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

[Kai Luo via cfe-commits]

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@@ -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;
+    for (SDNode &Node : DAG.allnodes()) {
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bzEq wrote:

One DAG is mapped to a single basic block, I notice your description is about whole function. So the size of `TLSGV` is smaller than what you really want to count.

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