[NFC]Fix IR/MC depency issue for function descriptor SDAG implementation

[Xiangling_L]

Summary

llvm/IR/GlobalValue.h can't be included in MC, that creates a circular dependency between MC and IR libraries. This circular dependency is causing an issue for build system that enforce layering.

[gribozavr]

Thank you very much for the fix!

[Xiangling_L]

delete the unused variable

llvm/include/llvm/MC/MCSymbolXCOFF.h

 //===- MCSymbolXCOFF.h -  ----------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 #ifndef LLVM_MC_MCSYMBOLXCOFF_H
 #define LLVM_MC_MCSYMBOLXCOFF_H
 
 #include "llvm/BinaryFormat/XCOFF.h"
 #include "llvm/MC/MCSymbol.h"
 
 namespace llvm {
 
-class GlobalValue;
-
 class MCSymbolXCOFF : public MCSymbol {
-  // The IR symbol this MCSymbolXCOFF is based on. It is set on function
-  // entry point symbols when they are the callee operand of a direct call
-  // SDNode.
-  const GlobalValue *GV = nullptr;
-
 public:
   MCSymbolXCOFF(const StringMapEntry<bool> *Name, bool isTemporary)
       : MCSymbol(SymbolKindXCOFF, Name, isTemporary) {}
 
-  void setGlobalValue(const GlobalValue *G) { GV = G; }
-  const GlobalValue *getGlobalValue() const { return GV; }
-
   static bool classof(const MCSymbol *S) { return S->isXCOFF(); }
 };
 
 } // end namespace llvm
 
 #endif // LLVM_MC_MCSYMBOLXCOFF_H

llvm/lib/Target/PowerPC/PPCISelLowering.cpp

static int CalculateTailCallSPDiff(SelectionDAG& DAG, bool isTailCall,
   return SPDiff;
 }
 
 static bool isFunctionGlobalAddress(SDValue Callee);
 
 static bool
 callsShareTOCBase(const Function *Caller, SDValue Callee,
                     const TargetMachine &TM) {
-  // Need a GlobalValue to determine if a Caller and Callee share the same
-  // TOCBase.
-  const GlobalValue *GV = nullptr;
-
-  if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee)) {
-    GV = G->getGlobal();
-  } else if (MCSymbolSDNode *M = dyn_cast<MCSymbolSDNode>(Callee)) {
-    // On AIX only, we replace GlobalAddressSDNode with MCSymbolSDNode for
-    // the callee of a direct function call. The MCSymbolSDNode contains the
-    // MCSymbol for the funtion entry point.
-    const auto *S = cast<MCSymbolXCOFF>(M->getMCSymbol());
-    GV = S->getGlobalValue();
-  }
-
-  // If we failed to get a GlobalValue, then pessimistically assume they do not
-  // share a TOCBase.
-  if (!GV)
+   // Callee is either a GlobalAddress or an ExternalSymbol. ExternalSymbols
+   // don't have enough information to determine if the caller and calle share
+   // the same  TOC base, so we have to pessimistically assume they don't for
+   // correctness.
+   GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee);
+   if (!G)
      return false;
 
+   const GlobalValue *GV = G->getGlobal();
   // The medium and large code models are expected to provide a sufficiently
   // large TOC to provide all data addressing needs of a module with a
   // single TOC. Since each module will be addressed with a single TOC then we
   // only need to check that caller and callee don't cross dso boundaries.
   if (CodeModel::Medium == TM.getCodeModel() ||
       CodeModel::Large == TM.getCodeModel())
     return TM.shouldAssumeDSOLocal(*Caller->getParent(), GV);
 
if (SDNode *Dest = isBLACompatibleAddress(Callee, DAG)) {
       Callee = SDValue(Dest, 0);
       needIndirectCall = false;
     }
 
   // PC-relative references to external symbols should go through $stub, unless
   // we're building with the leopard linker or later, which automatically
   // synthesizes these stubs.
   const TargetMachine &TM = DAG.getTarget();
-  MachineFunction &MF = DAG.getMachineFunction();
-  const Module *Mod = MF.getFunction().getParent();
+  const Module *Mod = DAG.getMachineFunction().getFunction().getParent();
   const GlobalValue *GV = nullptr;
   if (auto *G = dyn_cast<GlobalAddressSDNode>(Callee))
     GV = G->getGlobal();
   bool Local = TM.shouldAssumeDSOLocal(*Mod, GV);
   bool UsePlt = !Local && Subtarget.isTargetELF() && !isPPC64;
 
+  // If the callee is a GlobalAddress/ExternalSymbol node (quite common,
+  // every direct call is) turn it into a TargetGlobalAddress /
+  // TargetExternalSymbol node so that legalize doesn't hack it.
   if (isFunctionGlobalAddress(Callee)) {
     GlobalAddressSDNode *G = cast<GlobalAddressSDNode>(Callee);
 
-    if (TM.getTargetTriple().isOSAIX()) {
-      // Direct function calls reference the symbol for the function's entry
-      // point, which is named by inserting a "." before the function's
-      // C-linkage name.
-      auto &Context = MF.getMMI().getContext();
-      MCSymbol *S = Context.getOrCreateSymbol(Twine(".") +
-                                              Twine(G->getGlobal()->getName()));
-      cast<MCSymbolXCOFF>(S)->setGlobalValue(GV);
-      Callee = DAG.getMCSymbol(S, PtrVT);
-    } else {
-      // A call to a TLS address is actually an indirect call to a
-      // thread-specific pointer.
-      unsigned OpFlags = 0;
-      if (UsePlt)
-        OpFlags = PPCII::MO_PLT;
 
-      // If the callee is a GlobalAddress/ExternalSymbol node (quite common,
-      // every direct call is) turn it into a TargetGlobalAddress /
-      // TargetExternalSymbol node so that legalize doesn't hack it.
-      Callee = DAG.getTargetGlobalAddress(G->getGlobal(), dl,
-                                          Callee.getValueType(), 0, OpFlags);
-    }
     needIndirectCall = false;
   }
 
   if (ExternalSymbolSDNode *S = dyn_cast<ExternalSymbolSDNode>(Callee)) {
     unsigned char OpFlags = 0;
 
     if (UsePlt)
       OpFlags = PPCII::MO_PLT;
SDValue PPCTargetLowering::FinishCall(
   // thus have a different TOC, the call will be replaced with a call to a stub
   // function which saves the current TOC, loads the TOC of the callee and
   // branches to the callee. The NOP will be replaced with a load instruction
   // which restores the TOC of the caller from the TOC save slot of the current
   // stack frame. If caller and callee belong to the same module (and have the
   // same TOC), the NOP will remain unchanged, or become some other NOP.
 
   MachineFunction &MF = DAG.getMachineFunction();
+  EVT PtrVT = getPointerTy(DAG.getDataLayout());
   if (!isTailCall && !isPatchPoint &&
       ((Subtarget.isSVR4ABI() && Subtarget.isPPC64()) ||
        Subtarget.isAIXABI())) {
     if (CallOpc == PPCISD::BCTRL) {
       if (Subtarget.isAIXABI())
         report_fatal_error("Indirect call on AIX is not implemented.");
 
       // This is a call through a function pointer.
       // Restore the caller TOC from the save area into R2.
       // See PrepareCall() for more information about calls through function
       // pointers in the 64-bit SVR4 ABI.
       // We are using a target-specific load with r2 hard coded, because the
       // result of a target-independent load would never go directly into r2,
       // since r2 is a reserved register (which prevents the register allocator
       // from allocating it), resulting in an additional register being
       // allocated and an unnecessary move instruction being generated.
       CallOpc = PPCISD::BCTRL_LOAD_TOC;
 
-      EVT PtrVT = getPointerTy(DAG.getDataLayout());
       SDValue StackPtr = DAG.getRegister(PPC::X1, PtrVT);
       unsigned TOCSaveOffset = Subtarget.getFrameLowering()->getTOCSaveOffset();
       SDValue TOCOff = DAG.getIntPtrConstant(TOCSaveOffset, dl);
       SDValue AddTOC = DAG.getNode(ISD::ADD, dl, MVT::i64, StackPtr, TOCOff);
 
       // The address needs to go after the chain input but before the flag (or
       // any other variadic arguments).
       Ops.insert(std::next(Ops.begin()), AddTOC);
     } else if (CallOpc == PPCISD::CALL &&
       !callsShareTOCBase(&MF.getFunction(), Callee, DAG.getTarget())) {
       // Otherwise insert NOP for non-local calls.
       CallOpc = PPCISD::CALL_NOP;
     }
   }
   
+  const TargetMachine &TM = getTargetMachine();
+  if (Subtarget.isAIXABI() && isFunctionGlobalAddress(Callee)) {
+    // On AIX, direct function calls reference the symbol for the function's
+    // entry point, which is named by inserting a "." before the function's
+    // C-linkage name.
+    GlobalAddressSDNode *G = cast<GlobalAddressSDNode>(Callee);
+    auto &Context = DAG.getMachineFunction().getMMI().getContext();
+    MCSymbol *S = Context.getOrCreateSymbol(Twine(".") +
+                                            Twine(G->getGlobal()->getName()));
+    Callee = DAG.getMCSymbol(S, PtrVT);
+    // Replace the GlobalAddressSDNode Callee with the MCSymbolSDNode.
+    Ops[1] = Callee;
+  }
+
   Chain = DAG.getNode(CallOpc, dl, NodeTys, Ops);
   InFlag = Chain.getValue(1);
 
   Chain = DAG.getCALLSEQ_END(Chain, DAG.getIntPtrConstant(NumBytes, dl, true),
                              DAG.getIntPtrConstant(BytesCalleePops, dl, true),
                              InFlag, dl);
   if (!Ins.empty())
     InFlag = Chain.getValue(1);