[llvm-branch-commits] [lld] [lld][macho] Track max thunks to create and remove --slop_scale (PR #193372)

[Ellis Hoag via llvm-branch-commits]

================
@@ -200,27 +200,35 @@ void TextOutputSection::finalize() {
       branchesToProcess;
   SmallVector<std::tuple<ConcatInputSection *, Relocation *, Defined *>>
       deferredBranchRedirects;
+  unsigned numPendingThunkTargets = 0;
 
-  const uint64_t slop = config->slopScale * thunkSize;
   for (auto *isec : inputs) {
     while (!branchesToProcess.empty()) {
       auto &[callerIsec, r, thunkKey] = branchesToProcess.front();
       assert(callerIsec->isFinal);
+      auto &thunkInfo = thunkMap[thunkKey];
       if (isTargetInRange(*callerIsec, *r)) {
+        if (thunkInfo.pendingBranches.erase(r))
+          if (thunkInfo.pendingBranches.empty())
+            --numPendingThunkTargets;
         branchesToProcess.pop_front();
         continue;
       }
       if (auto *sym = getThunkInRange(*callerIsec, *r)) {
+        // The pending thunk target was already decremented when we created the
+        // thunk
         deferredBranchRedirects.emplace_back(callerIsec, r, sym);
         branchesToProcess.pop_front();
         continue;
       }
       uint64_t highVA = callerIsec->getVA() + r->offset + forwardBranchRange;
       uint64_t nextEnd =
           alignToPowerOf2(addr + size, isec->align) + isec->getSize();
-      if (nextEnd + slop <= highVA)
+      if (nextEnd + numPendingThunkTargets * thunkSize <= highVA)
         break;
 
+      thunkInfo.pendingBranches.clear();
----------------
ellishg wrote:

Yes there could be. But we are about to create this thunk so we know it is no longer pending. This is why when we resolve a relocation we must check if we deleted it from `pendingBranches`.

```
if (thunkInfo.pendingBranches.erase(r))
  if (thunkInfo.pendingBranches.empty())
    --numPendingThunkTargets;
```

https://github.com/llvm/llvm-project/pull/193372