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[lld-macho] Use fixed chunk size for UUID

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Chunk size decided by the thread count makes the UUID less deterministic
(e.g. across machines with different core counts.)
Follow ELF and just use a fixed chunksize.

Fixes: https://github.com/llvm/llvm-project/issues/63961

Reviewed By: #lld-macho, keith

Differential Revision: https://reviews.llvm.org/D155761
This commit is contained in:
Fangrui Song 2023-07-19 17:24:36 -07:00
parent fc5dcb0c22
commit 359f170f5f
1 changed files with 1 additions and 4 deletions
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5
lld/MachO/Writer.cpp
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@ -1182,10 +1182,7 @@ void Writer::writeUuid() {
TimeTraceScope timeScope("Computing UUID");
ArrayRef<uint8_t> data{buffer->getBufferStart(), buffer->getBufferEnd()};
unsigned chunkCount = parallel::strategy.compute_thread_count() * 10;
// Round-up integer division
size_t chunkSize = (data.size() + chunkCount - 1) / chunkCount;
std::vector<ArrayRef<uint8_t>> chunks = split(data, chunkSize);
std::vector<ArrayRef<uint8_t>> chunks = split(data, 1024 * 1024);
// Leave one slot for filename
std::vector<uint64_t> hashes(chunks.size() + 1);
SmallVector<std::shared_future<void>> threadFutures;