[bazel] Fix build with GCC and older versions of Clang.

Clang 12 doesn't support -Wno-bitwise-instead-of-logical,
so silence it with -Wno-unknown-warning-option.

GCC requires using GNU dialect of the C++ standard, using
optimizations (otherwise "always_inline" fails to inline),
and produces a lot of warnings that had to be silenced.

Signed-off-by: Piotr Sikora <piotrsikora@google.com>
Change-Id: I9ddd4f39dca2167b5b208dc2d0ba8e60030eddfc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3333635
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78499}

.bazelrc

@@ -2,12 +2,16 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-# V8 bazel port only supports clang
-build --action_env=BAZEL_COMPILER=clang
-build --action_env=CC=clang
-build --action_env=CXX=clang++
+# Pass CC, CXX and PATH from the environment
+build --action_env=CC
+build --action_env=CXX
 build --action_env=PATH
 
+# Use Clang compiler
+build:clang --action_env=BAZEL_COMPILER=clang
+build:clang --action_env=CC=clang
+build:clang --action_env=CXX=clang++
+
 # V8 debug config
 build:debug --compilation_mode=dbg
 build:debug --config=v8_enable_debugging_features

BUILD.bazel

@@ -18,13 +18,6 @@ load(
 )
 load(":bazel/v8-non-pointer-compression.bzl", "v8_binary_non_pointer_compression")
 
-config_setting(
-    name = "is_debug",
-    values = {
-        "compilation_mode": "dbg",
-    },
-)
-
 # =================================================
 # Flags
 # =================================================
@@ -290,7 +283,7 @@ v8_config(
         "V8_ADVANCED_BIGINT_ALGORITHMS",
         "V8_CONCURRENT_MARKING",
     ] + select({
-        ":is_debug": [
+        "@v8//bazel/config:is_debug": [
             "DEBUG",
             "V8_ENABLE_CHECKS",
         ],

bazel/config/BUILD.bazel

@@ -15,6 +15,20 @@ package(
     ],
 )
 
+config_setting(
+    name = "is_fastbuild",
+    values = {
+        "compilation_mode": "fastbuild",
+    },
+)
+
+config_setting(
+    name = "is_debug",
+    values = {
+        "compilation_mode": "dbg",
+    },
+)
+
 config_setting(
     name = "platform_cpu_x64",
     constraint_values = ["@platforms//cpu:x86_64"],
@@ -172,3 +186,64 @@ selects.config_setting_group(
     name = "is_msvc_asm_arm64",
     match_all = [":is_windows", ":is_arm64"],
 )
+
+config_setting(
+    name = "is_compiler_default",
+    flag_values = {
+        "@bazel_tools//tools/cpp:compiler": "compiler",
+    },
+)
+
+selects.config_setting_group(
+    name = "is_compiler_default_on_linux",
+    match_all = [
+        ":is_compiler_default",
+        ":is_linux",
+    ],
+)
+
+selects.config_setting_group(
+    name = "is_compiler_default_on_macos",
+    match_all = [
+        ":is_compiler_default",
+        ":is_macos",
+    ],
+)
+
+config_setting(
+    name = "is_compiler_clang",
+    flag_values = {
+        "@bazel_tools//tools/cpp:compiler": "clang",
+    },
+)
+
+selects.config_setting_group(
+    name = "is_clang",
+    match_any = [
+        ":is_compiler_default_on_macos",
+        ":is_compiler_clang",
+    ],
+)
+
+config_setting(
+    name = "is_compiler_gcc",
+    flag_values = {
+        "@bazel_tools//tools/cpp:compiler": "gcc",
+    },
+)
+
+selects.config_setting_group(
+    name = "is_gcc",
+    match_any = [
+        ":is_compiler_default_on_linux",
+        ":is_compiler_gcc",
+    ],
+)
+
+selects.config_setting_group(
+    name = "is_gcc_fastbuild",
+    match_all = [
+        ":is_gcc",
+        ":is_fastbuild",
+    ],
+)

bazel/defs.bzl

@@ -100,18 +100,48 @@ def _default_args():
         copts = select({
             "@v8//bazel/config:is_posix": [
                 "-fPIC",
+                "-fno-strict-aliasing",
                 "-Werror",
                 "-Wextra",
+                "-Wno-unknown-warning-option",
                 "-Wno-bitwise-instead-of-logical",
                 "-Wno-builtin-assume-aligned-alignment",
                 "-Wno-unused-parameter",
                 "-Wno-implicit-int-float-conversion",
                 "-Wno-deprecated-copy",
                 "-Wno-non-virtual-dtor",
-                "-std=c++17",
                 "-isystem .",
             ],
             "//conditions:default": [],
+        }) + select({
+            "@v8//bazel/config:is_clang": [
+                "-Wno-invalid-offsetof",
+                "-std=c++17",
+            ],
+            "@v8//bazel/config:is_gcc": [
+                "-Wno-extra",
+                "-Wno-comments",
+                "-Wno-deprecated-declarations",
+                "-Wno-implicit-fallthrough",
+                "-Wno-maybe-uninitialized",
+                "-Wno-mismatched-new-delete",
+                "-Wno-redundant-move",
+                "-Wno-return-type",
+                # Use GNU dialect, because GCC doesn't allow using
+                # ##__VA_ARGS__ when in standards-conforming mode.
+                "-std=gnu++17",
+            ],
+            "@v8//bazel/config:is_windows": [
+                "/std:c++17",
+            ],
+            "//conditions:default": [],
+        }) + select({
+            "@v8//bazel/config:is_gcc_fastbuild": [
+                # Non-debug builds without optimizations fail because
+                # of recursive inlining of "always_inline" functions.
+                "-O1",
+            ],
+            "//conditions:default": [],
         }),
         includes = ["include"],
         linkopts = select({