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LibJS: Coerce empty completion to "undefined" early in Interpreter

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Instead of always checking if we're about to return an empty completion
value in Interpreter::run_executable(), we now coerce empty completions
to the undefined value earlier instead.

This simplifies the most common path through run_executable(), giving us
a small speedup.
This commit is contained in:
Andreas Kling 2025-10-31 21:10:51 +01:00 committed by Andreas Kling
parent 75d49c4b55
commit 6f9d297c3c
2 changed files with 8 additions and 6 deletions
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12
Libraries/LibJS/Bytecode/Interpreter.cpp
View File

@ -380,7 +380,10 @@ FLATTEN_ON_CLANG void Interpreter::run_bytecode(size_t entry_point)
handle_End: {
auto& instruction = *reinterpret_cast<Op::End const*>(&bytecode[program_counter]);
reg(Register::return_value()) = get(instruction.value());
auto value = get(instruction.value());
if (value.is_special_empty_value())
value = js_undefined();
reg(Register::return_value()) = value;
return;
}
@ -489,7 +492,7 @@ FLATTEN_ON_CLANG void Interpreter::run_bytecode(size_t entry_point)
auto& unwind_context = unwind_contexts.last();
VERIFY(unwind_context.executable == &current_executable());
reg(Register::saved_return_value()) = reg(Register::return_value());
reg(Register::return_value()) = js_special_empty_value();
reg(Register::return_value()) = js_undefined();
program_counter = finalizer.value();
// the unwind_context will be pop'ed when entering the finally block
goto start;
@ -752,10 +755,7 @@ ThrowCompletionOr<Value> Interpreter::run_executable(ExecutionContext& context,
if (!exception.is_special_empty_value()) [[unlikely]]
return throw_completion(exception);
auto return_value = reg(Register::return_value());
if (return_value.is_special_empty_value())
return_value = js_undefined();
return return_value;
return reg(Register::return_value());
}
void Interpreter::enter_unwind_context()

2
Libraries/LibJS/Bytecode/Interpreter.h
View File

@ -58,6 +58,8 @@ public:
Value do_yield(Value value, Optional<Label> continuation);
void do_return(Value value)
{
if (value.is_special_empty_value())
value = js_undefined();
reg(Register::return_value()) = value;
reg(Register::exception()) = js_special_empty_value();
}