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   bool Nested = MF.getFunction()->getAttributes().hasAttrSomewhere(Attribute::Nest);
104 
105   if (Nested) {
106     loadFromStack(MBB, MBBI, XCore::R11, 0, dl, TII);
107   }
108 
109   // Work out frame sizes.
110   int FrameSize = MFI->getStackSize();
111   assert(FrameSize%4 == 0 && "Misaligned frame size");
112   FrameSize/=4;
113 
114   bool isU6 = isImmU6(FrameSize);
115 
116   if (!isU6 && !isImmU16(FrameSize)) {
117     // FIXME could emit multiple instructions.
118     report_fatal_error("emitPrologue Frame size too big: " + Twine(FrameSize));
119   }
120   bool emitFrameMoves = RegInfo->needsFrameMoves(MF);
121 
122   // Do we need to allocate space on the stack?
123   if (FrameSize) {
124     bool saveLR = XFI->getUsesLR();
125     bool LRSavedOnEntry = false;
126     int Opcode;
127     if (saveLR && (MFI->getObjectOffset(XFI->getLRSpillSlot()) == 0)) {
128       Opcode = (isU6) ? XCore::ENTSP_u6 : XCore::ENTSP_lu6;
129       MBB.addLiveIn(XCore::LR);
130       saveLR = false;
131       LRSavedOnEntry = true;
132     } else {
133       Opcode = (isU6) ? XCore::EXTSP_u6 : XCore::EXTSP_lu6;
134     }
135     BuildMI(MBB, MBBI, dl, TII.get(Opcode)).addImm(FrameSize);
136 
137     if (emitFrameMoves) {
138       std::vector<MachineMove> &Moves = MMI->getFrameMoves();
139 
140       // Show update of SP.
141       MCSymbol *FrameLabel = MMI->getContext().CreateTempSymbol();
142       BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(FrameLabel);
143 
144       MachineLocation SPDst(MachineLocation::VirtualFP);
145       MachineLocation SPSrc(MachineLocation::VirtualFP, -FrameSize * 4);
146       Moves.push_back(MachineMove(FrameLabel, SPDst, SPSrc));
147 
148       if (LRSavedOnEntry) {
149         MachineLocation CSDst(MachineLocation::VirtualFP, 0);
150         MachineLocation CSSrc(XCore::LR);
151         Moves.push_back(MachineMove(FrameLabel, CSDst, CSSrc));
152       }
153     }
154     if (saveLR) {
155       int LRSpillOffset = MFI->getObjectOffset(XFI->getLRSpillSlot());
156       storeToStack(MBB, MBBI, XCore::LR, LRSpillOffset + FrameSize*4, dl, TII);
157       MBB.addLiveIn(XCore::LR);
158 
159       if (emitFrameMoves) {
160         MCSymbol *SaveLRLabel = MMI->getContext().CreateTempSymbol();
161         BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(SaveLRLabel);
162         MachineLocation CSDst(MachineLocation::VirtualFP, LRSpillOffset);
163         MachineLocation CSSrc(XCore::LR);
164         MMI->getFrameMoves().push_back(MachineMove(SaveLRLabel, CSDst, CSSrc));
165       }
166     }
167   }
168 
169   if (FP) {
170     // Save R10 to the stack.
171     int FPSpillOffset = MFI->getObjectOffset(XFI->getFPSpillSlot());
172     storeToStack(MBB, MBBI, XCore::R10, FPSpillOffset + FrameSize*4, dl, TII);
173     // R10 is live-in. It is killed at the spill.
174     MBB.addLiveIn(XCore::R10);
175     if (emitFrameMoves) {
176       MCSymbol *SaveR10Label = MMI->getContext().CreateTempSymbol();
177       BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(SaveR10Label);
178       MachineLocation CSDst(MachineLocation::VirtualFP, FPSpillOffset);
179       MachineLocation CSSrc(XCore::R10);
180       MMI->getFrameMoves().push_back(MachineMove(SaveR10Label, CSDst, CSSrc));
181     }
182     // Set the FP from the SP.
183     unsigned FramePtr = XCore::R10;
184     BuildMI(MBB, MBBI, dl, TII.get(XCore::LDAWSP_ru6), FramePtr)
185       .addImm(0);
186     if (emitFrameMoves) {
187       // Show FP is now valid.
188       MCSymbol *FrameLabel = MMI->getContext().CreateTempSymbol();
189       BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(FrameLabel);
190       MachineLocation SPDst(FramePtr);
191       MachineLocation SPSrc(MachineLocation::VirtualFP);
192       MMI->getFrameMoves().push_back(MachineMove(FrameLabel, SPDst, SPSrc));
193     }
194   }
195 
196   if (emitFrameMoves) {
197     // Frame moves for callee saved.
198     std::vector<MachineMove> &Moves = MMI->getFrameMoves();
199     std::vector<std::pair<MCSymbol*, CalleeSavedInfo> >&SpillLabels =
200         XFI->getSpillLabels();
201     for (unsigned I = 0, E = SpillLabels.size(); I != E; ++I) {
202       MCSymbol *SpillLabel = SpillLabels[I].first;
203       CalleeSavedInfo &CSI = SpillLabels[I].second;
204       int Offset = MFI->getObjectOffset(CSI.getFrameIdx());
205       unsigned Reg = CSI.getReg();
206       MachineLocation CSDst(MachineLocation::VirtualFP, Offset);
207       MachineLocation CSSrc(Reg);
208       Moves.push_back(MachineMove(SpillLabel, CSDst, CSSrc));
209     }
210   }
211 }
212 
213 void XCoreFrameLowering::emitEpilogue(MachineFunction &MF,
214                                      MachineBasicBlock &MBB) const {
215   MachineFrameInfo *MFI            = MF.getFrameInfo();
216   MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
217   const XCoreInstrInfo &TII =
218     *static_cast<const XCoreInstrInfo*>(MF.getTarget().getInstrInfo());
219   DebugLoc dl = MBBI->getDebugLoc();
220 
221   bool FP = hasFP(MF);
222   if (FP) {
223     // Restore the stack pointer.
224     unsigned FramePtr = XCore::R10;
225     BuildMI(MBB, MBBI, dl, TII.get(XCore::SETSP_1r))
226       .addReg(FramePtr);
227   }
228 
229   // Work out frame sizes.
230   int FrameSize = MFI->getStackSize();
231 
232   assert(FrameSize%4 == 0 && "Misaligned frame size");
233 
234   FrameSize/=4;
235 
236   bool isU6 = isImmU6(FrameSize);
237 
238   if (!isU6 && !isImmU16(FrameSize)) {
239     // FIXME could emit multiple instructions.
240     report_fatal_error("emitEpilogue Frame size too big: " + Twine(FrameSize));
241   }
242 
243   if (FrameSize) {
244     XCoreFunctionInfo *XFI = MF.getInfo<XCoreFunctionInfo>();
245 
246     if (FP) {
247       // Restore R10
248       int FPSpillOffset = MFI->getObjectOffset(XFI->getFPSpillSlot());
249       FPSpillOffset += FrameSize*4;
250       loadFromStack(MBB, MBBI, XCore::R10, FPSpillOffset, dl, TII);
251     }
252     bool restoreLR = XFI->getUsesLR();
253     if (restoreLR && MFI->getObjectOffset(XFI->getLRSpillSlot()) != 0) {
254       int LRSpillOffset = MFI->getObjectOffset(XFI->getLRSpillSlot());
255       LRSpillOffset += FrameSize*4;
256       loadFromStack(MBB, MBBI, XCore::LR, LRSpillOffset, dl, TII);
257       restoreLR = false;
258     }
259     if (restoreLR) {
260       // Fold prologue into return instruction
261       assert(MBBI->getOpcode() == XCore::RETSP_u6
262         || MBBI->getOpcode() == XCore::RETSP_lu6);
263       int Opcode = (isU6) ? XCore::RETSP_u6 : XCore::RETSP_lu6;
264       BuildMI(MBB, MBBI, dl, TII.get(Opcode)).addImm(FrameSize);
265       MBB.erase(MBBI);
266     } else {
267       int Opcode = (isU6) ? XCore::LDAWSP_ru6_RRegs : XCore::LDAWSP_lru6_RRegs;
268       BuildMI(MBB, MBBI, dl, TII.get(Opcode), XCore::SP).addImm(FrameSize);
269     }
270   }
271 }
272 
273 void XCoreFrameLowering::getInitialFrameState(std::vector<MachineMove> &Moves)
274                                                                         const {
275   // Initial state of the frame pointer is SP.
276   MachineLocation Dst(MachineLocation::VirtualFP);
277   MachineLocation Src(XCore::SP, 0);
278   Moves.push_back(MachineMove(0, Dst, Src));
279 }
280 
281 bool XCoreFrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB,
282                                                MachineBasicBlock::iterator MI,
283                                         const std::vector<CalleeSavedInfo> &CSI,
284                                           const TargetRegisterInfo *TRI) const {
285   if (CSI.empty())
286     return true;
287 
288   MachineFunction *MF = MBB.getParent();
289   const TargetInstrInfo &TII = *MF->getTarget().getInstrInfo();
290 
291   XCoreFunctionInfo *XFI = MF->getInfo<XCoreFunctionInfo>();
292   bool emitFrameMoves = XCoreRegisterInfo::needsFrameMoves(*MF);
293 
294   DebugLoc DL;
295   if (MI != MBB.end()) DL = MI->getDebugLoc();
296 
297   for (std::vector<CalleeSavedInfo>::const_iterator it = CSI.begin();
298                                                     it != CSI.end(); ++it) {
299     // Add the callee-saved register as live-in. It's killed at the spill.
300     MBB.addLiveIn(it->getReg());
301 
302     unsigned Reg = it->getReg();
303     const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
304     TII.storeRegToStackSlot(MBB, MI, Reg, true,
305                             it->getFrameIdx(), RC, TRI);
306     if (emitFrameMoves) {
307       MCSymbol *SaveLabel = MF->getContext().CreateTempSymbol();
308       BuildMI(MBB, MI, DL, TII.get(XCore::PROLOG_LABEL)).addSym(SaveLabel);
309       XFI->getSpillLabels().push_back(std::make_pair(SaveLabel, *it));
310     }
311   }
312   return true;
313 }
314 
315 bool XCoreFrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
316                                                  MachineBasicBlock::iterator MI,
317                                         const std::vector<CalleeSavedInfo> &CSI,
318                                             const TargetRegisterInfo *TRI) const{
319   MachineFunction *MF = MBB.getParent();
320   const TargetInstrInfo &TII = *MF->getTarget().getInstrInfo();
321 
322   bool AtStart = MI == MBB.begin();
323   MachineBasicBlock::iterator BeforeI = MI;
324   if (!AtStart)
325     --BeforeI;
326   for (std::vector<CalleeSavedInfo>::const_iterator it = CSI.begin();
327                                                     it != CSI.end(); ++it) {
328     unsigned Reg = it->getReg();
329     const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
330     TII.loadRegFromStackSlot(MBB, MI, it->getReg(), it->getFrameIdx(),
331                              RC, TRI);
332     assert(MI != MBB.begin() &&
333            "loadRegFromStackSlot didn't insert any code!");
334     // Insert in reverse order.  loadRegFromStackSlot can insert multiple
335     // instructions.
336     if (AtStart)
337       MI = MBB.begin();
338     else {
339       MI = BeforeI;
340       ++MI;
341     }
342   }
343   return true;
344 }
345 
346 void
347 XCoreFrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
348                                                      RegScavenger *RS) const {
349   MachineFrameInfo *MFI = MF.getFrameInfo();
350   const TargetRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
351   bool LRUsed = MF.getRegInfo().isPhysRegUsed(XCore::LR);
352   const TargetRegisterClass *RC = XCore::GRRegsRegisterClass;
353   XCoreFunctionInfo *XFI = MF.getInfo<XCoreFunctionInfo>();
354   if (LRUsed) {
355     MF.getRegInfo().setPhysRegUnused(XCore::LR);
356 
357     bool isVarArg = MF.getFunction()->isVarArg();
358     int FrameIdx;
359     if (! isVarArg) {
360       // A fixed offset of 0 allows us to save / restore LR using entsp / retsp.
361       FrameIdx = MFI->CreateFixedObject(RC->getSize(), 0, true);
362     } else {
363       FrameIdx = MFI->CreateStackObject(RC->getSize(), RC->getAlignment(),
364                                         false);
365     }
366     XFI->setUsesLR(FrameIdx);
367     XFI->setLRSpillSlot(FrameIdx);
368   }
369   if (RegInfo->requiresRegisterScavenging(MF)) {
370     // Reserve a slot close to SP or frame pointer.
371     RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
372                                                        RC->getAlignment(),
373                                                        false));
374   }
375   if (hasFP(MF)) {
376     // A callee save register is used to hold the FP.
377     // This needs saving / restoring in the epilogue / prologue.
378     XFI->setFPSpillSlot(MFI->CreateStackObject(RC->getSize(),
379                                                RC->getAlignment(),
380                                                false));
381   }
382 }
383 
384 void XCoreFrameLowering::
385 processFunctionBeforeFrameFinalized(MachineFunction &MF) const {
386 
387 }
388