1//=====- SystemZFrameLowering.cpp - SystemZ Frame Information ------*- C++ -*-====//
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 SystemZ implementation of TargetFrameLowering class.
11//
12//===----------------------------------------------------------------------===//
13
14#include "SystemZFrameLowering.h"
15#include "SystemZInstrBuilder.h"
16#include "SystemZInstrInfo.h"
17#include "SystemZMachineFunctionInfo.h"
18#include "llvm/Function.h"
19#include "llvm/CodeGen/MachineFrameInfo.h"
20#include "llvm/CodeGen/MachineFunction.h"
21#include "llvm/CodeGen/MachineInstrBuilder.h"
22#include "llvm/CodeGen/MachineModuleInfo.h"
23#include "llvm/CodeGen/MachineRegisterInfo.h"
24#include "llvm/Target/TargetData.h"
25#include "llvm/Target/TargetOptions.h"
26#include "llvm/Support/CommandLine.h"
27
28using namespace llvm;
29
30SystemZFrameLowering::SystemZFrameLowering(const SystemZSubtarget &sti)
31  : TargetFrameLowering(TargetFrameLowering::StackGrowsDown, 8, -160), STI(sti) {
32  // Fill the spill offsets map
33  static const unsigned SpillOffsTab[][2] = {
34    { SystemZ::R2D,  0x10 },
35    { SystemZ::R3D,  0x18 },
36    { SystemZ::R4D,  0x20 },
37    { SystemZ::R5D,  0x28 },
38    { SystemZ::R6D,  0x30 },
39    { SystemZ::R7D,  0x38 },
40    { SystemZ::R8D,  0x40 },
41    { SystemZ::R9D,  0x48 },
42    { SystemZ::R10D, 0x50 },
43    { SystemZ::R11D, 0x58 },
44    { SystemZ::R12D, 0x60 },
45    { SystemZ::R13D, 0x68 },
46    { SystemZ::R14D, 0x70 },
47    { SystemZ::R15D, 0x78 }
48  };
49
50  RegSpillOffsets.grow(SystemZ::NUM_TARGET_REGS);
51
52  for (unsigned i = 0, e = array_lengthof(SpillOffsTab); i != e; ++i)
53    RegSpillOffsets[SpillOffsTab[i][0]] = SpillOffsTab[i][1];
54}
55
56/// needsFP - Return true if the specified function should have a dedicated
57/// frame pointer register.  This is true if the function has variable sized
58/// allocas or if frame pointer elimination is disabled.
59bool SystemZFrameLowering::hasFP(const MachineFunction &MF) const {
60  const MachineFrameInfo *MFI = MF.getFrameInfo();
61  return DisableFramePointerElim(MF) || MFI->hasVarSizedObjects();
62}
63
64/// emitSPUpdate - Emit a series of instructions to increment / decrement the
65/// stack pointer by a constant value.
66static
67void emitSPUpdate(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
68                  int64_t NumBytes, const TargetInstrInfo &TII) {
69  unsigned Opc; uint64_t Chunk;
70  bool isSub = NumBytes < 0;
71  uint64_t Offset = isSub ? -NumBytes : NumBytes;
72
73  if (Offset >= (1LL << 15) - 1) {
74    Opc = SystemZ::ADD64ri32;
75    Chunk = (1LL << 31) - 1;
76  } else {
77    Opc = SystemZ::ADD64ri16;
78    Chunk = (1LL << 15) - 1;
79  }
80
81  DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
82
83  while (Offset) {
84    uint64_t ThisVal = (Offset > Chunk) ? Chunk : Offset;
85    MachineInstr *MI =
86      BuildMI(MBB, MBBI, DL, TII.get(Opc), SystemZ::R15D)
87      .addReg(SystemZ::R15D).addImm(isSub ? -ThisVal : ThisVal);
88    // The PSW implicit def is dead.
89    MI->getOperand(3).setIsDead();
90    Offset -= ThisVal;
91  }
92}
93
94void SystemZFrameLowering::emitPrologue(MachineFunction &MF) const {
95  MachineBasicBlock &MBB = MF.front();   // Prolog goes in entry BB
96  MachineFrameInfo *MFI = MF.getFrameInfo();
97  const SystemZInstrInfo &TII =
98    *static_cast<const SystemZInstrInfo*>(MF.getTarget().getInstrInfo());
99  SystemZMachineFunctionInfo *SystemZMFI =
100    MF.getInfo<SystemZMachineFunctionInfo>();
101  MachineBasicBlock::iterator MBBI = MBB.begin();
102  DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
103
104  // Get the number of bytes to allocate from the FrameInfo.
105  // Note that area for callee-saved stuff is already allocated, thus we need to
106  // 'undo' the stack movement.
107  uint64_t StackSize = MFI->getStackSize();
108  StackSize -= SystemZMFI->getCalleeSavedFrameSize();
109
110  uint64_t NumBytes = StackSize - getOffsetOfLocalArea();
111
112  // Skip the callee-saved push instructions.
113  while (MBBI != MBB.end() &&
114         (MBBI->getOpcode() == SystemZ::MOV64mr ||
115          MBBI->getOpcode() == SystemZ::MOV64mrm))
116    ++MBBI;
117
118  if (MBBI != MBB.end())
119    DL = MBBI->getDebugLoc();
120
121  // adjust stack pointer: R15 -= numbytes
122  if (StackSize || MFI->hasCalls()) {
123    assert(MF.getRegInfo().isPhysRegUsed(SystemZ::R15D) &&
124           "Invalid stack frame calculation!");
125    emitSPUpdate(MBB, MBBI, -(int64_t)NumBytes, TII);
126  }
127
128  if (hasFP(MF)) {
129    // Update R11 with the new base value...
130    BuildMI(MBB, MBBI, DL, TII.get(SystemZ::MOV64rr), SystemZ::R11D)
131      .addReg(SystemZ::R15D);
132
133    // Mark the FramePtr as live-in in every block except the entry.
134    for (MachineFunction::iterator I = llvm::next(MF.begin()), E = MF.end();
135         I != E; ++I)
136      I->addLiveIn(SystemZ::R11D);
137
138  }
139}
140
141void SystemZFrameLowering::emitEpilogue(MachineFunction &MF,
142                                    MachineBasicBlock &MBB) const {
143  const MachineFrameInfo *MFI = MF.getFrameInfo();
144  MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
145  const SystemZInstrInfo &TII =
146    *static_cast<const SystemZInstrInfo*>(MF.getTarget().getInstrInfo());
147  SystemZMachineFunctionInfo *SystemZMFI =
148    MF.getInfo<SystemZMachineFunctionInfo>();
149  unsigned RetOpcode = MBBI->getOpcode();
150
151  switch (RetOpcode) {
152  case SystemZ::RET: break;  // These are ok
153  default:
154    assert(0 && "Can only insert epilog into returning blocks");
155  }
156
157  // Get the number of bytes to allocate from the FrameInfo
158  // Note that area for callee-saved stuff is already allocated, thus we need to
159  // 'undo' the stack movement.
160  uint64_t StackSize =
161    MFI->getStackSize() - SystemZMFI->getCalleeSavedFrameSize();
162  uint64_t NumBytes = StackSize - getOffsetOfLocalArea();
163
164  // Skip the final terminator instruction.
165  while (MBBI != MBB.begin()) {
166    MachineBasicBlock::iterator PI = prior(MBBI);
167    --MBBI;
168    if (!PI->getDesc().isTerminator())
169      break;
170  }
171
172  // During callee-saved restores emission stack frame was not yet finialized
173  // (and thus - the stack size was unknown). Tune the offset having full stack
174  // size in hands.
175  if (StackSize || MFI->hasCalls()) {
176    assert((MBBI->getOpcode() == SystemZ::MOV64rmm ||
177            MBBI->getOpcode() == SystemZ::MOV64rm) &&
178           "Expected to see callee-save register restore code");
179    assert(MF.getRegInfo().isPhysRegUsed(SystemZ::R15D) &&
180           "Invalid stack frame calculation!");
181
182    unsigned i = 0;
183    MachineInstr &MI = *MBBI;
184    while (!MI.getOperand(i).isImm()) {
185      ++i;
186      assert(i < MI.getNumOperands() && "Unexpected restore code!");
187    }
188
189    uint64_t Offset = NumBytes + MI.getOperand(i).getImm();
190    // If Offset does not fit into 20-bit signed displacement field we need to
191    // emit some additional code...
192    if (Offset > 524287) {
193      // Fold the displacement into load instruction as much as possible.
194      NumBytes = Offset - 524287;
195      Offset = 524287;
196      emitSPUpdate(MBB, MBBI, NumBytes, TII);
197    }
198
199    MI.getOperand(i).ChangeToImmediate(Offset);
200  }
201}
202
203int SystemZFrameLowering::getFrameIndexOffset(const MachineFunction &MF,
204                                          int FI) const {
205  const MachineFrameInfo *MFI = MF.getFrameInfo();
206  const SystemZMachineFunctionInfo *SystemZMFI =
207    MF.getInfo<SystemZMachineFunctionInfo>();
208  int Offset = MFI->getObjectOffset(FI) + MFI->getOffsetAdjustment();
209  uint64_t StackSize = MFI->getStackSize();
210
211  // Fixed objects are really located in the "previous" frame.
212  if (FI < 0)
213    StackSize -= SystemZMFI->getCalleeSavedFrameSize();
214
215  Offset += StackSize - getOffsetOfLocalArea();
216
217  // Skip the register save area if we generated the stack frame.
218  if (StackSize || MFI->hasCalls())
219    Offset -= getOffsetOfLocalArea();
220
221  return Offset;
222}
223
224bool
225SystemZFrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB,
226                                            MachineBasicBlock::iterator MI,
227                                        const std::vector<CalleeSavedInfo> &CSI,
228                                          const TargetRegisterInfo *TRI) const {
229  if (CSI.empty())
230    return false;
231
232  DebugLoc DL;
233  if (MI != MBB.end()) DL = MI->getDebugLoc();
234
235  MachineFunction &MF = *MBB.getParent();
236  const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
237  SystemZMachineFunctionInfo *MFI = MF.getInfo<SystemZMachineFunctionInfo>();
238  unsigned CalleeFrameSize = 0;
239
240  // Scan the callee-saved and find the bounds of register spill area.
241  unsigned LowReg = 0, HighReg = 0, StartOffset = -1U, EndOffset = 0;
242  for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
243    unsigned Reg = CSI[i].getReg();
244    if (!SystemZ::FP64RegClass.contains(Reg)) {
245      unsigned Offset = RegSpillOffsets[Reg];
246      CalleeFrameSize += 8;
247      if (StartOffset > Offset) {
248        LowReg = Reg; StartOffset = Offset;
249      }
250      if (EndOffset < Offset) {
251        HighReg = Reg; EndOffset = RegSpillOffsets[Reg];
252      }
253    }
254  }
255
256  // Save information for epilogue inserter.
257  MFI->setCalleeSavedFrameSize(CalleeFrameSize);
258  MFI->setLowReg(LowReg); MFI->setHighReg(HighReg);
259
260  // Save GPRs
261  if (StartOffset) {
262    // Build a store instruction. Use STORE MULTIPLE instruction if there are many
263    // registers to store, otherwise - just STORE.
264    MachineInstrBuilder MIB =
265      BuildMI(MBB, MI, DL, TII.get((LowReg == HighReg ?
266                                    SystemZ::MOV64mr : SystemZ::MOV64mrm)));
267
268    // Add store operands.
269    MIB.addReg(SystemZ::R15D).addImm(StartOffset);
270    if (LowReg == HighReg)
271      MIB.addReg(0);
272    MIB.addReg(LowReg, RegState::Kill);
273    if (LowReg != HighReg)
274      MIB.addReg(HighReg, RegState::Kill);
275
276    // Do a second scan adding regs as being killed by instruction
277    for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
278      unsigned Reg = CSI[i].getReg();
279      // Add the callee-saved register as live-in. It's killed at the spill.
280      MBB.addLiveIn(Reg);
281      if (Reg != LowReg && Reg != HighReg)
282        MIB.addReg(Reg, RegState::ImplicitKill);
283    }
284  }
285
286  // Save FPRs
287  for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
288    unsigned Reg = CSI[i].getReg();
289    if (SystemZ::FP64RegClass.contains(Reg)) {
290      MBB.addLiveIn(Reg);
291      TII.storeRegToStackSlot(MBB, MI, Reg, true, CSI[i].getFrameIdx(),
292                              &SystemZ::FP64RegClass, TRI);
293    }
294  }
295
296  return true;
297}
298
299bool
300SystemZFrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
301                                              MachineBasicBlock::iterator MI,
302                                        const std::vector<CalleeSavedInfo> &CSI,
303                                          const TargetRegisterInfo *TRI) const {
304  if (CSI.empty())
305    return false;
306
307  DebugLoc DL;
308  if (MI != MBB.end()) DL = MI->getDebugLoc();
309
310  MachineFunction &MF = *MBB.getParent();
311  const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
312  SystemZMachineFunctionInfo *MFI = MF.getInfo<SystemZMachineFunctionInfo>();
313
314  // Restore FP registers
315  for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
316    unsigned Reg = CSI[i].getReg();
317    if (SystemZ::FP64RegClass.contains(Reg))
318      TII.loadRegFromStackSlot(MBB, MI, Reg, CSI[i].getFrameIdx(),
319                               &SystemZ::FP64RegClass, TRI);
320  }
321
322  // Restore GP registers
323  unsigned LowReg = MFI->getLowReg(), HighReg = MFI->getHighReg();
324  unsigned StartOffset = RegSpillOffsets[LowReg];
325
326  if (StartOffset) {
327    // Build a load instruction. Use LOAD MULTIPLE instruction if there are many
328    // registers to load, otherwise - just LOAD.
329    MachineInstrBuilder MIB =
330      BuildMI(MBB, MI, DL, TII.get((LowReg == HighReg ?
331                                    SystemZ::MOV64rm : SystemZ::MOV64rmm)));
332    // Add store operands.
333    MIB.addReg(LowReg, RegState::Define);
334    if (LowReg != HighReg)
335      MIB.addReg(HighReg, RegState::Define);
336
337    MIB.addReg(hasFP(MF) ? SystemZ::R11D : SystemZ::R15D);
338    MIB.addImm(StartOffset);
339    if (LowReg == HighReg)
340      MIB.addReg(0);
341
342    // Do a second scan adding regs as being defined by instruction
343    for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
344      unsigned Reg = CSI[i].getReg();
345      if (Reg != LowReg && Reg != HighReg)
346        MIB.addReg(Reg, RegState::ImplicitDefine);
347    }
348  }
349
350  return true;
351}
352
353void
354SystemZFrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
355                                                       RegScavenger *RS) const {
356  // Determine whether R15/R14 will ever be clobbered inside the function. And
357  // if yes - mark it as 'callee' saved.
358  MachineFrameInfo *FFI = MF.getFrameInfo();
359  MachineRegisterInfo &MRI = MF.getRegInfo();
360
361  // Check whether high FPRs are ever used, if yes - we need to save R15 as
362  // well.
363  static const unsigned HighFPRs[] = {
364    SystemZ::F8L,  SystemZ::F9L,  SystemZ::F10L, SystemZ::F11L,
365    SystemZ::F12L, SystemZ::F13L, SystemZ::F14L, SystemZ::F15L,
366    SystemZ::F8S,  SystemZ::F9S,  SystemZ::F10S, SystemZ::F11S,
367    SystemZ::F12S, SystemZ::F13S, SystemZ::F14S, SystemZ::F15S,
368  };
369
370  bool HighFPRsUsed = false;
371  for (unsigned i = 0, e = array_lengthof(HighFPRs); i != e; ++i)
372    HighFPRsUsed |= MRI.isPhysRegUsed(HighFPRs[i]);
373
374  if (FFI->hasCalls())
375    /* FIXME: function is varargs */
376    /* FIXME: function grabs RA */
377    /* FIXME: function calls eh_return */
378    MRI.setPhysRegUsed(SystemZ::R14D);
379
380  if (HighFPRsUsed ||
381      FFI->hasCalls() ||
382      FFI->getObjectIndexEnd() != 0 || // Contains automatic variables
383      FFI->hasVarSizedObjects() // Function calls dynamic alloca's
384      /* FIXME: function is varargs */)
385    MRI.setPhysRegUsed(SystemZ::R15D);
386}
387