From f084847373210540f345698295af333834493322 Mon Sep 17 00:00:00 2001
From: Akira Hatanaka <ahatanaka@mips.com>
Date: Sat, 27 Oct 2012 00:21:13 +0000
Subject: [PATCH] Add method MipsTargetLowering::writeVarArgRegs which copies
 argument registers of vararg functions back to the stack.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166844 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/Mips/MipsISelLowering.cpp | 45 ++++++++++++++++++++++++++++
 lib/Target/Mips/MipsISelLowering.h   |  6 ++++
 2 files changed, 51 insertions(+)

diff --git a/lib/Target/Mips/MipsISelLowering.cpp b/lib/Target/Mips/MipsISelLowering.cpp
index bbcd189047a..48c7f66de67 100644
--- a/lib/Target/Mips/MipsISelLowering.cpp
+++ b/lib/Target/Mips/MipsISelLowering.cpp
@@ -4076,3 +4076,48 @@ passByValArg(SDValue Chain, DebugLoc DL,
                         MachinePointerInfo(0), MachinePointerInfo(0));
   MemOpChains.push_back(Chain);
 }
+
+void
+MipsTargetLowering::writeVarArgRegs(std::vector<SDValue> &OutChains,
+                                    const MipsCC &CC, SDValue Chain,
+                                    DebugLoc DL, SelectionDAG &DAG) const {
+  unsigned NumRegs = CC.numIntArgRegs();
+  const uint16_t *ArgRegs = CC.intArgRegs();
+  const CCState &CCInfo = CC.getCCInfo();
+  unsigned Idx = CCInfo.getFirstUnallocated(ArgRegs, NumRegs);
+  unsigned RegSize = CC.regSize();
+  EVT RegTy = MVT::getIntegerVT(RegSize * 8);
+  const TargetRegisterClass *RC = getRegClassFor(RegTy);
+  MachineFunction &MF = DAG.getMachineFunction();
+  MachineFrameInfo *MFI = MF.getFrameInfo();
+  MipsFunctionInfo *MipsFI = MF.getInfo<MipsFunctionInfo>();
+
+  // Offset of the first variable argument from stack pointer.
+  int VaArgOffset;
+
+  if (NumRegs == Idx)
+    VaArgOffset = RoundUpToAlignment(CCInfo.getNextStackOffset(), RegSize);
+  else
+    VaArgOffset =
+      (int)CC.reservedArgArea() - (int)(RegSize * (NumRegs - Idx));
+
+  // Record the frame index of the first variable argument
+  // which is a value necessary to VASTART.
+  int FI = MFI->CreateFixedObject(RegSize, VaArgOffset, true);
+  MipsFI->setVarArgsFrameIndex(FI);
+
+  // Copy the integer registers that have not been used for argument passing
+  // to the argument register save area. For O32, the save area is allocated
+  // in the caller's stack frame, while for N32/64, it is allocated in the
+  // callee's stack frame.
+  for (unsigned I = Idx; I < NumRegs; ++I, VaArgOffset += RegSize) {
+    unsigned Reg = AddLiveIn(MF, ArgRegs[I], RC);
+    SDValue ArgValue = DAG.getCopyFromReg(Chain, DL, Reg, RegTy);
+    FI = MFI->CreateFixedObject(RegSize, VaArgOffset, true);
+    SDValue PtrOff = DAG.getFrameIndex(FI, getPointerTy());
+    SDValue Store = DAG.getStore(Chain, DL, ArgValue, PtrOff,
+                                 MachinePointerInfo(), false, false, 0);
+    cast<StoreSDNode>(Store.getNode())->getMemOperand()->setValue(0);
+    OutChains.push_back(Store);
+  }
+}
diff --git a/lib/Target/Mips/MipsISelLowering.h b/lib/Target/Mips/MipsISelLowering.h
index 51f3e21eae6..160349e4aaa 100644
--- a/lib/Target/Mips/MipsISelLowering.h
+++ b/lib/Target/Mips/MipsISelLowering.h
@@ -295,6 +295,12 @@ namespace llvm {
                       const MipsCC &CC, const ByValArgInfo &ByVal,
                       const ISD::ArgFlagsTy &Flags, bool isLittle) const;
 
+    /// writeVarArgRegs - Write variable function arguments passed in registers
+    /// to the stack. Also create a stack frame object for the first variable
+    /// argument.
+    void writeVarArgRegs(std::vector<SDValue> &OutChains, const MipsCC &CC,
+                         SDValue Chain, DebugLoc DL, SelectionDAG &DAG) const;
+
     virtual SDValue
       LowerFormalArguments(SDValue Chain,
                            CallingConv::ID CallConv, bool isVarArg,