From d5ab35f2658f785efc7bc1e684f72c83d02e7668 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Sat, 21 Feb 2015 05:49:45 +0000
Subject: [PATCH] X86: Call __main using the SelectionDAG

Synthesizing a call directly using the MI layer would confuse the frame
lowering code.  This is problematic as frame lowering is highly
sensitive the particularities of calls, etc.

llvm-svn: 230129
---
 .../CodeGen/SelectionDAG/SelectionDAGBuilder.cpp   |  1 -
 llvm/lib/Target/X86/X86ISelDAGToDAG.cpp            | 22 +++++++++++++---------
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 139ba3b..29c0360 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -7884,7 +7884,6 @@ void SelectionDAGISel::LowerArguments(const Function &F) {
   assert(i == InVals.size() && "Argument register count mismatch!");
 
   // Finally, if the target has anything special to do, allow it to do so.
-  // FIXME: this should insert code into the DAG!
   EmitFunctionEntryCode();
 }
 
diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index ade6c77..8d50ae1 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -231,7 +231,7 @@ namespace {
                                       char ConstraintCode,
                                       std::vector<SDValue> &OutOps) override;
 
-    void EmitSpecialCodeForMain(MachineBasicBlock *BB, MachineFrameInfo *MFI);
+    void EmitSpecialCodeForMain();
 
     inline void getAddressOperands(X86ISelAddressMode &AM, SDValue &Base,
                                    SDValue &Scale, SDValue &Index,
@@ -565,14 +565,18 @@ void X86DAGToDAGISel::PreprocessISelDAG() {
 
 /// EmitSpecialCodeForMain - Emit any code that needs to be executed only in
 /// the main function.
-void X86DAGToDAGISel::EmitSpecialCodeForMain(MachineBasicBlock *BB,
-                                             MachineFrameInfo *MFI) {
-  const TargetInstrInfo *TII = getInstrInfo();
+void X86DAGToDAGISel::EmitSpecialCodeForMain() {
   if (Subtarget->isTargetCygMing()) {
-    unsigned CallOp =
-      Subtarget->is64Bit() ? X86::CALL64pcrel32 : X86::CALLpcrel32;
-    BuildMI(BB, DebugLoc(),
-            TII->get(CallOp)).addExternalSymbol("__main");
+    TargetLowering::ArgListTy Args;
+
+    TargetLowering::CallLoweringInfo CLI(*CurDAG);
+    CLI.setChain(CurDAG->getRoot())
+        .setCallee(CallingConv::C, Type::getVoidTy(*CurDAG->getContext()),
+                   CurDAG->getExternalSymbol("__main", TLI->getPointerTy()),
+                   std::move(Args), 0);
+    const TargetLowering &TLI = CurDAG->getTargetLoweringInfo();
+    std::pair<SDValue, SDValue> Result = TLI.LowerCallTo(CLI);
+    CurDAG->setRoot(Result.second);
   }
 }
 
@@ -580,7 +584,7 @@ void X86DAGToDAGISel::EmitFunctionEntryCode() {
   // If this is main, emit special code for main.
   if (const Function *Fn = MF->getFunction())
     if (Fn->hasExternalLinkage() && Fn->getName() == "main")
-      EmitSpecialCodeForMain(MF->begin(), MF->getFrameInfo());
+      EmitSpecialCodeForMain();
 }
 
 static bool isDispSafeForFrameIndex(int64_t Val) {
-- 
2.7.4