[SelectionDAG] Remove lowerCallToExternalSymbol (#127408)

The last use was removed in:

  commit 05e6bb4
  Author: Roger Ferrer Ibáñez <[email protected]>
  Date:   Thu May 30 14:55:32 2024 +0200

Author: kazutakahirata

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -6281,15 +6281,6 @@ static unsigned FixedPointIntrinsicToOpcode(unsigned Intrinsic) {
   }
 }
 
-void SelectionDAGBuilder::lowerCallToExternalSymbol(const CallInst &I,
-                                           const char *FunctionName) {
-  assert(FunctionName && "FunctionName must not be nullptr");
-  SDValue Callee = DAG.getExternalSymbol(
-      FunctionName,
-      DAG.getTargetLoweringInfo().getPointerTy(DAG.getDataLayout()));
-  LowerCallTo(I, Callee, I.isTailCall(), I.isMustTailCall());
-}
-
 /// Given a @llvm.call.preallocated.setup, return the corresponding
 /// preallocated call.
 static const CallBase *FindPreallocatedCall(const Value *PreallocatedSetup) {

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h

@@ -705,9 +705,6 @@ class SelectionDAGBuilder {
                           DIExpression *Expr, const DebugLoc &dl,
                           unsigned DbgSDNodeOrder);
 
-  /// Lowers CallInst to an external symbol.
-  void lowerCallToExternalSymbol(const CallInst &I, const char *FunctionName);
-
   SDValue lowerStartEH(SDValue Chain, const BasicBlock *EHPadBB,
                        MCSymbol *&BeginLabel);
   SDValue lowerEndEH(SDValue Chain, const InvokeInst *II,