1 //===-- XCoreFrameLowering.cpp - Frame info for XCore Target -----*- 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 XCore frame information that doesn't fit anywhere else
11 // cleanly...
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "XCore.h"
16 #include "XCoreFrameLowering.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 
30 using namespace llvm;
31 
32 // helper functions. FIXME: Eliminate.
33 static inline bool isImmUs(unsigned val) {
34   return val <= 11;
35 }
36 
37 static inline bool isImmU6(unsigned val) {
38   return val < (1 << 6);
39 }
40 
41 static inline bool isImmU16(unsigned val) {
42   return val < (1 << 16);
43 }
44 
45 static 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 
60 static 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 
80 XCoreFrameLowering::XCoreFrameLowering(const XCoreSubtarget &sti)
81   : TargetFrameLowering(TargetFrameLowering::StackGrowsDown, 4, 0),
82     STI(sti) {
83   // Do nothing
84 }
85 
86 bool XCoreFrameLowering::hasFP(const MachineFunction &MF) const {
87   return DisableFramePointerElim(MF) || MF.getFrameInfo()->hasVarSizedObjects();
88 }
89 
90 void 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 XCoreRegisterInfo *RegInfo =
96     static_cast<const XCoreRegisterInfo*>(MF.getTarget().getRegisterInfo());
97   const XCoreInstrInfo &TII =
98     *static_cast<const XCoreInstrInfo*>(MF.getTarget().getInstrInfo());
99   XCoreFunctionInfo *XFI = MF.getInfo<XCoreFunctionInfo>();
100   DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
101 
102   bool FP = hasFP(MF);
103 
104   // Work out frame sizes.
105   int FrameSize = MFI->getStackSize();
106   assert(FrameSize%4 == 0 && "Misaligned frame size");
107   FrameSize/=4;
108 
109   bool isU6 = isImmU6(FrameSize);
110 
111   if (!isU6 && !isImmU16(FrameSize)) {
112     // FIXME could emit multiple instructions.
113     report_fatal_error("emitPrologue Frame size too big: " + Twine(FrameSize));
114   }
115   bool emitFrameMoves = RegInfo->needsFrameMoves(MF);
116 
117   // Do we need to allocate space on the stack?
118   if (FrameSize) {
119     bool saveLR = XFI->getUsesLR();
120     bool LRSavedOnEntry = false;
121     int Opcode;
122     if (saveLR && (MFI->getObjectOffset(XFI->getLRSpillSlot()) == 0)) {
123       Opcode = (isU6) ? XCore::ENTSP_u6 : XCore::ENTSP_lu6;
124       MBB.addLiveIn(XCore::LR);
125       saveLR = false;
126       LRSavedOnEntry = true;
127     } else {
128       Opcode = (isU6) ? XCore::EXTSP_u6 : XCore::EXTSP_lu6;
129     }
130     BuildMI(MBB, MBBI, dl, TII.get(Opcode)).addImm(FrameSize);
131 
132     if (emitFrameMoves) {
133       std::vector<MachineMove> &Moves = MMI->getFrameMoves();
134 
135       // Show update of SP.
136       MCSymbol *FrameLabel = MMI->getContext().CreateTempSymbol();
137       BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(FrameLabel);
138 
139       MachineLocation SPDst(MachineLocation::VirtualFP);
140       MachineLocation SPSrc(MachineLocation::VirtualFP, -FrameSize * 4);
141       Moves.push_back(MachineMove(FrameLabel, SPDst, SPSrc));
142 
143       if (LRSavedOnEntry) {
144         MachineLocation CSDst(MachineLocation::VirtualFP, 0);
145         MachineLocation CSSrc(XCore::LR);
146         Moves.push_back(MachineMove(FrameLabel, CSDst, CSSrc));
147       }
148     }
149     if (saveLR) {
150       int LRSpillOffset = MFI->getObjectOffset(XFI->getLRSpillSlot());
151       storeToStack(MBB, MBBI, XCore::LR, LRSpillOffset + FrameSize*4, dl, TII);
152       MBB.addLiveIn(XCore::LR);
153 
154       if (emitFrameMoves) {
155         MCSymbol *SaveLRLabel = MMI->getContext().CreateTempSymbol();
156         BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(SaveLRLabel);
157         MachineLocation CSDst(MachineLocation::VirtualFP, LRSpillOffset);
158         MachineLocation CSSrc(XCore::LR);
159         MMI->getFrameMoves().push_back(MachineMove(SaveLRLabel, CSDst, CSSrc));
160       }
161     }
162   }
163 
164   if (FP) {
165     // Save R10 to the stack.
166     int FPSpillOffset = MFI->getObjectOffset(XFI->getFPSpillSlot());
167     storeToStack(MBB, MBBI, XCore::R10, FPSpillOffset + FrameSize*4, dl, TII);
168     // R10 is live-in. It is killed at the spill.
169     MBB.addLiveIn(XCore::R10);
170     if (emitFrameMoves) {
171       MCSymbol *SaveR10Label = MMI->getContext().CreateTempSymbol();
172       BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(SaveR10Label);
173       MachineLocation CSDst(MachineLocation::VirtualFP, FPSpillOffset);
174       MachineLocation CSSrc(XCore::R10);
175       MMI->getFrameMoves().push_back(MachineMove(SaveR10Label, CSDst, CSSrc));
176     }
177     // Set the FP from the SP.
178     unsigned FramePtr = XCore::R10;
179     BuildMI(MBB, MBBI, dl, TII.get(XCore::LDAWSP_ru6), FramePtr)
180       .addImm(0);
181     if (emitFrameMoves) {
182       // Show FP is now valid.
183       MCSymbol *FrameLabel = MMI->getContext().CreateTempSymbol();
184       BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(FrameLabel);
185       MachineLocation SPDst(FramePtr);
186       MachineLocation SPSrc(MachineLocation::VirtualFP);
187       MMI->getFrameMoves().push_back(MachineMove(FrameLabel, SPDst, SPSrc));
188     }
189   }
190 
191   if (emitFrameMoves) {
192     // Frame moves for callee saved.
193     std::vector<MachineMove> &Moves = MMI->getFrameMoves();
194     std::vector<std::pair<MCSymbol*, CalleeSavedInfo> >&SpillLabels =
195         XFI->getSpillLabels();
196     for (unsigned I = 0, E = SpillLabels.size(); I != E; ++I) {
197       MCSymbol *SpillLabel = SpillLabels[I].first;
198       CalleeSavedInfo &CSI = SpillLabels[I].second;
199       int Offset = MFI->getObjectOffset(CSI.getFrameIdx());
200       unsigned Reg = CSI.getReg();
201       MachineLocation CSDst(MachineLocation::VirtualFP, Offset);
202       MachineLocation CSSrc(Reg);
203       Moves.push_back(MachineMove(SpillLabel, CSDst, CSSrc));
204     }
205   }
206 }
207 
208 void XCoreFrameLowering::emitEpilogue(MachineFunction &MF,
209                                      MachineBasicBlock &MBB) const {
210   MachineFrameInfo *MFI            = MF.getFrameInfo();
211   MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
212   const XCoreInstrInfo &TII =
213     *static_cast<const XCoreInstrInfo*>(MF.getTarget().getInstrInfo());
214   DebugLoc dl = MBBI->getDebugLoc();
215 
216   bool FP = hasFP(MF);
217   if (FP) {
218     // Restore the stack pointer.
219     unsigned FramePtr = XCore::R10;
220     BuildMI(MBB, MBBI, dl, TII.get(XCore::SETSP_1r))
221       .addReg(FramePtr);
222   }
223 
224   // Work out frame sizes.
225   int FrameSize = MFI->getStackSize();
226 
227   assert(FrameSize%4 == 0 && "Misaligned frame size");
228 
229   FrameSize/=4;
230 
231   bool isU6 = isImmU6(FrameSize);
232 
233   if (!isU6 && !isImmU16(FrameSize)) {
234     // FIXME could emit multiple instructions.
235     report_fatal_error("emitEpilogue Frame size too big: " + Twine(FrameSize));
236   }
237 
238   if (FrameSize) {
239     XCoreFunctionInfo *XFI = MF.getInfo<XCoreFunctionInfo>();
240 
241     if (FP) {
242       // Restore R10
243       int FPSpillOffset = MFI->getObjectOffset(XFI->getFPSpillSlot());
244       FPSpillOffset += FrameSize*4;
245       loadFromStack(MBB, MBBI, XCore::R10, FPSpillOffset, dl, TII);
246     }
247     bool restoreLR = XFI->getUsesLR();
248     if (restoreLR && MFI->getObjectOffset(XFI->getLRSpillSlot()) != 0) {
249       int LRSpillOffset = MFI->getObjectOffset(XFI->getLRSpillSlot());
250       LRSpillOffset += FrameSize*4;
251       loadFromStack(MBB, MBBI, XCore::LR, LRSpillOffset, dl, TII);
252       restoreLR = false;
253     }
254     if (restoreLR) {
255       // Fold prologue into return instruction
256       assert(MBBI->getOpcode() == XCore::RETSP_u6
257         || MBBI->getOpcode() == XCore::RETSP_lu6);
258       int Opcode = (isU6) ? XCore::RETSP_u6 : XCore::RETSP_lu6;
259       BuildMI(MBB, MBBI, dl, TII.get(Opcode)).addImm(FrameSize);
260       MBB.erase(MBBI);
261     } else {
262       int Opcode = (isU6) ? XCore::LDAWSP_ru6_RRegs : XCore::LDAWSP_lru6_RRegs;
263       BuildMI(MBB, MBBI, dl, TII.get(Opcode), XCore::SP).addImm(FrameSize);
264     }
265   }
266 }
267 
268 void XCoreFrameLowering::getInitialFrameState(std::vector<MachineMove> &Moves)
269                                                                         const {
270   // Initial state of the frame pointer is SP.
271   MachineLocation Dst(MachineLocation::VirtualFP);
272   MachineLocation Src(XCore::SP, 0);
273   Moves.push_back(MachineMove(0, Dst, Src));
274 }
275 
276 bool XCoreFrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB,
277                                                MachineBasicBlock::iterator MI,
278                                         const std::vector<CalleeSavedInfo> &CSI,
279                                           const TargetRegisterInfo *TRI) const {
280   if (CSI.empty())
281     return true;
282 
283   MachineFunction *MF = MBB.getParent();
284   const TargetInstrInfo &TII = *MF->getTarget().getInstrInfo();
285 
286   XCoreFunctionInfo *XFI = MF->getInfo<XCoreFunctionInfo>();
287   bool emitFrameMoves = XCoreRegisterInfo::needsFrameMoves(*MF);
288 
289   DebugLoc DL;
290   if (MI != MBB.end()) DL = MI->getDebugLoc();
291 
292   for (std::vector<CalleeSavedInfo>::const_iterator it = CSI.begin();
293                                                     it != CSI.end(); ++it) {
294     // Add the callee-saved register as live-in. It's killed at the spill.
295     MBB.addLiveIn(it->getReg());
296 
297     unsigned Reg = it->getReg();
298     const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
299     TII.storeRegToStackSlot(MBB, MI, Reg, true,
300                             it->getFrameIdx(), RC, TRI);
301     if (emitFrameMoves) {
302       MCSymbol *SaveLabel = MF->getContext().CreateTempSymbol();
303       BuildMI(MBB, MI, DL, TII.get(XCore::PROLOG_LABEL)).addSym(SaveLabel);
304       XFI->getSpillLabels().push_back(std::make_pair(SaveLabel, *it));
305     }
306   }
307   return true;
308 }
309 
310 bool XCoreFrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
311                                                  MachineBasicBlock::iterator MI,
312                                         const std::vector<CalleeSavedInfo> &CSI,
313                                             const TargetRegisterInfo *TRI) const{
314   MachineFunction *MF = MBB.getParent();
315   const TargetInstrInfo &TII = *MF->getTarget().getInstrInfo();
316 
317   bool AtStart = MI == MBB.begin();
318   MachineBasicBlock::iterator BeforeI = MI;
319   if (!AtStart)
320     --BeforeI;
321   for (std::vector<CalleeSavedInfo>::const_iterator it = CSI.begin();
322                                                     it != CSI.end(); ++it) {
323     unsigned Reg = it->getReg();
324     const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
325     TII.loadRegFromStackSlot(MBB, MI, it->getReg(), it->getFrameIdx(),
326                              RC, TRI);
327     assert(MI != MBB.begin() &&
328            "loadRegFromStackSlot didn't insert any code!");
329     // Insert in reverse order.  loadRegFromStackSlot can insert multiple
330     // instructions.
331     if (AtStart)
332       MI = MBB.begin();
333     else {
334       MI = BeforeI;
335       ++MI;
336     }
337   }
338   return true;
339 }
340 
341 void
342 XCoreFrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
343                                                      RegScavenger *RS) const {
344   MachineFrameInfo *MFI = MF.getFrameInfo();
345   const TargetRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
346   bool LRUsed = MF.getRegInfo().isPhysRegUsed(XCore::LR);
347   const TargetRegisterClass *RC = XCore::GRRegsRegisterClass;
348   XCoreFunctionInfo *XFI = MF.getInfo<XCoreFunctionInfo>();
349   if (LRUsed) {
350     MF.getRegInfo().setPhysRegUnused(XCore::LR);
351 
352     bool isVarArg = MF.getFunction()->isVarArg();
353     int FrameIdx;
354     if (! isVarArg) {
355       // A fixed offset of 0 allows us to save / restore LR using entsp / retsp.
356       FrameIdx = MFI->CreateFixedObject(RC->getSize(), 0, true);
357     } else {
358       FrameIdx = MFI->CreateStackObject(RC->getSize(), RC->getAlignment(),
359                                         false);
360     }
361     XFI->setUsesLR(FrameIdx);
362     XFI->setLRSpillSlot(FrameIdx);
363   }
364   if (RegInfo->requiresRegisterScavenging(MF)) {
365     // Reserve a slot close to SP or frame pointer.
366     RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
367                                                        RC->getAlignment(),
368                                                        false));
369   }
370   if (hasFP(MF)) {
371     // A callee save register is used to hold the FP.
372     // This needs saving / restoring in the epilogue / prologue.
373     XFI->setFPSpillSlot(MFI->CreateStackObject(RC->getSize(),
374                                                RC->getAlignment(),
375                                                false));
376   }
377 }
378 
379 void XCoreFrameLowering::
380 processFunctionBeforeFrameFinalized(MachineFunction &MF) const {
381 
382 }
383