[lld] [lld][ELF] Sort thunks by their destination to allow quicker convergence (PR #209962)

[Arthur Eubanks via llvm-commits]

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@@ -4107,7 +4084,21 @@ InputSection *ThunkSection::getTargetInputSection() const {
   return t->getTargetInputSection();
 }
 
-bool ThunkSection::assignOffsets() {
+bool ThunkSection::assignOffsets(bool sort) {
+  if (sort) {
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aeubanks wrote:

I wonder if we should also sort by short vs long thunks? If we place the long thunks further than short thunks (and make sure to never change a long thunk to a short thunk which could introduce instability) then the short thunks won't increase in range at least due to short -> long thunk upgrade, although we can still get more passes due to the short -> long size increase making other branches through the thunk pool longer.

Maybe not worth the extra complexity, especially since it requires more work on potentially every thunk insertion rather than a one time sort.

https://github.com/llvm/llvm-project/pull/209962