Title: [200992] trunk/Source/_javascript_Core
- Revision
- 200992
- Author
- [email protected]
- Date
- 2016-05-16 20:36:45 -0700 (Mon, 16 May 2016)
Log Message
[JSC] "return this" in a constructor does not need a branch on isObject(this)
https://bugs.webkit.org/show_bug.cgi?id=157775
Patch by Benjamin Poulain <[email protected]> on 2016-05-16
Reviewed by Saam Barati and Ryosuke Niwa.
When returning "this" in a constructor, the bytecode generator was generating:
is_object locX, this
jtrue locX, 5(->second ret)
ret this
ret this
That code is eliminated in DFG but it is pretty costly lower tiers.
This patch changes bytecode generation to avoid the is_object test
when possible and not generate two ret if they encode the same thing.
* bytecompiler/BytecodeGenerator.cpp:
(JSC::BytecodeGenerator::emitReturn):
Modified Paths
Diff
Modified: trunk/Source/_javascript_Core/ChangeLog (200991 => 200992)
--- trunk/Source/_javascript_Core/ChangeLog 2016-05-17 03:31:12 UTC (rev 200991)
+++ trunk/Source/_javascript_Core/ChangeLog 2016-05-17 03:36:45 UTC (rev 200992)
@@ -1,5 +1,26 @@
2016-05-16 Benjamin Poulain <[email protected]>
+ [JSC] "return this" in a constructor does not need a branch on isObject(this)
+ https://bugs.webkit.org/show_bug.cgi?id=157775
+
+ Reviewed by Saam Barati and Ryosuke Niwa.
+
+ When returning "this" in a constructor, the bytecode generator was generating:
+ is_object locX, this
+ jtrue locX, 5(->second ret)
+ ret this
+ ret this
+
+ That code is eliminated in DFG but it is pretty costly lower tiers.
+
+ This patch changes bytecode generation to avoid the is_object test
+ when possible and not generate two ret if they encode the same thing.
+
+ * bytecompiler/BytecodeGenerator.cpp:
+ (JSC::BytecodeGenerator::emitReturn):
+
+2016-05-16 Benjamin Poulain <[email protected]>
+
[JSC] Remove the index check from op_get_by_val/op_put_by_val when the index is constant
https://bugs.webkit.org/show_bug.cgi?id=157766
Modified: trunk/Source/_javascript_Core/bytecompiler/BytecodeGenerator.cpp (200991 => 200992)
--- trunk/Source/_javascript_Core/bytecompiler/BytecodeGenerator.cpp 2016-05-17 03:31:12 UTC (rev 200991)
+++ trunk/Source/_javascript_Core/bytecompiler/BytecodeGenerator.cpp 2016-05-17 03:36:45 UTC (rev 200992)
@@ -3219,24 +3219,26 @@
{
if (isConstructor()) {
bool derived = constructorKind() == ConstructorKind::Derived;
- if (derived && src->index() == m_thisRegister.index())
+ bool srcIsThis = src->index() == m_thisRegister.index();
+
+ if (derived && srcIsThis)
emitTDZCheck(src);
- RefPtr<Label> isObjectLabel = newLabel();
- emitJumpIfTrue(emitIsObject(newTemporary(), src), isObjectLabel.get());
+ if (!srcIsThis) {
+ RefPtr<Label> isObjectLabel = newLabel();
+ emitJumpIfTrue(emitIsObject(newTemporary(), src), isObjectLabel.get());
- if (derived) {
- RefPtr<Label> isUndefinedLabel = newLabel();
- emitJumpIfTrue(emitIsUndefined(newTemporary(), src), isUndefinedLabel.get());
- emitThrowTypeError("Cannot return a non-object type in the constructor of a derived class.");
- emitLabel(isUndefinedLabel.get());
- if (constructorKind() == ConstructorKind::Derived)
+ if (derived) {
+ RefPtr<Label> isUndefinedLabel = newLabel();
+ emitJumpIfTrue(emitIsUndefined(newTemporary(), src), isUndefinedLabel.get());
+ emitThrowTypeError("Cannot return a non-object type in the constructor of a derived class.");
+ emitLabel(isUndefinedLabel.get());
emitTDZCheck(&m_thisRegister);
+ }
+
+ emitUnaryNoDstOp(op_ret, &m_thisRegister);
+ emitLabel(isObjectLabel.get());
}
-
- emitUnaryNoDstOp(op_ret, &m_thisRegister);
-
- emitLabel(isObjectLabel.get());
}
return emitUnaryNoDstOp(op_ret, src);
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