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