LLVM  4.0.0
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/ADT/DenseMap.h"
64 #include "llvm/ADT/SmallPtrSet.h"
65 #include "llvm/ADT/Statistic.h"
66 #include "llvm/CodeGen/Passes.h"
67 #include "llvm/IR/Attributes.h"
68 #include "llvm/IR/Constants.h"
69 #include "llvm/IR/DataLayout.h"
70 #include "llvm/IR/DerivedTypes.h"
71 #include "llvm/IR/Function.h"
72 #include "llvm/IR/GlobalVariable.h"
73 #include "llvm/IR/Instructions.h"
74 #include "llvm/IR/Intrinsics.h"
75 #include "llvm/IR/Module.h"
76 #include "llvm/Pass.h"
78 #include "llvm/Support/Debug.h"
83 #include <algorithm>
84 using namespace llvm;
85 
86 #define DEBUG_TYPE "global-merge"
87 
88 // FIXME: This is only useful as a last-resort way to disable the pass.
89 static cl::opt<bool>
90 EnableGlobalMerge("enable-global-merge", cl::Hidden,
91  cl::desc("Enable the global merge pass"),
92  cl::init(true));
93 
94 static cl::opt<unsigned>
95 GlobalMergeMaxOffset("global-merge-max-offset", cl::Hidden,
96  cl::desc("Set maximum offset for global merge pass"),
97  cl::init(0));
98 
100  "global-merge-group-by-use", cl::Hidden,
101  cl::desc("Improve global merge pass to look at uses"), cl::init(true));
102 
104  "global-merge-ignore-single-use", cl::Hidden,
105  cl::desc("Improve global merge pass to ignore globals only used alone"),
106  cl::init(true));
107 
108 static cl::opt<bool>
109 EnableGlobalMergeOnConst("global-merge-on-const", cl::Hidden,
110  cl::desc("Enable global merge pass on constants"),
111  cl::init(false));
112 
113 // FIXME: this could be a transitional option, and we probably need to remove
114 // it if only we are sure this optimization could always benefit all targets.
116 EnableGlobalMergeOnExternal("global-merge-on-external", cl::Hidden,
117  cl::desc("Enable global merge pass on external linkage"));
118 
119 STATISTIC(NumMerged, "Number of globals merged");
120 namespace {
121  class GlobalMerge : public FunctionPass {
122  const TargetMachine *TM;
123  // FIXME: Infer the maximum possible offset depending on the actual users
124  // (these max offsets are different for the users inside Thumb or ARM
125  // functions), see the code that passes in the offset in the ARM backend
126  // for more information.
127  unsigned MaxOffset;
128 
129  /// Whether we should try to optimize for size only.
130  /// Currently, this applies a dead simple heuristic: only consider globals
131  /// used in minsize functions for merging.
132  /// FIXME: This could learn about optsize, and be used in the cost model.
133  bool OnlyOptimizeForSize;
134 
135  /// Whether we should merge global variables that have external linkage.
136  bool MergeExternalGlobals;
137 
138  bool IsMachO;
139 
140  bool doMerge(SmallVectorImpl<GlobalVariable*> &Globals,
141  Module &M, bool isConst, unsigned AddrSpace) const;
142  /// \brief Merge everything in \p Globals for which the corresponding bit
143  /// in \p GlobalSet is set.
144  bool doMerge(const SmallVectorImpl<GlobalVariable *> &Globals,
145  const BitVector &GlobalSet, Module &M, bool isConst,
146  unsigned AddrSpace) const;
147 
148  /// \brief Check if the given variable has been identified as must keep
149  /// \pre setMustKeepGlobalVariables must have been called on the Module that
150  /// contains GV
151  bool isMustKeepGlobalVariable(const GlobalVariable *GV) const {
152  return MustKeepGlobalVariables.count(GV);
153  }
154 
155  /// Collect every variables marked as "used" or used in a landing pad
156  /// instruction for this Module.
157  void setMustKeepGlobalVariables(Module &M);
158 
159  /// Collect every variables marked as "used"
161 
162  /// Keep track of the GlobalVariable that must not be merged away
163  SmallPtrSet<const GlobalVariable *, 16> MustKeepGlobalVariables;
164 
165  public:
166  static char ID; // Pass identification, replacement for typeid.
167  explicit GlobalMerge()
168  : FunctionPass(ID), TM(nullptr), MaxOffset(GlobalMergeMaxOffset),
169  OnlyOptimizeForSize(false), MergeExternalGlobals(false) {
171  }
172 
173  explicit GlobalMerge(const TargetMachine *TM, unsigned MaximalOffset,
174  bool OnlyOptimizeForSize, bool MergeExternalGlobals)
175  : FunctionPass(ID), TM(TM), MaxOffset(MaximalOffset),
176  OnlyOptimizeForSize(OnlyOptimizeForSize),
177  MergeExternalGlobals(MergeExternalGlobals) {
179  }
180 
181  bool doInitialization(Module &M) override;
182  bool runOnFunction(Function &F) override;
183  bool doFinalization(Module &M) override;
184 
185  StringRef getPassName() const override { return "Merge internal globals"; }
186 
187  void getAnalysisUsage(AnalysisUsage &AU) const override {
188  AU.setPreservesCFG();
190  }
191  };
192 } // end anonymous namespace
193 
194 char GlobalMerge::ID = 0;
195 INITIALIZE_PASS_BEGIN(GlobalMerge, "global-merge", "Merge global variables",
196  false, false)
197 INITIALIZE_PASS_END(GlobalMerge, "global-merge", "Merge global variables",
198  false, false)
199 
200 bool GlobalMerge::doMerge(SmallVectorImpl<GlobalVariable*> &Globals,
201  Module &M, bool isConst, unsigned AddrSpace) const {
202  auto &DL = M.getDataLayout();
203  // FIXME: Find better heuristics
204  std::stable_sort(Globals.begin(), Globals.end(),
205  [&DL](const GlobalVariable *GV1, const GlobalVariable *GV2) {
206  return DL.getTypeAllocSize(GV1->getValueType()) <
207  DL.getTypeAllocSize(GV2->getValueType());
208  });
209 
210  // If we want to just blindly group all globals together, do so.
211  if (!GlobalMergeGroupByUse) {
212  BitVector AllGlobals(Globals.size());
213  AllGlobals.set();
214  return doMerge(Globals, AllGlobals, M, isConst, AddrSpace);
215  }
216 
217  // If we want to be smarter, look at all uses of each global, to try to
218  // discover all sets of globals used together, and how many times each of
219  // these sets occurred.
220  //
221  // Keep this reasonably efficient, by having an append-only list of all sets
222  // discovered so far (UsedGlobalSet), and mapping each "together-ness" unit of
223  // code (currently, a Function) to the set of globals seen so far that are
224  // used together in that unit (GlobalUsesByFunction).
225  //
226  // When we look at the Nth global, we now that any new set is either:
227  // - the singleton set {N}, containing this global only, or
228  // - the union of {N} and a previously-discovered set, containing some
229  // combination of the previous N-1 globals.
230  // Using that knowledge, when looking at the Nth global, we can keep:
231  // - a reference to the singleton set {N} (CurGVOnlySetIdx)
232  // - a list mapping each previous set to its union with {N} (EncounteredUGS),
233  // if it actually occurs.
234 
235  // We keep track of the sets of globals used together "close enough".
236  struct UsedGlobalSet {
237  UsedGlobalSet(size_t Size) : Globals(Size), UsageCount(1) {}
238  BitVector Globals;
239  unsigned UsageCount;
240  };
241 
242  // Each set is unique in UsedGlobalSets.
243  std::vector<UsedGlobalSet> UsedGlobalSets;
244 
245  // Avoid repeating the create-global-set pattern.
246  auto CreateGlobalSet = [&]() -> UsedGlobalSet & {
247  UsedGlobalSets.emplace_back(Globals.size());
248  return UsedGlobalSets.back();
249  };
250 
251  // The first set is the empty set.
252  CreateGlobalSet().UsageCount = 0;
253 
254  // We define "close enough" to be "in the same function".
255  // FIXME: Grouping uses by function is way too aggressive, so we should have
256  // a better metric for distance between uses.
257  // The obvious alternative would be to group by BasicBlock, but that's in
258  // turn too conservative..
259  // Anything in between wouldn't be trivial to compute, so just stick with
260  // per-function grouping.
261 
262  // The value type is an index into UsedGlobalSets.
263  // The default (0) conveniently points to the empty set.
264  DenseMap<Function *, size_t /*UsedGlobalSetIdx*/> GlobalUsesByFunction;
265 
266  // Now, look at each merge-eligible global in turn.
267 
268  // Keep track of the sets we already encountered to which we added the
269  // current global.
270  // Each element matches the same-index element in UsedGlobalSets.
271  // This lets us efficiently tell whether a set has already been expanded to
272  // include the current global.
273  std::vector<size_t> EncounteredUGS;
274 
275  for (size_t GI = 0, GE = Globals.size(); GI != GE; ++GI) {
276  GlobalVariable *GV = Globals[GI];
277 
278  // Reset the encountered sets for this global...
279  std::fill(EncounteredUGS.begin(), EncounteredUGS.end(), 0);
280  // ...and grow it in case we created new sets for the previous global.
281  EncounteredUGS.resize(UsedGlobalSets.size());
282 
283  // We might need to create a set that only consists of the current global.
284  // Keep track of its index into UsedGlobalSets.
285  size_t CurGVOnlySetIdx = 0;
286 
287  // For each global, look at all its Uses.
288  for (auto &U : GV->uses()) {
289  // This Use might be a ConstantExpr. We're interested in Instruction
290  // users, so look through ConstantExpr...
291  Use *UI, *UE;
292  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U.getUser())) {
293  if (CE->use_empty())
294  continue;
295  UI = &*CE->use_begin();
296  UE = nullptr;
297  } else if (isa<Instruction>(U.getUser())) {
298  UI = &U;
299  UE = UI->getNext();
300  } else {
301  continue;
302  }
303 
304  // ...to iterate on all the instruction users of the global.
305  // Note that we iterate on Uses and not on Users to be able to getNext().
306  for (; UI != UE; UI = UI->getNext()) {
307  Instruction *I = dyn_cast<Instruction>(UI->getUser());
308  if (!I)
309  continue;
310 
311  Function *ParentFn = I->getParent()->getParent();
312 
313  // If we're only optimizing for size, ignore non-minsize functions.
314  if (OnlyOptimizeForSize && !ParentFn->optForMinSize())
315  continue;
316 
317  size_t UGSIdx = GlobalUsesByFunction[ParentFn];
318 
319  // If this is the first global the basic block uses, map it to the set
320  // consisting of this global only.
321  if (!UGSIdx) {
322  // If that set doesn't exist yet, create it.
323  if (!CurGVOnlySetIdx) {
324  CurGVOnlySetIdx = UsedGlobalSets.size();
325  CreateGlobalSet().Globals.set(GI);
326  } else {
327  ++UsedGlobalSets[CurGVOnlySetIdx].UsageCount;
328  }
329 
330  GlobalUsesByFunction[ParentFn] = CurGVOnlySetIdx;
331  continue;
332  }
333 
334  // If we already encountered this BB, just increment the counter.
335  if (UsedGlobalSets[UGSIdx].Globals.test(GI)) {
336  ++UsedGlobalSets[UGSIdx].UsageCount;
337  continue;
338  }
339 
340  // If not, the previous set wasn't actually used in this function.
341  --UsedGlobalSets[UGSIdx].UsageCount;
342 
343  // If we already expanded the previous set to include this global, just
344  // reuse that expanded set.
345  if (size_t ExpandedIdx = EncounteredUGS[UGSIdx]) {
346  ++UsedGlobalSets[ExpandedIdx].UsageCount;
347  GlobalUsesByFunction[ParentFn] = ExpandedIdx;
348  continue;
349  }
350 
351  // If not, create a new set consisting of the union of the previous set
352  // and this global. Mark it as encountered, so we can reuse it later.
353  GlobalUsesByFunction[ParentFn] = EncounteredUGS[UGSIdx] =
354  UsedGlobalSets.size();
355 
356  UsedGlobalSet &NewUGS = CreateGlobalSet();
357  NewUGS.Globals.set(GI);
358  NewUGS.Globals |= UsedGlobalSets[UGSIdx].Globals;
359  }
360  }
361  }
362 
363  // Now we found a bunch of sets of globals used together. We accumulated
364  // the number of times we encountered the sets (i.e., the number of blocks
365  // that use that exact set of globals).
366  //
367  // Multiply that by the size of the set to give us a crude profitability
368  // metric.
369  std::sort(UsedGlobalSets.begin(), UsedGlobalSets.end(),
370  [](const UsedGlobalSet &UGS1, const UsedGlobalSet &UGS2) {
371  return UGS1.Globals.count() * UGS1.UsageCount <
372  UGS2.Globals.count() * UGS2.UsageCount;
373  });
374 
375  // We can choose to merge all globals together, but ignore globals never used
376  // with another global. This catches the obviously non-profitable cases of
377  // having a single global, but is aggressive enough for any other case.
379  BitVector AllGlobals(Globals.size());
380  for (size_t i = 0, e = UsedGlobalSets.size(); i != e; ++i) {
381  const UsedGlobalSet &UGS = UsedGlobalSets[e - i - 1];
382  if (UGS.UsageCount == 0)
383  continue;
384  if (UGS.Globals.count() > 1)
385  AllGlobals |= UGS.Globals;
386  }
387  return doMerge(Globals, AllGlobals, M, isConst, AddrSpace);
388  }
389 
390  // Starting from the sets with the best (=biggest) profitability, find a
391  // good combination.
392  // The ideal (and expensive) solution can only be found by trying all
393  // combinations, looking for the one with the best profitability.
394  // Don't be smart about it, and just pick the first compatible combination,
395  // starting with the sets with the best profitability.
396  BitVector PickedGlobals(Globals.size());
397  bool Changed = false;
398 
399  for (size_t i = 0, e = UsedGlobalSets.size(); i != e; ++i) {
400  const UsedGlobalSet &UGS = UsedGlobalSets[e - i - 1];
401  if (UGS.UsageCount == 0)
402  continue;
403  if (PickedGlobals.anyCommon(UGS.Globals))
404  continue;
405  PickedGlobals |= UGS.Globals;
406  // If the set only contains one global, there's no point in merging.
407  // Ignore the global for inclusion in other sets though, so keep it in
408  // PickedGlobals.
409  if (UGS.Globals.count() < 2)
410  continue;
411  Changed |= doMerge(Globals, UGS.Globals, M, isConst, AddrSpace);
412  }
413 
414  return Changed;
415 }
416 
417 bool GlobalMerge::doMerge(const SmallVectorImpl<GlobalVariable *> &Globals,
418  const BitVector &GlobalSet, Module &M, bool isConst,
419  unsigned AddrSpace) const {
420  assert(Globals.size() > 1);
421 
423  auto &DL = M.getDataLayout();
424 
425  DEBUG(dbgs() << " Trying to merge set, starts with #"
426  << GlobalSet.find_first() << "\n");
427 
428  ssize_t i = GlobalSet.find_first();
429  while (i != -1) {
430  ssize_t j = 0;
431  uint64_t MergedSize = 0;
432  std::vector<Type*> Tys;
433  std::vector<Constant*> Inits;
434 
435  bool HasExternal = false;
436  StringRef FirstExternalName;
437  for (j = i; j != -1; j = GlobalSet.find_next(j)) {
438  Type *Ty = Globals[j]->getValueType();
439  MergedSize += DL.getTypeAllocSize(Ty);
440  if (MergedSize > MaxOffset) {
441  break;
442  }
443  Tys.push_back(Ty);
444  Inits.push_back(Globals[j]->getInitializer());
445 
446  if (Globals[j]->hasExternalLinkage() && !HasExternal) {
447  HasExternal = true;
448  FirstExternalName = Globals[j]->getName();
449  }
450  }
451 
452  // If merged variables doesn't have external linkage, we needn't to expose
453  // the symbol after merging.
454  GlobalValue::LinkageTypes Linkage = HasExternal
457  StructType *MergedTy = StructType::get(M.getContext(), Tys);
458  Constant *MergedInit = ConstantStruct::get(MergedTy, Inits);
459 
460  // On Darwin external linkage needs to be preserved, otherwise
461  // dsymutil cannot preserve the debug info for the merged
462  // variables. If they have external linkage, use the symbol name
463  // of the first variable merged as the suffix of global symbol
464  // name. This avoids a link-time naming conflict for the
465  // _MergedGlobals symbols.
466  Twine MergedName =
467  (IsMachO && HasExternal)
468  ? "_MergedGlobals_" + FirstExternalName
469  : "_MergedGlobals";
470  auto MergedLinkage = IsMachO ? Linkage : GlobalValue::PrivateLinkage;
471  auto *MergedGV = new GlobalVariable(
472  M, MergedTy, isConst, MergedLinkage, MergedInit, MergedName, nullptr,
473  GlobalVariable::NotThreadLocal, AddrSpace);
474 
475  const StructLayout *MergedLayout = DL.getStructLayout(MergedTy);
476 
477  for (ssize_t k = i, idx = 0; k != j; k = GlobalSet.find_next(k), ++idx) {
478  GlobalValue::LinkageTypes Linkage = Globals[k]->getLinkage();
479  std::string Name = Globals[k]->getName();
480 
481  // Copy metadata while adjusting any debug info metadata by the original
482  // global's offset within the merged global.
483  MergedGV->copyMetadata(Globals[k], MergedLayout->getElementOffset(idx));
484 
485  Constant *Idx[2] = {
486  ConstantInt::get(Int32Ty, 0),
487  ConstantInt::get(Int32Ty, idx),
488  };
489  Constant *GEP =
490  ConstantExpr::getInBoundsGetElementPtr(MergedTy, MergedGV, Idx);
491  Globals[k]->replaceAllUsesWith(GEP);
492  Globals[k]->eraseFromParent();
493 
494  // When the linkage is not internal we must emit an alias for the original
495  // variable name as it may be accessed from another object. On non-Mach-O
496  // we can also emit an alias for internal linkage as it's safe to do so.
497  // It's not safe on Mach-O as the alias (and thus the portion of the
498  // MergedGlobals variable) may be dead stripped at link time.
499  if (Linkage != GlobalValue::InternalLinkage || !IsMachO) {
500  GlobalAlias::create(Tys[idx], AddrSpace, Linkage, Name, GEP, &M);
501  }
502 
503  NumMerged++;
504  }
505  i = j;
506  }
507 
508  return true;
509 }
510 
512  // Extract global variables from llvm.used array
513  const GlobalVariable *GV = M.getGlobalVariable("llvm.used");
514  if (!GV || !GV->hasInitializer()) return;
515 
516  // Should be an array of 'i8*'.
517  const ConstantArray *InitList = cast<ConstantArray>(GV->getInitializer());
518 
519  for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
520  if (const GlobalVariable *G =
521  dyn_cast<GlobalVariable>(InitList->getOperand(i)->stripPointerCasts()))
522  MustKeepGlobalVariables.insert(G);
523 }
524 
525 void GlobalMerge::setMustKeepGlobalVariables(Module &M) {
527 
528  for (Function &F : M) {
529  for (BasicBlock &BB : F) {
530  Instruction *Pad = BB.getFirstNonPHI();
531  if (!Pad->isEHPad())
532  continue;
533 
534  // Keep globals used by landingpads and catchpads.
535  for (const Use &U : Pad->operands()) {
536  if (const GlobalVariable *GV =
537  dyn_cast<GlobalVariable>(U->stripPointerCasts()))
538  MustKeepGlobalVariables.insert(GV);
539  }
540  }
541  }
542 }
543 
544 bool GlobalMerge::doInitialization(Module &M) {
545  if (!EnableGlobalMerge)
546  return false;
547 
548  IsMachO = Triple(M.getTargetTriple()).isOSBinFormatMachO();
549 
550  auto &DL = M.getDataLayout();
552  BSSGlobals;
553  bool Changed = false;
554  setMustKeepGlobalVariables(M);
555 
556  // Grab all non-const globals.
557  for (auto &GV : M.globals()) {
558  // Merge is safe for "normal" internal or external globals only
559  if (GV.isDeclaration() || GV.isThreadLocal() || GV.hasSection())
560  continue;
561 
562  if (!(MergeExternalGlobals && GV.hasExternalLinkage()) &&
563  !GV.hasInternalLinkage())
564  continue;
565 
567  assert(PT && "Global variable is not a pointer!");
568 
569  unsigned AddressSpace = PT->getAddressSpace();
570 
571  // Ignore fancy-aligned globals for now.
572  unsigned Alignment = DL.getPreferredAlignment(&GV);
573  Type *Ty = GV.getValueType();
574  if (Alignment > DL.getABITypeAlignment(Ty))
575  continue;
576 
577  // Ignore all 'special' globals.
578  if (GV.getName().startswith("llvm.") ||
579  GV.getName().startswith(".llvm."))
580  continue;
581 
582  // Ignore all "required" globals:
583  if (isMustKeepGlobalVariable(&GV))
584  continue;
585 
586  if (DL.getTypeAllocSize(Ty) < MaxOffset) {
587  if (TM &&
589  BSSGlobals[AddressSpace].push_back(&GV);
590  else if (GV.isConstant())
591  ConstGlobals[AddressSpace].push_back(&GV);
592  else
593  Globals[AddressSpace].push_back(&GV);
594  }
595  }
596 
597  for (auto &P : Globals)
598  if (P.second.size() > 1)
599  Changed |= doMerge(P.second, M, false, P.first);
600 
601  for (auto &P : BSSGlobals)
602  if (P.second.size() > 1)
603  Changed |= doMerge(P.second, M, false, P.first);
604 
606  for (auto &P : ConstGlobals)
607  if (P.second.size() > 1)
608  Changed |= doMerge(P.second, M, true, P.first);
609 
610  return Changed;
611 }
612 
613 bool GlobalMerge::runOnFunction(Function &F) {
614  return false;
615 }
616 
617 bool GlobalMerge::doFinalization(Module &M) {
618  MustKeepGlobalVariables.clear();
619  return false;
620 }
621 
623  bool OnlyOptimizeForSize,
624  bool MergeExternalByDefault) {
625  bool MergeExternal = (EnableGlobalMergeOnExternal == cl::BOU_UNSET) ?
626  MergeExternalByDefault : (EnableGlobalMergeOnExternal == cl::BOU_TRUE);
627  return new GlobalMerge(TM, Offset, OnlyOptimizeForSize, MergeExternal);
628 }
Pass interface - Implemented by all 'passes'.
Definition: Pass.h:81
BitVector & set()
Definition: BitVector.h:219
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:157
iterator_range< use_iterator > uses()
Definition: Value.h:326
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
STATISTIC(NumFunctions,"Total number of functions")
size_t i
GlobalVariable * collectUsedGlobalVariables(const 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: Module.cpp:528
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:52
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:167
int find_next(unsigned Prev) const
find_next - Returns the index of the next set bit following the "Prev" bit.
Definition: BitVector.h:166
virtual void getAnalysisUsage(AnalysisUsage &) const
getAnalysisUsage - This function should be overriden by passes that need analysis information to do t...
Definition: Pass.cpp:84
Type * getValueType() const
Definition: GlobalValue.h:261
Like Internal, but omit from symbol table.
Definition: GlobalValue.h:57
INITIALIZE_PASS_BEGIN(GlobalMerge,"global-merge","Merge global variables", false, false) INITIALIZE_PASS_END(GlobalMerge
Externally visible function.
Definition: GlobalValue.h:49
Pass * createGlobalMergePass(const TargetMachine *TM, unsigned MaximalOffset, bool OnlyOptimizeForSize=false, bool MergeExternalByDefault=false)
GlobalMerge - This pass merges internal (by default) globals into structs to enable reuse of a base p...
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:100
unsigned getAddressSpace() const
Return the address space of the Pointer type.
Definition: DerivedTypes.h:471
Hexagon Common GEP
const Constant * getInitializer() const
getInitializer - Return the initializer for this global variable.
const std::string & getTargetTriple() const
Get the target triple which is a string describing the target host.
Definition: Module.h:218
bool optForMinSize() const
Optimize this function for minimum size (-Oz).
Definition: Function.h:461
StringRef getName() const
Return a constant reference to the value's name.
Definition: Value.cpp:191
global Merge global variables
Used to lazily calculate structure layout information for a target machine, based on the DataLayout s...
Definition: DataLayout.h:496
global merge
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
Class to represent struct types.
Definition: DerivedTypes.h:199
A Use represents the edge between a Value definition and its users.
Definition: Use.h:56
bool hasInternalLinkage() const
Definition: GlobalValue.h:413
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APFloat.h:32
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))
A constant value that is initialized with an expression using other constant values.
Definition: Constants.h:873
#define F(x, y, z)
Definition: MD5.cpp:51
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE bool startswith(StringRef Prefix) const
Check if this string starts with the given Prefix.
Definition: StringRef.h:264
Class to represent pointers.
Definition: DerivedTypes.h:443
uint64_t getElementOffset(unsigned Idx) const
Definition: DataLayout.h:517
bool hasSection() const
Check if this global has a custom object file section.
Definition: GlobalObject.h:73
#define P(N)
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:395
static Constant * getInBoundsGetElementPtr(Type *Ty, Constant *C, ArrayRef< Constant * > IdxList)
Create an "inbounds" getelementptr.
Definition: Constants.h:1153
LLVM Basic Block Representation.
Definition: BasicBlock.h:51
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
This is an important base class in LLVM.
Definition: Constant.h:42
This file contains the declarations for the subclasses of Constant, which represent the different fla...
Represent the analysis usage information of a pass.
uint32_t Offset
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE,"Assign register bank of generic virtual registers", false, false) RegBankSelect
size_t size() const
Definition: Function.h:540
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:298
Value * getOperand(unsigned i) const
Definition: User.h:145
op_range operands()
Definition: User.h:213
static Constant * get(StructType *T, ArrayRef< Constant * > V)
Definition: Constants.cpp:949
global Merge global false
bool isThreadLocal() const
If the value is "Thread Local", its value isn't shared by the threads.
Definition: GlobalValue.h:232
bool isBSSLocal() const
Definition: SectionKind.h:161
Triple - Helper class for working with autoconf configuration names.
Definition: Triple.h:44
bool hasExternalLinkage() const
Definition: GlobalValue.h:401
static void Merge(const std::string &Input, const std::vector< std::string > Result, size_t NumNewFeatures)
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:425
static StructType * get(LLVMContext &Context, ArrayRef< Type * > Elements, bool isPacked=false)
This static method is the primary way to create a literal StructType.
Definition: Type.cpp:330
Module.h This file contains the declarations for the Module class.
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))
const DataFlowGraph & G
Definition: RDFGraph.cpp:206
Value * stripPointerCasts()
Strip off pointer casts, all-zero GEPs, and aliases.
Definition: Value.cpp:490
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:558
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:276
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
static cl::opt< cl::boolOrDefault > EnableGlobalMergeOnExternal("global-merge-on-external", cl::Hidden, cl::desc("Enable global merge pass on external linkage"))
ConstantArray - Constant Array Declarations.
Definition: Constants.h:411
bool hasInitializer() const
Definitions have initializers, declarations don't.
LinkageTypes
An enumeration for the kinds of linkage for global values.
Definition: GlobalValue.h:48
bool isConstant() const
If the value is a global constant, its value is immutable throughout the runtime execution of the pro...
bool isEHPad() const
Return true if the instruction is a variety of EH-block.
Definition: Instruction.h:453
PointerType * getType() const
Global values are always pointers.
Definition: GlobalValue.h:259
const DataLayout & getDataLayout() const
Get the data layout for the module's target platform.
Definition: Module.cpp:384
static IntegerType * getInt32Ty(LLVMContext &C)
Definition: Type.cpp:169
bool isDeclaration() const
Return true if the primary definition of this global value is outside of the current translation unit...
Definition: Globals.cpp:188
#define I(x, y, z)
Definition: MD5.cpp:54
LLVM_ATTRIBUTE_ALWAYS_INLINE size_type size() const
Definition: SmallVector.h:135
LLVM_NODISCARD 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:287
Rename collisions when linking (static functions).
Definition: GlobalValue.h:56
static cl::opt< unsigned > GlobalMergeMaxOffset("global-merge-max-offset", cl::Hidden, cl::desc("Set maximum offset for global merge pass"), cl::init(0))
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
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 &)
#define DEBUG(X)
Definition: Debug.h:100
Primary interface to the complete machine description for the target machine.
iterator_range< global_iterator > globals()
Definition: Module.h:524
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:47
static SectionKind getKindForGlobal(const GlobalObject *GO, const TargetMachine &TM)
Classify the specified global variable into a set of target independent categories embodied in Sectio...
const BasicBlock * getParent() const
Definition: Instruction.h:62
static GlobalAlias * create(Type *Ty, unsigned AddressSpace, 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:384
GlobalVariable * getGlobalVariable(StringRef Name) const
Look up the specified global variable in the module symbol table.
Definition: Module.h:344
IntegerType * Int32Ty
LLVMContext & getContext() const
Get the global data context.
Definition: Module.h:222
This file describes how to lower LLVM code to machine code.