Enable swift.cacheable_swiftmodules by default (#957)

bazelbuild · Dec 21, 2022 · cb64a41 · cb64a41
1 parent c7ed06e
commit cb64a41
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Showing 5 changed files with 18 additions and 12 deletions.
diff --git a/README.md b/README.md
@@ -72,10 +72,10 @@ bazel run @build_bazel_rules_swift//tools/dump_toolchains
 **Linux hosts:** At this time, Bazel uses whichever `swift` executable is
 encountered first on your `PATH`.
 
-## Supporting remote builds
+## Supporting debugging
 
-To make remote builds work correctly with debugging and general
-reproducibility see [this doc](doc/debuggable_remote_swift.md)
+To make cacheable builds work correctly with debugging see
+[this doc](doc/debuggable_remote_swift.md).
 
 ## Swift Package Manager Support
 

diff --git a/doc/debuggable_remote_swift.md b/doc/debuggable_remote_swift.md
@@ -1,6 +1,6 @@
-# Debuggable Remotely Built Swift
+# Debugging Cacheable Swift Modules
 
-This is a guide to using remotely built Swift modules in local debug builds.
+This is a guide to enable debugging of cacheable Swift modules in local debug builds.
 
 At the time of writing, `lldb` depends on debugging options embedded in `.swiftmodule` files. These options include paths that are only valid on the build host. For local builds, this all just works, but for remote builds, it doesn't.
 
@@ -13,15 +13,13 @@ Globally disabling debugging options makes those `.swiftmodule`s usable on any m
 
 An lldb bug has been filed here: https://bugs.swift.org/browse/SR-11485
 
-### Disable Debugging Options Globally
-
-To globally disable debugging options, use the `swift.cacheable_swiftmodules` feature in rules_swift. For example, your `.bazelrc` could look like this:
+> **Note**
+>
+> If you don't care about cache misses, instead of following this guide you can instead disable the `swift.cacheable_swiftmodules` feature: `--features=-swift.cacheable_swiftmodules`. This is not recommended though if you use a remote cache.
 
-```
-build --features=swift.cacheable_swiftmodules
-```
+### Disable Debugging Options Globally
 
-What this does is ensure all modules are built explicitly with `-no-serialize-debugging-options`. It has to be explicit because `swiftc` enables `-serialize-debugging-options` in some cases.
+To globally disable debugging options, use the `swift.cacheable_swiftmodules` feature, which is enabled by default, in rules_swift. What this does is ensure all modules are built explicitly with `-no-serialize-debugging-options`. It has to be explicit because `swiftc` enables `-serialize-debugging-options` in some cases.
 
 ### Add Debug Build Config
 

diff --git a/swift/internal/swift_toolchain.bzl b/swift/internal/swift_toolchain.bzl
@@ -29,6 +29,7 @@ load(":compiling.bzl", "compile_action_configs", "features_from_swiftcopts")
 load(":debugging.bzl", "modulewrap_action_configs")
 load(
     ":feature_names.bzl",
+    "SWIFT_FEATURE_CACHEABLE_SWIFTMODULES",
     "SWIFT_FEATURE_MODULE_MAP_HOME_IS_CWD",
     "SWIFT_FEATURE_NO_GENERATED_MODULE_MAP",
     "SWIFT_FEATURE_OPT_USES_WMO",
@@ -284,6 +285,7 @@ def _swift_toolchain_impl(ctx):
         features_from_swiftcopts(swiftcopts = ctx.fragments.swift.copts())
     )
     requested_features.extend([
+        SWIFT_FEATURE_CACHEABLE_SWIFTMODULES,
         SWIFT_FEATURE_NO_GENERATED_MODULE_MAP,
         SWIFT_FEATURE_OPT_USES_WMO,
         SWIFT_FEATURE_USE_GLOBAL_MODULE_CACHE,

diff --git a/swift/internal/xcode_swift_toolchain.bzl b/swift/internal/xcode_swift_toolchain.bzl
@@ -31,6 +31,7 @@ load(
     "SWIFT_FEATURE_BITCODE_EMBEDDED",
     "SWIFT_FEATURE_BITCODE_EMBEDDED_MARKERS",
     "SWIFT_FEATURE_BUNDLED_XCTESTS",
+    "SWIFT_FEATURE_CACHEABLE_SWIFTMODULES",
     "SWIFT_FEATURE_COVERAGE",
     "SWIFT_FEATURE_COVERAGE_PREFIX_MAP",
     "SWIFT_FEATURE_DEBUG_PREFIX_MAP",
@@ -607,6 +608,7 @@ def _xcode_swift_toolchain_impl(ctx):
     )
     requested_features.extend([
         SWIFT_FEATURE_BUNDLED_XCTESTS,
+        SWIFT_FEATURE_CACHEABLE_SWIFTMODULES,
         SWIFT_FEATURE_ENABLE_BATCH_MODE,
         SWIFT_FEATURE_DEBUG_PREFIX_MAP,
         SWIFT_FEATURE_OPT_USES_WMO,

diff --git a/test/debug_settings_tests.bzl b/test/debug_settings_tests.bzl
@@ -22,6 +22,7 @@ load(
 DBG_CONFIG_SETTINGS = {
     "//command_line_option:compilation_mode": "dbg",
     "//command_line_option:features": [
+        "-swift.cacheable_swiftmodules",
         "swift.debug_prefix_map",
     ],
 }
@@ -37,13 +38,15 @@ CACHEABLE_DBG_CONFIG_SETTINGS = {
 FASTBUILD_CONFIG_SETTINGS = {
     "//command_line_option:compilation_mode": "fastbuild",
     "//command_line_option:features": [
+        "-swift.cacheable_swiftmodules",
         "swift.debug_prefix_map",
     ],
 }
 
 FASTBUILD_FULL_DI_CONFIG_SETTINGS = {
     "//command_line_option:compilation_mode": "fastbuild",
     "//command_line_option:features": [
+        "-swift.cacheable_swiftmodules",
         "swift.debug_prefix_map",
         "swift.full_debug_info",
     ],
@@ -52,6 +55,7 @@ FASTBUILD_FULL_DI_CONFIG_SETTINGS = {
 OPT_CONFIG_SETTINGS = {
     "//command_line_option:compilation_mode": "opt",
     "//command_line_option:features": [
+        "-swift.cacheable_swiftmodules",
         # This feature indicates *support*, not unconditional enablement, which
         # is why it is present for `opt` mode as well.
         "swift.debug_prefix_map",