Steven Wu 72c8c21104 [build-script] Add --enable-caching support with clang-cache and Swift compilation caching ...

Add a new --enable-caching option that enables compilation caching for both
C/C++ (via clang-cache as compiler launcher) and Swift code (via
-cache-compile-job flags when bootstrapping=hosttools).

New options:
- --enable-caching: main toggle, incompatible with --sccache/--distcc
- --caching-cas-path: CAS directory (default: $BUILD_ROOT/cas)
- --caching-depscan-socket: depscan daemon socket path
- --caching-plugin-path: CAS plugin library path
- --caching-plugin-option: CAS plugin options (repeatable)
- --caching-prefix-map: enable source/SDK/toolchain prefix mapping
- --caching-remote-service-path: remote caching service with auto
  plugin inference from Xcode and implied prefix mapping

The build script starts a clang-cache depscan daemon with reliable cleanup
via atexit and SIGTERM handlers. Per-product build directories get .cas-config
and compilation-prefix-map.json files written automatically.

Caching flags are applied to all Swift host compilation targets: compiler
sources, pure-swift host libraries (ASTGen, macros), swift-syntax, and
the new runtime build when --build-runtime-with-host-compiler is used.

When not using --caching-remote-service-path, enables CAS backend
(-Xfrontend -cas-backend -Xllvm -cas-friendly-debug-info) unless
SWIFT_CACHE_DISABLE_MCCAS is set.

A ninja wrapper is generated at build/<subdir>/build-utils/ninja for
cached incremental builds outside the build-script.

rdar://155876033

Assisted-By: Claude

2026-04-29 14:42:17 -07:00

..

CMakeLists.txt

[build-script] Add --enable-caching support with clang-cache and Swift compilation caching

2026-04-29 14:42:17 -07:00