XCoreFrameLowering.cpp revision 239462 
1//===-- XCoreFrameLowering.cpp - Frame info for XCore Target --------------===//
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 XCore frame information that doesn't fit anywhere else
11// cleanly...
12//
13//===----------------------------------------------------------------------===//
14
15#include "XCoreFrameLowering.h"
16#include "XCore.h"
17#include "XCoreInstrInfo.h"
18#include "XCoreMachineFunctionInfo.h"
19#include "llvm/Function.h"
20#include "llvm/CodeGen/MachineFrameInfo.h"
21#include "llvm/CodeGen/MachineFunction.h"
22#include "llvm/CodeGen/MachineInstrBuilder.h"
23#include "llvm/CodeGen/MachineModuleInfo.h"
24#include "llvm/CodeGen/MachineRegisterInfo.h"
25#include "llvm/CodeGen/RegisterScavenging.h"
26#include "llvm/Target/TargetData.h"
27#include "llvm/Target/TargetOptions.h"
28#include "llvm/Support/ErrorHandling.h"
29
30using namespace llvm;
31
32// helper functions. FIXME: Eliminate.
33static inline bool isImmUs(unsigned val) {
34  return val <= 11;
35}
36
37static inline bool isImmU6(unsigned val) {
38  return val < (1 << 6);
39}
40
41static inline bool isImmU16(unsigned val) {
42  return val < (1 << 16);
43}
44
45static void loadFromStack(MachineBasicBlock &MBB,
46                          MachineBasicBlock::iterator I,
47                          unsigned DstReg, int Offset, DebugLoc dl,
48                          const TargetInstrInfo &TII) {
49  assert(Offset%4 == 0 && "Misaligned stack offset");
50  Offset/=4;
51  bool isU6 = isImmU6(Offset);
52  if (!isU6 && !isImmU16(Offset))
53    report_fatal_error("loadFromStack offset too big " + Twine(Offset));
54  int Opcode = isU6 ? XCore::LDWSP_ru6 : XCore::LDWSP_lru6;
55  BuildMI(MBB, I, dl, TII.get(Opcode), DstReg)
56    .addImm(Offset);
57}
58
59
60static void storeToStack(MachineBasicBlock &MBB,
61                         MachineBasicBlock::iterator I,
62                         unsigned SrcReg, int Offset, DebugLoc dl,
63                         const TargetInstrInfo &TII) {
64  assert(Offset%4 == 0 && "Misaligned stack offset");
65  Offset/=4;
66  bool isU6 = isImmU6(Offset);
67  if (!isU6 && !isImmU16(Offset))
68    report_fatal_error("storeToStack offset too big " + Twine(Offset));
69  int Opcode = isU6 ? XCore::STWSP_ru6 : XCore::STWSP_lru6;
70  BuildMI(MBB, I, dl, TII.get(Opcode))
71    .addReg(SrcReg)
72    .addImm(Offset);
73}
74
75
76//===----------------------------------------------------------------------===//
77// XCoreFrameLowering:
78//===----------------------------------------------------------------------===//
79
80XCoreFrameLowering::XCoreFrameLowering(const XCoreSubtarget &sti)
81  : TargetFrameLowering(TargetFrameLowering::StackGrowsDown, 4, 0) {
82  // Do nothing
83}
84
85bool XCoreFrameLowering::hasFP(const MachineFunction &MF) const {
86  return MF.getTarget().Options.DisableFramePointerElim(MF) ||
87    MF.getFrameInfo()->hasVarSizedObjects();
88}
89
90void XCoreFrameLowering::emitPrologue(MachineFunction &MF) const {
91  MachineBasicBlock &MBB = MF.front();   // Prolog goes in entry BB
92  MachineBasicBlock::iterator MBBI = MBB.begin();
93  MachineFrameInfo *MFI = MF.getFrameInfo();
94  MachineModuleInfo *MMI = &MF.getMMI();
95  const XCoreInstrInfo &TII =
96    *static_cast<const XCoreInstrInfo*>(MF.getTarget().getInstrInfo());
97  XCoreFunctionInfo *XFI = MF.getInfo<XCoreFunctionInfo>();
98  DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
99
100  bool FP = hasFP(MF);
101  bool Nested = MF.getFunction()->
102                getAttributes().hasAttrSomewhere(Attribute::Nest);
103
104  if (Nested) {
105    loadFromStack(MBB, MBBI, XCore::R11, 0, dl, TII);
106  }
107
108  // Work out frame sizes.
109  int FrameSize = MFI->getStackSize();
110  assert(FrameSize%4 == 0 && "Misaligned frame size");
111  FrameSize/=4;
112
113  bool isU6 = isImmU6(FrameSize);
114
115  if (!isU6 && !isImmU16(FrameSize)) {
116    // FIXME could emit multiple instructions.
117    report_fatal_error("emitPrologue Frame size too big: " + Twine(FrameSize));
118  }
119  bool emitFrameMoves = XCoreRegisterInfo::needsFrameMoves(MF);
120
121  // Do we need to allocate space on the stack?
122  if (FrameSize) {
123    bool saveLR = XFI->getUsesLR();
124    bool LRSavedOnEntry = false;
125    int Opcode;
126    if (saveLR && (MFI->getObjectOffset(XFI->getLRSpillSlot()) == 0)) {
127      Opcode = (isU6) ? XCore::ENTSP_u6 : XCore::ENTSP_lu6;
128      MBB.addLiveIn(XCore::LR);
129      saveLR = false;
130      LRSavedOnEntry = true;
131    } else {
132      Opcode = (isU6) ? XCore::EXTSP_u6 : XCore::EXTSP_lu6;
133    }
134    BuildMI(MBB, MBBI, dl, TII.get(Opcode)).addImm(FrameSize);
135
136    if (emitFrameMoves) {
137      std::vector<MachineMove> &Moves = MMI->getFrameMoves();
138
139      // Show update of SP.
140      MCSymbol *FrameLabel = MMI->getContext().CreateTempSymbol();
141      BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(FrameLabel);
142
143      MachineLocation SPDst(MachineLocation::VirtualFP);
144      MachineLocation SPSrc(MachineLocation::VirtualFP, -FrameSize * 4);
145      Moves.push_back(MachineMove(FrameLabel, SPDst, SPSrc));
146
147      if (LRSavedOnEntry) {
148        MachineLocation CSDst(MachineLocation::VirtualFP, 0);
149        MachineLocation CSSrc(XCore::LR);
150        Moves.push_back(MachineMove(FrameLabel, CSDst, CSSrc));
151      }
152    }
153    if (saveLR) {
154      int LRSpillOffset = MFI->getObjectOffset(XFI->getLRSpillSlot());
155      storeToStack(MBB, MBBI, XCore::LR, LRSpillOffset + FrameSize*4, dl, TII);
156      MBB.addLiveIn(XCore::LR);
157
158      if (emitFrameMoves) {
159        MCSymbol *SaveLRLabel = MMI->getContext().CreateTempSymbol();
160        BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(SaveLRLabel);
161        MachineLocation CSDst(MachineLocation::VirtualFP, LRSpillOffset);
162        MachineLocation CSSrc(XCore::LR);
163        MMI->getFrameMoves().push_back(MachineMove(SaveLRLabel, CSDst, CSSrc));
164      }
165    }
166  }
167
168  if (FP) {
169    // Save R10 to the stack.
170    int FPSpillOffset = MFI->getObjectOffset(XFI->getFPSpillSlot());
171    storeToStack(MBB, MBBI, XCore::R10, FPSpillOffset + FrameSize*4, dl, TII);
172    // R10 is live-in. It is killed at the spill.
173    MBB.addLiveIn(XCore::R10);
174    if (emitFrameMoves) {
175      MCSymbol *SaveR10Label = MMI->getContext().CreateTempSymbol();
176      BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(SaveR10Label);
177      MachineLocation CSDst(MachineLocation::VirtualFP, FPSpillOffset);
178      MachineLocation CSSrc(XCore::R10);
179      MMI->getFrameMoves().push_back(MachineMove(SaveR10Label, CSDst, CSSrc));
180    }
181    // Set the FP from the SP.
182    unsigned FramePtr = XCore::R10;
183    BuildMI(MBB, MBBI, dl, TII.get(XCore::LDAWSP_ru6), FramePtr)
184      .addImm(0);
185    if (emitFrameMoves) {
186      // Show FP is now valid.
187      MCSymbol *FrameLabel = MMI->getContext().CreateTempSymbol();
188      BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(FrameLabel);
189      MachineLocation SPDst(FramePtr);
190      MachineLocation SPSrc(MachineLocation::VirtualFP);
191      MMI->getFrameMoves().push_back(MachineMove(FrameLabel, SPDst, SPSrc));
192    }
193  }
194
195  if (emitFrameMoves) {
196    // Frame moves for callee saved.
197    std::vector<MachineMove> &Moves = MMI->getFrameMoves();
198    std::vector<std::pair<MCSymbol*, CalleeSavedInfo> >&SpillLabels =
199        XFI->getSpillLabels();
200    for (unsigned I = 0, E = SpillLabels.size(); I != E; ++I) {
201      MCSymbol *SpillLabel = SpillLabels[I].first;
202      CalleeSavedInfo &CSI = SpillLabels[I].second;
203      int Offset = MFI->getObjectOffset(CSI.getFrameIdx());
204      unsigned Reg = CSI.getReg();
205      MachineLocation CSDst(MachineLocation::VirtualFP, Offset);
206      MachineLocation CSSrc(Reg);
207      Moves.push_back(MachineMove(SpillLabel, CSDst, CSSrc));
208    }
209  }
210}
211
212void XCoreFrameLowering::emitEpilogue(MachineFunction &MF,
213                                     MachineBasicBlock &MBB) const {
214  MachineFrameInfo *MFI            = MF.getFrameInfo();
215  MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
216  const XCoreInstrInfo &TII =
217    *static_cast<const XCoreInstrInfo*>(MF.getTarget().getInstrInfo());
218  DebugLoc dl = MBBI->getDebugLoc();
219
220  bool FP = hasFP(MF);
221  if (FP) {
222    // Restore the stack pointer.
223    unsigned FramePtr = XCore::R10;
224    BuildMI(MBB, MBBI, dl, TII.get(XCore::SETSP_1r))
225      .addReg(FramePtr);
226  }
227
228  // Work out frame sizes.
229  int FrameSize = MFI->getStackSize();
230
231  assert(FrameSize%4 == 0 && "Misaligned frame size");
232
233  FrameSize/=4;
234
235  bool isU6 = isImmU6(FrameSize);
236
237  if (!isU6 && !isImmU16(FrameSize)) {
238    // FIXME could emit multiple instructions.
239    report_fatal_error("emitEpilogue Frame size too big: " + Twine(FrameSize));
240  }
241
242  if (FrameSize) {
243    XCoreFunctionInfo *XFI = MF.getInfo<XCoreFunctionInfo>();
244
245    if (FP) {
246      // Restore R10
247      int FPSpillOffset = MFI->getObjectOffset(XFI->getFPSpillSlot());
248      FPSpillOffset += FrameSize*4;
249      loadFromStack(MBB, MBBI, XCore::R10, FPSpillOffset, dl, TII);
250    }
251    bool restoreLR = XFI->getUsesLR();
252    if (restoreLR && MFI->getObjectOffset(XFI->getLRSpillSlot()) != 0) {
253      int LRSpillOffset = MFI->getObjectOffset(XFI->getLRSpillSlot());
254      LRSpillOffset += FrameSize*4;
255      loadFromStack(MBB, MBBI, XCore::LR, LRSpillOffset, dl, TII);
256      restoreLR = false;
257    }
258    if (restoreLR) {
259      // Fold prologue into return instruction
260      assert(MBBI->getOpcode() == XCore::RETSP_u6
261        || MBBI->getOpcode() == XCore::RETSP_lu6);
262      int Opcode = (isU6) ? XCore::RETSP_u6 : XCore::RETSP_lu6;
263      BuildMI(MBB, MBBI, dl, TII.get(Opcode)).addImm(FrameSize);
264      MBB.erase(MBBI);
265    } else {
266      int Opcode = (isU6) ? XCore::LDAWSP_ru6_RRegs : XCore::LDAWSP_lru6_RRegs;
267      BuildMI(MBB, MBBI, dl, TII.get(Opcode), XCore::SP).addImm(FrameSize);
268    }
269  }
270}
271
272bool XCoreFrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB,
273                                               MachineBasicBlock::iterator MI,
274                                        const std::vector<CalleeSavedInfo> &CSI,
275                                          const TargetRegisterInfo *TRI) const {
276  if (CSI.empty())
277    return true;
278
279  MachineFunction *MF = MBB.getParent();
280  const TargetInstrInfo &TII = *MF->getTarget().getInstrInfo();
281
282  XCoreFunctionInfo *XFI = MF->getInfo<XCoreFunctionInfo>();
283  bool emitFrameMoves = XCoreRegisterInfo::needsFrameMoves(*MF);
284
285  DebugLoc DL;
286  if (MI != MBB.end()) DL = MI->getDebugLoc();
287
288  for (std::vector<CalleeSavedInfo>::const_iterator it = CSI.begin();
289                                                    it != CSI.end(); ++it) {
290    // Add the callee-saved register as live-in. It's killed at the spill.
291    MBB.addLiveIn(it->getReg());
292
293    unsigned Reg = it->getReg();
294    const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
295    TII.storeRegToStackSlot(MBB, MI, Reg, true,
296                            it->getFrameIdx(), RC, TRI);
297    if (emitFrameMoves) {
298      MCSymbol *SaveLabel = MF->getContext().CreateTempSymbol();
299      BuildMI(MBB, MI, DL, TII.get(XCore::PROLOG_LABEL)).addSym(SaveLabel);
300      XFI->getSpillLabels().push_back(std::make_pair(SaveLabel, *it));
301    }
302  }
303  return true;
304}
305
306bool XCoreFrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
307                                                 MachineBasicBlock::iterator MI,
308                                        const std::vector<CalleeSavedInfo> &CSI,
309                                            const TargetRegisterInfo *TRI) const{
310  MachineFunction *MF = MBB.getParent();
311  const TargetInstrInfo &TII = *MF->getTarget().getInstrInfo();
312
313  bool AtStart = MI == MBB.begin();
314  MachineBasicBlock::iterator BeforeI = MI;
315  if (!AtStart)
316    --BeforeI;
317  for (std::vector<CalleeSavedInfo>::const_iterator it = CSI.begin();
318                                                    it != CSI.end(); ++it) {
319    unsigned Reg = it->getReg();
320    const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
321    TII.loadRegFromStackSlot(MBB, MI, it->getReg(), it->getFrameIdx(),
322                             RC, TRI);
323    assert(MI != MBB.begin() &&
324           "loadRegFromStackSlot didn't insert any code!");
325    // Insert in reverse order.  loadRegFromStackSlot can insert multiple
326    // instructions.
327    if (AtStart)
328      MI = MBB.begin();
329    else {
330      MI = BeforeI;
331      ++MI;
332    }
333  }
334  return true;
335}
336
337void
338XCoreFrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
339                                                     RegScavenger *RS) const {
340  MachineFrameInfo *MFI = MF.getFrameInfo();
341  const TargetRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
342  bool LRUsed = MF.getRegInfo().isPhysRegUsed(XCore::LR);
343  const TargetRegisterClass *RC = &XCore::GRRegsRegClass;
344  XCoreFunctionInfo *XFI = MF.getInfo<XCoreFunctionInfo>();
345  if (LRUsed) {
346    MF.getRegInfo().setPhysRegUnused(XCore::LR);
347
348    bool isVarArg = MF.getFunction()->isVarArg();
349    int FrameIdx;
350    if (! isVarArg) {
351      // A fixed offset of 0 allows us to save / restore LR using entsp / retsp.
352      FrameIdx = MFI->CreateFixedObject(RC->getSize(), 0, true);
353    } else {
354      FrameIdx = MFI->CreateStackObject(RC->getSize(), RC->getAlignment(),
355                                        false);
356    }
357    XFI->setUsesLR(FrameIdx);
358    XFI->setLRSpillSlot(FrameIdx);
359  }
360  if (RegInfo->requiresRegisterScavenging(MF)) {
361    // Reserve a slot close to SP or frame pointer.
362    RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
363                                                       RC->getAlignment(),
364                                                       false));
365  }
366  if (hasFP(MF)) {
367    // A callee save register is used to hold the FP.
368    // This needs saving / restoring in the epilogue / prologue.
369    XFI->setFPSpillSlot(MFI->CreateStackObject(RC->getSize(),
370                                               RC->getAlignment(),
371                                               false));
372  }
373}
374