Partly revert invalid r41774

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@42322 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 20 insertions, 0 deletions

diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp
index 117d2734c5..94803cea27 100644
--- a/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -130,6 +130,8 @@ namespace {
     /// SelectionDAGISel when it has created a SelectionDAG for us to codegen.
     virtual void InstructionSelectBasicBlock(SelectionDAG &DAG);
 
+    virtual void EmitFunctionEntryCode(Function &Fn, MachineFunction &MF);
+
     virtual bool CanBeFoldedBy(SDNode *N, SDNode *U, SDNode *Root) const;
 
 // Include the pieces autogenerated from the target description.
@@ -162,6 +164,8 @@ namespace {
                                               std::vector<SDOperand> &OutOps,
                                               SelectionDAG &DAG);
     
+    void EmitSpecialCodeForMain(MachineBasicBlock *BB, MachineFrameInfo *MFI);
+
     inline void getAddressOperands(X86ISelAddressMode &AM, SDOperand &Base, 
                                    SDOperand &Scale, SDOperand &Index,
                                    SDOperand &Disp) {
@@ -540,6 +544,22 @@ void X86DAGToDAGISel::InstructionSelectBasicBlock(SelectionDAG &DAG) {
   } while (&*(MBBI++) != BB);
 }
 
+/// EmitSpecialCodeForMain - Emit any code that needs to be executed only in
+/// the main function.
+void X86DAGToDAGISel::EmitSpecialCodeForMain(MachineBasicBlock *BB,
+                                             MachineFrameInfo *MFI) {
+  const TargetInstrInfo *TII = TM.getInstrInfo();
+  if (Subtarget->isTargetCygMing())
+    BuildMI(BB, TII->get(X86::CALLpcrel32)).addExternalSymbol("__main");
+}
+
+void X86DAGToDAGISel::EmitFunctionEntryCode(Function &Fn, MachineFunction &MF) {
+  // If this is main, emit special code for main.
+  MachineBasicBlock *BB = MF.begin();
+  if (Fn.hasExternalLinkage() && Fn.getName() == "main")
+    EmitSpecialCodeForMain(BB, MF.getFrameInfo());
+}
+
 /// MatchAddress - Add the specified node to the specified addressing mode,
 /// returning true if it cannot be done.  This just pattern matches for the
 /// addressing mode