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LibJS/Bytecode: Turn JumpIf condition,@a,@next into JumpTrue/JumpFalse

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If one of the jump targets is the very next block, we can convert the
jump instruction into a smaller JumpTrue or JumpFalse.
This commit is contained in:
Andreas Kling
2024-05-06 10:15:17 +02:00
parent 37d722f4a6
commit fae1527a18
4 changed files with 120 additions and 0 deletions
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24
Userland/Libraries/LibJS/Bytecode/Generator.cpp
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@@ -132,6 +132,30 @@ CodeGenerationErrorOr<NonnullGCPtr<Executable>> Generator::generate(VM& vm, ASTN
}
}
// OPTIMIZATION: For `JumpIf` where one of the targets is the very next block,
// we can emit a `JumpTrue` or `JumpFalse` (to the other block) instead.
if (instruction.type() == Instruction::Type::JumpIf) {
auto& jump = static_cast<Bytecode::Op::JumpIf&>(instruction);
if (jump.true_target().basic_block_index() == block->index() + 1) {
Op::JumpFalse jump_false(jump.condition(), Label { jump.false_target() });
auto& label = jump_false.target();
size_t label_offset = bytecode.size() + (bit_cast<FlatPtr>(&label) - bit_cast<FlatPtr>(&jump_false));
label_offsets.append(label_offset);
bytecode.append(reinterpret_cast<u8 const*>(&jump_false), jump_false.length());
++it;
continue;
}
if (jump.false_target().basic_block_index() == block->index() + 1) {
Op::JumpTrue jump_true(jump.condition(), Label { jump.true_target() });
auto& label = jump_true.target();
size_t label_offset = bytecode.size() + (bit_cast<FlatPtr>(&label) - bit_cast<FlatPtr>(&jump_true));
label_offsets.append(label_offset);
bytecode.append(reinterpret_cast<u8 const*>(&jump_true), jump_true.length());
++it;
continue;
}
}
instruction.visit_labels([&](Label& label) {
size_t label_offset = bytecode.size() + (bit_cast<FlatPtr>(&label) - bit_cast<FlatPtr>(&instruction));
label_offsets.append(label_offset);