IfConversion.cpp revision 303595942502f17c087fa28874c2b89117148c45 
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
29// Hidden options for help debugging.
30static cl::opt<int> IfCvtFnStart("ifcvt-fn-start", cl::init(-1), cl::Hidden);
31static cl::opt<int> IfCvtFnStop("ifcvt-fn-stop", cl::init(-1), cl::Hidden);
32static cl::opt<int> IfCvtLimit("ifcvt-limit", cl::init(-1), cl::Hidden);
33static cl::opt<bool> DisableSimple("disable-ifcvt-simple",
34                                   cl::init(false), cl::Hidden);
35static cl::opt<bool> DisableSimpleF("disable-ifcvt-simple-false",
36                                    cl::init(false), cl::Hidden);
37static cl::opt<bool> DisableTriangle("disable-ifcvt-triangle",
38                                     cl::init(false), cl::Hidden);
39static cl::opt<bool> DisableTriangleR("disable-ifcvt-triangle-rev",
40                                      cl::init(false), cl::Hidden);
41static cl::opt<bool> DisableTriangleF("disable-ifcvt-triangle-false",
42                                      cl::init(false), cl::Hidden);
43static cl::opt<bool> DisableTriangleFR("disable-ifcvt-triangle-false-rev",
44                                       cl::init(false), cl::Hidden);
45static cl::opt<bool> DisableDiamond("disable-ifcvt-diamond",
46                                    cl::init(false), cl::Hidden);
47
48STATISTIC(NumSimple,       "Number of simple if-conversions performed");
49STATISTIC(NumSimpleFalse,  "Number of simple (F) if-conversions performed");
50STATISTIC(NumTriangle,     "Number of triangle if-conversions performed");
51STATISTIC(NumTriangleRev,  "Number of triangle (R) if-conversions performed");
52STATISTIC(NumTriangleFalse,"Number of triangle (F) if-conversions performed");
53STATISTIC(NumTriangleFRev, "Number of triangle (F/R) if-conversions performed");
54STATISTIC(NumDiamonds,     "Number of diamond if-conversions performed");
55STATISTIC(NumIfConvBBs,    "Number of if-converted blocks");
56STATISTIC(NumDupBBs,       "Number of duplicated blocks");
57
58namespace {
59  class IfConverter : public MachineFunctionPass {
60    enum IfcvtKind {
61      ICNotClassfied,  // BB data valid, but not classified.
62      ICSimpleFalse,   // Same as ICSimple, but on the false path.
63      ICSimple,        // BB is entry of an one split, no rejoin sub-CFG.
64      ICTriangleFRev,  // Same as ICTriangleFalse, but false path rev condition.
65      ICTriangleRev,   // Same as ICTriangle, but true path rev condition.
66      ICTriangleFalse, // Same as ICTriangle, but on the false path.
67      ICTriangle,      // BB is entry of a triangle sub-CFG.
68      ICDiamond        // BB is entry of a diamond sub-CFG.
69    };
70
71    /// BBInfo - One per MachineBasicBlock, this is used to cache the result
72    /// if-conversion feasibility analysis. This includes results from
73    /// TargetInstrInfo::AnalyzeBranch() (i.e. TBB, FBB, and Cond), and its
74    /// classification, and common tail block of its successors (if it's a
75    /// diamond shape), its size, whether it's predicable, and whether any
76    /// instruction can clobber the 'would-be' predicate.
77    ///
78    /// IsDone          - True if BB is not to be considered for ifcvt.
79    /// IsBeingAnalyzed - True if BB is currently being analyzed.
80    /// IsAnalyzed      - True if BB has been analyzed (info is still valid).
81    /// IsEnqueued      - True if BB has been enqueued to be ifcvt'ed.
82    /// IsBrAnalyzable  - True if AnalyzeBranch() returns false.
83    /// HasFallThrough  - True if BB may fallthrough to the following BB.
84    /// IsUnpredicable  - True if BB is known to be unpredicable.
85    /// ClobbersPred    - True if BB could modify predicates (e.g. has
86    ///                   cmp, call, etc.)
87    /// NonPredSize     - Number of non-predicated instructions.
88    /// BB              - Corresponding MachineBasicBlock.
89    /// TrueBB / FalseBB- See AnalyzeBranch().
90    /// BrCond          - Conditions for end of block conditional branches.
91    /// Predicate       - Predicate used in the BB.
92    struct BBInfo {
93      bool IsDone          : 1;
94      bool IsBeingAnalyzed : 1;
95      bool IsAnalyzed      : 1;
96      bool IsEnqueued      : 1;
97      bool IsBrAnalyzable  : 1;
98      bool HasFallThrough  : 1;
99      bool IsUnpredicable  : 1;
100      bool CannotBeCopied  : 1;
101      bool ClobbersPred    : 1;
102      unsigned NonPredSize;
103      MachineBasicBlock *BB;
104      MachineBasicBlock *TrueBB;
105      MachineBasicBlock *FalseBB;
106      std::vector<MachineOperand> BrCond;
107      std::vector<MachineOperand> Predicate;
108      BBInfo() : IsDone(false), IsBeingAnalyzed(false),
109                 IsAnalyzed(false), IsEnqueued(false), IsBrAnalyzable(false),
110                 HasFallThrough(false), IsUnpredicable(false),
111                 CannotBeCopied(false), ClobbersPred(false), NonPredSize(0),
112                 BB(0), TrueBB(0), FalseBB(0) {}
113    };
114
115    /// IfcvtToken - Record information about pending if-conversions to attemp:
116    /// BBI             - Corresponding BBInfo.
117    /// Kind            - Type of block. See IfcvtKind.
118    /// NeedSubsumsion  - True if the to be predicated BB has already been
119    ///                   predicated.
120    /// NumDups      - Number of instructions that would be duplicated due
121    ///                   to this if-conversion. (For diamonds, the number of
122    ///                   identical instructions at the beginnings of both
123    ///                   paths).
124    /// NumDups2     - For diamonds, the number of identical instructions
125    ///                   at the ends of both paths.
126    struct IfcvtToken {
127      BBInfo &BBI;
128      IfcvtKind Kind;
129      bool NeedSubsumsion;
130      unsigned NumDups;
131      unsigned NumDups2;
132      IfcvtToken(BBInfo &b, IfcvtKind k, bool s, unsigned d, unsigned d2 = 0)
133        : BBI(b), Kind(k), NeedSubsumsion(s), NumDups(d), NumDups2(d2) {}
134    };
135
136    /// Roots - Basic blocks that do not have successors. These are the starting
137    /// points of Graph traversal.
138    std::vector<MachineBasicBlock*> Roots;
139
140    /// BBAnalysis - Results of if-conversion feasibility analysis indexed by
141    /// basic block number.
142    std::vector<BBInfo> BBAnalysis;
143
144    const TargetLowering *TLI;
145    const TargetInstrInfo *TII;
146    bool MadeChange;
147  public:
148    static char ID;
149    IfConverter() : MachineFunctionPass((intptr_t)&ID) {}
150
151    virtual bool runOnMachineFunction(MachineFunction &MF);
152    virtual const char *getPassName() const { return "If converter"; }
153
154  private:
155    bool ReverseBranchCondition(BBInfo &BBI);
156    bool ValidSimple(BBInfo &TrueBBI, unsigned &Dups) const;
157    bool ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
158                       bool FalseBranch, unsigned &Dups) const;
159    bool ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI,
160                      unsigned &Dups1, unsigned &Dups2) const;
161    void ScanInstructions(BBInfo &BBI);
162    BBInfo &AnalyzeBlock(MachineBasicBlock *BB,
163                         std::vector<IfcvtToken*> &Tokens);
164    bool FeasibilityAnalysis(BBInfo &BBI, std::vector<MachineOperand> &Cond,
165                             bool isTriangle = false, bool RevBranch = false);
166    bool AnalyzeBlocks(MachineFunction &MF,
167                       std::vector<IfcvtToken*> &Tokens);
168    void InvalidatePreds(MachineBasicBlock *BB);
169    void RemoveExtraEdges(BBInfo &BBI);
170    bool IfConvertSimple(BBInfo &BBI, IfcvtKind Kind);
171    bool IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind);
172    bool IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind,
173                          unsigned NumDups1, unsigned NumDups2);
174    void PredicateBlock(BBInfo &BBI,
175                        MachineBasicBlock::iterator E,
176                        std::vector<MachineOperand> &Cond);
177    void CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI,
178                               std::vector<MachineOperand> &Cond,
179                               bool IgnoreBr = false);
180    void MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI);
181
182    bool MeetIfcvtSizeLimit(unsigned Size) const {
183      return Size > 0 && Size <= TLI->getIfCvtBlockSizeLimit();
184    }
185
186    // blockAlwaysFallThrough - Block ends without a terminator.
187    bool blockAlwaysFallThrough(BBInfo &BBI) const {
188      return BBI.IsBrAnalyzable && BBI.TrueBB == NULL;
189    }
190
191    // IfcvtTokenCmp - Used to sort if-conversion candidates.
192    static bool IfcvtTokenCmp(IfcvtToken *C1, IfcvtToken *C2) {
193      int Incr1 = (C1->Kind == ICDiamond)
194        ? -(int)(C1->NumDups + C1->NumDups2) : (int)C1->NumDups;
195      int Incr2 = (C2->Kind == ICDiamond)
196        ? -(int)(C2->NumDups + C2->NumDups2) : (int)C2->NumDups;
197      if (Incr1 > Incr2)
198        return true;
199      else if (Incr1 == Incr2) {
200        // Favors subsumsion.
201        if (C1->NeedSubsumsion == false && C2->NeedSubsumsion == true)
202          return true;
203        else if (C1->NeedSubsumsion == C2->NeedSubsumsion) {
204          // Favors diamond over triangle, etc.
205          if ((unsigned)C1->Kind < (unsigned)C2->Kind)
206            return true;
207          else if (C1->Kind == C2->Kind)
208            return C1->BBI.BB->getNumber() < C2->BBI.BB->getNumber();
209        }
210      }
211      return false;
212    }
213  };
214
215  char IfConverter::ID = 0;
216}
217
218FunctionPass *llvm::createIfConverterPass() { return new IfConverter(); }
219
220bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
221  TLI = MF.getTarget().getTargetLowering();
222  TII = MF.getTarget().getInstrInfo();
223  if (!TII) return false;
224
225  static int FnNum = -1;
226  DOUT << "\nIfcvt: function (" << ++FnNum <<  ") \'"
227       << MF.getFunction()->getName() << "\'";
228
229  if (FnNum < IfCvtFnStart || (IfCvtFnStop != -1 && FnNum > IfCvtFnStop)) {
230    DOUT << " skipped\n";
231    return false;
232  }
233  DOUT << "\n";
234
235  MF.RenumberBlocks();
236  BBAnalysis.resize(MF.getNumBlockIDs());
237
238  // Look for root nodes, i.e. blocks without successors.
239  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
240    if (I->succ_empty())
241      Roots.push_back(I);
242
243  std::vector<IfcvtToken*> Tokens;
244  MadeChange = false;
245  unsigned NumIfCvts = NumSimple + NumSimpleFalse + NumTriangle +
246    NumTriangleRev + NumTriangleFalse + NumTriangleFRev + NumDiamonds;
247  while (IfCvtLimit == -1 || (int)NumIfCvts < IfCvtLimit) {
248    // Do an intial analysis for each basic block and finding all the potential
249    // candidates to perform if-convesion.
250    bool Change = AnalyzeBlocks(MF, Tokens);
251    while (!Tokens.empty()) {
252      IfcvtToken *Token = Tokens.back();
253      Tokens.pop_back();
254      BBInfo &BBI = Token->BBI;
255      IfcvtKind Kind = Token->Kind;
256
257      // If the block has been evicted out of the queue or it has already been
258      // marked dead (due to it being predicated), then skip it.
259      if (BBI.IsDone)
260        BBI.IsEnqueued = false;
261      if (!BBI.IsEnqueued)
262        continue;
263
264      BBI.IsEnqueued = false;
265
266      bool RetVal = false;
267      switch (Kind) {
268      default: assert(false && "Unexpected!");
269        break;
270      case ICSimple:
271      case ICSimpleFalse: {
272        bool isFalse = Kind == ICSimpleFalse;
273        if ((isFalse && DisableSimpleF) || (!isFalse && DisableSimple)) break;
274        DOUT << "Ifcvt (Simple" << (Kind == ICSimpleFalse ? " false" :"")
275             << "): BB#" << BBI.BB->getNumber() << " ("
276             << ((Kind == ICSimpleFalse)
277                 ? BBI.FalseBB->getNumber()
278                 : BBI.TrueBB->getNumber()) << ") ";
279        RetVal = IfConvertSimple(BBI, Kind);
280        DOUT << (RetVal ? "succeeded!" : "failed!") << "\n";
281        if (RetVal)
282          if (isFalse) NumSimpleFalse++;
283          else         NumSimple++;
284       break;
285      }
286      case ICTriangle:
287      case ICTriangleRev:
288      case ICTriangleFalse:
289      case ICTriangleFRev: {
290        bool isFalse = Kind == ICTriangleFalse;
291        bool isRev   = (Kind == ICTriangleRev || Kind == ICTriangleFRev);
292        if (DisableTriangle && !isFalse && !isRev) break;
293        if (DisableTriangleR && !isFalse && isRev) break;
294        if (DisableTriangleF && isFalse && !isRev) break;
295        if (DisableTriangleFR && isFalse && isRev) break;
296        DOUT << "Ifcvt (Triangle";
297        if (isFalse)
298          DOUT << " false";
299        if (isRev)
300          DOUT << " rev";
301        DOUT << "): BB#" << BBI.BB->getNumber() << " (T:"
302             << BBI.TrueBB->getNumber() << ",F:"
303             << BBI.FalseBB->getNumber() << ") ";
304        RetVal = IfConvertTriangle(BBI, Kind);
305        DOUT << (RetVal ? "succeeded!" : "failed!") << "\n";
306        if (RetVal) {
307          if (isFalse) {
308            if (isRev) NumTriangleFRev++;
309            else       NumTriangleFalse++;
310          } else {
311            if (isRev) NumTriangleRev++;
312            else       NumTriangle++;
313          }
314        }
315        break;
316      }
317      case ICDiamond: {
318        if (DisableDiamond) break;
319        DOUT << "Ifcvt (Diamond): BB#" << BBI.BB->getNumber() << " (T:"
320             << BBI.TrueBB->getNumber() << ",F:"
321             << BBI.FalseBB->getNumber() << ") ";
322        RetVal = IfConvertDiamond(BBI, Kind, Token->NumDups, Token->NumDups2);
323        DOUT << (RetVal ? "succeeded!" : "failed!") << "\n";
324        if (RetVal) NumDiamonds++;
325        break;
326      }
327      }
328
329      Change |= RetVal;
330
331      NumIfCvts = NumSimple + NumSimpleFalse + NumTriangle + NumTriangleRev +
332        NumTriangleFalse + NumTriangleFRev + NumDiamonds;
333      if (IfCvtLimit != -1 && (int)NumIfCvts >= IfCvtLimit)
334        break;
335    }
336
337    if (!Change)
338      break;
339    MadeChange |= Change;
340  }
341
342  // Delete tokens in case of early exit.
343  while (!Tokens.empty()) {
344    IfcvtToken *Token = Tokens.back();
345    Tokens.pop_back();
346    delete Token;
347  }
348
349  Tokens.clear();
350  Roots.clear();
351  BBAnalysis.clear();
352
353  return MadeChange;
354}
355
356/// findFalseBlock - BB has a fallthrough. Find its 'false' successor given
357/// its 'true' successor.
358static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB,
359                                         MachineBasicBlock *TrueBB) {
360  for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
361         E = BB->succ_end(); SI != E; ++SI) {
362    MachineBasicBlock *SuccBB = *SI;
363    if (SuccBB != TrueBB)
364      return SuccBB;
365  }
366  return NULL;
367}
368
369/// ReverseBranchCondition - Reverse the condition of the end of the block
370/// branchs. Swap block's 'true' and 'false' successors.
371bool IfConverter::ReverseBranchCondition(BBInfo &BBI) {
372  if (!TII->ReverseBranchCondition(BBI.BrCond)) {
373    TII->RemoveBranch(*BBI.BB);
374    TII->InsertBranch(*BBI.BB, BBI.FalseBB, BBI.TrueBB, BBI.BrCond);
375    std::swap(BBI.TrueBB, BBI.FalseBB);
376    return true;
377  }
378  return false;
379}
380
381/// getNextBlock - Returns the next block in the function blocks ordering. If
382/// it is the end, returns NULL.
383static inline MachineBasicBlock *getNextBlock(MachineBasicBlock *BB) {
384  MachineFunction::iterator I = BB;
385  MachineFunction::iterator E = BB->getParent()->end();
386  if (++I == E)
387    return NULL;
388  return I;
389}
390
391/// ValidSimple - Returns true if the 'true' block (along with its
392/// predecessor) forms a valid simple shape for ifcvt. It also returns the
393/// number of instructions that the ifcvt would need to duplicate if performed
394/// in Dups.
395bool IfConverter::ValidSimple(BBInfo &TrueBBI, unsigned &Dups) const {
396  Dups = 0;
397  if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone)
398    return false;
399
400  if (TrueBBI.IsBrAnalyzable)
401    return false;
402
403  if (TrueBBI.BB->pred_size() > 1) {
404    if (TrueBBI.CannotBeCopied ||
405        TrueBBI.NonPredSize > TLI->getIfCvtDupBlockSizeLimit())
406      return false;
407    Dups = TrueBBI.NonPredSize;
408  }
409
410  return true;
411}
412
413/// ValidTriangle - Returns true if the 'true' and 'false' blocks (along
414/// with their common predecessor) forms a valid triangle shape for ifcvt.
415/// If 'FalseBranch' is true, it checks if 'true' block's false branch
416/// branches to the false branch rather than the other way around. It also
417/// returns the number of instructions that the ifcvt would need to duplicate
418/// if performed in 'Dups'.
419bool IfConverter::ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
420                                bool FalseBranch, unsigned &Dups) const {
421  Dups = 0;
422  if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone)
423    return false;
424
425  if (TrueBBI.BB->pred_size() > 1) {
426    if (TrueBBI.CannotBeCopied)
427      return false;
428
429    unsigned Size = TrueBBI.NonPredSize;
430    if (TrueBBI.IsBrAnalyzable) {
431      if (TrueBBI.TrueBB && TrueBBI.BrCond.empty())
432        // End with an unconditional branch. It will be removed.
433        --Size;
434      else {
435        MachineBasicBlock *FExit = FalseBranch
436          ? TrueBBI.TrueBB : TrueBBI.FalseBB;
437        if (FExit)
438          // Require a conditional branch
439          ++Size;
440      }
441    }
442    if (Size > TLI->getIfCvtDupBlockSizeLimit())
443      return false;
444    Dups = Size;
445  }
446
447  MachineBasicBlock *TExit = FalseBranch ? TrueBBI.FalseBB : TrueBBI.TrueBB;
448  if (!TExit && blockAlwaysFallThrough(TrueBBI)) {
449    MachineFunction::iterator I = TrueBBI.BB;
450    if (++I == TrueBBI.BB->getParent()->end())
451      return false;
452    TExit = I;
453  }
454  return TExit && TExit == FalseBBI.BB;
455}
456
457static
458MachineBasicBlock::iterator firstNonBranchInst(MachineBasicBlock *BB,
459                                               const TargetInstrInfo *TII) {
460  MachineBasicBlock::iterator I = BB->end();
461  while (I != BB->begin()) {
462    --I;
463    if (!I->getDesc().isBranch())
464      break;
465  }
466  return I;
467}
468
469/// ValidDiamond - Returns true if the 'true' and 'false' blocks (along
470/// with their common predecessor) forms a valid diamond shape for ifcvt.
471bool IfConverter::ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI,
472                               unsigned &Dups1, unsigned &Dups2) const {
473  Dups1 = Dups2 = 0;
474  if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone ||
475      FalseBBI.IsBeingAnalyzed || FalseBBI.IsDone)
476    return false;
477
478  MachineBasicBlock *TT = TrueBBI.TrueBB;
479  MachineBasicBlock *FT = FalseBBI.TrueBB;
480
481  if (!TT && blockAlwaysFallThrough(TrueBBI))
482    TT = getNextBlock(TrueBBI.BB);
483  if (!FT && blockAlwaysFallThrough(FalseBBI))
484    FT = getNextBlock(FalseBBI.BB);
485  if (TT != FT)
486    return false;
487  if (TT == NULL && (TrueBBI.IsBrAnalyzable || FalseBBI.IsBrAnalyzable))
488    return false;
489  if  (TrueBBI.BB->pred_size() > 1 || FalseBBI.BB->pred_size() > 1)
490    return false;
491
492  // FIXME: Allow true block to have an early exit?
493  if (TrueBBI.FalseBB || FalseBBI.FalseBB ||
494      (TrueBBI.ClobbersPred && FalseBBI.ClobbersPred))
495    return false;
496
497  MachineBasicBlock::iterator TI = TrueBBI.BB->begin();
498  MachineBasicBlock::iterator FI = FalseBBI.BB->begin();
499  while (TI != TrueBBI.BB->end() && FI != FalseBBI.BB->end()) {
500    if (!TI->isIdenticalTo(FI))
501      break;
502    ++Dups1;
503    ++TI;
504    ++FI;
505  }
506
507  TI = firstNonBranchInst(TrueBBI.BB, TII);
508  FI = firstNonBranchInst(FalseBBI.BB, TII);
509  while (TI != TrueBBI.BB->begin() && FI != FalseBBI.BB->begin()) {
510    if (!TI->isIdenticalTo(FI))
511      break;
512    ++Dups2;
513    --TI;
514    --FI;
515  }
516
517  return true;
518}
519
520/// ScanInstructions - Scan all the instructions in the block to determine if
521/// the block is predicable. In most cases, that means all the instructions
522/// in the block are isPredicable(). Also checks if the block contains any
523/// instruction which can clobber a predicate (e.g. condition code register).
524/// If so, the block is not predicable unless it's the last instruction.
525void IfConverter::ScanInstructions(BBInfo &BBI) {
526  if (BBI.IsDone)
527    return;
528
529  bool AlreadyPredicated = BBI.Predicate.size() > 0;
530  // First analyze the end of BB branches.
531  BBI.TrueBB = BBI.FalseBB = NULL;
532  BBI.BrCond.clear();
533  BBI.IsBrAnalyzable =
534    !TII->AnalyzeBranch(*BBI.BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond);
535  BBI.HasFallThrough = BBI.IsBrAnalyzable && BBI.FalseBB == NULL;
536
537  if (BBI.BrCond.size()) {
538    // No false branch. This BB must end with a conditional branch and a
539    // fallthrough.
540    if (!BBI.FalseBB)
541      BBI.FalseBB = findFalseBlock(BBI.BB, BBI.TrueBB);
542    assert(BBI.FalseBB && "Expected to find the fallthrough block!");
543  }
544
545  // Then scan all the instructions.
546  BBI.NonPredSize = 0;
547  BBI.ClobbersPred = false;
548  bool SeenCondBr = false;
549  for (MachineBasicBlock::iterator I = BBI.BB->begin(), E = BBI.BB->end();
550       I != E; ++I) {
551    const TargetInstrDesc &TID = I->getDesc();
552    if (TID.isNotDuplicable())
553      BBI.CannotBeCopied = true;
554
555    bool isPredicated = TII->isPredicated(I);
556    bool isCondBr = BBI.IsBrAnalyzable && TID.isConditionalBranch();
557
558    if (!isCondBr) {
559      if (!isPredicated)
560        BBI.NonPredSize++;
561      else if (!AlreadyPredicated) {
562        // FIXME: This instruction is already predicated before the
563        // if-conversion pass. It's probably something like a conditional move.
564        // Mark this block unpredicable for now.
565        BBI.IsUnpredicable = true;
566        return;
567      }
568
569    }
570
571    if (BBI.ClobbersPred && !isPredicated) {
572      // Predicate modification instruction should end the block (except for
573      // already predicated instructions and end of block branches).
574      if (isCondBr) {
575        SeenCondBr = true;
576
577        // Conditional branches is not predicable. But it may be eliminated.
578        continue;
579      }
580
581      // Predicate may have been modified, the subsequent (currently)
582      // unpredicated instructions cannot be correctly predicated.
583      BBI.IsUnpredicable = true;
584      return;
585    }
586
587    // FIXME: Make use of PredDefs? e.g. ADDC, SUBC sets predicates but are
588    // still potentially predicable.
589    std::vector<MachineOperand> PredDefs;
590    if (TII->DefinesPredicate(I, PredDefs))
591      BBI.ClobbersPred = true;
592
593    if (!TID.isPredicable()) {
594      BBI.IsUnpredicable = true;
595      return;
596    }
597  }
598}
599
600/// FeasibilityAnalysis - Determine if the block is a suitable candidate to be
601/// predicated by the specified predicate.
602bool IfConverter::FeasibilityAnalysis(BBInfo &BBI,
603                                      std::vector<MachineOperand> &Pred,
604                                      bool isTriangle, bool RevBranch) {
605  // If the block is dead or unpredicable, then it cannot be predicated.
606  if (BBI.IsDone || BBI.IsUnpredicable)
607    return false;
608
609  // If it is already predicated, check if its predicate subsumes the new
610  // predicate.
611  if (BBI.Predicate.size() && !TII->SubsumesPredicate(BBI.Predicate, Pred))
612    return false;
613
614  if (BBI.BrCond.size()) {
615    if (!isTriangle)
616      return false;
617
618    // Test predicate subsumsion.
619    std::vector<MachineOperand> RevPred(Pred);
620    std::vector<MachineOperand> Cond(BBI.BrCond);
621    if (RevBranch) {
622      if (TII->ReverseBranchCondition(Cond))
623        return false;
624    }
625    if (TII->ReverseBranchCondition(RevPred) ||
626        !TII->SubsumesPredicate(Cond, RevPred))
627      return false;
628  }
629
630  return true;
631}
632
633/// AnalyzeBlock - Analyze the structure of the sub-CFG starting from
634/// the specified block. Record its successors and whether it looks like an
635/// if-conversion candidate.
636IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
637                                             std::vector<IfcvtToken*> &Tokens) {
638  BBInfo &BBI = BBAnalysis[BB->getNumber()];
639
640  if (BBI.IsAnalyzed || BBI.IsBeingAnalyzed)
641    return BBI;
642
643  BBI.BB = BB;
644  BBI.IsBeingAnalyzed = true;
645
646  ScanInstructions(BBI);
647
648  // Unanalyable or ends with fallthrough or unconditional branch.
649  if (!BBI.IsBrAnalyzable || BBI.BrCond.empty()) {
650    BBI.IsBeingAnalyzed = false;
651    BBI.IsAnalyzed = true;
652    return BBI;
653  }
654
655  // Do not ifcvt if either path is a back edge to the entry block.
656  if (BBI.TrueBB == BB || BBI.FalseBB == BB) {
657    BBI.IsBeingAnalyzed = false;
658    BBI.IsAnalyzed = true;
659    return BBI;
660  }
661
662  BBInfo &TrueBBI  = AnalyzeBlock(BBI.TrueBB, Tokens);
663  BBInfo &FalseBBI = AnalyzeBlock(BBI.FalseBB, Tokens);
664
665  if (TrueBBI.IsDone && FalseBBI.IsDone) {
666    BBI.IsBeingAnalyzed = false;
667    BBI.IsAnalyzed = true;
668    return BBI;
669  }
670
671  std::vector<MachineOperand> RevCond(BBI.BrCond);
672  bool CanRevCond = !TII->ReverseBranchCondition(RevCond);
673
674  unsigned Dups = 0;
675  unsigned Dups2 = 0;
676  bool TNeedSub = TrueBBI.Predicate.size() > 0;
677  bool FNeedSub = FalseBBI.Predicate.size() > 0;
678  bool Enqueued = false;
679  if (CanRevCond && ValidDiamond(TrueBBI, FalseBBI, Dups, Dups2) &&
680      MeetIfcvtSizeLimit(TrueBBI.NonPredSize - (Dups + Dups2)) &&
681      MeetIfcvtSizeLimit(FalseBBI.NonPredSize - (Dups + Dups2)) &&
682      FeasibilityAnalysis(TrueBBI, BBI.BrCond) &&
683      FeasibilityAnalysis(FalseBBI, RevCond)) {
684    // Diamond:
685    //   EBB
686    //   / \_
687    //  |   |
688    // TBB FBB
689    //   \ /
690    //  TailBB
691    // Note TailBB can be empty.
692    Tokens.push_back(new IfcvtToken(BBI, ICDiamond, TNeedSub|FNeedSub, Dups,
693                                    Dups2));
694    Enqueued = true;
695  }
696
697  if (ValidTriangle(TrueBBI, FalseBBI, false, Dups) &&
698      MeetIfcvtSizeLimit(TrueBBI.NonPredSize) &&
699      FeasibilityAnalysis(TrueBBI, BBI.BrCond, true)) {
700    // Triangle:
701    //   EBB
702    //   | \_
703    //   |  |
704    //   | TBB
705    //   |  /
706    //   FBB
707    Tokens.push_back(new IfcvtToken(BBI, ICTriangle, TNeedSub, Dups));
708    Enqueued = true;
709  }
710
711  if (ValidTriangle(TrueBBI, FalseBBI, true, Dups) &&
712      MeetIfcvtSizeLimit(TrueBBI.NonPredSize) &&
713      FeasibilityAnalysis(TrueBBI, BBI.BrCond, true, true)) {
714    Tokens.push_back(new IfcvtToken(BBI, ICTriangleRev, TNeedSub, Dups));
715    Enqueued = true;
716  }
717
718  if (ValidSimple(TrueBBI, Dups) &&
719      MeetIfcvtSizeLimit(TrueBBI.NonPredSize) &&
720      FeasibilityAnalysis(TrueBBI, BBI.BrCond)) {
721    // Simple (split, no rejoin):
722    //   EBB
723    //   | \_
724    //   |  |
725    //   | TBB---> exit
726    //   |
727    //   FBB
728    Tokens.push_back(new IfcvtToken(BBI, ICSimple, TNeedSub, Dups));
729    Enqueued = true;
730  }
731
732  if (CanRevCond) {
733    // Try the other path...
734    if (ValidTriangle(FalseBBI, TrueBBI, false, Dups) &&
735        MeetIfcvtSizeLimit(FalseBBI.NonPredSize) &&
736        FeasibilityAnalysis(FalseBBI, RevCond, true)) {
737      Tokens.push_back(new IfcvtToken(BBI, ICTriangleFalse, FNeedSub, Dups));
738      Enqueued = true;
739    }
740
741    if (ValidTriangle(FalseBBI, TrueBBI, true, Dups) &&
742        MeetIfcvtSizeLimit(FalseBBI.NonPredSize) &&
743        FeasibilityAnalysis(FalseBBI, RevCond, true, true)) {
744      Tokens.push_back(new IfcvtToken(BBI, ICTriangleFRev, FNeedSub, Dups));
745      Enqueued = true;
746    }
747
748    if (ValidSimple(FalseBBI, Dups) &&
749        MeetIfcvtSizeLimit(FalseBBI.NonPredSize) &&
750        FeasibilityAnalysis(FalseBBI, RevCond)) {
751      Tokens.push_back(new IfcvtToken(BBI, ICSimpleFalse, FNeedSub, Dups));
752      Enqueued = true;
753    }
754  }
755
756  BBI.IsEnqueued = Enqueued;
757  BBI.IsBeingAnalyzed = false;
758  BBI.IsAnalyzed = true;
759  return BBI;
760}
761
762/// AnalyzeBlocks - Analyze all blocks and find entries for all if-conversion
763/// candidates. It returns true if any CFG restructuring is done to expose more
764/// if-conversion opportunities.
765bool IfConverter::AnalyzeBlocks(MachineFunction &MF,
766                                std::vector<IfcvtToken*> &Tokens) {
767  bool Change = false;
768  std::set<MachineBasicBlock*> Visited;
769  for (unsigned i = 0, e = Roots.size(); i != e; ++i) {
770    for (idf_ext_iterator<MachineBasicBlock*> I=idf_ext_begin(Roots[i],Visited),
771           E = idf_ext_end(Roots[i], Visited); I != E; ++I) {
772      MachineBasicBlock *BB = *I;
773      AnalyzeBlock(BB, Tokens);
774    }
775  }
776
777  // Sort to favor more complex ifcvt scheme.
778  std::stable_sort(Tokens.begin(), Tokens.end(), IfcvtTokenCmp);
779
780  return Change;
781}
782
783/// canFallThroughTo - Returns true either if ToBB is the next block after BB or
784/// that all the intervening blocks are empty (given BB can fall through to its
785/// next block).
786static bool canFallThroughTo(MachineBasicBlock *BB, MachineBasicBlock *ToBB) {
787  MachineFunction::iterator I = BB;
788  MachineFunction::iterator TI = ToBB;
789  MachineFunction::iterator E = BB->getParent()->end();
790  while (++I != TI)
791    if (I == E || !I->empty())
792      return false;
793  return true;
794}
795
796/// InvalidatePreds - Invalidate predecessor BB info so it would be re-analyzed
797/// to determine if it can be if-converted. If predecessor is already enqueued,
798/// dequeue it!
799void IfConverter::InvalidatePreds(MachineBasicBlock *BB) {
800  for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(),
801         E = BB->pred_end(); PI != E; ++PI) {
802    BBInfo &PBBI = BBAnalysis[(*PI)->getNumber()];
803    if (PBBI.IsDone || PBBI.BB == BB)
804      continue;
805    PBBI.IsAnalyzed = false;
806    PBBI.IsEnqueued = false;
807  }
808}
809
810/// InsertUncondBranch - Inserts an unconditional branch from BB to ToBB.
811///
812static void InsertUncondBranch(MachineBasicBlock *BB, MachineBasicBlock *ToBB,
813                               const TargetInstrInfo *TII) {
814  std::vector<MachineOperand> NoCond;
815  TII->InsertBranch(*BB, ToBB, NULL, NoCond);
816}
817
818/// RemoveExtraEdges - Remove true / false edges if either / both are no longer
819/// successors.
820void IfConverter::RemoveExtraEdges(BBInfo &BBI) {
821  MachineBasicBlock *TBB = NULL, *FBB = NULL;
822  std::vector<MachineOperand> Cond;
823  if (!TII->AnalyzeBranch(*BBI.BB, TBB, FBB, Cond))
824    BBI.BB->CorrectExtraCFGEdges(TBB, FBB, !Cond.empty());
825}
826
827/// IfConvertSimple - If convert a simple (split, no rejoin) sub-CFG.
828///
829bool IfConverter::IfConvertSimple(BBInfo &BBI, IfcvtKind Kind) {
830  BBInfo &TrueBBI  = BBAnalysis[BBI.TrueBB->getNumber()];
831  BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
832  BBInfo *CvtBBI = &TrueBBI;
833  BBInfo *NextBBI = &FalseBBI;
834
835  std::vector<MachineOperand> Cond(BBI.BrCond);
836  if (Kind == ICSimpleFalse)
837    std::swap(CvtBBI, NextBBI);
838
839  if (CvtBBI->IsDone ||
840      (CvtBBI->CannotBeCopied && CvtBBI->BB->pred_size() > 1)) {
841    // Something has changed. It's no longer safe to predicate this block.
842    BBI.IsAnalyzed = false;
843    CvtBBI->IsAnalyzed = false;
844    return false;
845  }
846
847  if (Kind == ICSimpleFalse)
848    TII->ReverseBranchCondition(Cond);
849
850  if (CvtBBI->BB->pred_size() > 1) {
851    BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
852    // Copy instructions in the true block, predicate them add them to
853    // the entry block.
854    CopyAndPredicateBlock(BBI, *CvtBBI, Cond);
855  } else {
856    PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond);
857
858    // Merge converted block into entry block.
859    BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
860    MergeBlocks(BBI, *CvtBBI);
861  }
862
863  bool IterIfcvt = true;
864  if (!canFallThroughTo(BBI.BB, NextBBI->BB)) {
865    InsertUncondBranch(BBI.BB, NextBBI->BB, TII);
866    BBI.HasFallThrough = false;
867    // Now ifcvt'd block will look like this:
868    // BB:
869    // ...
870    // t, f = cmp
871    // if t op
872    // b BBf
873    //
874    // We cannot further ifcvt this block because the unconditional branch
875    // will have to be predicated on the new condition, that will not be
876    // available if cmp executes.
877    IterIfcvt = false;
878  }
879
880  RemoveExtraEdges(BBI);
881
882  // Update block info. BB can be iteratively if-converted.
883  if (!IterIfcvt)
884    BBI.IsDone = true;
885  InvalidatePreds(BBI.BB);
886  CvtBBI->IsDone = true;
887
888  // FIXME: Must maintain LiveIns.
889  return true;
890}
891
892/// IfConvertTriangle - If convert a triangle sub-CFG.
893///
894bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) {
895  BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
896  BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
897  BBInfo *CvtBBI = &TrueBBI;
898  BBInfo *NextBBI = &FalseBBI;
899
900  std::vector<MachineOperand> Cond(BBI.BrCond);
901  if (Kind == ICTriangleFalse || Kind == ICTriangleFRev)
902    std::swap(CvtBBI, NextBBI);
903
904  if (CvtBBI->IsDone ||
905      (CvtBBI->CannotBeCopied && CvtBBI->BB->pred_size() > 1)) {
906    // Something has changed. It's no longer safe to predicate this block.
907    BBI.IsAnalyzed = false;
908    CvtBBI->IsAnalyzed = false;
909    return false;
910  }
911
912  if (Kind == ICTriangleFalse || Kind == ICTriangleFRev)
913    TII->ReverseBranchCondition(Cond);
914
915  if (Kind == ICTriangleRev || Kind == ICTriangleFRev) {
916    ReverseBranchCondition(*CvtBBI);
917    // BB has been changed, modify its predecessors (except for this
918    // one) so they don't get ifcvt'ed based on bad intel.
919    for (MachineBasicBlock::pred_iterator PI = CvtBBI->BB->pred_begin(),
920           E = CvtBBI->BB->pred_end(); PI != E; ++PI) {
921      MachineBasicBlock *PBB = *PI;
922      if (PBB == BBI.BB)
923        continue;
924      BBInfo &PBBI = BBAnalysis[PBB->getNumber()];
925      if (PBBI.IsEnqueued) {
926        PBBI.IsAnalyzed = false;
927        PBBI.IsEnqueued = false;
928      }
929    }
930  }
931
932  bool HasEarlyExit = CvtBBI->FalseBB != NULL;
933  bool DupBB = CvtBBI->BB->pred_size() > 1;
934  if (DupBB) {
935    BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
936    // Copy instructions in the true block, predicate them add them to
937    // the entry block.
938    CopyAndPredicateBlock(BBI, *CvtBBI, Cond, true);
939  } else {
940    // Predicate the 'true' block after removing its branch.
941    CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB);
942    PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond);
943  }
944
945  if (!DupBB) {
946    // Now merge the entry of the triangle with the true block.
947    BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
948    MergeBlocks(BBI, *CvtBBI);
949  }
950
951  // If 'true' block has a 'false' successor, add an exit branch to it.
952  if (HasEarlyExit) {
953    std::vector<MachineOperand> RevCond(CvtBBI->BrCond);
954    if (TII->ReverseBranchCondition(RevCond))
955      assert(false && "Unable to reverse branch condition!");
956    TII->InsertBranch(*BBI.BB, CvtBBI->FalseBB, NULL, RevCond);
957    BBI.BB->addSuccessor(CvtBBI->FalseBB);
958  }
959
960  // Merge in the 'false' block if the 'false' block has no other
961  // predecessors. Otherwise, add a unconditional branch from to 'false'.
962  bool FalseBBDead = false;
963  bool IterIfcvt = true;
964  bool isFallThrough = canFallThroughTo(BBI.BB, NextBBI->BB);
965  if (!isFallThrough) {
966    // Only merge them if the true block does not fallthrough to the false
967    // block. By not merging them, we make it possible to iteratively
968    // ifcvt the blocks.
969    if (!HasEarlyExit &&
970        NextBBI->BB->pred_size() == 1 && !NextBBI->HasFallThrough) {
971      MergeBlocks(BBI, *NextBBI);
972      FalseBBDead = true;
973    } else {
974      InsertUncondBranch(BBI.BB, NextBBI->BB, TII);
975      BBI.HasFallThrough = false;
976    }
977    // Mixed predicated and unpredicated code. This cannot be iteratively
978    // predicated.
979    IterIfcvt = false;
980  }
981
982  RemoveExtraEdges(BBI);
983
984  // Update block info. BB can be iteratively if-converted.
985  if (!IterIfcvt)
986    BBI.IsDone = true;
987  InvalidatePreds(BBI.BB);
988  CvtBBI->IsDone = true;
989  if (FalseBBDead)
990    NextBBI->IsDone = true;
991
992  // FIXME: Must maintain LiveIns.
993  return true;
994}
995
996/// IfConvertDiamond - If convert a diamond sub-CFG.
997///
998bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind,
999                                   unsigned NumDups1, unsigned NumDups2) {
1000  BBInfo &TrueBBI  = BBAnalysis[BBI.TrueBB->getNumber()];
1001  BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
1002  MachineBasicBlock *TailBB = TrueBBI.TrueBB;
1003  // True block must fall through or ended with unanalyzable terminator.
1004  if (!TailBB) {
1005    if (blockAlwaysFallThrough(TrueBBI))
1006      TailBB = FalseBBI.TrueBB;
1007    assert((TailBB || !TrueBBI.IsBrAnalyzable) && "Unexpected!");
1008  }
1009
1010  if (TrueBBI.IsDone || FalseBBI.IsDone ||
1011      TrueBBI.BB->pred_size() > 1 ||
1012      FalseBBI.BB->pred_size() > 1) {
1013    // Something has changed. It's no longer safe to predicate these blocks.
1014    BBI.IsAnalyzed = false;
1015    TrueBBI.IsAnalyzed = false;
1016    FalseBBI.IsAnalyzed = false;
1017    return false;
1018  }
1019
1020  // Merge the 'true' and 'false' blocks by copying the instructions
1021  // from the 'false' block to the 'true' block. That is, unless the true
1022  // block would clobber the predicate, in that case, do the opposite.
1023  BBInfo *BBI1 = &TrueBBI;
1024  BBInfo *BBI2 = &FalseBBI;
1025  std::vector<MachineOperand> RevCond(BBI.BrCond);
1026  TII->ReverseBranchCondition(RevCond);
1027  std::vector<MachineOperand> *Cond1 = &BBI.BrCond;
1028  std::vector<MachineOperand> *Cond2 = &RevCond;
1029
1030  // Figure out the more profitable ordering.
1031  bool DoSwap = false;
1032  if (TrueBBI.ClobbersPred && !FalseBBI.ClobbersPred)
1033    DoSwap = true;
1034  else if (TrueBBI.ClobbersPred == FalseBBI.ClobbersPred) {
1035    if (TrueBBI.NonPredSize > FalseBBI.NonPredSize)
1036      DoSwap = true;
1037  }
1038  if (DoSwap) {
1039    std::swap(BBI1, BBI2);
1040    std::swap(Cond1, Cond2);
1041  }
1042
1043  // Remove the conditional branch from entry to the blocks.
1044  BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
1045
1046  // Remove the duplicated instructions at the beginnings of both paths.
1047  MachineBasicBlock::iterator DI1 = BBI1->BB->begin();
1048  MachineBasicBlock::iterator DI2 = BBI2->BB->begin();
1049  BBI1->NonPredSize -= NumDups1;
1050  BBI2->NonPredSize -= NumDups1;
1051  while (NumDups1 != 0) {
1052    ++DI1;
1053    ++DI2;
1054    --NumDups1;
1055  }
1056  BBI.BB->splice(BBI.BB->end(), BBI1->BB, BBI1->BB->begin(), DI1);
1057  BBI2->BB->erase(BBI2->BB->begin(), DI2);
1058
1059  // Predicate the 'true' block after removing its branch.
1060  BBI1->NonPredSize -= TII->RemoveBranch(*BBI1->BB);
1061  DI1 = BBI1->BB->end();
1062  for (unsigned i = 0; i != NumDups2; ++i)
1063    --DI1;
1064  BBI1->BB->erase(DI1, BBI1->BB->end());
1065  PredicateBlock(*BBI1, BBI1->BB->end(), *Cond1);
1066
1067  // Predicate the 'false' block.
1068  BBI2->NonPredSize -= TII->RemoveBranch(*BBI2->BB);
1069  DI2 = BBI2->BB->end();
1070  while (NumDups2 != 0) {
1071    --DI2;
1072    --NumDups2;
1073  }
1074  PredicateBlock(*BBI2, DI2, *Cond2);
1075
1076  // Merge the true block into the entry of the diamond.
1077  MergeBlocks(BBI, *BBI1);
1078  MergeBlocks(BBI, *BBI2);
1079
1080  // If the if-converted block fallthrough or unconditionally branch into the
1081  // tail block, and the tail block does not have other predecessors, then
1082  // fold the tail block in as well. Otherwise, unless it falls through to the
1083  // tail, add a unconditional branch to it.
1084  if (TailBB) {
1085    BBInfo TailBBI = BBAnalysis[TailBB->getNumber()];
1086    if (TailBB->pred_size() == 1 && !TailBBI.HasFallThrough) {
1087      BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
1088      MergeBlocks(BBI, TailBBI);
1089      TailBBI.IsDone = true;
1090    } else {
1091      InsertUncondBranch(BBI.BB, TailBB, TII);
1092      BBI.HasFallThrough = false;
1093    }
1094  }
1095
1096  RemoveExtraEdges(BBI);
1097
1098  // Update block info.
1099  BBI.IsDone = TrueBBI.IsDone = FalseBBI.IsDone = true;
1100  InvalidatePreds(BBI.BB);
1101
1102  // FIXME: Must maintain LiveIns.
1103  return true;
1104}
1105
1106/// PredicateBlock - Predicate instructions from the start of the block to the
1107/// specified end with the specified condition.
1108void IfConverter::PredicateBlock(BBInfo &BBI,
1109                                 MachineBasicBlock::iterator E,
1110                                 std::vector<MachineOperand> &Cond) {
1111  for (MachineBasicBlock::iterator I = BBI.BB->begin(); I != E; ++I) {
1112    if (TII->isPredicated(I))
1113      continue;
1114    if (!TII->PredicateInstruction(I, Cond)) {
1115      cerr << "Unable to predicate " << *I << "!\n";
1116      abort();
1117    }
1118  }
1119
1120  std::copy(Cond.begin(), Cond.end(), std::back_inserter(BBI.Predicate));
1121
1122  BBI.IsAnalyzed = false;
1123  BBI.NonPredSize = 0;
1124
1125  NumIfConvBBs++;
1126}
1127
1128/// CopyAndPredicateBlock - Copy and predicate instructions from source BB to
1129/// the destination block. Skip end of block branches if IgnoreBr is true.
1130void IfConverter::CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI,
1131                                        std::vector<MachineOperand> &Cond,
1132                                        bool IgnoreBr) {
1133  for (MachineBasicBlock::iterator I = FromBBI.BB->begin(),
1134         E = FromBBI.BB->end(); I != E; ++I) {
1135    const TargetInstrDesc &TID = I->getDesc();
1136    bool isPredicated = TII->isPredicated(I);
1137    // Do not copy the end of the block branches.
1138    if (IgnoreBr && !isPredicated && TID.isBranch())
1139      break;
1140
1141    MachineInstr *MI = I->clone();
1142    ToBBI.BB->insert(ToBBI.BB->end(), MI);
1143    ToBBI.NonPredSize++;
1144
1145    if (!isPredicated)
1146      if (!TII->PredicateInstruction(MI, Cond)) {
1147        cerr << "Unable to predicate " << *MI << "!\n";
1148        abort();
1149      }
1150  }
1151
1152  std::vector<MachineBasicBlock *> Succs(FromBBI.BB->succ_begin(),
1153                                         FromBBI.BB->succ_end());
1154  MachineBasicBlock *NBB = getNextBlock(FromBBI.BB);
1155  MachineBasicBlock *FallThrough = FromBBI.HasFallThrough ? NBB : NULL;
1156
1157  for (unsigned i = 0, e = Succs.size(); i != e; ++i) {
1158    MachineBasicBlock *Succ = Succs[i];
1159    // Fallthrough edge can't be transferred.
1160    if (Succ == FallThrough)
1161      continue;
1162    if (!ToBBI.BB->isSuccessor(Succ))
1163      ToBBI.BB->addSuccessor(Succ);
1164  }
1165
1166  std::copy(FromBBI.Predicate.begin(), FromBBI.Predicate.end(),
1167            std::back_inserter(ToBBI.Predicate));
1168  std::copy(Cond.begin(), Cond.end(), std::back_inserter(ToBBI.Predicate));
1169
1170  ToBBI.ClobbersPred |= FromBBI.ClobbersPred;
1171  ToBBI.IsAnalyzed = false;
1172
1173  NumDupBBs++;
1174}
1175
1176/// MergeBlocks - Move all instructions from FromBB to the end of ToBB.
1177///
1178void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI) {
1179  ToBBI.BB->splice(ToBBI.BB->end(),
1180                   FromBBI.BB, FromBBI.BB->begin(), FromBBI.BB->end());
1181
1182  // Redirect all branches to FromBB to ToBB.
1183  std::vector<MachineBasicBlock *> Preds(FromBBI.BB->pred_begin(),
1184                                         FromBBI.BB->pred_end());
1185  for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
1186    MachineBasicBlock *Pred = Preds[i];
1187    if (Pred == ToBBI.BB)
1188      continue;
1189    Pred->ReplaceUsesOfBlockWith(FromBBI.BB, ToBBI.BB);
1190  }
1191
1192  std::vector<MachineBasicBlock *> Succs(FromBBI.BB->succ_begin(),
1193                                         FromBBI.BB->succ_end());
1194  MachineBasicBlock *NBB = getNextBlock(FromBBI.BB);
1195  MachineBasicBlock *FallThrough = FromBBI.HasFallThrough ? NBB : NULL;
1196
1197  for (unsigned i = 0, e = Succs.size(); i != e; ++i) {
1198    MachineBasicBlock *Succ = Succs[i];
1199    // Fallthrough edge can't be transferred.
1200    if (Succ == FallThrough)
1201      continue;
1202    FromBBI.BB->removeSuccessor(Succ);
1203    if (!ToBBI.BB->isSuccessor(Succ))
1204      ToBBI.BB->addSuccessor(Succ);
1205  }
1206
1207  // Now FromBBI always fall through to the next block!
1208  if (NBB && !FromBBI.BB->isSuccessor(NBB))
1209    FromBBI.BB->addSuccessor(NBB);
1210
1211  std::copy(FromBBI.Predicate.begin(), FromBBI.Predicate.end(),
1212            std::back_inserter(ToBBI.Predicate));
1213  FromBBI.Predicate.clear();
1214
1215  ToBBI.NonPredSize += FromBBI.NonPredSize;
1216  FromBBI.NonPredSize = 0;
1217
1218  ToBBI.ClobbersPred |= FromBBI.ClobbersPred;
1219  ToBBI.HasFallThrough = FromBBI.HasFallThrough;
1220  ToBBI.IsAnalyzed = false;
1221  FromBBI.IsAnalyzed = false;
1222}
1223