Changeset 254152 in webkit

Timestamp:

Jan 7, 2020, 1:13:23 PM (7 years ago)

Author:

ysuzuki@apple.com

Message:

[JSC] Remove vm accessor in JSVirtualMachine to reduce binary size
​https://bugs.webkit.org/show_bug.cgi?id=205880

Reviewed by Mark Lam.

Objective-C has reflection mechanism. This means that fields, methods, and their types
need to hold its string representations in binary even if we are using release build.
While typical Objective-C class does not have large size of type names, C++ struct / class
has very large one, and putting them in Objective-C method names, parameter types, or fields
makes binary size very large.

By analyzing JavaScriptCore binary, I found that Objective-C method type symbols are taking 200~KB
binary size. (Section objc_methtype: 235081 (addr 0x105e9a3 offset 17164707)). And it is due to
JSC::VM type included in [JSVirtualMachine vm] accessor.

This patch removes this accessor and gets 200KB binary size reduction.

• API/JSScript.mm:

(-[JSScript readCache]):
(-[JSScript sourceCode]):
(-[JSScript jsSourceCode]):
(-[JSScript writeCache:]):

• API/JSVirtualMachine.mm:

(-[JSVirtualMachine JSContextGroupRef]):
(-[JSVirtualMachine isWebThreadAware]):
(-[JSVirtualMachine vm]): Deleted.

• API/JSVirtualMachineInternal.h:

Location:

trunk/Source/JavaScriptCore

Files:

• API/JSScript.mm (modified) (4 diffs)
• API/JSVirtualMachine.mm (modified) (1 diff)
• API/JSVirtualMachineInternal.h (modified) (1 diff)
• ChangeLog (modified) (1 diff)

trunk/Source/JavaScriptCore/API/JSScript.mm

@@ -168 +168 @@
     Ref<JSC::CachedBytecode> cachedBytecode = JSC::CachedBytecode::create(WTFMove(mappedFile));
 
-    JSC::VM& vm = [m_virtualMachine vm];
+    JSC::VM& vm = *toJS([m_virtualMachine JSContextGroupRef]);
     JSC::SourceCode sourceCode = [self sourceCode];
     JSC::SourceCodeKey key = m_type == kJSScriptTypeProgram ? sourceCodeKeyForSerializedProgram(vm, sourceCode) : sourceCodeKeyForSerializedModule(vm, sourceCode);
@@ -236 +236 @@
 - (JSC::SourceCode)sourceCode
 {
-    JSC::VM& vm = [m_virtualMachine vm];
+    JSC::VM& vm = *toJS([m_virtualMachine JSContextGroupRef]);
     JSC::JSLockHolder locker(vm);
 
@@ -249 +249 @@
 - (JSC::JSSourceCode*)jsSourceCode
 {
-    JSC::VM& vm = [m_virtualMachine vm];
+    JSC::VM& vm = *toJS([m_virtualMachine JSContextGroupRef]);
     JSC::JSLockHolder locker(vm);
     JSC::JSSourceCode* jsSourceCode = JSC::JSSourceCode::create(vm, [self sourceCode]);
@@ -278 +278 @@
     JSC::BytecodeCacheError cacheError;
     JSC::SourceCode sourceCode = [self sourceCode];
+    JSC::VM& vm = *toJS([m_virtualMachine JSContextGroupRef]);
     switch (m_type) {
     case kJSScriptTypeModule:
-        m_cachedBytecode = JSC::generateModuleBytecode([m_virtualMachine vm], sourceCode, fd, cacheError);
+        m_cachedBytecode = JSC::generateModuleBytecode(vm, sourceCode, fd, cacheError);
         break;
     case kJSScriptTypeProgram:
-        m_cachedBytecode = JSC::generateProgramBytecode([m_virtualMachine vm], sourceCode, fd, cacheError);
+        m_cachedBytecode = JSC::generateProgramBytecode(vm, sourceCode, fd, cacheError);
         break;
     }

trunk/Source/JavaScriptCore/API/JSVirtualMachine.mm

@@ -299 +299 @@
 #endif // ENABLE(DFG_JIT)
 
-- (JSC::VM&)vm
-{
-    return *toJS(m_group);
+- (JSContextGroupRef)JSContextGroupRef
+{
+    return m_group;
 }
 
 - (BOOL)isWebThreadAware
 {
-    return [self vm].apiLock().isWebThreadAware();
+    JSC::VM* vm = toJS(m_group);
+    return vm->apiLock().isWebThreadAware();
 }
 

trunk/Source/JavaScriptCore/API/JSVirtualMachineInternal.h

@@ -47 +47 @@
 - (JSContext *)contextForGlobalContextRef:(JSGlobalContextRef)globalContext;
 - (void)addContext:(JSContext *)wrapper forGlobalContextRef:(JSGlobalContextRef)globalContext;
-- (JSC::VM&)vm;
+- (BOOL)isWebThreadAware;
 
-- (BOOL)isWebThreadAware;
+@property (readonly) JSContextGroupRef JSContextGroupRef;
 
 @end

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2020-01-07  Yusuke Suzuki  <ysuzuki@apple.com>
+
+        [JSC] Remove vm accessor in JSVirtualMachine to reduce binary size
+        https://bugs.webkit.org/show_bug.cgi?id=205880
+
+        Reviewed by Mark Lam.
+
+        Objective-C has reflection mechanism. This means that fields, methods, and their types
+        need to hold its string representations in binary even if we are using release build.
+        While typical Objective-C class does not have large size of type names, C++ struct / class
+        has very large one, and putting them in Objective-C method names, parameter types, or fields
+        makes binary size very large.
+
+        By analyzing JavaScriptCore binary, I found that Objective-C method type symbols are taking 200~KB
+        binary size. (Section __objc_methtype: 235081 (addr 0x105e9a3 offset 17164707)). And it is due to
+        JSC::VM type included in `[JSVirtualMachine vm]` accessor.
+
+        This patch removes this accessor and gets 200KB binary size reduction.
+
+        * API/JSScript.mm:
+        (-[JSScript readCache]):
+        (-[JSScript sourceCode]):
+        (-[JSScript jsSourceCode]):
+        (-[JSScript writeCache:]):
+        * API/JSVirtualMachine.mm:
+        (-[JSVirtualMachine JSContextGroupRef]):
+        (-[JSVirtualMachine isWebThreadAware]):
+        (-[JSVirtualMachine vm]): Deleted.
+        * API/JSVirtualMachineInternal.h:
+
 2020-01-07  Keith Miller  <keith_miller@apple.com>