SystemZRegisterInfo.cpp revision dff4b4c5a7cc894d3b4b6c6e779ea8f47fa50630 
1//===- SystemZRegisterInfo.cpp - SystemZ Register 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 the TargetRegisterInfo class.
11//
12//===----------------------------------------------------------------------===//
13
14#include "SystemZ.h"
15#include "SystemZInstrInfo.h"
16#include "SystemZMachineFunctionInfo.h"
17#include "SystemZRegisterInfo.h"
18#include "SystemZSubtarget.h"
19#include "llvm/CodeGen/MachineInstrBuilder.h"
20#include "llvm/CodeGen/MachineFrameInfo.h"
21#include "llvm/CodeGen/MachineFunction.h"
22#include "llvm/CodeGen/MachineRegisterInfo.h"
23#include "llvm/Target/TargetFrameInfo.h"
24#include "llvm/Target/TargetInstrInfo.h"
25#include "llvm/Target/TargetMachine.h"
26#include "llvm/Target/TargetOptions.h"
27#include "llvm/ADT/BitVector.h"
28using namespace llvm;
29
30SystemZRegisterInfo::SystemZRegisterInfo(SystemZTargetMachine &tm,
31                                         const SystemZInstrInfo &tii)
32  : SystemZGenRegisterInfo(SystemZ::ADJCALLSTACKUP, SystemZ::ADJCALLSTACKDOWN),
33    TM(tm), TII(tii) {
34}
35
36const unsigned*
37SystemZRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
38  static const unsigned CalleeSavedRegs[] = {
39    SystemZ::R6D,  SystemZ::R7D,  SystemZ::R8D,  SystemZ::R9D,
40    SystemZ::R10D, SystemZ::R11D, SystemZ::R12D, SystemZ::R13D,
41    SystemZ::R14D, SystemZ::R15D,
42    SystemZ::F8L,  SystemZ::F9L,  SystemZ::F10L, SystemZ::F11L,
43    SystemZ::F12L, SystemZ::F13L, SystemZ::F14L, SystemZ::F15L,
44    0
45  };
46
47  return CalleeSavedRegs;
48}
49
50const TargetRegisterClass* const*
51SystemZRegisterInfo::getCalleeSavedRegClasses(const MachineFunction *MF) const {
52  static const TargetRegisterClass * const CalleeSavedRegClasses[] = {
53    &SystemZ::GR64RegClass, &SystemZ::GR64RegClass,
54    &SystemZ::GR64RegClass, &SystemZ::GR64RegClass,
55    &SystemZ::GR64RegClass, &SystemZ::GR64RegClass,
56    &SystemZ::GR64RegClass, &SystemZ::GR64RegClass,
57    &SystemZ::GR64RegClass, &SystemZ::GR64RegClass,
58    &SystemZ::FP64RegClass, &SystemZ::FP64RegClass,
59    &SystemZ::FP64RegClass, &SystemZ::FP64RegClass,
60    &SystemZ::FP64RegClass, &SystemZ::FP64RegClass,
61    &SystemZ::FP64RegClass, &SystemZ::FP64RegClass, 0
62  };
63  return CalleeSavedRegClasses;
64}
65
66BitVector SystemZRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
67  BitVector Reserved(getNumRegs());
68  if (hasFP(MF))
69    Reserved.set(SystemZ::R11D);
70  Reserved.set(SystemZ::R14D);
71  Reserved.set(SystemZ::R15D);
72  return Reserved;
73}
74
75/// needsFP - Return true if the specified function should have a dedicated
76/// frame pointer register.  This is true if the function has variable sized
77/// allocas or if frame pointer elimination is disabled.
78bool SystemZRegisterInfo::hasFP(const MachineFunction &MF) const {
79  const MachineFrameInfo *MFI = MF.getFrameInfo();
80  return NoFramePointerElim || MFI->hasVarSizedObjects();
81}
82
83void SystemZRegisterInfo::
84eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
85                              MachineBasicBlock::iterator I) const {
86  MBB.erase(I);
87}
88
89int SystemZRegisterInfo::getFrameIndexOffset(const MachineFunction &MF,
90                                             int FI) const {
91  const TargetFrameInfo &TFI = *MF.getTarget().getFrameInfo();
92  const MachineFrameInfo *MFI = MF.getFrameInfo();
93  const SystemZMachineFunctionInfo *SystemZMFI =
94    MF.getInfo<SystemZMachineFunctionInfo>();
95  int Offset = MFI->getObjectOffset(FI) + MFI->getOffsetAdjustment();
96  uint64_t StackSize = MFI->getStackSize();
97
98  // Fixed objects are really located in the "previous" frame.
99  if (FI < 0)
100    StackSize -= SystemZMFI->getCalleeSavedFrameSize();
101
102  Offset += StackSize - TFI.getOffsetOfLocalArea();
103
104  // Skip the register save area if we generated the stack frame.
105  if (StackSize || MFI->hasCalls())
106    Offset -= TFI.getOffsetOfLocalArea();
107
108  return Offset;
109}
110
111unsigned
112SystemZRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
113                                         int SPAdj, FrameIndexValue *Value,
114                                         RegScavenger *RS) const {
115  assert(SPAdj == 0 && "Unxpected");
116
117  unsigned i = 0;
118  MachineInstr &MI = *II;
119  MachineFunction &MF = *MI.getParent()->getParent();
120  while (!MI.getOperand(i).isFI()) {
121    ++i;
122    assert(i < MI.getNumOperands() && "Instr doesn't have FrameIndex operand!");
123  }
124
125  int FrameIndex = MI.getOperand(i).getIndex();
126
127  unsigned BasePtr = (hasFP(MF) ? SystemZ::R11D : SystemZ::R15D);
128
129  // This must be part of a rri or ri operand memory reference.  Replace the
130  // FrameIndex with base register with BasePtr.  Add an offset to the
131  // displacement field.
132  MI.getOperand(i).ChangeToRegister(BasePtr, false);
133
134  // Offset is a either 12-bit unsigned or 20-bit signed integer.
135  // FIXME: handle "too long" displacements.
136  int Offset = getFrameIndexOffset(MF, FrameIndex) + MI.getOperand(i+1).getImm();
137
138  // Check whether displacement is too long to fit into 12 bit zext field.
139  MI.setDesc(TII.getMemoryInstr(MI.getOpcode(), Offset));
140
141  MI.getOperand(i+1).ChangeToImmediate(Offset);
142  return 0;
143}
144
145void
146SystemZRegisterInfo::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
147                                                       RegScavenger *RS) const {
148  // Determine whether R15/R14 will ever be clobbered inside the function. And
149  // if yes - mark it as 'callee' saved.
150  MachineFrameInfo *FFI = MF.getFrameInfo();
151  MachineRegisterInfo &MRI = MF.getRegInfo();
152
153  // Check whether high FPRs are ever used, if yes - we need to save R15 as
154  // well.
155  static const unsigned HighFPRs[] = {
156    SystemZ::F8L,  SystemZ::F9L,  SystemZ::F10L, SystemZ::F11L,
157    SystemZ::F12L, SystemZ::F13L, SystemZ::F14L, SystemZ::F15L,
158    SystemZ::F8S,  SystemZ::F9S,  SystemZ::F10S, SystemZ::F11S,
159    SystemZ::F12S, SystemZ::F13S, SystemZ::F14S, SystemZ::F15S,
160  };
161
162  bool HighFPRsUsed = false;
163  for (unsigned i = 0, e = array_lengthof(HighFPRs); i != e; ++i)
164    HighFPRsUsed |= MRI.isPhysRegUsed(HighFPRs[i]);
165
166  if (FFI->hasCalls())
167    /* FIXME: function is varargs */
168    /* FIXME: function grabs RA */
169    /* FIXME: function calls eh_return */
170    MRI.setPhysRegUsed(SystemZ::R14D);
171
172  if (HighFPRsUsed ||
173      FFI->hasCalls() ||
174      FFI->getObjectIndexEnd() != 0 || // Contains automatic variables
175      FFI->hasVarSizedObjects() // Function calls dynamic alloca's
176      /* FIXME: function is varargs */)
177    MRI.setPhysRegUsed(SystemZ::R15D);
178}
179
180/// emitSPUpdate - Emit a series of instructions to increment / decrement the
181/// stack pointer by a constant value.
182static
183void emitSPUpdate(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
184                  int64_t NumBytes, const TargetInstrInfo &TII) {
185  unsigned Opc; uint64_t Chunk;
186  bool isSub = NumBytes < 0;
187  uint64_t Offset = isSub ? -NumBytes : NumBytes;
188
189  if (Offset >= (1LL << 15) - 1) {
190    Opc = SystemZ::ADD64ri32;
191    Chunk = (1LL << 31) - 1;
192  } else {
193    Opc = SystemZ::ADD64ri16;
194    Chunk = (1LL << 15) - 1;
195  }
196
197  DebugLoc DL = (MBBI != MBB.end() ? MBBI->getDebugLoc() :
198                 DebugLoc::getUnknownLoc());
199
200  while (Offset) {
201    uint64_t ThisVal = (Offset > Chunk) ? Chunk : Offset;
202    MachineInstr *MI =
203      BuildMI(MBB, MBBI, DL, TII.get(Opc), SystemZ::R15D)
204      .addReg(SystemZ::R15D).addImm((isSub ? -(int64_t)ThisVal : ThisVal));
205    // The PSW implicit def is dead.
206    MI->getOperand(3).setIsDead();
207    Offset -= ThisVal;
208  }
209}
210
211void SystemZRegisterInfo::emitPrologue(MachineFunction &MF) const {
212  MachineBasicBlock &MBB = MF.front();   // Prolog goes in entry BB
213  const TargetFrameInfo &TFI = *MF.getTarget().getFrameInfo();
214  MachineFrameInfo *MFI = MF.getFrameInfo();
215  SystemZMachineFunctionInfo *SystemZMFI =
216    MF.getInfo<SystemZMachineFunctionInfo>();
217  MachineBasicBlock::iterator MBBI = MBB.begin();
218  DebugLoc DL = (MBBI != MBB.end() ? MBBI->getDebugLoc() :
219                 DebugLoc::getUnknownLoc());
220
221  // Get the number of bytes to allocate from the FrameInfo.
222  // Note that area for callee-saved stuff is already allocated, thus we need to
223  // 'undo' the stack movement.
224  uint64_t StackSize = MFI->getStackSize();
225  StackSize -= SystemZMFI->getCalleeSavedFrameSize();
226
227  uint64_t NumBytes = StackSize - TFI.getOffsetOfLocalArea();
228
229  // Skip the callee-saved push instructions.
230  while (MBBI != MBB.end() &&
231         (MBBI->getOpcode() == SystemZ::MOV64mr ||
232          MBBI->getOpcode() == SystemZ::MOV64mrm))
233    ++MBBI;
234
235  if (MBBI != MBB.end())
236    DL = MBBI->getDebugLoc();
237
238  // adjust stack pointer: R15 -= numbytes
239  if (StackSize || MFI->hasCalls()) {
240    assert(MF.getRegInfo().isPhysRegUsed(SystemZ::R15D) &&
241           "Invalid stack frame calculation!");
242    emitSPUpdate(MBB, MBBI, -(int64_t)NumBytes, TII);
243  }
244
245  if (hasFP(MF)) {
246    // Update R11 with the new base value...
247    BuildMI(MBB, MBBI, DL, TII.get(SystemZ::MOV64rr), SystemZ::R11D)
248      .addReg(SystemZ::R15D);
249
250    // Mark the FramePtr as live-in in every block except the entry.
251    for (MachineFunction::iterator I = llvm::next(MF.begin()), E = MF.end();
252         I != E; ++I)
253      I->addLiveIn(SystemZ::R11D);
254
255  }
256}
257
258void SystemZRegisterInfo::emitEpilogue(MachineFunction &MF,
259                                     MachineBasicBlock &MBB) const {
260  const MachineFrameInfo *MFI = MF.getFrameInfo();
261  const TargetFrameInfo &TFI = *MF.getTarget().getFrameInfo();
262  MachineBasicBlock::iterator MBBI = prior(MBB.end());
263  SystemZMachineFunctionInfo *SystemZMFI =
264    MF.getInfo<SystemZMachineFunctionInfo>();
265  unsigned RetOpcode = MBBI->getOpcode();
266
267  switch (RetOpcode) {
268  case SystemZ::RET: break;  // These are ok
269  default:
270    assert(0 && "Can only insert epilog into returning blocks");
271  }
272
273  // Get the number of bytes to allocate from the FrameInfo
274  // Note that area for callee-saved stuff is already allocated, thus we need to
275  // 'undo' the stack movement.
276  uint64_t StackSize =
277    MFI->getStackSize() - SystemZMFI->getCalleeSavedFrameSize();
278  uint64_t NumBytes = StackSize - TFI.getOffsetOfLocalArea();
279
280  // Skip the final terminator instruction.
281  while (MBBI != MBB.begin()) {
282    MachineBasicBlock::iterator PI = prior(MBBI);
283    --MBBI;
284    if (!PI->getDesc().isTerminator())
285      break;
286  }
287
288  // During callee-saved restores emission stack frame was not yet finialized
289  // (and thus - the stack size was unknown). Tune the offset having full stack
290  // size in hands.
291  if (StackSize || MFI->hasCalls()) {
292    assert((MBBI->getOpcode() == SystemZ::MOV64rmm ||
293            MBBI->getOpcode() == SystemZ::MOV64rm) &&
294           "Expected to see callee-save register restore code");
295    assert(MF.getRegInfo().isPhysRegUsed(SystemZ::R15D) &&
296           "Invalid stack frame calculation!");
297
298    unsigned i = 0;
299    MachineInstr &MI = *MBBI;
300    while (!MI.getOperand(i).isImm()) {
301      ++i;
302      assert(i < MI.getNumOperands() && "Unexpected restore code!");
303    }
304
305    uint64_t Offset = NumBytes + MI.getOperand(i).getImm();
306    // If Offset does not fit into 20-bit signed displacement field we need to
307    // emit some additional code...
308    if (Offset > 524287) {
309      // Fold the displacement into load instruction as much as possible.
310      NumBytes = Offset - 524287;
311      Offset = 524287;
312      emitSPUpdate(MBB, MBBI, NumBytes, TII);
313    }
314
315    MI.getOperand(i).ChangeToImmediate(Offset);
316  }
317}
318
319unsigned SystemZRegisterInfo::getRARegister() const {
320  assert(0 && "What is the return address register");
321  return 0;
322}
323
324unsigned
325SystemZRegisterInfo::getFrameRegister(const MachineFunction &MF) const {
326  assert(0 && "What is the frame register");
327  return 0;
328}
329
330unsigned SystemZRegisterInfo::getEHExceptionRegister() const {
331  assert(0 && "What is the exception register");
332  return 0;
333}
334
335unsigned SystemZRegisterInfo::getEHHandlerRegister() const {
336  assert(0 && "What is the exception handler register");
337  return 0;
338}
339
340int SystemZRegisterInfo::getDwarfRegNum(unsigned RegNum, bool isEH) const {
341  assert(0 && "What is the dwarf register number");
342  return -1;
343}
344
345#include "SystemZGenRegisterInfo.inc"
346