Bug 39583 – Move creation of 'this' object from caller to callee in construction.

• Status: RESOLVED
• Resolution: FIXED
• Component: JavaScriptCore

[Gavin Barraclough]

Presently the caller of a constructor is responsible for providing a this
object.  Instead, move the object creation into a new op_create_this opcode,
planted in the head of the contructor bytecode for a function.  Since the
prototype for the object is provided by performing a get_by_id on the callee,
also add a new get_callee opcode (this is used to get the callee JSFunction
into a register so that a normal get_by_id can be used).

Currently the caller is also responsible for detecting when op_construct is
performed on a JSFunction representing a host function, in which case an
exception is thrown – and this check currently takes place when constructing
the this object.  Instead, mirroring the recent changes for non-host functions,
add a parallel code-path for native constructors to follow, with a thunk for
invoking native constructors provided by JITStubs, and a constructor-specific
NativeFunction on NativeExecutable.  Provide an implementation of a host
constructor which will throw an exception.

[Gavin Barraclough]

Created attachment 56858 [details]
The patch

No performance impact

[WebKit Review Bot]

Attachment 56858 [details] did not pass style-queue:

Failed to run "['WebKitTools/Scripts/check-webkit-style', '--no-squash']" exit_code: 1
JavaScriptCore/jit/JITOpcodes.cpp:221:  string_failureCases1Call is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/jit/JITOpcodes.cpp:222:  string_failureCases2Call is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/jit/JITOpcodes.cpp:223:  string_failureCases3Call is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/jit/JITOpcodes32_64.cpp:221:  string_failureCases1Call is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/jit/JITOpcodes32_64.cpp:222:  string_failureCases2Call is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
JavaScriptCore/jit/JITOpcodes32_64.cpp:223:  string_failureCases3Call is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 6 in 19 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Gavin Barraclough]

Transmitting file data ...................
Committed revision 60075.