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 MF.getTarget().Options.DisableFramePointerElim(MF) ||
88     MF.getFrameInfo()->hasVarSizedObjects();
89 }
90 
91 void XCoreFrameLowering::emitPrologue(MachineFunction &MF) const {
92   MachineBasicBlock &MBB = MF.front();   // Prolog goes in entry BB
93   MachineBasicBlock::iterator MBBI = MBB.begin();
94   MachineFrameInfo *MFI = MF.getFrameInfo();
95   MachineModuleInfo *MMI = &MF.getMMI();
96   const XCoreRegisterInfo *RegInfo =
97     static_cast<const XCoreRegisterInfo*>(MF.getTarget().getRegisterInfo());
98   const XCoreInstrInfo &TII =
99     *static_cast<const XCoreInstrInfo*>(MF.getTarget().getInstrInfo());
100   XCoreFunctionInfo *XFI = MF.getInfo<XCoreFunctionInfo>();
101   DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
102 
103   bool FP = hasFP(MF);
104   bool Nested = MF.getFunction()->
105                 getAttributes().hasAttrSomewhere(Attribute::Nest);
106 
107   if (Nested) {
108     loadFromStack(MBB, MBBI, XCore::R11, 0, dl, TII);
109   }
110 
111   // Work out frame sizes.
112   int FrameSize = MFI->getStackSize();
113   assert(FrameSize%4 == 0 && "Misaligned frame size");
114   FrameSize/=4;
115 
116   bool isU6 = isImmU6(FrameSize);
117 
118   if (!isU6 && !isImmU16(FrameSize)) {
119     // FIXME could emit multiple instructions.
120     report_fatal_error("emitPrologue Frame size too big: " + Twine(FrameSize));
121   }
122   bool emitFrameMoves = RegInfo->needsFrameMoves(MF);
123 
124   // Do we need to allocate space on the stack?
125   if (FrameSize) {
126     bool saveLR = XFI->getUsesLR();
127     bool LRSavedOnEntry = false;
128     int Opcode;
129     if (saveLR && (MFI->getObjectOffset(XFI->getLRSpillSlot()) == 0)) {
130       Opcode = (isU6) ? XCore::ENTSP_u6 : XCore::ENTSP_lu6;
131       MBB.addLiveIn(XCore::LR);
132       saveLR = false;
133       LRSavedOnEntry = true;
134     } else {
135       Opcode = (isU6) ? XCore::EXTSP_u6 : XCore::EXTSP_lu6;
136     }
137     BuildMI(MBB, MBBI, dl, TII.get(Opcode)).addImm(FrameSize);
138 
139     if (emitFrameMoves) {
140       std::vector<MachineMove> &Moves = MMI->getFrameMoves();
141 
142       // Show update of SP.
143       MCSymbol *FrameLabel = MMI->getContext().CreateTempSymbol();
144       BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(FrameLabel);
145 
146       MachineLocation SPDst(MachineLocation::VirtualFP);
147       MachineLocation SPSrc(MachineLocation::VirtualFP, -FrameSize * 4);
148       Moves.push_back(MachineMove(FrameLabel, SPDst, SPSrc));
149 
150       if (LRSavedOnEntry) {
151         MachineLocation CSDst(MachineLocation::VirtualFP, 0);
152         MachineLocation CSSrc(XCore::LR);
153         Moves.push_back(MachineMove(FrameLabel, CSDst, CSSrc));
154       }
155     }
156     if (saveLR) {
157       int LRSpillOffset = MFI->getObjectOffset(XFI->getLRSpillSlot());
158       storeToStack(MBB, MBBI, XCore::LR, LRSpillOffset + FrameSize*4, dl, TII);
159       MBB.addLiveIn(XCore::LR);
160 
161       if (emitFrameMoves) {
162         MCSymbol *SaveLRLabel = MMI->getContext().CreateTempSymbol();
163         BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(SaveLRLabel);
164         MachineLocation CSDst(MachineLocation::VirtualFP, LRSpillOffset);
165         MachineLocation CSSrc(XCore::LR);
166         MMI->getFrameMoves().push_back(MachineMove(SaveLRLabel, CSDst, CSSrc));
167       }
168     }
169   }
170 
171   if (FP) {
172     // Save R10 to the stack.
173     int FPSpillOffset = MFI->getObjectOffset(XFI->getFPSpillSlot());
174     storeToStack(MBB, MBBI, XCore::R10, FPSpillOffset + FrameSize*4, dl, TII);
175     // R10 is live-in. It is killed at the spill.
176     MBB.addLiveIn(XCore::R10);
177     if (emitFrameMoves) {
178       MCSymbol *SaveR10Label = MMI->getContext().CreateTempSymbol();
179       BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(SaveR10Label);
180       MachineLocation CSDst(MachineLocation::VirtualFP, FPSpillOffset);
181       MachineLocation CSSrc(XCore::R10);
182       MMI->getFrameMoves().push_back(MachineMove(SaveR10Label, CSDst, CSSrc));
183     }
184     // Set the FP from the SP.
185     unsigned FramePtr = XCore::R10;
186     BuildMI(MBB, MBBI, dl, TII.get(XCore::LDAWSP_ru6), FramePtr)
187       .addImm(0);
188     if (emitFrameMoves) {
189       // Show FP is now valid.
190       MCSymbol *FrameLabel = MMI->getContext().CreateTempSymbol();
191       BuildMI(MBB, MBBI, dl, TII.get(XCore::PROLOG_LABEL)).addSym(FrameLabel);
192       MachineLocation SPDst(FramePtr);
193       MachineLocation SPSrc(MachineLocation::VirtualFP);
194       MMI->getFrameMoves().push_back(MachineMove(FrameLabel, SPDst, SPSrc));
195     }
196   }
197 
198   if (emitFrameMoves) {
199     // Frame moves for callee saved.
200     std::vector<MachineMove> &Moves = MMI->getFrameMoves();
201     std::vector<std::pair<MCSymbol*, CalleeSavedInfo> >&SpillLabels =
202         XFI->getSpillLabels();
203     for (unsigned I = 0, E = SpillLabels.size(); I != E; ++I) {
204       MCSymbol *SpillLabel = SpillLabels[I].first;
205       CalleeSavedInfo &CSI = SpillLabels[I].second;
206       int Offset = MFI->getObjectOffset(CSI.getFrameIdx());
207       unsigned Reg = CSI.getReg();
208       MachineLocation CSDst(MachineLocation::VirtualFP, Offset);
209       MachineLocation CSSrc(Reg);
210       Moves.push_back(MachineMove(SpillLabel, CSDst, CSSrc));
211     }
212   }
213 }
214 
215 void XCoreFrameLowering::emitEpilogue(MachineFunction &MF,
216                                      MachineBasicBlock &MBB) const {
217   MachineFrameInfo *MFI            = MF.getFrameInfo();
218   MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
219   const XCoreInstrInfo &TII =
220     *static_cast<const XCoreInstrInfo*>(MF.getTarget().getInstrInfo());
221   DebugLoc dl = MBBI->getDebugLoc();
222 
223   bool FP = hasFP(MF);
224   if (FP) {
225     // Restore the stack pointer.
226     unsigned FramePtr = XCore::R10;
227     BuildMI(MBB, MBBI, dl, TII.get(XCore::SETSP_1r))
228       .addReg(FramePtr);
229   }
230 
231   // Work out frame sizes.
232   int FrameSize = MFI->getStackSize();
233 
234   assert(FrameSize%4 == 0 && "Misaligned frame size");
235 
236   FrameSize/=4;
237 
238   bool isU6 = isImmU6(FrameSize);
239 
240   if (!isU6 && !isImmU16(FrameSize)) {
241     // FIXME could emit multiple instructions.
242     report_fatal_error("emitEpilogue Frame size too big: " + Twine(FrameSize));
243   }
244 
245   if (FrameSize) {
246     XCoreFunctionInfo *XFI = MF.getInfo<XCoreFunctionInfo>();
247 
248     if (FP) {
249       // Restore R10
250       int FPSpillOffset = MFI->getObjectOffset(XFI->getFPSpillSlot());
251       FPSpillOffset += FrameSize*4;
252       loadFromStack(MBB, MBBI, XCore::R10, FPSpillOffset, dl, TII);
253     }
254     bool restoreLR = XFI->getUsesLR();
255     if (restoreLR && MFI->getObjectOffset(XFI->getLRSpillSlot()) != 0) {
256       int LRSpillOffset = MFI->getObjectOffset(XFI->getLRSpillSlot());
257       LRSpillOffset += FrameSize*4;
258       loadFromStack(MBB, MBBI, XCore::LR, LRSpillOffset, dl, TII);
259       restoreLR = false;
260     }
261     if (restoreLR) {
262       // Fold prologue into return instruction
263       assert(MBBI->getOpcode() == XCore::RETSP_u6
264         || MBBI->getOpcode() == XCore::RETSP_lu6);
265       int Opcode = (isU6) ? XCore::RETSP_u6 : XCore::RETSP_lu6;
266       BuildMI(MBB, MBBI, dl, TII.get(Opcode)).addImm(FrameSize);
267       MBB.erase(MBBI);
268     } else {
269       int Opcode = (isU6) ? XCore::LDAWSP_ru6_RRegs : XCore::LDAWSP_lru6_RRegs;
270       BuildMI(MBB, MBBI, dl, TII.get(Opcode), XCore::SP).addImm(FrameSize);
271     }
272   }
273 }
274 
275 bool XCoreFrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB,
276                                                MachineBasicBlock::iterator MI,
277                                         const std::vector<CalleeSavedInfo> &CSI,
278                                           const TargetRegisterInfo *TRI) const {
279   if (CSI.empty())
280     return true;
281 
282   MachineFunction *MF = MBB.getParent();
283   const TargetInstrInfo &TII = *MF->getTarget().getInstrInfo();
284 
285   XCoreFunctionInfo *XFI = MF->getInfo<XCoreFunctionInfo>();
286   bool emitFrameMoves = XCoreRegisterInfo::needsFrameMoves(*MF);
287 
288   DebugLoc DL;
289   if (MI != MBB.end()) DL = MI->getDebugLoc();
290 
291   for (std::vector<CalleeSavedInfo>::const_iterator it = CSI.begin();
292                                                     it != CSI.end(); ++it) {
293     // Add the callee-saved register as live-in. It's killed at the spill.
294     MBB.addLiveIn(it->getReg());
295 
296     unsigned Reg = it->getReg();
297     const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
298     TII.storeRegToStackSlot(MBB, MI, Reg, true,
299                             it->getFrameIdx(), RC, TRI);
300     if (emitFrameMoves) {
301       MCSymbol *SaveLabel = MF->getContext().CreateTempSymbol();
302       BuildMI(MBB, MI, DL, TII.get(XCore::PROLOG_LABEL)).addSym(SaveLabel);
303       XFI->getSpillLabels().push_back(std::make_pair(SaveLabel, *it));
304     }
305   }
306   return true;
307 }
308 
309 bool XCoreFrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
310                                                  MachineBasicBlock::iterator MI,
311                                         const std::vector<CalleeSavedInfo> &CSI,
312                                             const TargetRegisterInfo *TRI) const{
313   MachineFunction *MF = MBB.getParent();
314   const TargetInstrInfo &TII = *MF->getTarget().getInstrInfo();
315 
316   bool AtStart = MI == MBB.begin();
317   MachineBasicBlock::iterator BeforeI = MI;
318   if (!AtStart)
319     --BeforeI;
320   for (std::vector<CalleeSavedInfo>::const_iterator it = CSI.begin();
321                                                     it != CSI.end(); ++it) {
322     unsigned Reg = it->getReg();
323     const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
324     TII.loadRegFromStackSlot(MBB, MI, it->getReg(), it->getFrameIdx(),
325                              RC, TRI);
326     assert(MI != MBB.begin() &&
327            "loadRegFromStackSlot didn't insert any code!");
328     // Insert in reverse order.  loadRegFromStackSlot can insert multiple
329     // instructions.
330     if (AtStart)
331       MI = MBB.begin();
332     else {
333       MI = BeforeI;
334       ++MI;
335     }
336   }
337   return true;
338 }
339 
340 void
341 XCoreFrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
342                                                      RegScavenger *RS) const {
343   MachineFrameInfo *MFI = MF.getFrameInfo();
344   const TargetRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
345   bool LRUsed = MF.getRegInfo().isPhysRegUsed(XCore::LR);
346   const TargetRegisterClass *RC = XCore::GRRegsRegisterClass;
347   XCoreFunctionInfo *XFI = MF.getInfo<XCoreFunctionInfo>();
348   if (LRUsed) {
349     MF.getRegInfo().setPhysRegUnused(XCore::LR);
350 
351     bool isVarArg = MF.getFunction()->isVarArg();
352     int FrameIdx;
353     if (! isVarArg) {
354       // A fixed offset of 0 allows us to save / restore LR using entsp / retsp.
355       FrameIdx = MFI->CreateFixedObject(RC->getSize(), 0, true);
356     } else {
357       FrameIdx = MFI->CreateStackObject(RC->getSize(), RC->getAlignment(),
358                                         false);
359     }
360     XFI->setUsesLR(FrameIdx);
361     XFI->setLRSpillSlot(FrameIdx);
362   }
363   if (RegInfo->requiresRegisterScavenging(MF)) {
364     // Reserve a slot close to SP or frame pointer.
365     RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
366                                                        RC->getAlignment(),
367                                                        false));
368   }
369   if (hasFP(MF)) {
370     // A callee save register is used to hold the FP.
371     // This needs saving / restoring in the epilogue / prologue.
372     XFI->setFPSpillSlot(MFI->CreateStackObject(RC->getSize(),
373                                                RC->getAlignment(),
374                                                false));
375   }
376 }
377 
378 void XCoreFrameLowering::
379 processFunctionBeforeFrameFinalized(MachineFunction &MF) const {
380 
381 }
382