[llvm] [BOLT] Update LSDA encoding for x86-64 large code model (PR #190685)

[Maksim Panchenko via llvm-commits]

================
@@ -2241,6 +2238,19 @@ Error RewriteInstance::readSpecialSections() {
                   "Use -update-debug-sections to keep it.\n";
   }
 
+  // Detect large code model by the presence of .ltext sections.
+  if (opts::LargeCodeModel.getNumOccurrences() == 0 &&
+      BC->getUniqueSectionByName(".ltext")) {
+    BC->UseLargeCodeModel = true;
+  }
+
+  // Placed in a separate block so that we can check for it in lit tests
+  if (BC->TheTriple->getArch() == llvm::Triple::x86_64 &&
+      BC->UseLargeCodeModel) {
+    BC->outs() << "BOLT-INFO: large code model detected\n";
+    BC->updateLSDAEncoding();
+  }
----------------
maksfb wrote:

I'm thinking replacing the above with something like:
```
if (opts::LargeCodeModel.getNumOccurrences() == 0 &&
    !BC->UseLargeCodeModel &&
    BC->getUniqueSectionByName(".ltext")) {
  BC->outs() << "BOLT-INFO: .ltext detected - enabling large code model\n";
  BC->UseLargeCodeModel = true;
  BC->updateLSDAEncoding();
}

https://github.com/llvm/llvm-project/pull/190685