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LibJS+CI: Remove bytecode optimization passes for now

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These passes have not been shown to actually optimize any JS, and tests
have become very flaky with optimizations enabled. Until some measurable
benefit is shown, remove the optimization passes to reduce overhead of
maintaining bytecode operations and to reduce CI churn. The framework
for optimizations will live on in git history, and can be restored once
proven useful.
This commit is contained in:
Timothy Flynn 2023-07-21 09:59:50 -04:00 • committed by Ali Mohammad Pur
parent 164c132928
commit 77d7f715e3
17 changed files with 1 additions and 1311 deletions
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66
Userland/Libraries/LibJS/Bytecode/Pass/UnifySameBlocks.cpp
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@ -1,66 +0,0 @@
/*
* Copyright (c) 2021, Ali Mohammad Pur <mpfard@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibJS/Bytecode/PassManager.h>
#include <string.h>
namespace JS::Bytecode::Passes {
void UnifySameBlocks::perform(PassPipelineExecutable& executable)
{
started();
VERIFY(executable.cfg.has_value());
VERIFY(executable.inverted_cfg.has_value());
auto cfg = executable.cfg.release_value();
auto inverted_cfg = executable.inverted_cfg.release_value();
HashMap<BasicBlock const*, BasicBlock const*> equal_blocks;
for (size_t i = 0; i < executable.executable.basic_blocks.size(); ++i) {
auto& block = executable.executable.basic_blocks[i];
auto block_bytes = block->instruction_stream();
for (auto& candidate_block : executable.executable.basic_blocks.span().slice(i + 1)) {
if (equal_blocks.contains(&*candidate_block))
continue;
// FIXME: This can probably be relaxed a bit...
if (candidate_block->size() != block->size())
continue;
auto candidate_bytes = candidate_block->instruction_stream();
// FIXME: NewBigInt's value is not correctly reflected by its encoding in memory,
// this will yield false negatives for blocks containing that
if (memcmp(candidate_bytes.data(), block_bytes.data(), candidate_block->size()) == 0)
equal_blocks.set(candidate_block.ptr(), block);
}
}
auto replace_blocks = [&](auto& match, auto& replacement) {
Optional<size_t> first_successor_position;
auto it = executable.executable.basic_blocks.find_if([match](auto& block) { return match == block; });
VERIFY(!it.is_end());
executable.executable.basic_blocks.remove(it.index());
if (!first_successor_position.has_value())
first_successor_position = it.index();
for (auto& block : executable.executable.basic_blocks) {
InstructionStreamIterator it { block->instruction_stream() };
while (!it.at_end()) {
auto& instruction = *it;
++it;
const_cast<Instruction&>(instruction).replace_references(*match, replacement);
}
}
return first_successor_position;
};
for (auto& entry : equal_blocks)
(void)replace_blocks(entry.key, *entry.value);
finished();
}
}