[BOLT][BAT] Add entries for deleted basic blocks

Deleted basic blocks are required for correct mapping of branches
modified by SCTC.

Increases BAT size, bytes:
- large binary: 8622496 -> 8703244.
- small binary (X86/bolt-address-translation.test): 928 -> 940.

Test Plan: updated bb-with-two-tail-calls.s

Reviewers: ayermolo, dcci, maksfb, rafaelauler

Reviewed By: rafaelauler

Pull Request: https://github.com/llvm/llvm-project/pull/91906

bolt/lib/Profile/BoltAddressTranslation.cpp

@@ -54,7 +54,7 @@ void BoltAddressTranslation::writeEntriesForBB(
   // and this deleted block will both share the same output address (the same
   // key), and we need to map back. We choose here to privilege the successor by
   // allowing it to overwrite the previously inserted key in the map.
-  Map[BBOutputOffset] = BBInputOffset << 1;
+  Map.emplace(BBOutputOffset, BBInputOffset << 1);
 
   const auto &IOAddressMap =
       BB.getFunction()->getBinaryContext().getIOAddressMap();
@@ -71,8 +71,7 @@ void BoltAddressTranslation::writeEntriesForBB(
 
     LLVM_DEBUG(dbgs() << "  Key: " << Twine::utohexstr(OutputOffset) << " Val: "
                       << Twine::utohexstr(InputOffset) << " (branch)\n");
-    Map.insert(std::pair<uint32_t, uint32_t>(OutputOffset,
-                                             (InputOffset << 1) | BRANCHENTRY));
+    Map.emplace(OutputOffset, (InputOffset << 1) | BRANCHENTRY);
   }
 }
 
@@ -107,6 +106,19 @@ void BoltAddressTranslation::write(const BinaryContext &BC, raw_ostream &OS) {
     for (const BinaryBasicBlock *const BB :
          Function.getLayout().getMainFragment())
       writeEntriesForBB(Map, *BB, InputAddress, OutputAddress);
+    // Add entries for deleted blocks. They are still required for correct BB
+    // mapping of branches modified by SCTC. By convention, they would have the
+    // end of the function as output address.
+    const BBHashMapTy &BBHashMap = getBBHashMap(InputAddress);
+    if (BBHashMap.size() != Function.size()) {
+      const uint64_t EndOffset = Function.getOutputSize();
+      std::unordered_set<uint32_t> MappedInputOffsets;
+      for (const BinaryBasicBlock &BB : Function)
+        MappedInputOffsets.emplace(BB.getInputOffset());
+      for (const auto &[InputOffset, _] : BBHashMap)
+        if (!llvm::is_contained(MappedInputOffsets, InputOffset))
+          Map.emplace(EndOffset, InputOffset << 1);
+    }
     Maps.emplace(Function.getOutputAddress(), std::move(Map));
     ReverseMap.emplace(OutputAddress, InputAddress);