[llvm] [X86] Insert CALLSEQ when lowering GlobalTLSAddress for ELF targets (PR #113706)

[Matt Arsenault via llvm-commits]

================
@@ -18828,44 +18828,67 @@ X86TargetLowering::LowerGlobalAddress(SDValue Op, SelectionDAG &DAG) const {
   return LowerGlobalOrExternal(Op, DAG, /*ForCall=*/false);
 }
 
-static SDValue
-GetTLSADDR(SelectionDAG &DAG, SDValue Chain, GlobalAddressSDNode *GA,
-           SDValue *InGlue, const EVT PtrVT, unsigned ReturnReg,
-           unsigned char OperandFlags, bool LocalDynamic = false) {
+static SDValue GetTLSADDR(SelectionDAG &DAG, SDValue Chain,
+                          GlobalAddressSDNode *GA, const EVT PtrVT,
+                          unsigned ReturnReg, unsigned char OperandFlags,
+                          bool LoadGlobalBaseReg = false,
+                          bool LocalDynamic = false) {
   MachineFrameInfo &MFI = DAG.getMachineFunction().getFrameInfo();
   SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue);
   SDLoc dl(GA);
   SDValue TGA;
   bool UseTLSDESC = DAG.getTarget().useTLSDESC();
+  SDValue Ret;
   if (LocalDynamic && UseTLSDESC) {
     TGA = DAG.getTargetExternalSymbol("_TLS_MODULE_BASE_", PtrVT, OperandFlags);
     auto UI = TGA->use_begin();
     // Reuse existing GetTLSADDR node if we can find it.
-    if (UI != TGA->use_end())
-      return SDValue(*UI->use_begin()->use_begin(), 0);
+    if (UI != TGA->use_end()) {
+      // TLSDESC uses TGA.
+      auto TLSDescOp = UI;
+      assert(TLSDescOp->getOpcode() == X86ISD::TLSDESC &&
+             "Unexpected TLSDESC DAG");
+      // CALLSEQ_END uses TGA via a chain and glue.
+      auto *CallSeqEndOp = TLSDescOp->getGluedUser();
+      assert(CallSeqEndOp && CallSeqEndOp->getOpcode() == ISD::CALLSEQ_END &&
+             "Unexpected TLSDESC DAG");
+      // CopyFromReg uses CALLSEQ_END via a chain and glue.
+      auto *CopyFromRegOp = CallSeqEndOp->getGluedUser();
+      assert(CopyFromRegOp && CopyFromRegOp->getOpcode() == ISD::CopyFromReg &&
+             "Unexpected TLSDESC DAG");
+      Ret = SDValue(CopyFromRegOp, 0);
+    }
   } else {
     TGA = DAG.getTargetGlobalAddress(GA->getGlobal(), dl, GA->getValueType(0),
                                      GA->getOffset(), OperandFlags);
   }
 
-  X86ISD::NodeType CallType = UseTLSDESC     ? X86ISD::TLSDESC
-                              : LocalDynamic ? X86ISD::TLSBASEADDR
-                                             : X86ISD::TLSADDR;
-
-  if (InGlue) {
-    SDValue Ops[] = { Chain,  TGA, *InGlue };
-    Chain = DAG.getNode(CallType, dl, NodeTys, Ops);
-  } else {
-    SDValue Ops[]  = { Chain, TGA };
-    Chain = DAG.getNode(CallType, dl, NodeTys, Ops);
-  }
+  if (!Ret) {
+    X86ISD::NodeType CallType = UseTLSDESC     ? X86ISD::TLSDESC
+                                : LocalDynamic ? X86ISD::TLSBASEADDR
+                                               : X86ISD::TLSADDR;
+
+    Chain = DAG.getCALLSEQ_START(Chain, 0, 0, dl);
+    if (LoadGlobalBaseReg) {
+      SDValue InGlue;
+      Chain = DAG.getCopyToReg(Chain, dl, X86::EBX,
+                               DAG.getNode(X86ISD::GlobalBaseReg, dl, PtrVT),
+                               InGlue);
+      InGlue = Chain.getValue(1);
+      SDValue Ops[] = {Chain, TGA, InGlue};
+      Chain = DAG.getNode(CallType, dl, NodeTys, Ops);
----------------
arsenm wrote:

```suggestion
      Chain = DAG.getNode(CallType, dl, NodeTys, {Chain, TGA, InGlue});
```

https://github.com/llvm/llvm-project/pull/113706