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LibJS/Bytecode: Don't generate ResolveThisBinding if not needed

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Functions that don't have a FunctionEnvironment will get their `this`
value from the ExecutionContext. This patch stops generating
ResolveThisBinding instructions at all for functions like that, and
instead pre-populates the `this` register when entering a new bytecode
executable.
This commit is contained in:
Andreas Kling 2024-05-31 21:00:15 +02:00
parent 9d22db2802
commit e6b1e54c44
Notes: sideshowbarker 2024-07-17 06:33:00 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/e6b1e54c44
Pull-request: https://github.com/SerenityOS/serenity/pull/24504
2 changed files with 8 additions and 0 deletions
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7
Userland/Libraries/LibJS/Bytecode/Generator.cpp
View File

@ -1087,6 +1087,13 @@ ScopedOperand Generator::get_this(Optional<ScopedOperand> preferred_dst)
m_current_basic_block->set_has_resolved_this();
return this_value();
}
// OPTIMIZATION: If we're compiling a function that doesn't allocate a FunctionEnvironment,
// it will always have the same `this` value as the outer function,
// and so the `this` value is already in the `this` register!
if (m_function && !m_function->allocates_function_environment())
return this_value();
auto dst = preferred_dst.has_value() ? preferred_dst.value() : allocate_register();
emit<Bytecode::Op::ResolveThisBinding>();
m_current_basic_block->set_has_resolved_this();

1
Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
View File

@ -718,6 +718,7 @@ Interpreter::ResultAndReturnRegister Interpreter::run_executable(Executable& exe
reg(Register::accumulator()) = initial_accumulator_value;
reg(Register::return_value()) = {};
reg(Register::this_value()) = running_execution_context.this_value;
running_execution_context.executable = &executable;