iOS: Use pre-built hermesc if available (#33827)

Summary:
Use pre-built hermesc if available by generating a ImportHermesc.cmake file that points to the hermesc binary. Recent `react-native` releases should have hermesc available in sdks/hermesc.

Hermes build scripts have been updated to support a `HERMES_OVERRIDE_HERMESC_PATH` envvar which can point to this generated ImportHermesc.cmake file.

Pull Request resolved: #33827

Changelog:
[iOS] [Changed] - Use pre-built HermesC if available in current React Native release

Reviewed By: cortinico

Differential Revision: D36024615

fbshipit-source-id: 476569f73309f9bd142f28cb02d1f7d57b6cbc6a

.gitignore

@@ -115,8 +115,9 @@ package-lock.json
 /packages/rn-tester/NativeModuleExample/ScreenshotManagerSpec*
 
 # Additional SDKs
-/sdks/hermes
 /sdks/download
+/sdks/hermes
+/sdks/hermesc
 
 # Visual studio
 .vscode

scripts/hermes/hermes-utils.js

@@ -18,6 +18,12 @@ const HERMES_DIR = path.join(SDKS_DIR, 'hermes');
 const HERMES_TAG_FILE_PATH = path.join(SDKS_DIR, '.hermesversion');
 const HERMES_TARBALL_BASE_URL = 'https://github.com/facebook/hermes/tarball/';
 const HERMES_TARBALL_DOWNLOAD_DIR = path.join(SDKS_DIR, 'download');
+const MACOS_BIN_DIR = path.join(SDKS_DIR, 'hermesc', 'osx-bin');
+const MACOS_HERMESC_PATH = path.join(MACOS_BIN_DIR, 'hermesc');
+const MACOS_IMPORT_HERMESC_PATH = path.join(
+  MACOS_BIN_DIR,
+  'ImportHermesc.cmake',
+);
 
 function prepareFileSystem() {
   if (!fs.existsSync(SDKS_DIR)) {
@@ -143,11 +149,31 @@ function copyBuildScripts() {
   );
 }
 
+function shouldUsePrebuiltHermesC(os) {
+  if (os === 'macos') {
+    return fs.existsSync(MACOS_HERMESC_PATH);
+  }
+
+  return false;
+}
+
+function configureMakeForPrebuiltHermesC() {
+  const IMPORT_HERMESC_TEMPLATE = `add_executable(native-hermesc IMPORTED)
+set_target_properties(native-hermesc PROPERTIES
+  IMPORTED_LOCATION "${MACOS_HERMESC_PATH}"
+  )`;
+
+  fs.mkdirSync(MACOS_BIN_DIR, {recursive: true});
+  fs.writeFileSync(MACOS_IMPORT_HERMESC_PATH, IMPORT_HERMESC_TEMPLATE);
+}
+
 module.exports = {
+  configureMakeForPrebuiltHermesC,
   copyBuildScripts,
   downloadHermesTarball,
   expandHermesTarball,
   getHermesTagSHA,
   readHermesTag,
   setHermesTag,
+  shouldUsePrebuiltHermesC,
 };

scripts/hermes/prepare-hermes-for-build.js

@@ -14,11 +14,18 @@
  * iOS build pipeline on macOS.
  */
 const {
+  configureMakeForPrebuiltHermesC,
   copyBuildScripts,
   downloadHermesTarball,
   expandHermesTarball,
+  shouldUsePrebuiltHermesC,
 } = require('./hermes-utils');
 
 downloadHermesTarball();
 expandHermesTarball();
 copyBuildScripts();
+
+if (shouldUsePrebuiltHermesC('macos')) {
+  console.log('[Hermes] Using pre-built HermesC');
+  configureMakeForPrebuiltHermesC();
+}

sdks/hermes-engine/hermes-engine.podspec

@@ -18,6 +18,8 @@ end
 
 Pod::UI.puts '[Hermes] Hermes needs to be compiled, installing hermes-engine may take a while...'.yellow if Object.const_defined?("Pod::UI")
 
+import_hermesc_path=File.join(__dir__, "../hermesc/osx-bin/ImportHermesc.cmake")
+
 Pod::Spec.new do |spec|
   spec.name        = "hermes-engine"
   spec.version     = "1000.0.0-#{hermes_tag_sha.slice(0,6)}"
@@ -43,6 +45,10 @@ Pod::Spec.new do |spec|
     # See `build-apple-framework.sh` for details
     DEBUG=#{HermesHelper::BUILD_TYPE == :debug}
 
+    # Set HERMES_OVERRIDE_HERMESC_PATH if pre-built HermesC is available
+    #{File.exist?(import_hermesc_path) ? "export HERMES_OVERRIDE_HERMESC_PATH=#{import_hermesc_path}" : ""}
+    #{File.exist?(import_hermesc_path) ? "echo \"Overriding HermesC path...\"" : ""}
+
     # Build iOS framework
     ./utils/build-ios-framework.sh
 

sdks/hermes-engine/utils/build-apple-framework.sh

@@ -11,6 +11,7 @@ else
 fi
 
 NUM_CORES=$(sysctl -n hw.ncpu)
+IMPORT_HERMESC_PATH=${HERMES_OVERRIDE_HERMESC_PATH:-$PWD/build_host_hermesc/ImportHermesc.cmake}
 
 function get_release_version {
   ruby -rcocoapods-core -rjson -e "puts Pod::Specification.from_file('hermes-engine.podspec').version"
@@ -57,7 +58,7 @@ function configure_apple_framework {
     -DHERMES_BUILD_APPLE_FRAMEWORK:BOOLEAN=true \
     -DHERMES_BUILD_APPLE_DSYM:BOOLEAN=true \
     -DHERMES_ENABLE_TOOLS:BOOLEAN="$build_cli_tools" \
-    -DIMPORT_HERMESC:PATH="$PWD/build_host_hermesc/ImportHermesc.cmake" \
+    -DIMPORT_HERMESC:PATH="$IMPORT_HERMESC_PATH" \
     -DCMAKE_INSTALL_PREFIX:PATH=../destroot \
     -DCMAKE_BUILD_TYPE="$BUILD_TYPE"
 }
@@ -66,8 +67,12 @@ function configure_apple_framework {
 function build_apple_framework {
   echo "Building framework for $1 with architectures: $2"
 
+  # Only build host HermesC if no file found at $IMPORT_HERMESC_PATH
+  [ ! -f "$IMPORT_HERMESC_PATH" ] &&
   build_host_hermesc
-  [ ! -f "$PWD/build_host_hermesc/ImportHermesc.cmake" ] &&
+
+  # Confirm ImportHermesc.cmake is now available.
+  [ ! -f "$IMPORT_HERMESC_PATH" ] &&
   echo "Host hermesc is required to build apple frameworks!"
 
   configure_apple_framework "$1" "$2" "$3"