[lld] [ELF] Add BPSectionOrderer options (#120514) (PR #125559)

[Ellis Hoag via llvm-commits]

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@@ -98,10 +102,11 @@ static SmallVector<std::pair<unsigned, UtilityNodes>> getUnsForCompression(
     // Merge sections that are nearly identical
     SmallVector<std::pair<unsigned, SmallVector<uint64_t>>> newSectionHashes;
     DenseMap<uint64_t, unsigned> wholeHashToSectionIdx;
+    unsigned threshold = sectionHashes.size() > 10000 ? 5 : 0;
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ellishg wrote:

I built some large binaries with this change and I didn't see any large differences, so I think this is ok. I also realized that there is a bug. If `wholeHash` is zero, we should not insert into `duplicateSectionIdxs` because they have no hashes in common.

The more I think about this the more I realize this might be able to be improved quite a bit. I can imagine a set of small outlined functions that differ in one instructions. Ideally these should be in `duplicateSectionIdxs`, but this code won't catch that case.

https://github.com/llvm/llvm-project/pull/125559