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LibJS: Don't generate useless jumps for if statement

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If statements without an else clause generated jumps to the next
instruction, this commit fixes the if statement generation so that it
dosen't produce them anymore.

This is an example of JS code that generates the useless jumps
(a => if(a){}) ();
This commit is contained in:
samu698 2024-10-26 15:18:47 +02:00 committed by Andreas Kling
parent 257ebea364
commit 7865fbfe6d
Notes: github-actions[bot] 2024-10-26 15:40:26 +00:00 
Author: https://github.com/samu698
Commit: https://github.com/LadybirdBrowser/ladybird/commit/7865fbfe6d0
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/1979
1 changed files with 9 additions and 14 deletions
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23
Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
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@ -2330,7 +2330,8 @@ Bytecode::CodeGenerationErrorOr<Optional<ScopedOperand>> IfStatement::generate_b
auto& true_block = generator.make_block(); auto& true_block = generator.make_block();
auto& false_block = generator.make_block(); auto& false_block = generator.make_block();
auto& end_block = generator.make_block(); // NOTE: if there is no 'else' block the end block is the same as the false block
auto& end_block = m_alternate ? generator.make_block() : false_block;
Optional<ScopedOperand> completion; Optional<ScopedOperand> completion;
if (generator.must_propagate_completion()) { if (generator.must_propagate_completion()) {
@ -2347,25 +2348,19 @@ Bytecode::CodeGenerationErrorOr<Optional<ScopedOperand>> IfStatement::generate_b
generator.switch_to_basic_block(true_block); generator.switch_to_basic_block(true_block);
auto consequent = TRY(m_consequent->generate_bytecode(generator, completion)); auto consequent = TRY(m_consequent->generate_bytecode(generator, completion));
if (!generator.is_current_block_terminated()) { if (!generator.is_current_block_terminated()) {
if (generator.must_propagate_completion()) { if (generator.must_propagate_completion() && consequent.has_value())
if (consequent.has_value()) generator.emit<Bytecode::Op::Mov>(*completion, *consequent);
generator.emit<Bytecode::Op::Mov>(*completion, *consequent);
}
generator.emit<Bytecode::Op::Jump>(Bytecode::Label { end_block }); generator.emit<Bytecode::Op::Jump>(Bytecode::Label { end_block });
} }
generator.switch_to_basic_block(false_block);
Optional<ScopedOperand> alternate;
if (m_alternate) { if (m_alternate) {
alternate = TRY(m_alternate->generate_bytecode(generator, completion)); generator.switch_to_basic_block(false_block);
} auto alternate = TRY(m_alternate->generate_bytecode(generator, completion));
if (!generator.is_current_block_terminated()) { if (!generator.is_current_block_terminated()) {
if (generator.must_propagate_completion()) { if (generator.must_propagate_completion() && alternate.has_value())
if (alternate.has_value())
generator.emit<Bytecode::Op::Mov>(*completion, *alternate); generator.emit<Bytecode::Op::Mov>(*completion, *alternate);
generator.emit<Bytecode::Op::Jump>(Bytecode::Label { end_block });
} }
generator.emit<Bytecode::Op::Jump>(Bytecode::Label { end_block });
} }
generator.switch_to_basic_block(end_block); generator.switch_to_basic_block(end_block);