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LibJS/Bytecode: Do not clobber completion value with VariableDeclaration

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While the completion value of a variable declaration is specified to be
empty, we might already have a completion value in the accumulator from
a previous statement. Preserve it so as to avoid clobbering it.

This fixes 6 tests on test262.
This commit is contained in:
Daniel Bertalan 2023-07-02 10:48:17 +02:00 • committed by Andreas Kling
parent bd2c3ace68
commit 0df7255fe7
1 changed files with 6 additions and 0 deletions
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6
Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
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@ -1353,6 +1353,11 @@ static Bytecode::CodeGenerationErrorOr<void> assign_accumulator_to_variable_decl
Bytecode::CodeGenerationErrorOr<void> VariableDeclaration::generate_bytecode(Bytecode::Generator& generator) const
{
// The completion value of a VariableDeclaration is empty, but there might already be a non-empty
// completion value in the accumulator. We need to save it and restore it after the declaration executed.
auto saved_accumulator = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(saved_accumulator);
for (auto& declarator : m_declarations) {
if (declarator->init()) {
if (auto const* lhs = declarator->target().get_pointer<NonnullRefPtr<Identifier const>>()) {
@ -1367,6 +1372,7 @@ Bytecode::CodeGenerationErrorOr<void> VariableDeclaration::generate_bytecode(Byt
}
}
generator.emit<Bytecode::Op::Load>(saved_accumulator);
return {};
}