1//===-- DelaySlotFiller.cpp - SPARC delay slot filler ---------------------===//
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 is a simple local pass that attempts to fill delay slots with useful
11// instructions. If no instructions can be moved into the delay slot, then a
12// NOP is placed.
13//===----------------------------------------------------------------------===//
14
15#include "Sparc.h"
16#include "SparcSubtarget.h"
17#include "llvm/ADT/SmallSet.h"
18#include "llvm/ADT/Statistic.h"
19#include "llvm/CodeGen/MachineFunctionPass.h"
20#include "llvm/CodeGen/MachineInstrBuilder.h"
21#include "llvm/CodeGen/MachineRegisterInfo.h"
22#include "llvm/Support/CommandLine.h"
23#include "llvm/Target/TargetInstrInfo.h"
24#include "llvm/Target/TargetMachine.h"
25#include "llvm/Target/TargetRegisterInfo.h"
26
27using namespace llvm;
28
29#define DEBUG_TYPE "delay-slot-filler"
30
31STATISTIC(FilledSlots, "Number of delay slots filled");
32
33static cl::opt<bool> DisableDelaySlotFiller(
34  "disable-sparc-delay-filler",
35  cl::init(false),
36  cl::desc("Disable the Sparc delay slot filler."),
37  cl::Hidden);
38
39namespace {
40  struct Filler : public MachineFunctionPass {
41    /// Target machine description which we query for reg. names, data
42    /// layout, etc.
43    ///
44    TargetMachine &TM;
45    const SparcSubtarget *Subtarget;
46
47    static char ID;
48    Filler(TargetMachine &tm) : MachineFunctionPass(ID), TM(tm) {}
49
50    const char *getPassName() const override {
51      return "SPARC Delay Slot Filler";
52    }
53
54    bool runOnMachineBasicBlock(MachineBasicBlock &MBB);
55    bool runOnMachineFunction(MachineFunction &F) override {
56      bool Changed = false;
57      Subtarget = &F.getSubtarget<SparcSubtarget>();
58
59      // This pass invalidates liveness information when it reorders
60      // instructions to fill delay slot.
61      F.getRegInfo().invalidateLiveness();
62
63      for (MachineFunction::iterator FI = F.begin(), FE = F.end();
64           FI != FE; ++FI)
65        Changed |= runOnMachineBasicBlock(*FI);
66      return Changed;
67    }
68
69    void insertCallDefsUses(MachineBasicBlock::iterator MI,
70                            SmallSet<unsigned, 32>& RegDefs,
71                            SmallSet<unsigned, 32>& RegUses);
72
73    void insertDefsUses(MachineBasicBlock::iterator MI,
74                        SmallSet<unsigned, 32>& RegDefs,
75                        SmallSet<unsigned, 32>& RegUses);
76
77    bool IsRegInSet(SmallSet<unsigned, 32>& RegSet,
78                    unsigned Reg);
79
80    bool delayHasHazard(MachineBasicBlock::iterator candidate,
81                        bool &sawLoad, bool &sawStore,
82                        SmallSet<unsigned, 32> &RegDefs,
83                        SmallSet<unsigned, 32> &RegUses);
84
85    MachineBasicBlock::iterator
86    findDelayInstr(MachineBasicBlock &MBB, MachineBasicBlock::iterator slot);
87
88    bool needsUnimp(MachineBasicBlock::iterator I, unsigned &StructSize);
89
90    bool tryCombineRestoreWithPrevInst(MachineBasicBlock &MBB,
91                                       MachineBasicBlock::iterator MBBI);
92
93  };
94  char Filler::ID = 0;
95} // end of anonymous namespace
96
97/// createSparcDelaySlotFillerPass - Returns a pass that fills in delay
98/// slots in Sparc MachineFunctions
99///
100FunctionPass *llvm::createSparcDelaySlotFillerPass(TargetMachine &tm) {
101  return new Filler(tm);
102}
103
104
105/// runOnMachineBasicBlock - Fill in delay slots for the given basic block.
106/// We assume there is only one delay slot per delayed instruction.
107///
108bool Filler::runOnMachineBasicBlock(MachineBasicBlock &MBB) {
109  bool Changed = false;
110  Subtarget = &MBB.getParent()->getSubtarget<SparcSubtarget>();
111  const TargetInstrInfo *TII = Subtarget->getInstrInfo();
112
113  for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ) {
114    MachineBasicBlock::iterator MI = I;
115    ++I;
116
117    // If MI is restore, try combining it with previous inst.
118    if (!DisableDelaySlotFiller &&
119        (MI->getOpcode() == SP::RESTORErr
120         || MI->getOpcode() == SP::RESTOREri)) {
121      Changed |= tryCombineRestoreWithPrevInst(MBB, MI);
122      continue;
123    }
124
125    // TODO: If we ever want to support v7, this needs to be extended
126    // to cover all floating point operations.
127    if (!Subtarget->isV9() &&
128        (MI->getOpcode() == SP::FCMPS || MI->getOpcode() == SP::FCMPD
129         || MI->getOpcode() == SP::FCMPQ)) {
130      BuildMI(MBB, I, MI->getDebugLoc(), TII->get(SP::NOP));
131      Changed = true;
132      continue;
133    }
134
135    // If MI has no delay slot, skip.
136    if (!MI->hasDelaySlot())
137      continue;
138
139    MachineBasicBlock::iterator D = MBB.end();
140
141    if (!DisableDelaySlotFiller)
142      D = findDelayInstr(MBB, MI);
143
144    ++FilledSlots;
145    Changed = true;
146
147    if (D == MBB.end())
148      BuildMI(MBB, I, MI->getDebugLoc(), TII->get(SP::NOP));
149    else
150      MBB.splice(I, &MBB, D);
151
152    unsigned structSize = 0;
153    if (needsUnimp(MI, structSize)) {
154      MachineBasicBlock::iterator J = MI;
155      ++J; // skip the delay filler.
156      assert (J != MBB.end() && "MI needs a delay instruction.");
157      BuildMI(MBB, ++J, MI->getDebugLoc(),
158              TII->get(SP::UNIMP)).addImm(structSize);
159      // Bundle the delay filler and unimp with the instruction.
160      MIBundleBuilder(MBB, MachineBasicBlock::iterator(MI), J);
161    } else {
162      MIBundleBuilder(MBB, MachineBasicBlock::iterator(MI), I);
163    }
164  }
165  return Changed;
166}
167
168MachineBasicBlock::iterator
169Filler::findDelayInstr(MachineBasicBlock &MBB,
170                       MachineBasicBlock::iterator slot)
171{
172  SmallSet<unsigned, 32> RegDefs;
173  SmallSet<unsigned, 32> RegUses;
174  bool sawLoad = false;
175  bool sawStore = false;
176
177  if (slot == MBB.begin())
178    return MBB.end();
179
180  if (slot->getOpcode() == SP::RET || slot->getOpcode() == SP::TLS_CALL)
181    return MBB.end();
182
183  if (slot->getOpcode() == SP::RETL) {
184    MachineBasicBlock::iterator J = slot;
185    --J;
186
187    if (J->getOpcode() == SP::RESTORErr
188        || J->getOpcode() == SP::RESTOREri) {
189      // change retl to ret.
190      slot->setDesc(Subtarget->getInstrInfo()->get(SP::RET));
191      return J;
192    }
193  }
194
195  // Call's delay filler can def some of call's uses.
196  if (slot->isCall())
197    insertCallDefsUses(slot, RegDefs, RegUses);
198  else
199    insertDefsUses(slot, RegDefs, RegUses);
200
201  bool done = false;
202
203  MachineBasicBlock::iterator I = slot;
204
205  while (!done) {
206    done = (I == MBB.begin());
207
208    if (!done)
209      --I;
210
211    // skip debug value
212    if (I->isDebugValue())
213      continue;
214
215    if (I->hasUnmodeledSideEffects() || I->isInlineAsm() || I->isPosition() ||
216        I->hasDelaySlot() || I->isBundledWithSucc())
217      break;
218
219    if (delayHasHazard(I, sawLoad, sawStore, RegDefs, RegUses)) {
220      insertDefsUses(I, RegDefs, RegUses);
221      continue;
222    }
223
224    return I;
225  }
226  return MBB.end();
227}
228
229bool Filler::delayHasHazard(MachineBasicBlock::iterator candidate,
230                            bool &sawLoad,
231                            bool &sawStore,
232                            SmallSet<unsigned, 32> &RegDefs,
233                            SmallSet<unsigned, 32> &RegUses)
234{
235
236  if (candidate->isImplicitDef() || candidate->isKill())
237    return true;
238
239  if (candidate->mayLoad()) {
240    sawLoad = true;
241    if (sawStore)
242      return true;
243  }
244
245  if (candidate->mayStore()) {
246    if (sawStore)
247      return true;
248    sawStore = true;
249    if (sawLoad)
250      return true;
251  }
252
253  for (unsigned i = 0, e = candidate->getNumOperands(); i!= e; ++i) {
254    const MachineOperand &MO = candidate->getOperand(i);
255    if (!MO.isReg())
256      continue; // skip
257
258    unsigned Reg = MO.getReg();
259
260    if (MO.isDef()) {
261      // check whether Reg is defined or used before delay slot.
262      if (IsRegInSet(RegDefs, Reg) || IsRegInSet(RegUses, Reg))
263        return true;
264    }
265    if (MO.isUse()) {
266      // check whether Reg is defined before delay slot.
267      if (IsRegInSet(RegDefs, Reg))
268        return true;
269    }
270  }
271  return false;
272}
273
274
275void Filler::insertCallDefsUses(MachineBasicBlock::iterator MI,
276                                SmallSet<unsigned, 32>& RegDefs,
277                                SmallSet<unsigned, 32>& RegUses)
278{
279  // Call defines o7, which is visible to the instruction in delay slot.
280  RegDefs.insert(SP::O7);
281
282  switch(MI->getOpcode()) {
283  default: llvm_unreachable("Unknown opcode.");
284  case SP::CALL: break;
285  case SP::CALLrr:
286  case SP::CALLri:
287    assert(MI->getNumOperands() >= 2);
288    const MachineOperand &Reg = MI->getOperand(0);
289    assert(Reg.isReg() && "CALL first operand is not a register.");
290    assert(Reg.isUse() && "CALL first operand is not a use.");
291    RegUses.insert(Reg.getReg());
292
293    const MachineOperand &RegOrImm = MI->getOperand(1);
294    if (RegOrImm.isImm())
295        break;
296    assert(RegOrImm.isReg() && "CALLrr second operand is not a register.");
297    assert(RegOrImm.isUse() && "CALLrr second operand is not a use.");
298    RegUses.insert(RegOrImm.getReg());
299    break;
300  }
301}
302
303// Insert Defs and Uses of MI into the sets RegDefs and RegUses.
304void Filler::insertDefsUses(MachineBasicBlock::iterator MI,
305                            SmallSet<unsigned, 32>& RegDefs,
306                            SmallSet<unsigned, 32>& RegUses)
307{
308  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
309    const MachineOperand &MO = MI->getOperand(i);
310    if (!MO.isReg())
311      continue;
312
313    unsigned Reg = MO.getReg();
314    if (Reg == 0)
315      continue;
316    if (MO.isDef())
317      RegDefs.insert(Reg);
318    if (MO.isUse()) {
319      // Implicit register uses of retl are return values and
320      // retl does not use them.
321      if (MO.isImplicit() && MI->getOpcode() == SP::RETL)
322        continue;
323      RegUses.insert(Reg);
324    }
325  }
326}
327
328// returns true if the Reg or its alias is in the RegSet.
329bool Filler::IsRegInSet(SmallSet<unsigned, 32>& RegSet, unsigned Reg)
330{
331  // Check Reg and all aliased Registers.
332  for (MCRegAliasIterator AI(Reg, Subtarget->getRegisterInfo(), true);
333       AI.isValid(); ++AI)
334    if (RegSet.count(*AI))
335      return true;
336  return false;
337}
338
339bool Filler::needsUnimp(MachineBasicBlock::iterator I, unsigned &StructSize)
340{
341  if (!I->isCall())
342    return false;
343
344  unsigned structSizeOpNum = 0;
345  switch (I->getOpcode()) {
346  default: llvm_unreachable("Unknown call opcode.");
347  case SP::CALL: structSizeOpNum = 1; break;
348  case SP::CALLrr:
349  case SP::CALLri: structSizeOpNum = 2; break;
350  case SP::TLS_CALL: return false;
351  }
352
353  const MachineOperand &MO = I->getOperand(structSizeOpNum);
354  if (!MO.isImm())
355    return false;
356  StructSize = MO.getImm();
357  return true;
358}
359
360static bool combineRestoreADD(MachineBasicBlock::iterator RestoreMI,
361                              MachineBasicBlock::iterator AddMI,
362                              const TargetInstrInfo *TII)
363{
364  // Before:  add  <op0>, <op1>, %i[0-7]
365  //          restore %g0, %g0, %i[0-7]
366  //
367  // After :  restore <op0>, <op1>, %o[0-7]
368
369  unsigned reg = AddMI->getOperand(0).getReg();
370  if (reg < SP::I0 || reg > SP::I7)
371    return false;
372
373  // Erase RESTORE.
374  RestoreMI->eraseFromParent();
375
376  // Change ADD to RESTORE.
377  AddMI->setDesc(TII->get((AddMI->getOpcode() == SP::ADDrr)
378                          ? SP::RESTORErr
379                          : SP::RESTOREri));
380
381  // Map the destination register.
382  AddMI->getOperand(0).setReg(reg - SP::I0 + SP::O0);
383
384  return true;
385}
386
387static bool combineRestoreOR(MachineBasicBlock::iterator RestoreMI,
388                             MachineBasicBlock::iterator OrMI,
389                             const TargetInstrInfo *TII)
390{
391  // Before:  or  <op0>, <op1>, %i[0-7]
392  //          restore %g0, %g0, %i[0-7]
393  //    and <op0> or <op1> is zero,
394  //
395  // After :  restore <op0>, <op1>, %o[0-7]
396
397  unsigned reg = OrMI->getOperand(0).getReg();
398  if (reg < SP::I0 || reg > SP::I7)
399    return false;
400
401  // check whether it is a copy.
402  if (OrMI->getOpcode() == SP::ORrr
403      && OrMI->getOperand(1).getReg() != SP::G0
404      && OrMI->getOperand(2).getReg() != SP::G0)
405    return false;
406
407  if (OrMI->getOpcode() == SP::ORri
408      && OrMI->getOperand(1).getReg() != SP::G0
409      && (!OrMI->getOperand(2).isImm() || OrMI->getOperand(2).getImm() != 0))
410    return false;
411
412  // Erase RESTORE.
413  RestoreMI->eraseFromParent();
414
415  // Change OR to RESTORE.
416  OrMI->setDesc(TII->get((OrMI->getOpcode() == SP::ORrr)
417                         ? SP::RESTORErr
418                         : SP::RESTOREri));
419
420  // Map the destination register.
421  OrMI->getOperand(0).setReg(reg - SP::I0 + SP::O0);
422
423  return true;
424}
425
426static bool combineRestoreSETHIi(MachineBasicBlock::iterator RestoreMI,
427                                 MachineBasicBlock::iterator SetHiMI,
428                                 const TargetInstrInfo *TII)
429{
430  // Before:  sethi imm3, %i[0-7]
431  //          restore %g0, %g0, %g0
432  //
433  // After :  restore %g0, (imm3<<10), %o[0-7]
434
435  unsigned reg = SetHiMI->getOperand(0).getReg();
436  if (reg < SP::I0 || reg > SP::I7)
437    return false;
438
439  if (!SetHiMI->getOperand(1).isImm())
440    return false;
441
442  int64_t imm = SetHiMI->getOperand(1).getImm();
443
444  // Is it a 3 bit immediate?
445  if (!isInt<3>(imm))
446    return false;
447
448  // Make it a 13 bit immediate.
449  imm = (imm << 10) & 0x1FFF;
450
451  assert(RestoreMI->getOpcode() == SP::RESTORErr);
452
453  RestoreMI->setDesc(TII->get(SP::RESTOREri));
454
455  RestoreMI->getOperand(0).setReg(reg - SP::I0 + SP::O0);
456  RestoreMI->getOperand(1).setReg(SP::G0);
457  RestoreMI->getOperand(2).ChangeToImmediate(imm);
458
459
460  // Erase the original SETHI.
461  SetHiMI->eraseFromParent();
462
463  return true;
464}
465
466bool Filler::tryCombineRestoreWithPrevInst(MachineBasicBlock &MBB,
467                                        MachineBasicBlock::iterator MBBI)
468{
469  // No previous instruction.
470  if (MBBI == MBB.begin())
471    return false;
472
473  // assert that MBBI is a "restore %g0, %g0, %g0".
474  assert(MBBI->getOpcode() == SP::RESTORErr
475         && MBBI->getOperand(0).getReg() == SP::G0
476         && MBBI->getOperand(1).getReg() == SP::G0
477         && MBBI->getOperand(2).getReg() == SP::G0);
478
479  MachineBasicBlock::iterator PrevInst = std::prev(MBBI);
480
481  // It cannot be combined with a bundled instruction.
482  if (PrevInst->isBundledWithSucc())
483    return false;
484
485  const TargetInstrInfo *TII = Subtarget->getInstrInfo();
486
487  switch (PrevInst->getOpcode()) {
488  default: break;
489  case SP::ADDrr:
490  case SP::ADDri: return combineRestoreADD(MBBI, PrevInst, TII); break;
491  case SP::ORrr:
492  case SP::ORri:  return combineRestoreOR(MBBI, PrevInst, TII); break;
493  case SP::SETHIi: return combineRestoreSETHIi(MBBI, PrevInst, TII); break;
494  }
495  // It cannot combine with the previous instruction.
496  return false;
497}
498