Enable -wmo with opt by default (bazelbuild#910)

This matches Xcode's behavior and has a huge impact on performance in some cases.
tymurmustafaiev · Sep 28, 2022 · a666936 · a666936
1 parent 1543999
commit a666936
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Showing 3 changed files with 39 additions and 1 deletion.
diff --git a/swift/internal/swift_toolchain.bzl b/swift/internal/swift_toolchain.bzl
@@ -31,6 +31,7 @@ load(
     ":feature_names.bzl",
     "SWIFT_FEATURE_MODULE_MAP_HOME_IS_CWD",
     "SWIFT_FEATURE_NO_GENERATED_MODULE_MAP",
+    "SWIFT_FEATURE_OPT_USES_WMO",
     "SWIFT_FEATURE_USE_AUTOLINK_EXTRACT",
     "SWIFT_FEATURE_USE_MODULE_WRAP",
     "SWIFT_FEATURE_USE_RESPONSE_FILES",
@@ -281,7 +282,11 @@ def _swift_toolchain_impl(ctx):
         features_for_build_modes(ctx) +
         features_from_swiftcopts(swiftcopts = ctx.fragments.swift.copts())
     )
-    requested_features.append(SWIFT_FEATURE_NO_GENERATED_MODULE_MAP)
+    requested_features.extend([
+        SWIFT_FEATURE_NO_GENERATED_MODULE_MAP,
+        SWIFT_FEATURE_OPT_USES_WMO,
+    ])
+
     requested_features.extend(ctx.features)
 
     # Swift.org toolchains assume everything is just available on the PATH so we

diff --git a/swift/internal/xcode_swift_toolchain.bzl b/swift/internal/xcode_swift_toolchain.bzl
@@ -38,6 +38,7 @@ load(
     "SWIFT_FEATURE_ENABLE_SKIP_FUNCTION_BODIES",
     "SWIFT_FEATURE_FILE_PREFIX_MAP",
     "SWIFT_FEATURE_MODULE_MAP_HOME_IS_CWD",
+    "SWIFT_FEATURE_OPT_USES_WMO",
     "SWIFT_FEATURE_REMAP_XCODE_PATH",
     "SWIFT_FEATURE_SUPPORTS_BARE_SLASH_REGEX",
     "SWIFT_FEATURE_SUPPORTS_LIBRARY_EVOLUTION",
@@ -608,6 +609,7 @@ def _xcode_swift_toolchain_impl(ctx):
         SWIFT_FEATURE_ENABLE_BATCH_MODE,
         SWIFT_FEATURE_USE_RESPONSE_FILES,
         SWIFT_FEATURE_DEBUG_PREFIX_MAP,
+        SWIFT_FEATURE_OPT_USES_WMO,
         SWIFT_FEATURE_SUPPORTS_LIBRARY_EVOLUTION,
         SWIFT_FEATURE_SUPPORTS_PRIVATE_DEPS,
     ])

diff --git a/test/features_tests.bzl b/test/features_tests.bzl
@@ -6,6 +6,20 @@ load(
 )
 
 default_test = make_action_command_line_test_rule()
+default_opt_test = make_action_command_line_test_rule(
+    config_settings = {
+        "//command_line_option:compilation_mode": "opt",
+    },
+)
+
+opt_no_wmo_test = make_action_command_line_test_rule(
+    config_settings = {
+        "//command_line_option:compilation_mode": "opt",
+        "//command_line_option:features": [
+            "-swift.opt_uses_wmo",
+        ],
+    },
+)
 
 file_prefix_map_test = make_action_command_line_test_rule(
     config_settings = {
@@ -64,3 +78,20 @@ def features_test_suite(name):
         mnemonic = "SwiftCompile",
         target_under_test = "@build_bazel_rules_swift//test/fixtures/debug_settings:simple",
     )
+
+    default_opt_test(
+        name = "{}_default_opt_test".format(name),
+        tags = [name],
+        expected_argv = ["-emit-object", "-O", "-whole-module-optimization"],
+        mnemonic = "SwiftCompile",
+        target_under_test = "@build_bazel_rules_swift//test/fixtures/debug_settings:simple",
+    )
+
+    opt_no_wmo_test(
+        name = "{}_opt_no_wmo_test".format(name),
+        tags = [name],
+        expected_argv = ["-emit-object", "-O"],
+        not_expected_argv = ["-whole-module-optimization"],
+        mnemonic = "SwiftCompile",
+        target_under_test = "@build_bazel_rules_swift//test/fixtures/debug_settings:simple",
+    )