracking_compile_dbg': 'debug_x64_dict_tracking_trybot',
       'v8_linux64_disable_runtime_call_stats_compile_rel': 'release_x64_disable_runtime_call_stats',
@@ -499,6 +501,8 @@
       'release_bot', 'x64', 'cfi'],
     'release_x64_cfi_clusterfuzz': [
       'release_bot', 'x64', 'cfi_clusterfuzz'],
+    'release_x64_coverage': [
+      'release_bot', 'x64', 'clang_coverage'],
     'release_x64_fuzzilli': [
       'release_bot', 'x64', 'dcheck_always_on', 'v8_enable_slow_dchecks',
       'v8_verify_heap', 'v8_verify_csa', 'fuzzilli'],
@@ -699,6 +703,10 @@
       'gn_args': 'is_clang=true',
     },
 
+    'clang_coverage': {
+      'gn_args': 'use_clang_coverage=true',
+    },
+
     'conservative_stack_scanning': {
       'gn_args': 'v8_enable_conservative_stack_scanning=true '
                  'v8_enable_inner_pointer_resolution_mb=true',

infra/testing/builders.pyl

@@ -352,6 +352,18 @@
       {'name': 'v8testing', 'shards': 3},
     ],
   },
+  'v8_linux64_coverage': {
+    'swarming_dimensions' : {
+      'os': 'Ubuntu-18.04',
+    },
+    'tests': [
+      # TODO(https://crbug.com/1265931): Speed things up for now. Later replace
+      # mjsunit and unittests with full v8testing.
+      # {'name': 'v8testing'},
+      {'name': 'mjsunit', 'variant': 'default'},
+      {'name': 'unittests', 'variant': 'default'},
+    ],
+  },
   'v8_linux64_cppgc_non_default_dbg': {
     'swarming_dimensions' : {
       'cpu': 'x86-64-avx2',
@@ -1304,6 +1316,18 @@
       {'name': 'v8testing', 'shards': 2},
     ],
   },
+  'V8 Linux64 - coverage': {
+    'swarming_dimensions' : {
+      'os': 'Ubuntu-18.04',
+    },
+    'tests': [
+      # TODO(https://crbug.com/1265931): Speed things up for now. Later replace
+      # mjsunit and unittests with full v8testing.
+      # {'name': 'v8testing'},
+      {'name': 'mjsunit', 'variant': 'default'},
+      {'name': 'unittests', 'variant': 'default'},
+    ],
+  },
   'V8 Linux64 - custom snapshot - debug': {
     'swarming_dimensions' : {
       'os': 'Ubuntu-18.04',