LLVM  3.7.0
GlobalMerge.cpp
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1 //===-- GlobalMerge.cpp - Internal globals merging -----------------------===//
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 // This pass merges globals with internal linkage into one. This way all the
10 // globals which were merged into a biggest one can be addressed using offsets
11 // from the same base pointer (no need for separate base pointer for each of the
12 // global). Such a transformation can significantly reduce the register pressure
13 // when many globals are involved.
14 //
15 // For example, consider the code which touches several global variables at
16 // once:
17 //
18 // static int foo[N], bar[N], baz[N];
19 //
20 // for (i = 0; i < N; ++i) {
21 // foo[i] = bar[i] * baz[i];
22 // }
23 //
24 // On ARM the addresses of 3 arrays should be kept in the registers, thus
25 // this code has quite large register pressure (loop body):
26 //
27 // ldr r1, [r5], #4
28 // ldr r2, [r6], #4
29 // mul r1, r2, r1
30 // str r1, [r0], #4
31 //
32 // Pass converts the code to something like:
33 //
34 // static struct {
35 // int foo[N];
36 // int bar[N];
37 // int baz[N];
38 // } merged;
39 //
40 // for (i = 0; i < N; ++i) {
41 // merged.foo[i] = merged.bar[i] * merged.baz[i];
42 // }
43 //
44 // and in ARM code this becomes:
45 //
46 // ldr r0, [r5, #40]
47 // ldr r1, [r5, #80]
48 // mul r0, r1, r0
49 // str r0, [r5], #4
50 //
51 // note that we saved 2 registers here almostly "for free".
52 //
53 // However, merging globals can have tradeoffs:
54 // - it confuses debuggers, tools, and users
55 // - it makes linker optimizations less useful (order files, LOHs, ...)
56 // - it forces usage of indexed addressing (which isn't necessarily "free")
57 // - it can increase register pressure when the uses are disparate enough.
58 //
59 // We use heuristics to discover the best global grouping we can (cf cl::opts).
60 // ===---------------------------------------------------------------------===//
61 
62 #include "llvm/Transforms/Scalar.h"
63 #include "llvm/ADT/DenseMap.h"
65 #include "llvm/ADT/SmallPtrSet.h"
66 #include "llvm/ADT/Statistic.h"
67 #include "llvm/CodeGen/Passes.h"
68 #include "llvm/IR/Attributes.h"
69 #include "llvm/IR/Constants.h"
70 #include "llvm/IR/DataLayout.h"
71 #include "llvm/IR/DerivedTypes.h"
72 #include "llvm/IR/Function.h"
73 #include "llvm/IR/GlobalVariable.h"
74 #include "llvm/IR/Instructions.h"
75 #include "llvm/IR/Intrinsics.h"
76 #include "llvm/IR/Module.h"
77 #include "llvm/Pass.h"
79 #include "llvm/Support/Debug.h"
84 #include <algorithm>
85 using namespace llvm;
86 
87 #define DEBUG_TYPE "global-merge"
88 
89 // FIXME: This is only useful as a last-resort way to disable the pass.
90 static cl::opt<bool>
91 EnableGlobalMerge("enable-global-merge", cl::Hidden,
92  cl::desc("Enable the global merge pass"),
93  cl::init(true));
94 
96  "global-merge-group-by-use", cl::Hidden,
97  cl::desc("Improve global merge pass to look at uses"), cl::init(true));
98 
100  "global-merge-ignore-single-use", cl::Hidden,
101  cl::desc("Improve global merge pass to ignore globals only used alone"),
102  cl::init(true));
103 
104 static cl::opt<bool>
105 EnableGlobalMergeOnConst("global-merge-on-const", cl::Hidden,
106  cl::desc("Enable global merge pass on constants"),
107  cl::init(false));
108 
109 // FIXME: this could be a transitional option, and we probably need to remove
110 // it if only we are sure this optimization could always benefit all targets.
111 static cl::opt<bool>
112 EnableGlobalMergeOnExternal("global-merge-on-external", cl::Hidden,
113  cl::desc("Enable global merge pass on external linkage"),
114  cl::init(false));
115 
116 STATISTIC(NumMerged, "Number of globals merged");
117 namespace {
118  class GlobalMerge : public FunctionPass {
119  const TargetMachine *TM;
120  // FIXME: Infer the maximum possible offset depending on the actual users
121  // (these max offsets are different for the users inside Thumb or ARM
122  // functions), see the code that passes in the offset in the ARM backend
123  // for more information.
124  unsigned MaxOffset;
125 
126  /// Whether we should try to optimize for size only.
127  /// Currently, this applies a dead simple heuristic: only consider globals
128  /// used in minsize functions for merging.
129  /// FIXME: This could learn about optsize, and be used in the cost model.
130  bool OnlyOptimizeForSize;
131 
132  bool doMerge(SmallVectorImpl<GlobalVariable*> &Globals,
133  Module &M, bool isConst, unsigned AddrSpace) const;
134  /// \brief Merge everything in \p Globals for which the corresponding bit
135  /// in \p GlobalSet is set.
136  bool doMerge(SmallVectorImpl<GlobalVariable *> &Globals,
137  const BitVector &GlobalSet, Module &M, bool isConst,
138  unsigned AddrSpace) const;
139 
140  /// \brief Check if the given variable has been identified as must keep
141  /// \pre setMustKeepGlobalVariables must have been called on the Module that
142  /// contains GV
143  bool isMustKeepGlobalVariable(const GlobalVariable *GV) const {
144  return MustKeepGlobalVariables.count(GV);
145  }
146 
147  /// Collect every variables marked as "used" or used in a landing pad
148  /// instruction for this Module.
149  void setMustKeepGlobalVariables(Module &M);
150 
151  /// Collect every variables marked as "used"
153 
154  /// Keep track of the GlobalVariable that must not be merged away
155  SmallPtrSet<const GlobalVariable *, 16> MustKeepGlobalVariables;
156 
157  public:
158  static char ID; // Pass identification, replacement for typeid.
159  explicit GlobalMerge(const TargetMachine *TM = nullptr,
160  unsigned MaximalOffset = 0,
161  bool OnlyOptimizeForSize = false)
162  : FunctionPass(ID), TM(TM), MaxOffset(MaximalOffset),
163  OnlyOptimizeForSize(OnlyOptimizeForSize) {
165  }
166 
167  bool doInitialization(Module &M) override;
168  bool runOnFunction(Function &F) override;
169  bool doFinalization(Module &M) override;
170 
171  const char *getPassName() const override {
172  return "Merge internal globals";
173  }
174 
175  void getAnalysisUsage(AnalysisUsage &AU) const override {
176  AU.setPreservesCFG();
178  }
179  };
180 } // end anonymous namespace
181 
182 char GlobalMerge::ID = 0;
183 INITIALIZE_PASS_BEGIN(GlobalMerge, "global-merge", "Merge global variables",
184  false, false)
185 INITIALIZE_PASS_END(GlobalMerge, "global-merge", "Merge global variables",
186  false, false)
187 
188 bool GlobalMerge::doMerge(SmallVectorImpl<GlobalVariable*> &Globals,
189  Module &M, bool isConst, unsigned AddrSpace) const {
190  auto &DL = M.getDataLayout();
191  // FIXME: Find better heuristics
192  std::stable_sort(
193  Globals.begin(), Globals.end(),
194  [&DL](const GlobalVariable *GV1, const GlobalVariable *GV2) {
195  Type *Ty1 = cast<PointerType>(GV1->getType())->getElementType();
196  Type *Ty2 = cast<PointerType>(GV2->getType())->getElementType();
197 
198  return (DL.getTypeAllocSize(Ty1) < DL.getTypeAllocSize(Ty2));
199  });
200 
201  // If we want to just blindly group all globals together, do so.
202  if (!GlobalMergeGroupByUse) {
203  BitVector AllGlobals(Globals.size());
204  AllGlobals.set();
205  return doMerge(Globals, AllGlobals, M, isConst, AddrSpace);
206  }
207 
208  // If we want to be smarter, look at all uses of each global, to try to
209  // discover all sets of globals used together, and how many times each of
210  // these sets occured.
211  //
212  // Keep this reasonably efficient, by having an append-only list of all sets
213  // discovered so far (UsedGlobalSet), and mapping each "together-ness" unit of
214  // code (currently, a Function) to the set of globals seen so far that are
215  // used together in that unit (GlobalUsesByFunction).
216  //
217  // When we look at the Nth global, we now that any new set is either:
218  // - the singleton set {N}, containing this global only, or
219  // - the union of {N} and a previously-discovered set, containing some
220  // combination of the previous N-1 globals.
221  // Using that knowledge, when looking at the Nth global, we can keep:
222  // - a reference to the singleton set {N} (CurGVOnlySetIdx)
223  // - a list mapping each previous set to its union with {N} (EncounteredUGS),
224  // if it actually occurs.
225 
226  // We keep track of the sets of globals used together "close enough".
227  struct UsedGlobalSet {
228  UsedGlobalSet(size_t Size) : Globals(Size), UsageCount(1) {}
229  BitVector Globals;
230  unsigned UsageCount;
231  };
232 
233  // Each set is unique in UsedGlobalSets.
234  std::vector<UsedGlobalSet> UsedGlobalSets;
235 
236  // Avoid repeating the create-global-set pattern.
237  auto CreateGlobalSet = [&]() -> UsedGlobalSet & {
238  UsedGlobalSets.emplace_back(Globals.size());
239  return UsedGlobalSets.back();
240  };
241 
242  // The first set is the empty set.
243  CreateGlobalSet().UsageCount = 0;
244 
245  // We define "close enough" to be "in the same function".
246  // FIXME: Grouping uses by function is way too aggressive, so we should have
247  // a better metric for distance between uses.
248  // The obvious alternative would be to group by BasicBlock, but that's in
249  // turn too conservative..
250  // Anything in between wouldn't be trivial to compute, so just stick with
251  // per-function grouping.
252 
253  // The value type is an index into UsedGlobalSets.
254  // The default (0) conveniently points to the empty set.
255  DenseMap<Function *, size_t /*UsedGlobalSetIdx*/> GlobalUsesByFunction;
256 
257  // Now, look at each merge-eligible global in turn.
258 
259  // Keep track of the sets we already encountered to which we added the
260  // current global.
261  // Each element matches the same-index element in UsedGlobalSets.
262  // This lets us efficiently tell whether a set has already been expanded to
263  // include the current global.
264  std::vector<size_t> EncounteredUGS;
265 
266  for (size_t GI = 0, GE = Globals.size(); GI != GE; ++GI) {
267  GlobalVariable *GV = Globals[GI];
268 
269  // Reset the encountered sets for this global...
270  std::fill(EncounteredUGS.begin(), EncounteredUGS.end(), 0);
271  // ...and grow it in case we created new sets for the previous global.
272  EncounteredUGS.resize(UsedGlobalSets.size());
273 
274  // We might need to create a set that only consists of the current global.
275  // Keep track of its index into UsedGlobalSets.
276  size_t CurGVOnlySetIdx = 0;
277 
278  // For each global, look at all its Uses.
279  for (auto &U : GV->uses()) {
280  // This Use might be a ConstantExpr. We're interested in Instruction
281  // users, so look through ConstantExpr...
282  Use *UI, *UE;
283  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U.getUser())) {
284  if (CE->use_empty())
285  continue;
286  UI = &*CE->use_begin();
287  UE = nullptr;
288  } else if (isa<Instruction>(U.getUser())) {
289  UI = &U;
290  UE = UI->getNext();
291  } else {
292  continue;
293  }
294 
295  // ...to iterate on all the instruction users of the global.
296  // Note that we iterate on Uses and not on Users to be able to getNext().
297  for (; UI != UE; UI = UI->getNext()) {
298  Instruction *I = dyn_cast<Instruction>(UI->getUser());
299  if (!I)
300  continue;
301 
302  Function *ParentFn = I->getParent()->getParent();
303 
304  // If we're only optimizing for size, ignore non-minsize functions.
305  if (OnlyOptimizeForSize &&
307  continue;
308 
309  size_t UGSIdx = GlobalUsesByFunction[ParentFn];
310 
311  // If this is the first global the basic block uses, map it to the set
312  // consisting of this global only.
313  if (!UGSIdx) {
314  // If that set doesn't exist yet, create it.
315  if (!CurGVOnlySetIdx) {
316  CurGVOnlySetIdx = UsedGlobalSets.size();
317  CreateGlobalSet().Globals.set(GI);
318  } else {
319  ++UsedGlobalSets[CurGVOnlySetIdx].UsageCount;
320  }
321 
322  GlobalUsesByFunction[ParentFn] = CurGVOnlySetIdx;
323  continue;
324  }
325 
326  // If we already encountered this BB, just increment the counter.
327  if (UsedGlobalSets[UGSIdx].Globals.test(GI)) {
328  ++UsedGlobalSets[UGSIdx].UsageCount;
329  continue;
330  }
331 
332  // If not, the previous set wasn't actually used in this function.
333  --UsedGlobalSets[UGSIdx].UsageCount;
334 
335  // If we already expanded the previous set to include this global, just
336  // reuse that expanded set.
337  if (size_t ExpandedIdx = EncounteredUGS[UGSIdx]) {
338  ++UsedGlobalSets[ExpandedIdx].UsageCount;
339  GlobalUsesByFunction[ParentFn] = ExpandedIdx;
340  continue;
341  }
342 
343  // If not, create a new set consisting of the union of the previous set
344  // and this global. Mark it as encountered, so we can reuse it later.
345  GlobalUsesByFunction[ParentFn] = EncounteredUGS[UGSIdx] =
346  UsedGlobalSets.size();
347 
348  UsedGlobalSet &NewUGS = CreateGlobalSet();
349  NewUGS.Globals.set(GI);
350  NewUGS.Globals |= UsedGlobalSets[UGSIdx].Globals;
351  }
352  }
353  }
354 
355  // Now we found a bunch of sets of globals used together. We accumulated
356  // the number of times we encountered the sets (i.e., the number of blocks
357  // that use that exact set of globals).
358  //
359  // Multiply that by the size of the set to give us a crude profitability
360  // metric.
361  std::sort(UsedGlobalSets.begin(), UsedGlobalSets.end(),
362  [](const UsedGlobalSet &UGS1, const UsedGlobalSet &UGS2) {
363  return UGS1.Globals.count() * UGS1.UsageCount <
364  UGS2.Globals.count() * UGS2.UsageCount;
365  });
366 
367  // We can choose to merge all globals together, but ignore globals never used
368  // with another global. This catches the obviously non-profitable cases of
369  // having a single global, but is aggressive enough for any other case.
371  BitVector AllGlobals(Globals.size());
372  for (size_t i = 0, e = UsedGlobalSets.size(); i != e; ++i) {
373  const UsedGlobalSet &UGS = UsedGlobalSets[e - i - 1];
374  if (UGS.UsageCount == 0)
375  continue;
376  if (UGS.Globals.count() > 1)
377  AllGlobals |= UGS.Globals;
378  }
379  return doMerge(Globals, AllGlobals, M, isConst, AddrSpace);
380  }
381 
382  // Starting from the sets with the best (=biggest) profitability, find a
383  // good combination.
384  // The ideal (and expensive) solution can only be found by trying all
385  // combinations, looking for the one with the best profitability.
386  // Don't be smart about it, and just pick the first compatible combination,
387  // starting with the sets with the best profitability.
388  BitVector PickedGlobals(Globals.size());
389  bool Changed = false;
390 
391  for (size_t i = 0, e = UsedGlobalSets.size(); i != e; ++i) {
392  const UsedGlobalSet &UGS = UsedGlobalSets[e - i - 1];
393  if (UGS.UsageCount == 0)
394  continue;
395  if (PickedGlobals.anyCommon(UGS.Globals))
396  continue;
397  PickedGlobals |= UGS.Globals;
398  // If the set only contains one global, there's no point in merging.
399  // Ignore the global for inclusion in other sets though, so keep it in
400  // PickedGlobals.
401  if (UGS.Globals.count() < 2)
402  continue;
403  Changed |= doMerge(Globals, UGS.Globals, M, isConst, AddrSpace);
404  }
405 
406  return Changed;
407 }
408 
409 bool GlobalMerge::doMerge(SmallVectorImpl<GlobalVariable *> &Globals,
410  const BitVector &GlobalSet, Module &M, bool isConst,
411  unsigned AddrSpace) const {
412 
413  Type *Int32Ty = Type::getInt32Ty(M.getContext());
414  auto &DL = M.getDataLayout();
415 
416  assert(Globals.size() > 1);
417 
418  DEBUG(dbgs() << " Trying to merge set, starts with #"
419  << GlobalSet.find_first() << "\n");
420 
421  ssize_t i = GlobalSet.find_first();
422  while (i != -1) {
423  ssize_t j = 0;
424  uint64_t MergedSize = 0;
425  std::vector<Type*> Tys;
426  std::vector<Constant*> Inits;
427 
428  bool HasExternal = false;
429  GlobalVariable *TheFirstExternal = 0;
430  for (j = i; j != -1; j = GlobalSet.find_next(j)) {
431  Type *Ty = Globals[j]->getType()->getElementType();
432  MergedSize += DL.getTypeAllocSize(Ty);
433  if (MergedSize > MaxOffset) {
434  break;
435  }
436  Tys.push_back(Ty);
437  Inits.push_back(Globals[j]->getInitializer());
438 
439  if (Globals[j]->hasExternalLinkage() && !HasExternal) {
440  HasExternal = true;
441  TheFirstExternal = Globals[j];
442  }
443  }
444 
445  // If merged variables doesn't have external linkage, we needn't to expose
446  // the symbol after merging.
447  GlobalValue::LinkageTypes Linkage = HasExternal
450 
451  StructType *MergedTy = StructType::get(M.getContext(), Tys);
452  Constant *MergedInit = ConstantStruct::get(MergedTy, Inits);
453 
454  // If merged variables have external linkage, we use symbol name of the
455  // first variable merged as the suffix of global symbol name. This would
456  // be able to avoid the link-time naming conflict for globalm symbols.
457  GlobalVariable *MergedGV = new GlobalVariable(
458  M, MergedTy, isConst, Linkage, MergedInit,
459  HasExternal ? "_MergedGlobals_" + TheFirstExternal->getName()
460  : "_MergedGlobals",
461  nullptr, GlobalVariable::NotThreadLocal, AddrSpace);
462 
463  for (ssize_t k = i, idx = 0; k != j; k = GlobalSet.find_next(k)) {
464  GlobalValue::LinkageTypes Linkage = Globals[k]->getLinkage();
465  std::string Name = Globals[k]->getName();
466 
467  Constant *Idx[2] = {
468  ConstantInt::get(Int32Ty, 0),
469  ConstantInt::get(Int32Ty, idx++)
470  };
471  Constant *GEP =
472  ConstantExpr::getInBoundsGetElementPtr(MergedTy, MergedGV, Idx);
473  Globals[k]->replaceAllUsesWith(GEP);
474  Globals[k]->eraseFromParent();
475 
476  if (Linkage != GlobalValue::InternalLinkage) {
477  // Generate a new alias...
478  auto *PTy = cast<PointerType>(GEP->getType());
479  GlobalAlias::create(PTy, Linkage, Name, GEP, &M);
480  }
481 
482  NumMerged++;
483  }
484  i = j;
485  }
486 
487  return true;
488 }
489 
491  // Extract global variables from llvm.used array
492  const GlobalVariable *GV = M.getGlobalVariable("llvm.used");
493  if (!GV || !GV->hasInitializer()) return;
494 
495  // Should be an array of 'i8*'.
496  const ConstantArray *InitList = cast<ConstantArray>(GV->getInitializer());
497 
498  for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
499  if (const GlobalVariable *G =
500  dyn_cast<GlobalVariable>(InitList->getOperand(i)->stripPointerCasts()))
501  MustKeepGlobalVariables.insert(G);
502 }
503 
504 void GlobalMerge::setMustKeepGlobalVariables(Module &M) {
506 
507  for (Module::iterator IFn = M.begin(), IEndFn = M.end(); IFn != IEndFn;
508  ++IFn) {
509  for (Function::iterator IBB = IFn->begin(), IEndBB = IFn->end();
510  IBB != IEndBB; ++IBB) {
511  // Follow the invoke link to find the landing pad instruction
512  const InvokeInst *II = dyn_cast<InvokeInst>(IBB->getTerminator());
513  if (!II) continue;
514 
515  const LandingPadInst *LPInst = II->getUnwindDest()->getLandingPadInst();
516  // Look for globals in the clauses of the landing pad instruction
517  for (unsigned Idx = 0, NumClauses = LPInst->getNumClauses();
518  Idx != NumClauses; ++Idx)
519  if (const GlobalVariable *GV =
520  dyn_cast<GlobalVariable>(LPInst->getClause(Idx)
521  ->stripPointerCasts()))
522  MustKeepGlobalVariables.insert(GV);
523  }
524  }
525 }
526 
527 bool GlobalMerge::doInitialization(Module &M) {
528  if (!EnableGlobalMerge)
529  return false;
530 
531  auto &DL = M.getDataLayout();
533  BSSGlobals;
534  bool Changed = false;
535  setMustKeepGlobalVariables(M);
536 
537  // Grab all non-const globals.
539  E = M.global_end(); I != E; ++I) {
540  // Merge is safe for "normal" internal or external globals only
541  if (I->isDeclaration() || I->isThreadLocal() || I->hasSection())
542  continue;
543 
544  if (!(EnableGlobalMergeOnExternal && I->hasExternalLinkage()) &&
545  !I->hasInternalLinkage())
546  continue;
547 
548  PointerType *PT = dyn_cast<PointerType>(I->getType());
549  assert(PT && "Global variable is not a pointer!");
550 
551  unsigned AddressSpace = PT->getAddressSpace();
552 
553  // Ignore fancy-aligned globals for now.
554  unsigned Alignment = DL.getPreferredAlignment(I);
555  Type *Ty = I->getType()->getElementType();
556  if (Alignment > DL.getABITypeAlignment(Ty))
557  continue;
558 
559  // Ignore all 'special' globals.
560  if (I->getName().startswith("llvm.") ||
561  I->getName().startswith(".llvm."))
562  continue;
563 
564  // Ignore all "required" globals:
565  if (isMustKeepGlobalVariable(I))
566  continue;
567 
568  if (DL.getTypeAllocSize(Ty) < MaxOffset) {
570  BSSGlobals[AddressSpace].push_back(I);
571  else if (I->isConstant())
572  ConstGlobals[AddressSpace].push_back(I);
573  else
574  Globals[AddressSpace].push_back(I);
575  }
576  }
577 
578  for (DenseMap<unsigned, SmallVector<GlobalVariable*, 16> >::iterator
579  I = Globals.begin(), E = Globals.end(); I != E; ++I)
580  if (I->second.size() > 1)
581  Changed |= doMerge(I->second, M, false, I->first);
582 
583  for (DenseMap<unsigned, SmallVector<GlobalVariable*, 16> >::iterator
584  I = BSSGlobals.begin(), E = BSSGlobals.end(); I != E; ++I)
585  if (I->second.size() > 1)
586  Changed |= doMerge(I->second, M, false, I->first);
587 
589  for (DenseMap<unsigned, SmallVector<GlobalVariable*, 16> >::iterator
590  I = ConstGlobals.begin(), E = ConstGlobals.end(); I != E; ++I)
591  if (I->second.size() > 1)
592  Changed |= doMerge(I->second, M, true, I->first);
593 
594  return Changed;
595 }
596 
597 bool GlobalMerge::runOnFunction(Function &F) {
598  return false;
599 }
600 
601 bool GlobalMerge::doFinalization(Module &M) {
602  MustKeepGlobalVariables.clear();
603  return false;
604 }
605 
607  bool OnlyOptimizeForSize) {
608  return new GlobalMerge(TM, Offset, OnlyOptimizeForSize);
609 }
Pass interface - Implemented by all 'passes'.
Definition: Pass.h:82
BitVector & set()
Definition: BitVector.h:218
static SectionKind getKindForGlobal(const GlobalValue *GV, const TargetMachine &TM)
Classify the specified global variable into a set of target independent categories embodied in Sectio...
int find_first() const
find_first - Returns the index of the first set bit, -1 if none of the bits are set.
Definition: BitVector.h:156
iterator_range< use_iterator > uses()
Definition: Value.h:283
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
STATISTIC(NumFunctions,"Total number of functions")
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:114
Constant * getClause(unsigned Idx) const
Get the value of the clause at index Idx.
static cl::opt< bool > GlobalMergeGroupByUse("global-merge-group-by-use", cl::Hidden, cl::desc("Improve global merge pass to look at uses"), cl::init(true))
unsigned getNumOperands() const
Definition: User.h:138
int find_next(unsigned Prev) const
find_next - Returns the index of the next set bit following the "Prev" bit.
Definition: BitVector.h:165
virtual void getAnalysisUsage(AnalysisUsage &) const
getAnalysisUsage - This function should be overriden by passes that need analysis information to do t...
Definition: Pass.cpp:78
INITIALIZE_PASS_BEGIN(GlobalMerge,"global-merge","Merge global variables", false, false) INITIALIZE_PASS_END(GlobalMerge
Externally visible function.
Definition: GlobalValue.h:40
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:111
F(f)
unsigned getAddressSpace() const
Return the address space of the Pointer type.
Definition: DerivedTypes.h:472
Hexagon Common GEP
const Constant * getInitializer() const
getInitializer - Return the initializer for this global variable.
StringRef getName() const
Return a constant reference to the value's name.
Definition: Value.cpp:188
global Merge global variables
global merge
StructType - Class to represent struct types.
Definition: DerivedTypes.h:191
A Use represents the edge between a Value definition and its users.
Definition: Use.h:69
#define INITIALIZE_PASS_END(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:75
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APInt.h:33
This file contains the simple types necessary to represent the attributes associated with functions a...
static cl::opt< bool > EnableGlobalMerge("enable-global-merge", cl::Hidden, cl::desc("Enable the global merge pass"), cl::init(true))
#define G(x, y, z)
Definition: MD5.cpp:52
global_iterator global_begin()
Definition: Module.h:552
ConstantExpr - a constant value that is initialized with an expression using other constant values...
Definition: Constants.h:852
unsigned getNumClauses() const
getNumClauses - Get the number of clauses for this landing pad.
PointerType - Class to represent pointers.
Definition: DerivedTypes.h:449
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:325
static Constant * getInBoundsGetElementPtr(Type *Ty, Constant *C, ArrayRef< Constant * > IdxList)
Create an "inbounds" getelementptr.
Definition: Constants.h:1115
LandingPadInst - The landingpad instruction holds all of the information necessary to generate correc...
Constant * stripPointerCasts()
Definition: Constant.h:170
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
static GlobalAlias * create(PointerType *Ty, LinkageTypes Linkage, const Twine &Name, Constant *Aliasee, Module *Parent)
If a parent module is specified, the alias is automatically inserted into the end of the specified mo...
Definition: Globals.cpp:243
This is an important base class in LLVM.
Definition: Constant.h:41
This file contains the declarations for the subclasses of Constant, which represent the different fla...
LandingPadInst * getLandingPadInst()
Return the landingpad instruction associated with the landing pad.
Definition: BasicBlock.cpp:418
Represent the analysis usage information of a pass.
size_t size() const
Definition: Function.h:462
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:294
Value * getOperand(unsigned i) const
Definition: User.h:118
static Constant * get(StructType *T, ArrayRef< Constant * > V)
Definition: Constants.cpp:1008
global Merge global false
bool isBSSLocal() const
Definition: SectionKind.h:176
global_iterator global_end()
Definition: Module.h:554
BasicBlock * getUnwindDest() const
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:299
static StructType * get(LLVMContext &Context, ArrayRef< Type * > Elements, bool isPacked=false)
StructType::get - This static method is the primary way to create a literal StructType.
Definition: Type.cpp:404
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:861
Module.h This file contains the declarations for the Module class.
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:222
AddressSpace
Definition: NVPTXBaseInfo.h:22
static cl::opt< bool > GlobalMergeIgnoreSingleUse("global-merge-ignore-single-use", cl::Hidden, cl::desc("Improve global merge pass to ignore globals only used alone"), cl::init(true))
Value * stripPointerCasts()
Strip off pointer casts, all-zero GEPs, and aliases.
Definition: Value.cpp:458
static Constant * get(Type *Ty, uint64_t V, bool isSigned=false)
If Ty is a vector type, return a Constant with a splat of the given value.
Definition: Constants.cpp:582
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:263
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:123
ConstantArray - Constant Array Declarations.
Definition: Constants.h:356
bool hasInitializer() const
Definitions have initializers, declarations don't.
LinkageTypes
An enumeration for the kinds of linkage for global values.
Definition: GlobalValue.h:39
LLVM_ATTRIBUTE_UNUSED_RESULT std::enable_if< !is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:285
PointerType * getType() const
Global values are always pointers.
Definition: GlobalValue.h:185
const DataLayout & getDataLayout() const
Get the data layout for the module's target platform.
Definition: Module.cpp:372
iterator end()
Definition: Module.h:571
bool hasFnAttribute(Attribute::AttrKind Kind) const
Return true if the function has the attribute.
Definition: Function.h:217
static IntegerType * getInt32Ty(LLVMContext &C)
Definition: Type.cpp:239
#define I(x, y, z)
Definition: MD5.cpp:54
iterator begin()
Definition: Module.h:569
static cl::opt< bool > EnableGlobalMergeOnExternal("global-merge-on-external", cl::Hidden, cl::desc("Enable global merge pass on external linkage"), cl::init(false))
Rename collisions when linking (static functions).
Definition: GlobalValue.h:47
static cl::opt< bool > EnableGlobalMergeOnConst("global-merge-on-const", cl::Hidden, cl::desc("Enable global merge pass on constants"), cl::init(false))
void initializeGlobalMergePass(PassRegistry &)
GlobalVariable * collectUsedGlobalVariables(Module &M, SmallPtrSetImpl< GlobalValue * > &Set, bool CompilerUsed)
Given "llvm.used" or "llvm.compiler.used" as a global name, collect the initializer elements of that ...
Definition: ModuleUtils.cpp:82
InvokeInst - Invoke instruction.
#define DEBUG(X)
Definition: Debug.h:92
Primary interface to the complete machine description for the target machine.
const BasicBlock * getParent() const
Definition: Instruction.h:72
GlobalVariable * getGlobalVariable(StringRef Name) const
Look up the specified global variable in the module symbol table.
Definition: Module.h:381
Pass * createGlobalMergePass(const TargetMachine *TM, unsigned MaximalOffset, bool OnlyOptimizeForSize=false)
LLVMContext & getContext() const
Get the global data context.
Definition: Module.h:265
This file describes how to lower LLVM code to machine code.
Function must be optimized for size first.
Definition: Attributes.h:80