IfConversion.cpp revision 4ee451de366474b9c228b4e5fa573795a715216d 
1//===-- IfConversion.cpp - Machine code if conversion pass. ---------------===//
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 implements the machine instruction level if-conversion pass.
11//
12//===----------------------------------------------------------------------===//
13
14#define DEBUG_TYPE "ifcvt"
15#include "llvm/Function.h"
16#include "llvm/CodeGen/Passes.h"
17#include "llvm/CodeGen/MachineModuleInfo.h"
18#include "llvm/CodeGen/MachineFunctionPass.h"
19#include "llvm/Target/TargetInstrInfo.h"
20#include "llvm/Target/TargetLowering.h"
21#include "llvm/Target/TargetMachine.h"
22#include "llvm/Support/CommandLine.h"
23#include "llvm/Support/Debug.h"
24#include "llvm/ADT/DepthFirstIterator.h"
25#include "llvm/ADT/Statistic.h"
26#include "llvm/ADT/STLExtras.h"
27using namespace llvm;
28
29namespace {
30  // Hidden options for help debugging.
31  cl::opt<int> IfCvtFnStart("ifcvt-fn-start", cl::init(-1), cl::Hidden);
32  cl::opt<int> IfCvtFnStop("ifcvt-fn-stop", cl::init(-1), cl::Hidden);
33  cl::opt<int> IfCvtLimit("ifcvt-limit", cl::init(-1), cl::Hidden);
34  cl::opt<bool> DisableSimple("disable-ifcvt-simple",
35                              cl::init(false), cl::Hidden);
36  cl::opt<bool> DisableSimpleF("disable-ifcvt-simple-false",
37                               cl::init(false), cl::Hidden);
38  cl::opt<bool> DisableTriangle("disable-ifcvt-triangle",
39                                cl::init(false), cl::Hidden);
40  cl::opt<bool> DisableTriangleR("disable-ifcvt-triangle-rev",
41                                 cl::init(false), cl::Hidden);
42  cl::opt<bool> DisableTriangleF("disable-ifcvt-triangle-false",
43                                 cl::init(false), cl::Hidden);
44  cl::opt<bool> DisableTriangleFR("disable-ifcvt-triangle-false-rev",
45                                  cl::init(false), cl::Hidden);
46  cl::opt<bool> DisableDiamond("disable-ifcvt-diamond",
47                               cl::init(false), cl::Hidden);
48}
49
50STATISTIC(NumSimple,       "Number of simple if-conversions performed");
51STATISTIC(NumSimpleFalse,  "Number of simple (F) if-conversions performed");
52STATISTIC(NumTriangle,     "Number of triangle if-conversions performed");
53STATISTIC(NumTriangleRev,  "Number of triangle (R) if-conversions performed");
54STATISTIC(NumTriangleFalse,"Number of triangle (F) if-conversions performed");
55STATISTIC(NumTriangleFRev, "Number of triangle (F/R) if-conversions performed");
56STATISTIC(NumDiamonds,     "Number of diamond if-conversions performed");
57STATISTIC(NumIfConvBBs,    "Number of if-converted blocks");
58STATISTIC(NumDupBBs,       "Number of duplicated blocks");
59
60namespace {
61  class IfConverter : public MachineFunctionPass {
62    enum IfcvtKind {
63      ICNotClassfied,  // BB data valid, but not classified.
64      ICSimpleFalse,   // Same as ICSimple, but on the false path.
65      ICSimple,        // BB is entry of an one split, no rejoin sub-CFG.
66      ICTriangleFRev,  // Same as ICTriangleFalse, but false path rev condition.
67      ICTriangleRev,   // Same as ICTriangle, but true path rev condition.
68      ICTriangleFalse, // Same as ICTriangle, but on the false path.
69      ICTriangle,      // BB is entry of a triangle sub-CFG.
70      ICDiamond        // BB is entry of a diamond sub-CFG.
71    };
72
73    /// BBInfo - One per MachineBasicBlock, this is used to cache the result
74    /// if-conversion feasibility analysis. This includes results from
75    /// TargetInstrInfo::AnalyzeBranch() (i.e. TBB, FBB, and Cond), and its
76    /// classification, and common tail block of its successors (if it's a
77    /// diamond shape), its size, whether it's predicable, and whether any
78    /// instruction can clobber the 'would-be' predicate.
79    ///
80    /// IsDone          - True if BB is not to be considered for ifcvt.
81    /// IsBeingAnalyzed - True if BB is currently being analyzed.
82    /// IsAnalyzed      - True if BB has been analyzed (info is still valid).
83    /// IsEnqueued      - True if BB has been enqueued to be ifcvt'ed.
84    /// IsBrAnalyzable  - True if AnalyzeBranch() returns false.
85    /// HasFallThrough  - True if BB may fallthrough to the following BB.
86    /// IsUnpredicable  - True if BB is known to be unpredicable.
87    /// ClobbersPred    - True if BB could modify predicates (e.g. has
88    ///                   cmp, call, etc.)
89    /// NonPredSize     - Number of non-predicated instructions.
90    /// BB              - Corresponding MachineBasicBlock.
91    /// TrueBB / FalseBB- See AnalyzeBranch().
92    /// BrCond          - Conditions for end of block conditional branches.
93    /// Predicate       - Predicate used in the BB.
94    struct BBInfo {
95      bool IsDone          : 1;
96      bool IsBeingAnalyzed : 1;
97      bool IsAnalyzed      : 1;
98      bool IsEnqueued      : 1;
99      bool IsBrAnalyzable  : 1;
100      bool HasFallThrough  : 1;
101      bool IsUnpredicable  : 1;
102      bool CannotBeCopied  : 1;
103      bool ClobbersPred    : 1;
104      unsigned NonPredSize;
105      MachineBasicBlock *BB;
106      MachineBasicBlock *TrueBB;
107      MachineBasicBlock *FalseBB;
108      std::vector<MachineOperand> BrCond;
109      std::vector<MachineOperand> Predicate;
110      BBInfo() : IsDone(false), IsBeingAnalyzed(false),
111                 IsAnalyzed(false), IsEnqueued(false), IsBrAnalyzable(false),
112                 HasFallThrough(false), IsUnpredicable(false),
113                 CannotBeCopied(false), ClobbersPred(false), NonPredSize(0),
114                 BB(0), TrueBB(0), FalseBB(0) {}
115    };
116
117    /// IfcvtToken - Record information about pending if-conversions to attemp:
118    /// BBI             - Corresponding BBInfo.
119    /// Kind            - Type of block. See IfcvtKind.
120    /// NeedSubsumsion  - True if the to be predicated BB has already been
121    ///                   predicated.
122    /// NumDups      - Number of instructions that would be duplicated due
123    ///                   to this if-conversion. (For diamonds, the number of
124    ///                   identical instructions at the beginnings of both
125    ///                   paths).
126    /// NumDups2     - For diamonds, the number of identical instructions
127    ///                   at the ends of both paths.
128    struct IfcvtToken {
129      BBInfo &BBI;
130      IfcvtKind Kind;
131      bool NeedSubsumsion;
132      unsigned NumDups;
133      unsigned NumDups2;
134      IfcvtToken(BBInfo &b, IfcvtKind k, bool s, unsigned d, unsigned d2 = 0)
135        : BBI(b), Kind(k), NeedSubsumsion(s), NumDups(d), NumDups2(d2) {}
136    };
137
138    /// Roots - Basic blocks that do not have successors. These are the starting
139    /// points of Graph traversal.
140    std::vector<MachineBasicBlock*> Roots;
141
142    /// BBAnalysis - Results of if-conversion feasibility analysis indexed by
143    /// basic block number.
144    std::vector<BBInfo> BBAnalysis;
145
146    const TargetLowering *TLI;
147    const TargetInstrInfo *TII;
148    bool MadeChange;
149  public:
150    static char ID;
151    IfConverter() : MachineFunctionPass((intptr_t)&ID) {}
152
153    virtual bool runOnMachineFunction(MachineFunction &MF);
154    virtual const char *getPassName() const { return "If converter"; }
155
156  private:
157    bool ReverseBranchCondition(BBInfo &BBI);
158    bool ValidSimple(BBInfo &TrueBBI, unsigned &Dups) const;
159    bool ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
160                       bool FalseBranch, unsigned &Dups) const;
161    bool ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI,
162                      unsigned &Dups1, unsigned &Dups2) const;
163    void ScanInstructions(BBInfo &BBI);
164    BBInfo &AnalyzeBlock(MachineBasicBlock *BB,
165                         std::vector<IfcvtToken*> &Tokens);
166    bool FeasibilityAnalysis(BBInfo &BBI, std::vector<MachineOperand> &Cond,
167                             bool isTriangle = false, bool RevBranch = false);
168    bool AnalyzeBlocks(MachineFunction &MF,
169                       std::vector<IfcvtToken*> &Tokens);
170    void InvalidatePreds(MachineBasicBlock *BB);
171    void RemoveExtraEdges(BBInfo &BBI);
172    bool IfConvertSimple(BBInfo &BBI, IfcvtKind Kind);
173    bool IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind);
174    bool IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind,
175                          unsigned NumDups1, unsigned NumDups2);
176    void PredicateBlock(BBInfo &BBI,
177                        MachineBasicBlock::iterator E,
178                        std::vector<MachineOperand> &Cond);
179    void CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI,
180                               std::vector<MachineOperand> &Cond,
181                               bool IgnoreBr = false);
182    void MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI);
183
184    bool MeetIfcvtSizeLimit(unsigned Size) const {
185      return Size > 0 && Size <= TLI->getIfCvtBlockSizeLimit();
186    }
187
188    // blockAlwaysFallThrough - Block ends without a terminator.
189    bool blockAlwaysFallThrough(BBInfo &BBI) const {
190      return BBI.IsBrAnalyzable && BBI.TrueBB == NULL;
191    }
192
193    // IfcvtTokenCmp - Used to sort if-conversion candidates.
194    static bool IfcvtTokenCmp(IfcvtToken *C1, IfcvtToken *C2) {
195      int Incr1 = (C1->Kind == ICDiamond)
196        ? -(int)(C1->NumDups + C1->NumDups2) : (int)C1->NumDups;
197      int Incr2 = (C2->Kind == ICDiamond)
198        ? -(int)(C2->NumDups + C2->NumDups2) : (int)C2->NumDups;
199      if (Incr1 > Incr2)
200        return true;
201      else if (Incr1 == Incr2) {
202        // Favors subsumsion.
203        if (C1->NeedSubsumsion == false && C2->NeedSubsumsion == true)
204          return true;
205        else if (C1->NeedSubsumsion == C2->NeedSubsumsion) {
206          // Favors diamond over triangle, etc.
207          if ((unsigned)C1->Kind < (unsigned)C2->Kind)
208            return true;
209          else if (C1->Kind == C2->Kind)
210            return C1->BBI.BB->getNumber() < C2->BBI.BB->getNumber();
211        }
212      }
213      return false;
214    }
215  };
216
217  char IfConverter::ID = 0;
218}
219
220FunctionPass *llvm::createIfConverterPass() { return new IfConverter(); }
221
222bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
223  TLI = MF.getTarget().getTargetLowering();
224  TII = MF.getTarget().getInstrInfo();
225  if (!TII) return false;
226
227  static int FnNum = -1;
228  DOUT << "\nIfcvt: function (" << ++FnNum <<  ") \'"
229       << MF.getFunction()->getName() << "\'";
230
231  if (FnNum < IfCvtFnStart || (IfCvtFnStop != -1 && FnNum > IfCvtFnStop)) {
232    DOUT << " skipped\n";
233    return false;
234  }
235  DOUT << "\n";
236
237  MF.RenumberBlocks();
238  BBAnalysis.resize(MF.getNumBlockIDs());
239
240  // Look for root nodes, i.e. blocks without successors.
241  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
242    if (I->succ_size() == 0)
243      Roots.push_back(I);
244
245  std::vector<IfcvtToken*> Tokens;
246  MadeChange = false;
247  unsigned NumIfCvts = NumSimple + NumSimpleFalse + NumTriangle +
248    NumTriangleRev + NumTriangleFalse + NumTriangleFRev + NumDiamonds;
249  while (IfCvtLimit == -1 || (int)NumIfCvts < IfCvtLimit) {
250    // Do an intial analysis for each basic block and finding all the potential
251    // candidates to perform if-convesion.
252    bool Change = AnalyzeBlocks(MF, Tokens);
253    while (!Tokens.empty()) {
254      IfcvtToken *Token = Tokens.back();
255      Tokens.pop_back();
256      BBInfo &BBI = Token->BBI;
257      IfcvtKind Kind = Token->Kind;
258
259      // If the block has been evicted out of the queue or it has already been
260      // marked dead (due to it being predicated), then skip it.
261      if (BBI.IsDone)
262        BBI.IsEnqueued = false;
263      if (!BBI.IsEnqueued)
264        continue;
265
266      BBI.IsEnqueued = false;
267
268      bool RetVal = false;
269      switch (Kind) {
270      default: assert(false && "Unexpected!");
271        break;
272      case ICSimple:
273      case ICSimpleFalse: {
274        bool isFalse = Kind == ICSimpleFalse;
275        if ((isFalse && DisableSimpleF) || (!isFalse && DisableSimple)) break;
276        DOUT << "Ifcvt (Simple" << (Kind == ICSimpleFalse ? " false" :"")
277             << "): BB#" << BBI.BB->getNumber() << " ("
278             << ((Kind == ICSimpleFalse)
279                 ? BBI.FalseBB->getNumber()
280                 : BBI.TrueBB->getNumber()) << ") ";
281        RetVal = IfConvertSimple(BBI, Kind);
282        DOUT << (RetVal ? "succeeded!" : "failed!") << "\n";
283        if (RetVal)
284          if (isFalse) NumSimpleFalse++;
285          else         NumSimple++;
286       break;
287      }
288      case ICTriangle:
289      case ICTriangleRev:
290      case ICTriangleFalse:
291      case ICTriangleFRev: {
292        bool isFalse = Kind == ICTriangleFalse;
293        bool isRev   = (Kind == ICTriangleRev || Kind == ICTriangleFRev);
294        if (DisableTriangle && !isFalse && !isRev) break;
295        if (DisableTriangleR && !isFalse && isRev) break;
296        if (DisableTriangleF && isFalse && !isRev) break;
297        if (DisableTriangleFR && isFalse && isRev) break;
298        DOUT << "Ifcvt (Triangle";
299        if (isFalse)
300          DOUT << " false";
301        if (isRev)
302          DOUT << " rev";
303        DOUT << "): BB#" << BBI.BB->getNumber() << " (T:"
304             << BBI.TrueBB->getNumber() << ",F:"
305             << BBI.FalseBB->getNumber() << ") ";
306        RetVal = IfConvertTriangle(BBI, Kind);
307        DOUT << (RetVal ? "succeeded!" : "failed!") << "\n";
308        if (RetVal) {
309          if (isFalse) {
310            if (isRev) NumTriangleFRev++;
311            else       NumTriangleFalse++;
312          } else {
313            if (isRev) NumTriangleRev++;
314            else       NumTriangle++;
315          }
316        }
317        break;
318      }
319      case ICDiamond: {
320        if (DisableDiamond) break;
321        DOUT << "Ifcvt (Diamond): BB#" << BBI.BB->getNumber() << " (T:"
322             << BBI.TrueBB->getNumber() << ",F:"
323             << BBI.FalseBB->getNumber() << ") ";
324        RetVal = IfConvertDiamond(BBI, Kind, Token->NumDups, Token->NumDups2);
325        DOUT << (RetVal ? "succeeded!" : "failed!") << "\n";
326        if (RetVal) NumDiamonds++;
327        break;
328      }
329      }
330
331      Change |= RetVal;
332
333      NumIfCvts = NumSimple + NumSimpleFalse + NumTriangle + NumTriangleRev +
334        NumTriangleFalse + NumTriangleFRev + NumDiamonds;
335      if (IfCvtLimit != -1 && (int)NumIfCvts >= IfCvtLimit)
336        break;
337    }
338
339    if (!Change)
340      break;
341    MadeChange |= Change;
342  }
343
344  // Delete tokens in case of early exit.
345  while (!Tokens.empty()) {
346    IfcvtToken *Token = Tokens.back();
347    Tokens.pop_back();
348    delete Token;
349  }
350
351  Tokens.clear();
352  Roots.clear();
353  BBAnalysis.clear();
354
355  return MadeChange;
356}
357
358/// findFalseBlock - BB has a fallthrough. Find its 'false' successor given
359/// its 'true' successor.
360static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB,
361                                         MachineBasicBlock *TrueBB) {
362  for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
363         E = BB->succ_end(); SI != E; ++SI) {
364    MachineBasicBlock *SuccBB = *SI;
365    if (SuccBB != TrueBB)
366      return SuccBB;
367  }
368  return NULL;
369}
370
371/// ReverseBranchCondition - Reverse the condition of the end of the block
372/// branchs. Swap block's 'true' and 'false' successors.
373bool IfConverter::ReverseBranchCondition(BBInfo &BBI) {
374  if (!TII->ReverseBranchCondition(BBI.BrCond)) {
375    TII->RemoveBranch(*BBI.BB);
376    TII->InsertBranch(*BBI.BB, BBI.FalseBB, BBI.TrueBB, BBI.BrCond);
377    std::swap(BBI.TrueBB, BBI.FalseBB);
378    return true;
379  }
380  return false;
381}
382
383/// getNextBlock - Returns the next block in the function blocks ordering. If
384/// it is the end, returns NULL.
385static inline MachineBasicBlock *getNextBlock(MachineBasicBlock *BB) {
386  MachineFunction::iterator I = BB;
387  MachineFunction::iterator E = BB->getParent()->end();
388  if (++I == E)
389    return NULL;
390  return I;
391}
392
393/// ValidSimple - Returns true if the 'true' block (along with its
394/// predecessor) forms a valid simple shape for ifcvt. It also returns the
395/// number of instructions that the ifcvt would need to duplicate if performed
396/// in Dups.
397bool IfConverter::ValidSimple(BBInfo &TrueBBI, unsigned &Dups) const {
398  Dups = 0;
399  if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone)
400    return false;
401
402  if (TrueBBI.IsBrAnalyzable)
403    return false;
404
405  if (TrueBBI.BB->pred_size() > 1) {
406    if (TrueBBI.CannotBeCopied ||
407        TrueBBI.NonPredSize > TLI->getIfCvtDupBlockSizeLimit())
408      return false;
409    Dups = TrueBBI.NonPredSize;
410  }
411
412  return true;
413}
414
415/// ValidTriangle - Returns true if the 'true' and 'false' blocks (along
416/// with their common predecessor) forms a valid triangle shape for ifcvt.
417/// If 'FalseBranch' is true, it checks if 'true' block's false branch
418/// branches to the false branch rather than the other way around. It also
419/// returns the number of instructions that the ifcvt would need to duplicate
420/// if performed in 'Dups'.
421bool IfConverter::ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
422                                bool FalseBranch, unsigned &Dups) const {
423  Dups = 0;
424  if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone)
425    return false;
426
427  if (TrueBBI.BB->pred_size() > 1) {
428    if (TrueBBI.CannotBeCopied)
429      return false;
430
431    unsigned Size = TrueBBI.NonPredSize;
432    if (TrueBBI.IsBrAnalyzable) {
433      if (TrueBBI.TrueBB && TrueBBI.BrCond.size() == 0)
434        // End with an unconditional branch. It will be removed.
435        --Size;
436      else {
437        MachineBasicBlock *FExit = FalseBranch
438          ? TrueBBI.TrueBB : TrueBBI.FalseBB;
439        if (FExit)
440          // Require a conditional branch
441          ++Size;
442      }
443    }
444    if (Size > TLI->getIfCvtDupBlockSizeLimit())
445      return false;
446    Dups = Size;
447  }
448
449  MachineBasicBlock *TExit = FalseBranch ? TrueBBI.FalseBB : TrueBBI.TrueBB;
450  if (!TExit && blockAlwaysFallThrough(TrueBBI)) {
451    MachineFunction::iterator I = TrueBBI.BB;
452    if (++I == TrueBBI.BB->getParent()->end())
453      return false;
454    TExit = I;
455  }
456  return TExit && TExit == FalseBBI.BB;
457}
458
459static
460MachineBasicBlock::iterator firstNonBranchInst(MachineBasicBlock *BB,
461                                               const TargetInstrInfo *TII) {
462  MachineBasicBlock::iterator I = BB->end();
463  while (I != BB->begin()) {
464    --I;
465    const TargetInstrDescriptor *TID = I->getInstrDescriptor();
466    if ((TID->Flags & M_BRANCH_FLAG) == 0)
467      break;
468  }
469  return I;
470}
471
472/// ValidDiamond - Returns true if the 'true' and 'false' blocks (along
473/// with their common predecessor) forms a valid diamond shape for ifcvt.
474bool IfConverter::ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI,
475                               unsigned &Dups1, unsigned &Dups2) const {
476  Dups1 = Dups2 = 0;
477  if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone ||
478      FalseBBI.IsBeingAnalyzed || FalseBBI.IsDone)
479    return false;
480
481  MachineBasicBlock *TT = TrueBBI.TrueBB;
482  MachineBasicBlock *FT = FalseBBI.TrueBB;
483
484  if (!TT && blockAlwaysFallThrough(TrueBBI))
485    TT = getNextBlock(TrueBBI.BB);
486  if (!FT && blockAlwaysFallThrough(FalseBBI))
487    FT = getNextBlock(FalseBBI.BB);
488  if (TT != FT)
489    return false;
490  if (TT == NULL && (TrueBBI.IsBrAnalyzable || FalseBBI.IsBrAnalyzable))
491    return false;
492  if  (TrueBBI.BB->pred_size() > 1 || FalseBBI.BB->pred_size() > 1)
493    return false;
494
495  // FIXME: Allow true block to have an early exit?
496  if (TrueBBI.FalseBB || FalseBBI.FalseBB ||
497      (TrueBBI.ClobbersPred && FalseBBI.ClobbersPred))
498    return false;
499
500  MachineBasicBlock::iterator TI = TrueBBI.BB->begin();
501  MachineBasicBlock::iterator FI = FalseBBI.BB->begin();
502  while (TI != TrueBBI.BB->end() && FI != FalseBBI.BB->end()) {
503    if (!TI->isIdenticalTo(FI))
504      break;
505    ++Dups1;
506    ++TI;
507    ++FI;
508  }
509
510  TI = firstNonBranchInst(TrueBBI.BB, TII);
511  FI = firstNonBranchInst(FalseBBI.BB, TII);
512  while (TI != TrueBBI.BB->begin() && FI != FalseBBI.BB->begin()) {
513    if (!TI->isIdenticalTo(FI))
514      break;
515    ++Dups2;
516    --TI;
517    --FI;
518  }
519
520  return true;
521}
522
523/// ScanInstructions - Scan all the instructions in the block to determine if
524/// the block is predicable. In most cases, that means all the instructions
525/// in the block has M_PREDICABLE flag. Also checks if the block contains any
526/// instruction which can clobber a predicate (e.g. condition code register).
527/// If so, the block is not predicable unless it's the last instruction.
528void IfConverter::ScanInstructions(BBInfo &BBI) {
529  if (BBI.IsDone)
530    return;
531
532  bool AlreadyPredicated = BBI.Predicate.size() > 0;
533  // First analyze the end of BB branches.
534  BBI.TrueBB = BBI.FalseBB = NULL;
535  BBI.BrCond.clear();
536  BBI.IsBrAnalyzable =
537    !TII->AnalyzeBranch(*BBI.BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond);
538  BBI.HasFallThrough = BBI.IsBrAnalyzable && BBI.FalseBB == NULL;
539
540  if (BBI.BrCond.size()) {
541    // No false branch. This BB must end with a conditional branch and a
542    // fallthrough.
543    if (!BBI.FalseBB)
544      BBI.FalseBB = findFalseBlock(BBI.BB, BBI.TrueBB);
545    assert(BBI.FalseBB && "Expected to find the fallthrough block!");
546  }
547
548  // Then scan all the instructions.
549  BBI.NonPredSize = 0;
550  BBI.ClobbersPred = false;
551  bool SeenCondBr = false;
552  for (MachineBasicBlock::iterator I = BBI.BB->begin(), E = BBI.BB->end();
553       I != E; ++I) {
554    const TargetInstrDescriptor *TID = I->getInstrDescriptor();
555    if ((TID->Flags & M_NOT_DUPLICABLE) != 0)
556      BBI.CannotBeCopied = true;
557
558    bool isPredicated = TII->isPredicated(I);
559    bool isCondBr = BBI.IsBrAnalyzable &&
560      (TID->Flags & M_BRANCH_FLAG) != 0 && (TID->Flags & M_BARRIER_FLAG) == 0;
561
562    if (!isCondBr) {
563      if (!isPredicated)
564        BBI.NonPredSize++;
565      else if (!AlreadyPredicated) {
566        // FIXME: This instruction is already predicated before the
567        // if-conversion pass. It's probably something like a conditional move.
568        // Mark this block unpredicable for now.
569        BBI.IsUnpredicable = true;
570        return;
571      }
572
573    }
574
575    if (BBI.ClobbersPred && !isPredicated) {
576      // Predicate modification instruction should end the block (except for
577      // already predicated instructions and end of block branches).
578      if (isCondBr) {
579        SeenCondBr = true;
580
581        // Conditional branches is not predicable. But it may be eliminated.
582        continue;
583      }
584
585      // Predicate may have been modified, the subsequent (currently)
586      // unpredicated instructions cannot be correctly predicated.
587      BBI.IsUnpredicable = true;
588      return;
589    }
590
591    // FIXME: Make use of PredDefs? e.g. ADDC, SUBC sets predicates but are
592    // still potentially predicable.
593    std::vector<MachineOperand> PredDefs;
594    if (TII->DefinesPredicate(I, PredDefs))
595      BBI.ClobbersPred = true;
596
597    if ((TID->Flags & M_PREDICABLE) == 0) {
598      BBI.IsUnpredicable = true;
599      return;
600    }
601  }
602}
603
604/// FeasibilityAnalysis - Determine if the block is a suitable candidate to be
605/// predicated by the specified predicate.
606bool IfConverter::FeasibilityAnalysis(BBInfo &BBI,
607                                      std::vector<MachineOperand> &Pred,
608                                      bool isTriangle, bool RevBranch) {
609  // If the block is dead or unpredicable, then it cannot be predicated.
610  if (BBI.IsDone || BBI.IsUnpredicable)
611    return false;
612
613  // If it is already predicated, check if its predicate subsumes the new
614  // predicate.
615  if (BBI.Predicate.size() && !TII->SubsumesPredicate(BBI.Predicate, Pred))
616    return false;
617
618  if (BBI.BrCond.size()) {
619    if (!isTriangle)
620      return false;
621
622    // Test predicate subsumsion.
623    std::vector<MachineOperand> RevPred(Pred);
624    std::vector<MachineOperand> Cond(BBI.BrCond);
625    if (RevBranch) {
626      if (TII->ReverseBranchCondition(Cond))
627        return false;
628    }
629    if (TII->ReverseBranchCondition(RevPred) ||
630        !TII->SubsumesPredicate(Cond, RevPred))
631      return false;
632  }
633
634  return true;
635}
636
637/// AnalyzeBlock - Analyze the structure of the sub-CFG starting from
638/// the specified block. Record its successors and whether it looks like an
639/// if-conversion candidate.
640IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
641                                             std::vector<IfcvtToken*> &Tokens) {
642  BBInfo &BBI = BBAnalysis[BB->getNumber()];
643
644  if (BBI.IsAnalyzed || BBI.IsBeingAnalyzed)
645    return BBI;
646
647  BBI.BB = BB;
648  BBI.IsBeingAnalyzed = true;
649
650  ScanInstructions(BBI);
651
652  // Unanalyable or ends with fallthrough or unconditional branch.
653  if (!BBI.IsBrAnalyzable || BBI.BrCond.size() == 0) {
654    BBI.IsBeingAnalyzed = false;
655    BBI.IsAnalyzed = true;
656    return BBI;
657  }
658
659  // Do not ifcvt if either path is a back edge to the entry block.
660  if (BBI.TrueBB == BB || BBI.FalseBB == BB) {
661    BBI.IsBeingAnalyzed = false;
662    BBI.IsAnalyzed = true;
663    return BBI;
664  }
665
666  BBInfo &TrueBBI  = AnalyzeBlock(BBI.TrueBB, Tokens);
667  BBInfo &FalseBBI = AnalyzeBlock(BBI.FalseBB, Tokens);
668
669  if (TrueBBI.IsDone && FalseBBI.IsDone) {
670    BBI.IsBeingAnalyzed = false;
671    BBI.IsAnalyzed = true;
672    return BBI;
673  }
674
675  std::vector<MachineOperand> RevCond(BBI.BrCond);
676  bool CanRevCond = !TII->ReverseBranchCondition(RevCond);
677
678  unsigned Dups = 0;
679  unsigned Dups2 = 0;
680  bool TNeedSub = TrueBBI.Predicate.size() > 0;
681  bool FNeedSub = FalseBBI.Predicate.size() > 0;
682  bool Enqueued = false;
683  if (CanRevCond && ValidDiamond(TrueBBI, FalseBBI, Dups, Dups2) &&
684      MeetIfcvtSizeLimit(TrueBBI.NonPredSize - (Dups + Dups2)) &&
685      MeetIfcvtSizeLimit(FalseBBI.NonPredSize - (Dups + Dups2)) &&
686      FeasibilityAnalysis(TrueBBI, BBI.BrCond) &&
687      FeasibilityAnalysis(FalseBBI, RevCond)) {
688    // Diamond:
689    //   EBB
690    //   / \_
691    //  |   |
692    // TBB FBB
693    //   \ /
694    //  TailBB
695    // Note TailBB can be empty.
696    Tokens.push_back(new IfcvtToken(BBI, ICDiamond, TNeedSub|FNeedSub, Dups,
697                                    Dups2));
698    Enqueued = true;
699  }
700
701  if (ValidTriangle(TrueBBI, FalseBBI, false, Dups) &&
702      MeetIfcvtSizeLimit(TrueBBI.NonPredSize) &&
703      FeasibilityAnalysis(TrueBBI, BBI.BrCond, true)) {
704    // Triangle:
705    //   EBB
706    //   | \_
707    //   |  |
708    //   | TBB
709    //   |  /
710    //   FBB
711    Tokens.push_back(new IfcvtToken(BBI, ICTriangle, TNeedSub, Dups));
712    Enqueued = true;
713  }
714
715  if (ValidTriangle(TrueBBI, FalseBBI, true, Dups) &&
716      MeetIfcvtSizeLimit(TrueBBI.NonPredSize) &&
717      FeasibilityAnalysis(TrueBBI, BBI.BrCond, true, true)) {
718    Tokens.push_back(new IfcvtToken(BBI, ICTriangleRev, TNeedSub, Dups));
719    Enqueued = true;
720  }
721
722  if (ValidSimple(TrueBBI, Dups) &&
723      MeetIfcvtSizeLimit(TrueBBI.NonPredSize) &&
724      FeasibilityAnalysis(TrueBBI, BBI.BrCond)) {
725    // Simple (split, no rejoin):
726    //   EBB
727    //   | \_
728    //   |  |
729    //   | TBB---> exit
730    //   |
731    //   FBB
732    Tokens.push_back(new IfcvtToken(BBI, ICSimple, TNeedSub, Dups));
733    Enqueued = true;
734  }
735
736  if (CanRevCond) {
737    // Try the other path...
738    if (ValidTriangle(FalseBBI, TrueBBI, false, Dups) &&
739        MeetIfcvtSizeLimit(FalseBBI.NonPredSize) &&
740        FeasibilityAnalysis(FalseBBI, RevCond, true)) {
741      Tokens.push_back(new IfcvtToken(BBI, ICTriangleFalse, FNeedSub, Dups));
742      Enqueued = true;
743    }
744
745    if (ValidTriangle(FalseBBI, TrueBBI, true, Dups) &&
746        MeetIfcvtSizeLimit(FalseBBI.NonPredSize) &&
747        FeasibilityAnalysis(FalseBBI, RevCond, true, true)) {
748      Tokens.push_back(new IfcvtToken(BBI, ICTriangleFRev, FNeedSub, Dups));
749      Enqueued = true;
750    }
751
752    if (ValidSimple(FalseBBI, Dups) &&
753        MeetIfcvtSizeLimit(FalseBBI.NonPredSize) &&
754        FeasibilityAnalysis(FalseBBI, RevCond)) {
755      Tokens.push_back(new IfcvtToken(BBI, ICSimpleFalse, FNeedSub, Dups));
756      Enqueued = true;
757    }
758  }
759
760  BBI.IsEnqueued = Enqueued;
761  BBI.IsBeingAnalyzed = false;
762  BBI.IsAnalyzed = true;
763  return BBI;
764}
765
766/// AnalyzeBlocks - Analyze all blocks and find entries for all if-conversion
767/// candidates. It returns true if any CFG restructuring is done to expose more
768/// if-conversion opportunities.
769bool IfConverter::AnalyzeBlocks(MachineFunction &MF,
770                                std::vector<IfcvtToken*> &Tokens) {
771  bool Change = false;
772  std::set<MachineBasicBlock*> Visited;
773  for (unsigned i = 0, e = Roots.size(); i != e; ++i) {
774    for (idf_ext_iterator<MachineBasicBlock*> I=idf_ext_begin(Roots[i],Visited),
775           E = idf_ext_end(Roots[i], Visited); I != E; ++I) {
776      MachineBasicBlock *BB = *I;
777      AnalyzeBlock(BB, Tokens);
778    }
779  }
780
781  // Sort to favor more complex ifcvt scheme.
782  std::stable_sort(Tokens.begin(), Tokens.end(), IfcvtTokenCmp);
783
784  return Change;
785}
786
787/// canFallThroughTo - Returns true either if ToBB is the next block after BB or
788/// that all the intervening blocks are empty (given BB can fall through to its
789/// next block).
790static bool canFallThroughTo(MachineBasicBlock *BB, MachineBasicBlock *ToBB) {
791  MachineFunction::iterator I = BB;
792  MachineFunction::iterator TI = ToBB;
793  MachineFunction::iterator E = BB->getParent()->end();
794  while (++I != TI)
795    if (I == E || !I->empty())
796      return false;
797  return true;
798}
799
800/// InvalidatePreds - Invalidate predecessor BB info so it would be re-analyzed
801/// to determine if it can be if-converted. If predecessor is already enqueued,
802/// dequeue it!
803void IfConverter::InvalidatePreds(MachineBasicBlock *BB) {
804  for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(),
805         E = BB->pred_end(); PI != E; ++PI) {
806    BBInfo &PBBI = BBAnalysis[(*PI)->getNumber()];
807    if (PBBI.IsDone || PBBI.BB == BB)
808      continue;
809    PBBI.IsAnalyzed = false;
810    PBBI.IsEnqueued = false;
811  }
812}
813
814/// InsertUncondBranch - Inserts an unconditional branch from BB to ToBB.
815///
816static void InsertUncondBranch(MachineBasicBlock *BB, MachineBasicBlock *ToBB,
817                               const TargetInstrInfo *TII) {
818  std::vector<MachineOperand> NoCond;
819  TII->InsertBranch(*BB, ToBB, NULL, NoCond);
820}
821
822/// RemoveExtraEdges - Remove true / false edges if either / both are no longer
823/// successors.
824void IfConverter::RemoveExtraEdges(BBInfo &BBI) {
825  MachineBasicBlock *TBB = NULL, *FBB = NULL;
826  std::vector<MachineOperand> Cond;
827  if (!TII->AnalyzeBranch(*BBI.BB, TBB, FBB, Cond))
828    BBI.BB->CorrectExtraCFGEdges(TBB, FBB, !Cond.empty());
829}
830
831/// IfConvertSimple - If convert a simple (split, no rejoin) sub-CFG.
832///
833bool IfConverter::IfConvertSimple(BBInfo &BBI, IfcvtKind Kind) {
834  BBInfo &TrueBBI  = BBAnalysis[BBI.TrueBB->getNumber()];
835  BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
836  BBInfo *CvtBBI = &TrueBBI;
837  BBInfo *NextBBI = &FalseBBI;
838
839  std::vector<MachineOperand> Cond(BBI.BrCond);
840  if (Kind == ICSimpleFalse)
841    std::swap(CvtBBI, NextBBI);
842
843  if (CvtBBI->IsDone ||
844      (CvtBBI->CannotBeCopied && CvtBBI->BB->pred_size() > 1)) {
845    // Something has changed. It's no longer safe to predicate this block.
846    BBI.IsAnalyzed = false;
847    CvtBBI->IsAnalyzed = false;
848    return false;
849  }
850
851  if (Kind == ICSimpleFalse)
852    TII->ReverseBranchCondition(Cond);
853
854  if (CvtBBI->BB->pred_size() > 1) {
855    BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
856    // Copy instructions in the true block, predicate them add them to
857    // the entry block.
858    CopyAndPredicateBlock(BBI, *CvtBBI, Cond);
859  } else {
860    PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond);
861
862    // Merge converted block into entry block.
863    BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
864    MergeBlocks(BBI, *CvtBBI);
865  }
866
867  bool IterIfcvt = true;
868  if (!canFallThroughTo(BBI.BB, NextBBI->BB)) {
869    InsertUncondBranch(BBI.BB, NextBBI->BB, TII);
870    BBI.HasFallThrough = false;
871    // Now ifcvt'd block will look like this:
872    // BB:
873    // ...
874    // t, f = cmp
875    // if t op
876    // b BBf
877    //
878    // We cannot further ifcvt this block because the unconditional branch
879    // will have to be predicated on the new condition, that will not be
880    // available if cmp executes.
881    IterIfcvt = false;
882  }
883
884  RemoveExtraEdges(BBI);
885
886  // Update block info. BB can be iteratively if-converted.
887  if (!IterIfcvt)
888    BBI.IsDone = true;
889  InvalidatePreds(BBI.BB);
890  CvtBBI->IsDone = true;
891
892  // FIXME: Must maintain LiveIns.
893  return true;
894}
895
896/// IfConvertTriangle - If convert a triangle sub-CFG.
897///
898bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) {
899  BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
900  BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
901  BBInfo *CvtBBI = &TrueBBI;
902  BBInfo *NextBBI = &FalseBBI;
903
904  std::vector<MachineOperand> Cond(BBI.BrCond);
905  if (Kind == ICTriangleFalse || Kind == ICTriangleFRev)
906    std::swap(CvtBBI, NextBBI);
907
908  if (CvtBBI->IsDone ||
909      (CvtBBI->CannotBeCopied && CvtBBI->BB->pred_size() > 1)) {
910    // Something has changed. It's no longer safe to predicate this block.
911    BBI.IsAnalyzed = false;
912    CvtBBI->IsAnalyzed = false;
913    return false;
914  }
915
916  if (Kind == ICTriangleFalse || Kind == ICTriangleFRev)
917    TII->ReverseBranchCondition(Cond);
918
919  if (Kind == ICTriangleRev || Kind == ICTriangleFRev) {
920    ReverseBranchCondition(*CvtBBI);
921    // BB has been changed, modify its predecessors (except for this
922    // one) so they don't get ifcvt'ed based on bad intel.
923    for (MachineBasicBlock::pred_iterator PI = CvtBBI->BB->pred_begin(),
924           E = CvtBBI->BB->pred_end(); PI != E; ++PI) {
925      MachineBasicBlock *PBB = *PI;
926      if (PBB == BBI.BB)
927        continue;
928      BBInfo &PBBI = BBAnalysis[PBB->getNumber()];
929      if (PBBI.IsEnqueued) {
930        PBBI.IsAnalyzed = false;
931        PBBI.IsEnqueued = false;
932      }
933    }
934  }
935
936  bool HasEarlyExit = CvtBBI->FalseBB != NULL;
937  bool DupBB = CvtBBI->BB->pred_size() > 1;
938  if (DupBB) {
939    BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
940    // Copy instructions in the true block, predicate them add them to
941    // the entry block.
942    CopyAndPredicateBlock(BBI, *CvtBBI, Cond, true);
943  } else {
944    // Predicate the 'true' block after removing its branch.
945    CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB);
946    PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond);
947  }
948
949  if (!DupBB) {
950    // Now merge the entry of the triangle with the true block.
951    BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
952    MergeBlocks(BBI, *CvtBBI);
953  }
954
955  // If 'true' block has a 'false' successor, add an exit branch to it.
956  if (HasEarlyExit) {
957    std::vector<MachineOperand> RevCond(CvtBBI->BrCond);
958    if (TII->ReverseBranchCondition(RevCond))
959      assert(false && "Unable to reverse branch condition!");
960    TII->InsertBranch(*BBI.BB, CvtBBI->FalseBB, NULL, RevCond);
961    BBI.BB->addSuccessor(CvtBBI->FalseBB);
962  }
963
964  // Merge in the 'false' block if the 'false' block has no other
965  // predecessors. Otherwise, add a unconditional branch from to 'false'.
966  bool FalseBBDead = false;
967  bool IterIfcvt = true;
968  bool isFallThrough = canFallThroughTo(BBI.BB, NextBBI->BB);
969  if (!isFallThrough) {
970    // Only merge them if the true block does not fallthrough to the false
971    // block. By not merging them, we make it possible to iteratively
972    // ifcvt the blocks.
973    if (!HasEarlyExit &&
974        NextBBI->BB->pred_size() == 1 && !NextBBI->HasFallThrough) {
975      MergeBlocks(BBI, *NextBBI);
976      FalseBBDead = true;
977    } else {
978      InsertUncondBranch(BBI.BB, NextBBI->BB, TII);
979      BBI.HasFallThrough = false;
980    }
981    // Mixed predicated and unpredicated code. This cannot be iteratively
982    // predicated.
983    IterIfcvt = false;
984  }
985
986  RemoveExtraEdges(BBI);
987
988  // Update block info. BB can be iteratively if-converted.
989  if (!IterIfcvt)
990    BBI.IsDone = true;
991  InvalidatePreds(BBI.BB);
992  CvtBBI->IsDone = true;
993  if (FalseBBDead)
994    NextBBI->IsDone = true;
995
996  // FIXME: Must maintain LiveIns.
997  return true;
998}
999
1000/// IfConvertDiamond - If convert a diamond sub-CFG.
1001///
1002bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind,
1003                                   unsigned NumDups1, unsigned NumDups2) {
1004  BBInfo &TrueBBI  = BBAnalysis[BBI.TrueBB->getNumber()];
1005  BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
1006  MachineBasicBlock *TailBB = TrueBBI.TrueBB;
1007  // True block must fall through or ended with unanalyzable terminator.
1008  if (!TailBB) {
1009    if (blockAlwaysFallThrough(TrueBBI))
1010      TailBB = FalseBBI.TrueBB;
1011    assert((TailBB || !TrueBBI.IsBrAnalyzable) && "Unexpected!");
1012  }
1013
1014  if (TrueBBI.IsDone || FalseBBI.IsDone ||
1015      TrueBBI.BB->pred_size() > 1 ||
1016      FalseBBI.BB->pred_size() > 1) {
1017    // Something has changed. It's no longer safe to predicate these blocks.
1018    BBI.IsAnalyzed = false;
1019    TrueBBI.IsAnalyzed = false;
1020    FalseBBI.IsAnalyzed = false;
1021    return false;
1022  }
1023
1024  // Merge the 'true' and 'false' blocks by copying the instructions
1025  // from the 'false' block to the 'true' block. That is, unless the true
1026  // block would clobber the predicate, in that case, do the opposite.
1027  BBInfo *BBI1 = &TrueBBI;
1028  BBInfo *BBI2 = &FalseBBI;
1029  std::vector<MachineOperand> RevCond(BBI.BrCond);
1030  TII->ReverseBranchCondition(RevCond);
1031  std::vector<MachineOperand> *Cond1 = &BBI.BrCond;
1032  std::vector<MachineOperand> *Cond2 = &RevCond;
1033
1034  // Figure out the more profitable ordering.
1035  bool DoSwap = false;
1036  if (TrueBBI.ClobbersPred && !FalseBBI.ClobbersPred)
1037    DoSwap = true;
1038  else if (TrueBBI.ClobbersPred == FalseBBI.ClobbersPred) {
1039    if (TrueBBI.NonPredSize > FalseBBI.NonPredSize)
1040      DoSwap = true;
1041  }
1042  if (DoSwap) {
1043    std::swap(BBI1, BBI2);
1044    std::swap(Cond1, Cond2);
1045  }
1046
1047  // Remove the conditional branch from entry to the blocks.
1048  BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
1049
1050  // Remove the duplicated instructions at the beginnings of both paths.
1051  MachineBasicBlock::iterator DI1 = BBI1->BB->begin();
1052  MachineBasicBlock::iterator DI2 = BBI2->BB->begin();
1053  BBI1->NonPredSize -= NumDups1;
1054  BBI2->NonPredSize -= NumDups1;
1055  while (NumDups1 != 0) {
1056    ++DI1;
1057    ++DI2;
1058    --NumDups1;
1059  }
1060  BBI.BB->splice(BBI.BB->end(), BBI1->BB, BBI1->BB->begin(), DI1);
1061  BBI2->BB->erase(BBI2->BB->begin(), DI2);
1062
1063  // Predicate the 'true' block after removing its branch.
1064  BBI1->NonPredSize -= TII->RemoveBranch(*BBI1->BB);
1065  DI1 = BBI1->BB->end();
1066  for (unsigned i = 0; i != NumDups2; ++i)
1067    --DI1;
1068  BBI1->BB->erase(DI1, BBI1->BB->end());
1069  PredicateBlock(*BBI1, BBI1->BB->end(), *Cond1);
1070
1071  // Predicate the 'false' block.
1072  BBI2->NonPredSize -= TII->RemoveBranch(*BBI2->BB);
1073  DI2 = BBI2->BB->end();
1074  while (NumDups2 != 0) {
1075    --DI2;
1076    --NumDups2;
1077  }
1078  PredicateBlock(*BBI2, DI2, *Cond2);
1079
1080  // Merge the true block into the entry of the diamond.
1081  MergeBlocks(BBI, *BBI1);
1082  MergeBlocks(BBI, *BBI2);
1083
1084  // If the if-converted block fallthrough or unconditionally branch into the
1085  // tail block, and the tail block does not have other predecessors, then
1086  // fold the tail block in as well. Otherwise, unless it falls through to the
1087  // tail, add a unconditional branch to it.
1088  if (TailBB) {
1089    BBInfo TailBBI = BBAnalysis[TailBB->getNumber()];
1090    if (TailBB->pred_size() == 1 && !TailBBI.HasFallThrough) {
1091      BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
1092      MergeBlocks(BBI, TailBBI);
1093      TailBBI.IsDone = true;
1094    } else {
1095      InsertUncondBranch(BBI.BB, TailBB, TII);
1096      BBI.HasFallThrough = false;
1097    }
1098  }
1099
1100  RemoveExtraEdges(BBI);
1101
1102  // Update block info.
1103  BBI.IsDone = TrueBBI.IsDone = FalseBBI.IsDone = true;
1104  InvalidatePreds(BBI.BB);
1105
1106  // FIXME: Must maintain LiveIns.
1107  return true;
1108}
1109
1110/// PredicateBlock - Predicate instructions from the start of the block to the
1111/// specified end with the specified condition.
1112void IfConverter::PredicateBlock(BBInfo &BBI,
1113                                 MachineBasicBlock::iterator E,
1114                                 std::vector<MachineOperand> &Cond) {
1115  for (MachineBasicBlock::iterator I = BBI.BB->begin(); I != E; ++I) {
1116    if (TII->isPredicated(I))
1117      continue;
1118    if (!TII->PredicateInstruction(I, Cond)) {
1119      cerr << "Unable to predicate " << *I << "!\n";
1120      abort();
1121    }
1122  }
1123
1124  std::copy(Cond.begin(), Cond.end(), std::back_inserter(BBI.Predicate));
1125
1126  BBI.IsAnalyzed = false;
1127  BBI.NonPredSize = 0;
1128
1129  NumIfConvBBs++;
1130}
1131
1132/// CopyAndPredicateBlock - Copy and predicate instructions from source BB to
1133/// the destination block. Skip end of block branches if IgnoreBr is true.
1134void IfConverter::CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI,
1135                                        std::vector<MachineOperand> &Cond,
1136                                        bool IgnoreBr) {
1137  for (MachineBasicBlock::iterator I = FromBBI.BB->begin(),
1138         E = FromBBI.BB->end(); I != E; ++I) {
1139    const TargetInstrDescriptor *TID = I->getInstrDescriptor();
1140    bool isPredicated = TII->isPredicated(I);
1141    // Do not copy the end of the block branches.
1142    if (IgnoreBr && !isPredicated && (TID->Flags & M_BRANCH_FLAG) != 0)
1143      break;
1144
1145    MachineInstr *MI = I->clone();
1146    ToBBI.BB->insert(ToBBI.BB->end(), MI);
1147    ToBBI.NonPredSize++;
1148
1149    if (!isPredicated)
1150      if (!TII->PredicateInstruction(MI, Cond)) {
1151        cerr << "Unable to predicate " << *MI << "!\n";
1152        abort();
1153      }
1154  }
1155
1156  std::vector<MachineBasicBlock *> Succs(FromBBI.BB->succ_begin(),
1157                                         FromBBI.BB->succ_end());
1158  MachineBasicBlock *NBB = getNextBlock(FromBBI.BB);
1159  MachineBasicBlock *FallThrough = FromBBI.HasFallThrough ? NBB : NULL;
1160
1161  for (unsigned i = 0, e = Succs.size(); i != e; ++i) {
1162    MachineBasicBlock *Succ = Succs[i];
1163    // Fallthrough edge can't be transferred.
1164    if (Succ == FallThrough)
1165      continue;
1166    if (!ToBBI.BB->isSuccessor(Succ))
1167      ToBBI.BB->addSuccessor(Succ);
1168  }
1169
1170  std::copy(FromBBI.Predicate.begin(), FromBBI.Predicate.end(),
1171            std::back_inserter(ToBBI.Predicate));
1172  std::copy(Cond.begin(), Cond.end(), std::back_inserter(ToBBI.Predicate));
1173
1174  ToBBI.ClobbersPred |= FromBBI.ClobbersPred;
1175  ToBBI.IsAnalyzed = false;
1176
1177  NumDupBBs++;
1178}
1179
1180/// MergeBlocks - Move all instructions from FromBB to the end of ToBB.
1181///
1182void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI) {
1183  ToBBI.BB->splice(ToBBI.BB->end(),
1184                   FromBBI.BB, FromBBI.BB->begin(), FromBBI.BB->end());
1185
1186  // Redirect all branches to FromBB to ToBB.
1187  std::vector<MachineBasicBlock *> Preds(FromBBI.BB->pred_begin(),
1188                                         FromBBI.BB->pred_end());
1189  for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
1190    MachineBasicBlock *Pred = Preds[i];
1191    if (Pred == ToBBI.BB)
1192      continue;
1193    Pred->ReplaceUsesOfBlockWith(FromBBI.BB, ToBBI.BB);
1194  }
1195
1196  std::vector<MachineBasicBlock *> Succs(FromBBI.BB->succ_begin(),
1197                                         FromBBI.BB->succ_end());
1198  MachineBasicBlock *NBB = getNextBlock(FromBBI.BB);
1199  MachineBasicBlock *FallThrough = FromBBI.HasFallThrough ? NBB : NULL;
1200
1201  for (unsigned i = 0, e = Succs.size(); i != e; ++i) {
1202    MachineBasicBlock *Succ = Succs[i];
1203    // Fallthrough edge can't be transferred.
1204    if (Succ == FallThrough)
1205      continue;
1206    FromBBI.BB->removeSuccessor(Succ);
1207    if (!ToBBI.BB->isSuccessor(Succ))
1208      ToBBI.BB->addSuccessor(Succ);
1209  }
1210
1211  // Now FromBBI always fall through to the next block!
1212  if (NBB && !FromBBI.BB->isSuccessor(NBB))
1213    FromBBI.BB->addSuccessor(NBB);
1214
1215  std::copy(FromBBI.Predicate.begin(), FromBBI.Predicate.end(),
1216            std::back_inserter(ToBBI.Predicate));
1217  FromBBI.Predicate.clear();
1218
1219  ToBBI.NonPredSize += FromBBI.NonPredSize;
1220  FromBBI.NonPredSize = 0;
1221
1222  ToBBI.ClobbersPred |= FromBBI.ClobbersPred;
1223  ToBBI.HasFallThrough = FromBBI.HasFallThrough;
1224  ToBBI.IsAnalyzed = false;
1225  FromBBI.IsAnalyzed = false;
1226}
1227