1 //===-- Mips16FrameLowering.cpp - Mips16 Frame Information ----------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file contains the Mips16 implementation of TargetFrameLowering class.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "Mips16FrameLowering.h"
15 #include "MipsInstrInfo.h"
16 #include "MCTargetDesc/MipsBaseInfo.h"
17 #include "llvm/Function.h"
18 #include "llvm/CodeGen/MachineFrameInfo.h"
19 #include "llvm/CodeGen/MachineFunction.h"
20 #include "llvm/CodeGen/MachineInstrBuilder.h"
21 #include "llvm/CodeGen/MachineModuleInfo.h"
22 #include "llvm/CodeGen/MachineRegisterInfo.h"
23 #include "llvm/DataLayout.h"
24 #include "llvm/Target/TargetOptions.h"
25 #include "llvm/Support/CommandLine.h"
26 
27 using namespace llvm;
28 
29 void Mips16FrameLowering::emitPrologue(MachineFunction &MF) const {
30   MachineBasicBlock &MBB = MF.front();
31   MachineFrameInfo *MFI = MF.getFrameInfo();
32   const MipsInstrInfo &TII =
33     *static_cast<const MipsInstrInfo*>(MF.getTarget().getInstrInfo());
34   MachineBasicBlock::iterator MBBI = MBB.begin();
35   DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
36   uint64_t StackSize = MFI->getStackSize();
37 
38   // No need to allocate space on the stack.
39   if (StackSize == 0 && !MFI->adjustsStack()) return;
40 
41   // Adjust stack.
42   if (isInt<16>(-StackSize))
43     BuildMI(MBB, MBBI, dl, TII.get(Mips::SaveRaF16)).addImm(StackSize);
44 
45   if (hasFP(MF))
46     BuildMI(MBB, MBBI, dl, TII.get(Mips::MoveR3216), Mips::S0)
47       .addReg(Mips::SP);
48 
49 }
50 
51 void Mips16FrameLowering::emitEpilogue(MachineFunction &MF,
52                                  MachineBasicBlock &MBB) const {
53   MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
54   MachineFrameInfo *MFI = MF.getFrameInfo();
55   const MipsInstrInfo &TII =
56     *static_cast<const MipsInstrInfo*>(MF.getTarget().getInstrInfo());
57   DebugLoc dl = MBBI->getDebugLoc();
58   uint64_t StackSize = MFI->getStackSize();
59 
60   if (!StackSize)
61     return;
62 
63   if (hasFP(MF))
64     BuildMI(MBB, MBBI, dl, TII.get(Mips::Move32R16), Mips::SP)
65       .addReg(Mips::S0);
66 
67   // Adjust stack.
68   if (isInt<16>(StackSize))
69     // assumes stacksize multiple of 8
70     BuildMI(MBB, MBBI, dl, TII.get(Mips::RestoreRaF16)).addImm(StackSize);
71 }
72 
73 bool Mips16FrameLowering::
74 spillCalleeSavedRegisters(MachineBasicBlock &MBB,
75                           MachineBasicBlock::iterator MI,
76                           const std::vector<CalleeSavedInfo> &CSI,
77                           const TargetRegisterInfo *TRI) const {
78   MachineFunction *MF = MBB.getParent();
79   MachineBasicBlock *EntryBlock = MF->begin();
80 
81   //
82   // Registers RA, S0,S1 are the callee saved registers and they
83   // will be saved with the "save" instruction
84   // during emitPrologue
85   //
86   for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
87     // Add the callee-saved register as live-in. Do not add if the register is
88     // RA and return address is taken, because it has already been added in
89     // method MipsTargetLowering::LowerRETURNADDR.
90     // It's killed at the spill, unless the register is RA and return address
91     // is taken.
92     unsigned Reg = CSI[i].getReg();
93     bool IsRAAndRetAddrIsTaken = (Reg == Mips::RA)
94       && MF->getFrameInfo()->isReturnAddressTaken();
95     if (!IsRAAndRetAddrIsTaken)
96       EntryBlock->addLiveIn(Reg);
97   }
98 
99   return true;
100 }
101 
102 bool Mips16FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
103                                           MachineBasicBlock::iterator MI,
104                                        const std::vector<CalleeSavedInfo> &CSI,
105                                        const TargetRegisterInfo *TRI) const {
106   //
107   // Registers RA,S0,S1 are the callee saved registers and they will be restored
108   // with the restore instruction during emitEpilogue.
109   // We need to override this virtual function, otherwise llvm will try and
110   // restore the registers on it's on from the stack.
111   //
112 
113   return true;
114 }
115 
116 bool
117 Mips16FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
118   const MachineFrameInfo *MFI = MF.getFrameInfo();
119   // Reserve call frame if the size of the maximum call frame fits into 15-bit
120   // immediate field and there are no variable sized objects on the stack.
121   return isInt<15>(MFI->getMaxCallFrameSize()) && !MFI->hasVarSizedObjects();
122 }
123 
124 void Mips16FrameLowering::
125 processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
126                                      RegScavenger *RS) const {
127   MF.getRegInfo().setPhysRegUsed(Mips::RA);
128   MF.getRegInfo().setPhysRegUsed(Mips::S0);
129   MF.getRegInfo().setPhysRegUsed(Mips::S1);
130 }
131 
132 const MipsFrameLowering *
133 llvm::createMips16FrameLowering(const MipsSubtarget &ST) {
134   return new Mips16FrameLowering(ST);
135 }
136