Changeset 290975 in webkit for trunk/Source/JavaScriptCore/offlineasm/asm.rb

Timestamp:

Mar 7, 2022, 11:18:39 PM (3 years ago)

Author:

Elliott Williams

Message:

[XCBuild] Emit a discovered dependency file from offlineasm
​https://bugs.webkit.org/show_bug.cgi?id=237329

Reviewed by Keith Miller.

Xcode needs to know what files offlineasm uses and produces in order to schedule it
correctly in incremental builds. Rather than use generated xcfilelists like WebKit does
elsewhere in the project, emit a depfile from offlineasm based on the parse tree's source
files.

Discovered dependency files ("depfiles") are Makefile-formatted files which list the inputs
used to produce an output. They are emitting during the build to a temporary directory, and
ensure that subsequent incremental builds will re-run offlineasm when any of the included
sources change. This is the same mechanism clang uses to track header dependencies.

Unfortunately, the legacy build system will refuse to execute a script phase or rule that
emits a depfile. To work around this, convert the offlineasm pipeline to be based on build
rules, to be used by XCBuild only. The idea is that LowLevelInterpreter.asm is listed as a
source build file in JSCLLIntSettingsExtractor, JSCLLIntOffsetsExtractor, and
JavaScriptCore. Each target uses a build rule to generate its respective header from
LowLevelInterpreter.asm. Xcode schedules these rule executions before any clang tasks.

The legacy build system avoids executing the rules via EXCLUDED_SOURCE_FILE_NAMES, and
instead uses the existing build phases, which have "(Legacy)" in their names and are now
no-ops under XCBuild.

Aside from working around the legacy build system's limitations, using build rules is
probably a superior way to express what we're doing, as it gives Xcode the opportunity to
compile other objects in parallel, and could be easily extended to compile multiple discrete
asm files should the need arise.

• Configurations/ToolExecutable.xcconfig: Build rules are XCBuild-only.
• JavaScriptCore.xcodeproj/project.pbxproj: Add build rules, rename legacy scripts.
• offlineasm/asm.rb: Add --depfile flag.
• offlineasm/generate_offset_extractor.rb: Add --depfile flag.
• offlineasm/generate_settings_extractor.rb: Add --depfile flag.

File:

• trunk/Source/JavaScriptCore/offlineasm/asm.rb (modified) (5 diffs)

trunk/Source/JavaScriptCore/offlineasm/asm.rb

@@ -34 +34 @@
 require "self_hash"
 require "settings"
+require "shellwords"
 require "transform"
 
@@ -348 +349 @@
 $options = {}
 OptionParser.new do |opts|
-    opts.banner = "Usage: asm.rb asmFile offsetsFile outputFileName [--assembler=<ASM>] [--webkit-additions-path=<path>] [--binary-format=<format>]"
+    opts.banner = "Usage: asm.rb asmFile offsetsFile outputFileName [--assembler=<ASM>] [--webkit-additions-path=<path>] [--binary-format=<format>] [--depfile=<depfile>]"
     # This option is currently only used to specify the masm assembler
     opts.on("--assembler=[ASM]", "Specify an assembler to use.") do |assembler|
@@ -358 +359 @@
     opts.on("--binary-format=FORMAT", "Specify the binary format used by the target system.") do |format|
         $options[:binary_format] = format
+    end
+    opts.on("--depfile=DEPFILE", "Path to write Makefile-style discovered dependencies to.") do |path|
+        $options[:depfile] = path
     end
 end.parse!
@@ -385 +389 @@
     " " + Digest::SHA1.hexdigest($options.has_key?(:assembler) ? $options[:assembler] : "")
 
-if FileTest.exist? outputFlnm
+if FileTest.exist?(outputFlnm) and (not $options[:depfile] or FileTest.exist?($options[:depfile]))
     lastLine = nil
     File.open(outputFlnm, "r") {
@@ -408 +412 @@
 
     $asm = Assembler.new($output)
-    
-    ast = parse(asmFile, $options)
+
+    sources = Set.new
+    ast = parse(asmFile, $options, sources)
     settingsCombinations = computeSettingsCombinations(ast)
+    
+    if $options[:depfile]
+        depfile = File.open($options[:depfile], "w")
+        depfile.print(Shellwords.escape(outputFlnm), ": ")
+        depfile.puts(Shellwords.join(sources.sort))
+    end
 
     configurationList.each {