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LibJS/Bytecode: Elide jumps that land in the very next block

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Jumping to the next block is effectively a no-op, so let's save time and
space by just not emitting those jumps.
This commit is contained in:
Andreas Kling 2024-05-06 09:33:53 +02:00
parent 3a73eb99ac
commit 24d8b056c7
Notes: sideshowbarker 2024-07-16 20:39:14 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/24d8b056c7
Pull-request: https://github.com/SerenityOS/serenity/pull/24240
Reviewed-by: https://github.com/Hendiadyoin1
Reviewed-by: https://github.com/trflynn89 ✅
1 changed files with 14 additions and 0 deletions
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14
Userland/Libraries/LibJS/Bytecode/Generator.cpp
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@ -118,6 +118,20 @@ CodeGenerationErrorOr<NonnullGCPtr<Executable>> Generator::generate(VM& vm, ASTN
Bytecode::InstructionStreamIterator it(block->instruction_stream());
while (!it.at_end()) {
auto& instruction = const_cast<Instruction&>(*it);
// OPTIMIZATION: Don't emit jumps that just jump to the next block.
if (instruction.type() == Instruction::Type::Jump) {
auto& jump = static_cast<Bytecode::Op::Jump&>(instruction);
if (jump.target().basic_block_index() == block->index() + 1) {
if (basic_block_start_offsets.last() == bytecode.size()) {
// This block is empty, just skip it.
basic_block_start_offsets.take_last();
}
++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);