[clang] [llvm] [X86] Add Support for X86 TLSDESC Relocations (PR #83136)

[Paul Kirth via cfe-commits]

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@@ -18522,13 +18522,21 @@ GetTLSADDR(SelectionDAG &DAG, SDValue Chain, GlobalAddressSDNode *GA,
   MachineFrameInfo &MFI = DAG.getMachineFunction().getFrameInfo();
   SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue);
   SDLoc dl(GA);
-  SDValue TGA = DAG.getTargetGlobalAddress(GA->getGlobal(), dl,
-                                           GA->getValueType(0),
-                                           GA->getOffset(),
-                                           OperandFlags);
+  SDValue TGA;
+  bool UseTLSDESC = DAG.getTarget().useTLSDESC();
+  if (LocalDynamic && UseTLSDESC) {
+    TGA = DAG.getTargetExternalSymbol("_TLS_MODULE_BASE_", PtrVT, OperandFlags);
+    auto UI = TGA->use_begin();
+    if (UI != TGA->use_end())
+      return SDValue(*UI->use_begin()->use_begin(), 0);
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ilovepi wrote:

Can we get a comment here about why we're returning this value?

https://github.com/llvm/llvm-project/pull/83136