Changeset 59742 in webkit for trunk/JavaScriptCore/runtime/JSActivation.cpp

Timestamp:

May 18, 2010, 10:10:11 PM (15 years ago)

Author:

[email protected]

Message:

JavaScriptCore: Simplified handling of 'arguments' -- 1.2% SunSpider speedup
​https://bugs.webkit.org/show_bug.cgi?id=39200

Reviewed by Darin Adler.

Removed the reserved OptionalCalleeArguments slot from the CallFrame.
Now, slots for 'arguments' are allocated and initialized only by
functions that might need them.

• bytecode/CodeBlock.cpp:

(JSC::CodeBlock::dump): Updated for new bytecode operands.

(JSC::CodeBlock::CodeBlock):

• bytecode/CodeBlock.h:

(JSC::unmodifiedArgumentsRegister): Added a helper function for mapping
from the arguments register to its unmodified counterpart.

(JSC::CodeBlock::setArgumentsRegister):
(JSC::CodeBlock::argumentsRegister):
(JSC::CodeBlock::usesArguments): Changed from a "usesArguments" bool to
an optional int index representing the arguments register.

• bytecode/Opcode.h: Updated for new bytecode operands.

• bytecompiler/BytecodeGenerator.cpp:

(JSC::BytecodeGenerator::addVar): Factored out a helper function for
allocating an anonymous var.

(JSC::BytecodeGenerator::BytecodeGenerator): Merged / simplified some
arguments vs activation logic, and added code to allocate the arguments
registers when needed.

(JSC::BytecodeGenerator::createArgumentsIfNecessary): Updated for new bytecode operands.

(JSC::BytecodeGenerator::emitCallEval): No need to create the arguments
object before calling eval; the activation object will lazily create the
arguments object if eval resolves it.

(JSC::BytecodeGenerator::emitReturn): Updated for new bytecode operands.

(JSC::BytecodeGenerator::emitPushScope):
(JSC::BytecodeGenerator::emitPushNewScope): Ditto emitCallEval.

• bytecompiler/BytecodeGenerator.h:

(JSC::BytecodeGenerator::addVar): Factored out a helper function for
allocating an anonymous var.

(JSC::BytecodeGenerator::registerFor): No more need for special handling
of the arguments registers; they're allocated just like normal registers
now.

• interpreter/CallFrame.h:

(JSC::ExecState::callerFrame):
(JSC::ExecState::init):

• interpreter/CallFrameClosure.h:

(JSC::CallFrameClosure::resetCallFrame): Nixed optionalCalleeArguments.

• interpreter/Interpreter.cpp:

(JSC::Interpreter::dumpRegisters):
(JSC::Interpreter::unwindCallFrame):
(JSC::Interpreter::privateExecute):
(JSC::Interpreter::retrieveArguments): Opcodes accessing 'arguments' now
take operands specifying registers, just like all other opcodes.
JSActivation::copyRegisters is no longer responsible for tearing off the
arguments object; instead, the VM is responsible for both.

Also, a behavior change: Each access to f.arguments creates a new object,
unless f itself uses 'arguments'. This matches Chrome, and is necessary
for the optimization. f.arguments is a nonstandard, deprecated feature,
so high fidelity to a given implementation is not necessarily a goal.
Also, as illustrated by the new test case, the identity of f.arguments
has been broken since 2008, except in the case where f itself accesses
f.arguments -- but nobody seemed to notice. So, hopefully this change won't
break the web.

• interpreter/Register.h: Nixed the special arguments accessor. It's no

longer needed.

• interpreter/RegisterFile.h:

(JSC::RegisterFile::):

• jit/JITCall.cpp:

(JSC::JIT::compileOpCallInitializeCallFrame):
(JSC::JIT::compileOpCall):

• jit/JITOpcodes.cpp:

(JSC::JIT::emit_op_tear_off_activation):
(JSC::JIT::emit_op_tear_off_arguments):
(JSC::JIT::emit_op_create_arguments):
(JSC::JIT::emit_op_init_arguments):

• jit/JITOpcodes32_64.cpp:

(JSC::JIT::emit_op_tear_off_activation):
(JSC::JIT::emit_op_tear_off_arguments):
(JSC::JIT::emit_op_create_arguments):
(JSC::JIT::emit_op_init_arguments): The actual optimization: Removed
OptionalCalleeArguments from the callframe slot. Now, it doesn't need
to be initialized for most calls.

• jit/JITStubs.cpp:

(JSC::DEFINE_STUB_FUNCTION):

• jit/JITStubs.h:

(JSC::): Updated stubs to support arbitrary 'arguments' registers,
instead of hard-coding something in the call frame.

• runtime/Arguments.h:

(JSC::JSActivation::copyRegisters): Removed some obfuscatory abstraction.

• runtime/Executable.h:

(JSC::FunctionExecutable::generatedByteCode): Added a helper for accessing
the 'arguments' register. In a future patch, that kind of data should
probably move out of CodeBlock and into Executable.

• runtime/JSActivation.cpp:

(JSC::JSActivation::getOwnPropertySlot):
(JSC::JSActivation::argumentsGetter):

• runtime/JSActivation.h: Simplified / fixed access to 'arguments' via

the activation object. It now implements the same behavior implemented
by optimized variable access in the VM. This simplifies some other
things, too -- like eval code generation.

LayoutTests: Simplified handling of 'arguments' -- 1.2% SunSpider speedup
​https://bugs.webkit.org/show_bug.cgi?id=39200

Reviewed by Darin Adler.

• fast/js/function-dot-arguments-expected.txt:
• fast/js/script-tests/function-dot-arguments.js:

(argumentsIdentity): Updated to match new behavior.

• fast/js/function-dot-arguments2-expected.txt:
• fast/js/function-dot-arguments2.html: New tests for some things that

weren't covered before.

• fast/js/global-recursion-on-full-stack.html: Rejiggered the stack

usage in this test. Since stack usage is more efficient now, you
need a slightly different usage pattern to hit the exact thing this
test wanted to test.

• fast/js/kde/script-tests/function_arguments.js:

(f): Updated to more specifically test what this was trying to test,
to avoid just testing the identity of f.arguments.

File:

• trunk/JavaScriptCore/runtime/JSActivation.cpp (modified) (3 diffs)

trunk/JavaScriptCore/runtime/JSActivation.cpp

@@ -71 +71 @@
 bool JSActivation::getOwnPropertySlot(ExecState* exec, const Identifier& propertyName, PropertySlot& slot)
 {
+    if (propertyName == exec->propertyNames().arguments) {
+        slot.setCustom(this, getArgumentsGetter());
+        return true;
+    }
+
     if (symbolTableGet(propertyName, slot))
         return true;
@@ -76 +81 @@
     if (JSValue* location = getDirectLocation(propertyName)) {
         slot.setValueSlot(location);
-        return true;
-    }
-
-    // Only return the built-in arguments object if it wasn't overridden above.
-    if (propertyName == exec->propertyNames().arguments) {
-        slot.setCustom(this, getArgumentsGetter());
         return true;
     }
@@ -141 +140 @@
 }
 
-JSValue JSActivation::argumentsGetter(ExecState* exec, JSValue slotBase, const Identifier&)
+JSValue JSActivation::argumentsGetter(ExecState*, JSValue slotBase, const Identifier&)
 {
     JSActivation* activation = asActivation(slotBase);
-
-    if (activation->d()->functionExecutable->usesArguments()) {
-        PropertySlot slot;
-        activation->symbolTableGet(exec->propertyNames().arguments, slot);
-        return slot.getValue(exec, exec->propertyNames().arguments);
+    CallFrame* callFrame = CallFrame::create(activation->d()->registers);
+    int argumentsRegister = activation->d()->functionExecutable->generatedByteCode().argumentsRegister();
+    if (!callFrame->r(argumentsRegister).jsValue()) {
+        JSValue arguments = JSValue(new (callFrame) Arguments(callFrame));
+        callFrame->r(argumentsRegister) = arguments;
+        callFrame->r(unmodifiedArgumentsRegister(argumentsRegister)) = arguments;
     }
 
-    CallFrame* callFrame = CallFrame::create(activation->d()->registers);
-    Arguments* arguments = callFrame->optionalCalleeArguments();
-    if (!arguments) {
-        arguments = new (callFrame) Arguments(callFrame);
-        arguments->copyRegisters();
-        callFrame->setCalleeArguments(arguments);
-    }
-    ASSERT(arguments->inherits(&Arguments::info));
-
-    return arguments;
+    ASSERT(callFrame->r(argumentsRegister).jsValue().inherits(&Arguments::info));
+    return callFrame->r(argumentsRegister).jsValue();
 }