[clang] [llvm] [PowerPC] Tune AIX shared library TLS model at function level by heuristic (PR #84132)

[Kai Luo via cfe-commits]

================
@@ -3369,6 +3369,48 @@ SDValue PPCTargetLowering::LowerGlobalTLSAddressAIX(SDValue Op,
   bool Is64Bit = Subtarget.isPPC64();
   bool HasAIXSmallLocalExecTLS = Subtarget.hasAIXSmallLocalExecTLS();
   TLSModel::Model Model = getTargetMachine().getTLSModel(GV);
+  // Initialize heuristic setting lazily:
+  // (1) Use initial-exec for single TLS var reference within current function.
+  // (2) Use local-dynamic for multiple TLS var references within current func.
+  PPCFunctionInfo *FuncInfo =
+      DAG.getMachineFunction().getInfo<PPCFunctionInfo>();
+  if (Subtarget.hasAIXShLibTLSModelHeuristic() &&
+      !FuncInfo->isAIXFuncUseInitDone()) {
+    std::set<const GlobalValue *> TLSGV;
----------------
bzEq wrote:

```suggestion
    SmallPtrSet<const GlobalValue *, 8> TLSGV;
```

https://github.com/llvm/llvm-project/pull/84132