LLVM  6.0.0svn
DeadArgumentElimination.cpp
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1 //===-- DeadArgumentElimination.cpp - Eliminate dead arguments ------------===//
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 pass deletes dead arguments from internal functions. Dead argument
11 // elimination removes arguments which are directly dead, as well as arguments
12 // only passed into function calls as dead arguments of other functions. This
13 // pass also deletes dead return values in a similar way.
14 //
15 // This pass is often useful as a cleanup pass to run after aggressive
16 // interprocedural passes, which add possibly-dead arguments or return values.
17 //
18 //===----------------------------------------------------------------------===//
19 
21 #include "llvm/ADT/SmallVector.h"
22 #include "llvm/ADT/Statistic.h"
23 #include "llvm/ADT/StringExtras.h"
24 #include "llvm/IR/CallSite.h"
25 #include "llvm/IR/CallingConv.h"
26 #include "llvm/IR/Constant.h"
27 #include "llvm/IR/DIBuilder.h"
28 #include "llvm/IR/DebugInfo.h"
29 #include "llvm/IR/DerivedTypes.h"
30 #include "llvm/IR/Instructions.h"
31 #include "llvm/IR/IntrinsicInst.h"
32 #include "llvm/IR/LLVMContext.h"
33 #include "llvm/IR/Module.h"
34 #include "llvm/Pass.h"
35 #include "llvm/Support/Debug.h"
37 #include "llvm/Transforms/IPO.h"
39 #include <set>
40 #include <tuple>
41 using namespace llvm;
42 
43 #define DEBUG_TYPE "deadargelim"
44 
45 STATISTIC(NumArgumentsEliminated, "Number of unread args removed");
46 STATISTIC(NumRetValsEliminated , "Number of unused return values removed");
47 STATISTIC(NumArgumentsReplacedWithUndef,
48  "Number of unread args replaced with undef");
49 namespace {
50  /// DAE - The dead argument elimination pass.
51  ///
52  class DAE : public ModulePass {
53  protected:
54  // DAH uses this to specify a different ID.
55  explicit DAE(char &ID) : ModulePass(ID) {}
56 
57  public:
58  static char ID; // Pass identification, replacement for typeid
59  DAE() : ModulePass(ID) {
61  }
62 
63  bool runOnModule(Module &M) override {
64  if (skipModule(M))
65  return false;
66  DeadArgumentEliminationPass DAEP(ShouldHackArguments());
67  ModuleAnalysisManager DummyMAM;
68  PreservedAnalyses PA = DAEP.run(M, DummyMAM);
69  return !PA.areAllPreserved();
70  }
71 
72  virtual bool ShouldHackArguments() const { return false; }
73  };
74 }
75 
76 
77 char DAE::ID = 0;
78 INITIALIZE_PASS(DAE, "deadargelim", "Dead Argument Elimination", false, false)
79 
80 namespace {
81  /// DAH - DeadArgumentHacking pass - Same as dead argument elimination, but
82  /// deletes arguments to functions which are external. This is only for use
83  /// by bugpoint.
84  struct DAH : public DAE {
85  static char ID;
86  DAH() : DAE(ID) {}
87 
88  bool ShouldHackArguments() const override { return true; }
89  };
90 }
91 
92 char DAH::ID = 0;
93 INITIALIZE_PASS(DAH, "deadarghaX0r",
94  "Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)",
95  false, false)
96 
97 /// createDeadArgEliminationPass - This pass removes arguments from functions
98 /// which are not used by the body of the function.
99 ///
100 ModulePass *llvm::createDeadArgEliminationPass() { return new DAE(); }
102 
103 /// DeleteDeadVarargs - If this is an function that takes a ... list, and if
104 /// llvm.vastart is never called, the varargs list is dead for the function.
105 bool DeadArgumentEliminationPass::DeleteDeadVarargs(Function &Fn) {
106  assert(Fn.getFunctionType()->isVarArg() && "Function isn't varargs!");
107  if (Fn.isDeclaration() || !Fn.hasLocalLinkage()) return false;
108 
109  // Ensure that the function is only directly called.
110  if (Fn.hasAddressTaken())
111  return false;
112 
113  // Don't touch naked functions. The assembly might be using an argument, or
114  // otherwise rely on the frame layout in a way that this analysis will not
115  // see.
116  if (Fn.hasFnAttribute(Attribute::Naked)) {
117  return false;
118  }
119 
120  // Okay, we know we can transform this function if safe. Scan its body
121  // looking for calls marked musttail or calls to llvm.vastart.
122  for (BasicBlock &BB : Fn) {
123  for (Instruction &I : BB) {
124  CallInst *CI = dyn_cast<CallInst>(&I);
125  if (!CI)
126  continue;
127  if (CI->isMustTailCall())
128  return false;
129  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI)) {
130  if (II->getIntrinsicID() == Intrinsic::vastart)
131  return false;
132  }
133  }
134  }
135 
136  // If we get here, there are no calls to llvm.vastart in the function body,
137  // remove the "..." and adjust all the calls.
138 
139  // Start by computing a new prototype for the function, which is the same as
140  // the old function, but doesn't have isVarArg set.
141  FunctionType *FTy = Fn.getFunctionType();
142 
143  std::vector<Type*> Params(FTy->param_begin(), FTy->param_end());
145  Params, false);
146  unsigned NumArgs = Params.size();
147 
148  // Create the new function body and insert it into the module...
149  Function *NF = Function::Create(NFTy, Fn.getLinkage());
150  NF->copyAttributesFrom(&Fn);
151  NF->setComdat(Fn.getComdat());
152  Fn.getParent()->getFunctionList().insert(Fn.getIterator(), NF);
153  NF->takeName(&Fn);
154 
155  // Loop over all of the callers of the function, transforming the call sites
156  // to pass in a smaller number of arguments into the new function.
157  //
158  std::vector<Value*> Args;
159  for (Value::user_iterator I = Fn.user_begin(), E = Fn.user_end(); I != E; ) {
160  CallSite CS(*I++);
161  if (!CS)
162  continue;
163  Instruction *Call = CS.getInstruction();
164 
165  // Pass all the same arguments.
166  Args.assign(CS.arg_begin(), CS.arg_begin() + NumArgs);
167 
168  // Drop any attributes that were on the vararg arguments.
169  AttributeList PAL = CS.getAttributes();
170  if (!PAL.isEmpty()) {
172  for (unsigned ArgNo = 0; ArgNo < NumArgs; ++ArgNo)
173  ArgAttrs.push_back(PAL.getParamAttributes(ArgNo));
174  PAL = AttributeList::get(Fn.getContext(), PAL.getFnAttributes(),
175  PAL.getRetAttributes(), ArgAttrs);
176  }
177 
179  CS.getOperandBundlesAsDefs(OpBundles);
180 
181  CallSite NewCS;
182  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
183  NewCS = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
184  Args, OpBundles, "", Call);
185  } else {
186  NewCS = CallInst::Create(NF, Args, OpBundles, "", Call);
187  cast<CallInst>(NewCS.getInstruction())
188  ->setTailCallKind(cast<CallInst>(Call)->getTailCallKind());
189  }
190  NewCS.setCallingConv(CS.getCallingConv());
191  NewCS.setAttributes(PAL);
192  NewCS->setDebugLoc(Call->getDebugLoc());
193  uint64_t W;
194  if (Call->extractProfTotalWeight(W))
195  NewCS->setProfWeight(W);
196 
197  Args.clear();
198 
199  if (!Call->use_empty())
200  Call->replaceAllUsesWith(NewCS.getInstruction());
201 
202  NewCS->takeName(Call);
203 
204  // Finally, remove the old call from the program, reducing the use-count of
205  // F.
206  Call->eraseFromParent();
207  }
208 
209  // Since we have now created the new function, splice the body of the old
210  // function right into the new function, leaving the old rotting hulk of the
211  // function empty.
212  NF->getBasicBlockList().splice(NF->begin(), Fn.getBasicBlockList());
213 
214  // Loop over the argument list, transferring uses of the old arguments over to
215  // the new arguments, also transferring over the names as well. While we're at
216  // it, remove the dead arguments from the DeadArguments list.
217  //
218  for (Function::arg_iterator I = Fn.arg_begin(), E = Fn.arg_end(),
219  I2 = NF->arg_begin(); I != E; ++I, ++I2) {
220  // Move the name and users over to the new version.
221  I->replaceAllUsesWith(&*I2);
222  I2->takeName(&*I);
223  }
224 
225  // Patch the pointer to LLVM function in debug info descriptor.
226  NF->setSubprogram(Fn.getSubprogram());
227 
228  // Fix up any BlockAddresses that refer to the function.
229  Fn.replaceAllUsesWith(ConstantExpr::getBitCast(NF, Fn.getType()));
230  // Delete the bitcast that we just created, so that NF does not
231  // appear to be address-taken.
233  // Finally, nuke the old function.
234  Fn.eraseFromParent();
235  return true;
236 }
237 
238 /// RemoveDeadArgumentsFromCallers - Checks if the given function has any
239 /// arguments that are unused, and changes the caller parameters to be undefined
240 /// instead.
241 bool DeadArgumentEliminationPass::RemoveDeadArgumentsFromCallers(Function &Fn) {
242  // We cannot change the arguments if this TU does not define the function or
243  // if the linker may choose a function body from another TU, even if the
244  // nominal linkage indicates that other copies of the function have the same
245  // semantics. In the below example, the dead load from %p may not have been
246  // eliminated from the linker-chosen copy of f, so replacing %p with undef
247  // in callers may introduce undefined behavior.
248  //
249  // define linkonce_odr void @f(i32* %p) {
250  // %v = load i32 %p
251  // ret void
252  // }
253  if (!Fn.hasExactDefinition())
254  return false;
255 
256  // Functions with local linkage should already have been handled, except the
257  // fragile (variadic) ones which we can improve here.
258  if (Fn.hasLocalLinkage() && !Fn.getFunctionType()->isVarArg())
259  return false;
260 
261  // Don't touch naked functions. The assembly might be using an argument, or
262  // otherwise rely on the frame layout in a way that this analysis will not
263  // see.
264  if (Fn.hasFnAttribute(Attribute::Naked))
265  return false;
266 
267  if (Fn.use_empty())
268  return false;
269 
270  SmallVector<unsigned, 8> UnusedArgs;
271  for (Argument &Arg : Fn.args()) {
272  if (!Arg.hasSwiftErrorAttr() && Arg.use_empty() && !Arg.hasByValOrInAllocaAttr())
273  UnusedArgs.push_back(Arg.getArgNo());
274  }
275 
276  if (UnusedArgs.empty())
277  return false;
278 
279  bool Changed = false;
280 
281  for (Use &U : Fn.uses()) {
282  CallSite CS(U.getUser());
283  if (!CS || !CS.isCallee(&U))
284  continue;
285 
286  // Now go through all unused args and replace them with "undef".
287  for (unsigned I = 0, E = UnusedArgs.size(); I != E; ++I) {
288  unsigned ArgNo = UnusedArgs[I];
289 
290  Value *Arg = CS.getArgument(ArgNo);
291  CS.setArgument(ArgNo, UndefValue::get(Arg->getType()));
292  ++NumArgumentsReplacedWithUndef;
293  Changed = true;
294  }
295  }
296 
297  return Changed;
298 }
299 
300 /// Convenience function that returns the number of return values. It returns 0
301 /// for void functions and 1 for functions not returning a struct. It returns
302 /// the number of struct elements for functions returning a struct.
303 static unsigned NumRetVals(const Function *F) {
304  Type *RetTy = F->getReturnType();
305  if (RetTy->isVoidTy())
306  return 0;
307  else if (StructType *STy = dyn_cast<StructType>(RetTy))
308  return STy->getNumElements();
309  else if (ArrayType *ATy = dyn_cast<ArrayType>(RetTy))
310  return ATy->getNumElements();
311  else
312  return 1;
313 }
314 
315 /// Returns the sub-type a function will return at a given Idx. Should
316 /// correspond to the result type of an ExtractValue instruction executed with
317 /// just that one Idx (i.e. only top-level structure is considered).
318 static Type *getRetComponentType(const Function *F, unsigned Idx) {
319  Type *RetTy = F->getReturnType();
320  assert(!RetTy->isVoidTy() && "void type has no subtype");
321 
322  if (StructType *STy = dyn_cast<StructType>(RetTy))
323  return STy->getElementType(Idx);
324  else if (ArrayType *ATy = dyn_cast<ArrayType>(RetTy))
325  return ATy->getElementType();
326  else
327  return RetTy;
328 }
329 
330 /// MarkIfNotLive - This checks Use for liveness in LiveValues. If Use is not
331 /// live, it adds Use to the MaybeLiveUses argument. Returns the determined
332 /// liveness of Use.
334 DeadArgumentEliminationPass::MarkIfNotLive(RetOrArg Use,
335  UseVector &MaybeLiveUses) {
336  // We're live if our use or its Function is already marked as live.
337  if (LiveFunctions.count(Use.F) || LiveValues.count(Use))
338  return Live;
339 
340  // We're maybe live otherwise, but remember that we must become live if
341  // Use becomes live.
342  MaybeLiveUses.push_back(Use);
343  return MaybeLive;
344 }
345 
346 
347 /// SurveyUse - This looks at a single use of an argument or return value
348 /// and determines if it should be alive or not. Adds this use to MaybeLiveUses
349 /// if it causes the used value to become MaybeLive.
350 ///
351 /// RetValNum is the return value number to use when this use is used in a
352 /// return instruction. This is used in the recursion, you should always leave
353 /// it at 0.
355 DeadArgumentEliminationPass::SurveyUse(const Use *U, UseVector &MaybeLiveUses,
356  unsigned RetValNum) {
357  const User *V = U->getUser();
358  if (const ReturnInst *RI = dyn_cast<ReturnInst>(V)) {
359  // The value is returned from a function. It's only live when the
360  // function's return value is live. We use RetValNum here, for the case
361  // that U is really a use of an insertvalue instruction that uses the
362  // original Use.
363  const Function *F = RI->getParent()->getParent();
364  if (RetValNum != -1U) {
365  RetOrArg Use = CreateRet(F, RetValNum);
366  // We might be live, depending on the liveness of Use.
367  return MarkIfNotLive(Use, MaybeLiveUses);
368  } else {
369  DeadArgumentEliminationPass::Liveness Result = MaybeLive;
370  for (unsigned i = 0; i < NumRetVals(F); ++i) {
371  RetOrArg Use = CreateRet(F, i);
372  // We might be live, depending on the liveness of Use. If any
373  // sub-value is live, then the entire value is considered live. This
374  // is a conservative choice, and better tracking is possible.
376  MarkIfNotLive(Use, MaybeLiveUses);
377  if (Result != Live)
378  Result = SubResult;
379  }
380  return Result;
381  }
382  }
383  if (const InsertValueInst *IV = dyn_cast<InsertValueInst>(V)) {
384  if (U->getOperandNo() != InsertValueInst::getAggregateOperandIndex()
385  && IV->hasIndices())
386  // The use we are examining is inserted into an aggregate. Our liveness
387  // depends on all uses of that aggregate, but if it is used as a return
388  // value, only index at which we were inserted counts.
389  RetValNum = *IV->idx_begin();
390 
391  // Note that if we are used as the aggregate operand to the insertvalue,
392  // we don't change RetValNum, but do survey all our uses.
393 
394  Liveness Result = MaybeLive;
395  for (const Use &UU : IV->uses()) {
396  Result = SurveyUse(&UU, MaybeLiveUses, RetValNum);
397  if (Result == Live)
398  break;
399  }
400  return Result;
401  }
402 
403  if (auto CS = ImmutableCallSite(V)) {
404  const Function *F = CS.getCalledFunction();
405  if (F) {
406  // Used in a direct call.
407 
408  // The function argument is live if it is used as a bundle operand.
409  if (CS.isBundleOperand(U))
410  return Live;
411 
412  // Find the argument number. We know for sure that this use is an
413  // argument, since if it was the function argument this would be an
414  // indirect call and the we know can't be looking at a value of the
415  // label type (for the invoke instruction).
416  unsigned ArgNo = CS.getArgumentNo(U);
417 
418  if (ArgNo >= F->getFunctionType()->getNumParams())
419  // The value is passed in through a vararg! Must be live.
420  return Live;
421 
422  assert(CS.getArgument(ArgNo)
423  == CS->getOperand(U->getOperandNo())
424  && "Argument is not where we expected it");
425 
426  // Value passed to a normal call. It's only live when the corresponding
427  // argument to the called function turns out live.
428  RetOrArg Use = CreateArg(F, ArgNo);
429  return MarkIfNotLive(Use, MaybeLiveUses);
430  }
431  }
432  // Used in any other way? Value must be live.
433  return Live;
434 }
435 
436 /// SurveyUses - This looks at all the uses of the given value
437 /// Returns the Liveness deduced from the uses of this value.
438 ///
439 /// Adds all uses that cause the result to be MaybeLive to MaybeLiveRetUses. If
440 /// the result is Live, MaybeLiveUses might be modified but its content should
441 /// be ignored (since it might not be complete).
443 DeadArgumentEliminationPass::SurveyUses(const Value *V,
444  UseVector &MaybeLiveUses) {
445  // Assume it's dead (which will only hold if there are no uses at all..).
446  Liveness Result = MaybeLive;
447  // Check each use.
448  for (const Use &U : V->uses()) {
449  Result = SurveyUse(&U, MaybeLiveUses);
450  if (Result == Live)
451  break;
452  }
453  return Result;
454 }
455 
456 // SurveyFunction - This performs the initial survey of the specified function,
457 // checking out whether or not it uses any of its incoming arguments or whether
458 // any callers use the return value. This fills in the LiveValues set and Uses
459 // map.
460 //
461 // We consider arguments of non-internal functions to be intrinsically alive as
462 // well as arguments to functions which have their "address taken".
463 //
464 void DeadArgumentEliminationPass::SurveyFunction(const Function &F) {
465  // Functions with inalloca parameters are expecting args in a particular
466  // register and memory layout.
467  if (F.getAttributes().hasAttrSomewhere(Attribute::InAlloca)) {
468  MarkLive(F);
469  return;
470  }
471 
472  // Don't touch naked functions. The assembly might be using an argument, or
473  // otherwise rely on the frame layout in a way that this analysis will not
474  // see.
475  if (F.hasFnAttribute(Attribute::Naked)) {
476  MarkLive(F);
477  return;
478  }
479 
480  unsigned RetCount = NumRetVals(&F);
481  // Assume all return values are dead
482  typedef SmallVector<Liveness, 5> RetVals;
483  RetVals RetValLiveness(RetCount, MaybeLive);
484 
485  typedef SmallVector<UseVector, 5> RetUses;
486  // These vectors map each return value to the uses that make it MaybeLive, so
487  // we can add those to the Uses map if the return value really turns out to be
488  // MaybeLive. Initialized to a list of RetCount empty lists.
489  RetUses MaybeLiveRetUses(RetCount);
490 
491  for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
492  if (const ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
493  if (RI->getNumOperands() != 0 && RI->getOperand(0)->getType()
494  != F.getFunctionType()->getReturnType()) {
495  // We don't support old style multiple return values.
496  MarkLive(F);
497  return;
498  }
499 
500  if (!F.hasLocalLinkage() && (!ShouldHackArguments || F.isIntrinsic())) {
501  MarkLive(F);
502  return;
503  }
504 
505  DEBUG(dbgs() << "DeadArgumentEliminationPass - Inspecting callers for fn: "
506  << F.getName() << "\n");
507  // Keep track of the number of live retvals, so we can skip checks once all
508  // of them turn out to be live.
509  unsigned NumLiveRetVals = 0;
510  // Loop all uses of the function.
511  for (const Use &U : F.uses()) {
512  // If the function is PASSED IN as an argument, its address has been
513  // taken.
514  ImmutableCallSite CS(U.getUser());
515  if (!CS || !CS.isCallee(&U)) {
516  MarkLive(F);
517  return;
518  }
519 
520  // If this use is anything other than a call site, the function is alive.
521  const Instruction *TheCall = CS.getInstruction();
522  if (!TheCall) { // Not a direct call site?
523  MarkLive(F);
524  return;
525  }
526 
527  // If we end up here, we are looking at a direct call to our function.
528 
529  // Now, check how our return value(s) is/are used in this caller. Don't
530  // bother checking return values if all of them are live already.
531  if (NumLiveRetVals == RetCount)
532  continue;
533 
534  // Check all uses of the return value.
535  for (const Use &U : TheCall->uses()) {
536  if (ExtractValueInst *Ext = dyn_cast<ExtractValueInst>(U.getUser())) {
537  // This use uses a part of our return value, survey the uses of
538  // that part and store the results for this index only.
539  unsigned Idx = *Ext->idx_begin();
540  if (RetValLiveness[Idx] != Live) {
541  RetValLiveness[Idx] = SurveyUses(Ext, MaybeLiveRetUses[Idx]);
542  if (RetValLiveness[Idx] == Live)
543  NumLiveRetVals++;
544  }
545  } else {
546  // Used by something else than extractvalue. Survey, but assume that the
547  // result applies to all sub-values.
548  UseVector MaybeLiveAggregateUses;
549  if (SurveyUse(&U, MaybeLiveAggregateUses) == Live) {
550  NumLiveRetVals = RetCount;
551  RetValLiveness.assign(RetCount, Live);
552  break;
553  } else {
554  for (unsigned i = 0; i != RetCount; ++i) {
555  if (RetValLiveness[i] != Live)
556  MaybeLiveRetUses[i].append(MaybeLiveAggregateUses.begin(),
557  MaybeLiveAggregateUses.end());
558  }
559  }
560  }
561  }
562  }
563 
564  // Now we've inspected all callers, record the liveness of our return values.
565  for (unsigned i = 0; i != RetCount; ++i)
566  MarkValue(CreateRet(&F, i), RetValLiveness[i], MaybeLiveRetUses[i]);
567 
568  DEBUG(dbgs() << "DeadArgumentEliminationPass - Inspecting args for fn: "
569  << F.getName() << "\n");
570 
571  // Now, check all of our arguments.
572  unsigned i = 0;
573  UseVector MaybeLiveArgUses;
575  E = F.arg_end(); AI != E; ++AI, ++i) {
576  Liveness Result;
577  if (F.getFunctionType()->isVarArg()) {
578  // Variadic functions will already have a va_arg function expanded inside
579  // them, making them potentially very sensitive to ABI changes resulting
580  // from removing arguments entirely, so don't. For example AArch64 handles
581  // register and stack HFAs very differently, and this is reflected in the
582  // IR which has already been generated.
583  Result = Live;
584  } else {
585  // See what the effect of this use is (recording any uses that cause
586  // MaybeLive in MaybeLiveArgUses).
587  Result = SurveyUses(&*AI, MaybeLiveArgUses);
588  }
589 
590  // Mark the result.
591  MarkValue(CreateArg(&F, i), Result, MaybeLiveArgUses);
592  // Clear the vector again for the next iteration.
593  MaybeLiveArgUses.clear();
594  }
595 }
596 
597 /// MarkValue - This function marks the liveness of RA depending on L. If L is
598 /// MaybeLive, it also takes all uses in MaybeLiveUses and records them in Uses,
599 /// such that RA will be marked live if any use in MaybeLiveUses gets marked
600 /// live later on.
601 void DeadArgumentEliminationPass::MarkValue(const RetOrArg &RA, Liveness L,
602  const UseVector &MaybeLiveUses) {
603  switch (L) {
604  case Live: MarkLive(RA); break;
605  case MaybeLive:
606  {
607  // Note any uses of this value, so this return value can be
608  // marked live whenever one of the uses becomes live.
609  for (const auto &MaybeLiveUse : MaybeLiveUses)
610  Uses.insert(std::make_pair(MaybeLiveUse, RA));
611  break;
612  }
613  }
614 }
615 
616 /// MarkLive - Mark the given Function as alive, meaning that it cannot be
617 /// changed in any way. Additionally,
618 /// mark any values that are used as this function's parameters or by its return
619 /// values (according to Uses) live as well.
620 void DeadArgumentEliminationPass::MarkLive(const Function &F) {
621  DEBUG(dbgs() << "DeadArgumentEliminationPass - Intrinsically live fn: "
622  << F.getName() << "\n");
623  // Mark the function as live.
624  LiveFunctions.insert(&F);
625  // Mark all arguments as live.
626  for (unsigned i = 0, e = F.arg_size(); i != e; ++i)
627  PropagateLiveness(CreateArg(&F, i));
628  // Mark all return values as live.
629  for (unsigned i = 0, e = NumRetVals(&F); i != e; ++i)
630  PropagateLiveness(CreateRet(&F, i));
631 }
632 
633 /// MarkLive - Mark the given return value or argument as live. Additionally,
634 /// mark any values that are used by this value (according to Uses) live as
635 /// well.
636 void DeadArgumentEliminationPass::MarkLive(const RetOrArg &RA) {
637  if (LiveFunctions.count(RA.F))
638  return; // Function was already marked Live.
639 
640  if (!LiveValues.insert(RA).second)
641  return; // We were already marked Live.
642 
643  DEBUG(dbgs() << "DeadArgumentEliminationPass - Marking "
644  << RA.getDescription() << " live\n");
645  PropagateLiveness(RA);
646 }
647 
648 /// PropagateLiveness - Given that RA is a live value, propagate it's liveness
649 /// to any other values it uses (according to Uses).
650 void DeadArgumentEliminationPass::PropagateLiveness(const RetOrArg &RA) {
651  // We don't use upper_bound (or equal_range) here, because our recursive call
652  // to ourselves is likely to cause the upper_bound (which is the first value
653  // not belonging to RA) to become erased and the iterator invalidated.
654  UseMap::iterator Begin = Uses.lower_bound(RA);
655  UseMap::iterator E = Uses.end();
656  UseMap::iterator I;
657  for (I = Begin; I != E && I->first == RA; ++I)
658  MarkLive(I->second);
659 
660  // Erase RA from the Uses map (from the lower bound to wherever we ended up
661  // after the loop).
662  Uses.erase(Begin, I);
663 }
664 
665 // RemoveDeadStuffFromFunction - Remove any arguments and return values from F
666 // that are not in LiveValues. Transform the function and all of the callees of
667 // the function to not have these arguments and return values.
668 //
669 bool DeadArgumentEliminationPass::RemoveDeadStuffFromFunction(Function *F) {
670  // Don't modify fully live functions
671  if (LiveFunctions.count(F))
672  return false;
673 
674  // Start by computing a new prototype for the function, which is the same as
675  // the old function, but has fewer arguments and a different return type.
676  FunctionType *FTy = F->getFunctionType();
677  std::vector<Type*> Params;
678 
679  // Keep track of if we have a live 'returned' argument
680  bool HasLiveReturnedArg = false;
681 
682  // Set up to build a new list of parameter attributes.
683  SmallVector<AttributeSet, 8> ArgAttrVec;
684  const AttributeList &PAL = F->getAttributes();
685 
686  // Remember which arguments are still alive.
687  SmallVector<bool, 10> ArgAlive(FTy->getNumParams(), false);
688  // Construct the new parameter list from non-dead arguments. Also construct
689  // a new set of parameter attributes to correspond. Skip the first parameter
690  // attribute, since that belongs to the return value.
691  unsigned i = 0;
692  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
693  I != E; ++I, ++i) {
694  RetOrArg Arg = CreateArg(F, i);
695  if (LiveValues.erase(Arg)) {
696  Params.push_back(I->getType());
697  ArgAlive[i] = true;
698  ArgAttrVec.push_back(PAL.getParamAttributes(i));
699  HasLiveReturnedArg |= PAL.hasParamAttribute(i, Attribute::Returned);
700  } else {
701  ++NumArgumentsEliminated;
702  DEBUG(dbgs() << "DeadArgumentEliminationPass - Removing argument " << i
703  << " (" << I->getName() << ") from " << F->getName()
704  << "\n");
705  }
706  }
707 
708  // Find out the new return value.
709  Type *RetTy = FTy->getReturnType();
710  Type *NRetTy = nullptr;
711  unsigned RetCount = NumRetVals(F);
712 
713  // -1 means unused, other numbers are the new index
714  SmallVector<int, 5> NewRetIdxs(RetCount, -1);
715  std::vector<Type*> RetTypes;
716 
717  // If there is a function with a live 'returned' argument but a dead return
718  // value, then there are two possible actions:
719  // 1) Eliminate the return value and take off the 'returned' attribute on the
720  // argument.
721  // 2) Retain the 'returned' attribute and treat the return value (but not the
722  // entire function) as live so that it is not eliminated.
723  //
724  // It's not clear in the general case which option is more profitable because,
725  // even in the absence of explicit uses of the return value, code generation
726  // is free to use the 'returned' attribute to do things like eliding
727  // save/restores of registers across calls. Whether or not this happens is
728  // target and ABI-specific as well as depending on the amount of register
729  // pressure, so there's no good way for an IR-level pass to figure this out.
730  //
731  // Fortunately, the only places where 'returned' is currently generated by
732  // the FE are places where 'returned' is basically free and almost always a
733  // performance win, so the second option can just be used always for now.
734  //
735  // This should be revisited if 'returned' is ever applied more liberally.
736  if (RetTy->isVoidTy() || HasLiveReturnedArg) {
737  NRetTy = RetTy;
738  } else {
739  // Look at each of the original return values individually.
740  for (unsigned i = 0; i != RetCount; ++i) {
741  RetOrArg Ret = CreateRet(F, i);
742  if (LiveValues.erase(Ret)) {
743  RetTypes.push_back(getRetComponentType(F, i));
744  NewRetIdxs[i] = RetTypes.size() - 1;
745  } else {
746  ++NumRetValsEliminated;
747  DEBUG(dbgs() << "DeadArgumentEliminationPass - Removing return value "
748  << i << " from " << F->getName() << "\n");
749  }
750  }
751  if (RetTypes.size() > 1) {
752  // More than one return type? Reduce it down to size.
753  if (StructType *STy = dyn_cast<StructType>(RetTy)) {
754  // Make the new struct packed if we used to return a packed struct
755  // already.
756  NRetTy = StructType::get(STy->getContext(), RetTypes, STy->isPacked());
757  } else {
758  assert(isa<ArrayType>(RetTy) && "unexpected multi-value return");
759  NRetTy = ArrayType::get(RetTypes[0], RetTypes.size());
760  }
761  } else if (RetTypes.size() == 1)
762  // One return type? Just a simple value then, but only if we didn't use to
763  // return a struct with that simple value before.
764  NRetTy = RetTypes.front();
765  else if (RetTypes.size() == 0)
766  // No return types? Make it void, but only if we didn't use to return {}.
767  NRetTy = Type::getVoidTy(F->getContext());
768  }
769 
770  assert(NRetTy && "No new return type found?");
771 
772  // The existing function return attributes.
773  AttrBuilder RAttrs(PAL.getRetAttributes());
774 
775  // Remove any incompatible attributes, but only if we removed all return
776  // values. Otherwise, ensure that we don't have any conflicting attributes
777  // here. Currently, this should not be possible, but special handling might be
778  // required when new return value attributes are added.
779  if (NRetTy->isVoidTy())
781  else
782  assert(!RAttrs.overlaps(AttributeFuncs::typeIncompatible(NRetTy)) &&
783  "Return attributes no longer compatible?");
784 
785  AttributeSet RetAttrs = AttributeSet::get(F->getContext(), RAttrs);
786 
787  // Reconstruct the AttributesList based on the vector we constructed.
788  assert(ArgAttrVec.size() == Params.size());
790  F->getContext(), PAL.getFnAttributes(), RetAttrs, ArgAttrVec);
791 
792  // Create the new function type based on the recomputed parameters.
793  FunctionType *NFTy = FunctionType::get(NRetTy, Params, FTy->isVarArg());
794 
795  // No change?
796  if (NFTy == FTy)
797  return false;
798 
799  // Create the new function body and insert it into the module...
800  Function *NF = Function::Create(NFTy, F->getLinkage());
801  NF->copyAttributesFrom(F);
802  NF->setComdat(F->getComdat());
803  NF->setAttributes(NewPAL);
804  // Insert the new function before the old function, so we won't be processing
805  // it again.
806  F->getParent()->getFunctionList().insert(F->getIterator(), NF);
807  NF->takeName(F);
808 
809  // Loop over all of the callers of the function, transforming the call sites
810  // to pass in a smaller number of arguments into the new function.
811  //
812  std::vector<Value*> Args;
813  while (!F->use_empty()) {
814  CallSite CS(F->user_back());
815  Instruction *Call = CS.getInstruction();
816 
817  ArgAttrVec.clear();
818  const AttributeList &CallPAL = CS.getAttributes();
819 
820  // Adjust the call return attributes in case the function was changed to
821  // return void.
822  AttrBuilder RAttrs(CallPAL.getRetAttributes());
824  AttributeSet RetAttrs = AttributeSet::get(F->getContext(), RAttrs);
825 
826  // Declare these outside of the loops, so we can reuse them for the second
827  // loop, which loops the varargs.
828  CallSite::arg_iterator I = CS.arg_begin();
829  unsigned i = 0;
830  // Loop over those operands, corresponding to the normal arguments to the
831  // original function, and add those that are still alive.
832  for (unsigned e = FTy->getNumParams(); i != e; ++I, ++i)
833  if (ArgAlive[i]) {
834  Args.push_back(*I);
835  // Get original parameter attributes, but skip return attributes.
837  if (NRetTy != RetTy && Attrs.hasAttribute(Attribute::Returned)) {
838  // If the return type has changed, then get rid of 'returned' on the
839  // call site. The alternative is to make all 'returned' attributes on
840  // call sites keep the return value alive just like 'returned'
841  // attributes on function declaration but it's less clearly a win and
842  // this is not an expected case anyway
843  ArgAttrVec.push_back(AttributeSet::get(
844  F->getContext(),
845  AttrBuilder(Attrs).removeAttribute(Attribute::Returned)));
846  } else {
847  // Otherwise, use the original attributes.
848  ArgAttrVec.push_back(Attrs);
849  }
850  }
851 
852  // Push any varargs arguments on the list. Don't forget their attributes.
853  for (CallSite::arg_iterator E = CS.arg_end(); I != E; ++I, ++i) {
854  Args.push_back(*I);
855  ArgAttrVec.push_back(CallPAL.getParamAttributes(i));
856  }
857 
858  // Reconstruct the AttributesList based on the vector we constructed.
859  assert(ArgAttrVec.size() == Args.size());
860  AttributeList NewCallPAL = AttributeList::get(
861  F->getContext(), CallPAL.getFnAttributes(), RetAttrs, ArgAttrVec);
862 
864  CS.getOperandBundlesAsDefs(OpBundles);
865 
866  CallSite NewCS;
867  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
868  NewCS = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
869  Args, OpBundles, "", Call->getParent());
870  } else {
871  NewCS = CallInst::Create(NF, Args, OpBundles, "", Call);
872  cast<CallInst>(NewCS.getInstruction())
873  ->setTailCallKind(cast<CallInst>(Call)->getTailCallKind());
874  }
875  NewCS.setCallingConv(CS.getCallingConv());
876  NewCS.setAttributes(NewCallPAL);
877  NewCS->setDebugLoc(Call->getDebugLoc());
878  uint64_t W;
879  if (Call->extractProfTotalWeight(W))
880  NewCS->setProfWeight(W);
881  Args.clear();
882  ArgAttrVec.clear();
883 
884  Instruction *New = NewCS.getInstruction();
885  if (!Call->use_empty()) {
886  if (New->getType() == Call->getType()) {
887  // Return type not changed? Just replace users then.
888  Call->replaceAllUsesWith(New);
889  New->takeName(Call);
890  } else if (New->getType()->isVoidTy()) {
891  // Our return value has uses, but they will get removed later on.
892  // Replace by null for now.
893  if (!Call->getType()->isX86_MMXTy())
894  Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
895  } else {
896  assert((RetTy->isStructTy() || RetTy->isArrayTy()) &&
897  "Return type changed, but not into a void. The old return type"
898  " must have been a struct or an array!");
899  Instruction *InsertPt = Call;
900  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
901  BasicBlock *NewEdge = SplitEdge(New->getParent(), II->getNormalDest());
902  InsertPt = &*NewEdge->getFirstInsertionPt();
903  }
904 
905  // We used to return a struct or array. Instead of doing smart stuff
906  // with all the uses, we will just rebuild it using extract/insertvalue
907  // chaining and let instcombine clean that up.
908  //
909  // Start out building up our return value from undef
910  Value *RetVal = UndefValue::get(RetTy);
911  for (unsigned i = 0; i != RetCount; ++i)
912  if (NewRetIdxs[i] != -1) {
913  Value *V;
914  if (RetTypes.size() > 1)
915  // We are still returning a struct, so extract the value from our
916  // return value
917  V = ExtractValueInst::Create(New, NewRetIdxs[i], "newret",
918  InsertPt);
919  else
920  // We are now returning a single element, so just insert that
921  V = New;
922  // Insert the value at the old position
923  RetVal = InsertValueInst::Create(RetVal, V, i, "oldret", InsertPt);
924  }
925  // Now, replace all uses of the old call instruction with the return
926  // struct we built
927  Call->replaceAllUsesWith(RetVal);
928  New->takeName(Call);
929  }
930  }
931 
932  // Finally, remove the old call from the program, reducing the use-count of
933  // F.
934  Call->eraseFromParent();
935  }
936 
937  // Since we have now created the new function, splice the body of the old
938  // function right into the new function, leaving the old rotting hulk of the
939  // function empty.
940  NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
941 
942  // Loop over the argument list, transferring uses of the old arguments over to
943  // the new arguments, also transferring over the names as well.
944  i = 0;
945  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
946  I2 = NF->arg_begin(); I != E; ++I, ++i)
947  if (ArgAlive[i]) {
948  // If this is a live argument, move the name and users over to the new
949  // version.
950  I->replaceAllUsesWith(&*I2);
951  I2->takeName(&*I);
952  ++I2;
953  } else {
954  // If this argument is dead, replace any uses of it with null constants
955  // (these are guaranteed to become unused later on).
956  if (!I->getType()->isX86_MMXTy())
957  I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
958  }
959 
960  // If we change the return value of the function we must rewrite any return
961  // instructions. Check this now.
962  if (F->getReturnType() != NF->getReturnType())
963  for (BasicBlock &BB : *NF)
964  if (ReturnInst *RI = dyn_cast<ReturnInst>(BB.getTerminator())) {
965  Value *RetVal;
966 
967  if (NFTy->getReturnType()->isVoidTy()) {
968  RetVal = nullptr;
969  } else {
970  assert(RetTy->isStructTy() || RetTy->isArrayTy());
971  // The original return value was a struct or array, insert
972  // extractvalue/insertvalue chains to extract only the values we need
973  // to return and insert them into our new result.
974  // This does generate messy code, but we'll let it to instcombine to
975  // clean that up.
976  Value *OldRet = RI->getOperand(0);
977  // Start out building up our return value from undef
978  RetVal = UndefValue::get(NRetTy);
979  for (unsigned i = 0; i != RetCount; ++i)
980  if (NewRetIdxs[i] != -1) {
982  "oldret", RI);
983  if (RetTypes.size() > 1) {
984  // We're still returning a struct, so reinsert the value into
985  // our new return value at the new index
986 
987  RetVal = InsertValueInst::Create(RetVal, EV, NewRetIdxs[i],
988  "newret", RI);
989  } else {
990  // We are now only returning a simple value, so just return the
991  // extracted value.
992  RetVal = EV;
993  }
994  }
995  }
996  // Replace the return instruction with one returning the new return
997  // value (possibly 0 if we became void).
998  ReturnInst::Create(F->getContext(), RetVal, RI);
999  BB.getInstList().erase(RI);
1000  }
1001 
1002  // Patch the pointer to LLVM function in debug info descriptor.
1003  NF->setSubprogram(F->getSubprogram());
1004 
1005  // Now that the old function is dead, delete it.
1006  F->eraseFromParent();
1007 
1008  return true;
1009 }
1010 
1013  bool Changed = false;
1014 
1015  // First pass: Do a simple check to see if any functions can have their "..."
1016  // removed. We can do this if they never call va_start. This loop cannot be
1017  // fused with the next loop, because deleting a function invalidates
1018  // information computed while surveying other functions.
1019  DEBUG(dbgs() << "DeadArgumentEliminationPass - Deleting dead varargs\n");
1020  for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
1021  Function &F = *I++;
1022  if (F.getFunctionType()->isVarArg())
1023  Changed |= DeleteDeadVarargs(F);
1024  }
1025 
1026  // Second phase:loop through the module, determining which arguments are live.
1027  // We assume all arguments are dead unless proven otherwise (allowing us to
1028  // determine that dead arguments passed into recursive functions are dead).
1029  //
1030  DEBUG(dbgs() << "DeadArgumentEliminationPass - Determining liveness\n");
1031  for (auto &F : M)
1032  SurveyFunction(F);
1033 
1034  // Now, remove all dead arguments and return values from each function in
1035  // turn.
1036  for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
1037  // Increment now, because the function will probably get removed (ie.
1038  // replaced by a new one).
1039  Function *F = &*I++;
1040  Changed |= RemoveDeadStuffFromFunction(F);
1041  }
1042 
1043  // Finally, look for any unused parameters in functions with non-local
1044  // linkage and replace the passed in parameters with undef.
1045  for (auto &F : M)
1046  Changed |= RemoveDeadArgumentsFromCallers(F);
1047 
1048  if (!Changed)
1049  return PreservedAnalyses::all();
1050  return PreservedAnalyses::none();
1051 }
Return a value (possibly void), from a function.
User::op_iterator arg_iterator
The type of iterator to use when looping over actual arguments at this call site. ...
Definition: CallSite.h:210
bool isIntrinsic() const
isIntrinsic - Returns true if the function&#39;s name starts with "llvm.".
Definition: Function.h:172
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:69
iterator_range< use_iterator > uses()
Definition: Value.h:350
bool hasLocalLinkage() const
Definition: GlobalValue.h:416
This instruction extracts a struct member or array element value from an aggregate value...
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
This class represents an incoming formal argument to a Function.
Definition: Argument.h:30
Eliminate dead arguments (and return values) from functions.
CallingConv::ID getCallingConv() const
Get the calling convention of the call.
Definition: CallSite.h:309
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:63
LLVM_ATTRIBUTE_ALWAYS_INLINE size_type size() const
Definition: SmallVector.h:136
iterator end()
Definition: Function.h:582
This class represents a function call, abstracting a target machine&#39;s calling convention.
bool hasFnAttribute(Attribute::AttrKind Kind) const
Return true if the function has the attribute.
Definition: Function.h:254
arg_iterator arg_end()
Definition: Function.h:604
STATISTIC(NumFunctions, "Total number of functions")
static CallInst * Create(Value *Func, ArrayRef< Value *> Args, ArrayRef< OperandBundleDef > Bundles=None, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
param_iterator param_end() const
Definition: DerivedTypes.h:129
bool isMustTailCall() const
static Constant * getNullValue(Type *Ty)
Constructor to create a &#39;0&#39; constant of arbitrary type.
Definition: Constants.cpp:207
static ReturnInst * Create(LLVMContext &C, Value *retVal=nullptr, Instruction *InsertBefore=nullptr)
Class to represent struct types.
Definition: DerivedTypes.h:201
ModulePass * createDeadArgHackingPass()
DeadArgHacking pass - Same as DAE, but delete arguments of external functions as well.
A Use represents the edge between a Value definition and its users.
Definition: Use.h:56
AttributeSet getRetAttributes() const
The attributes for the ret value are returned.
InstrTy * getInstruction() const
Definition: CallSite.h:89
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:336
User * getUser() const LLVM_READONLY
Returns the User that contains this Use.
Definition: Use.cpp:41
Class to represent function types.
Definition: DerivedTypes.h:103
#define F(x, y, z)
Definition: MD5.cpp:55
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
INITIALIZE_PASS(DAH, "deadarghaX0r", "Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)", false, false) ModulePass *llvm
createDeadArgEliminationPass - This pass removes arguments from functions which are not used by the b...
Class to represent array types.
Definition: DerivedTypes.h:369
AttributeSet getParamAttributes(unsigned ArgNo) const
The attributes for the argument or parameter at the given index are returned.
void setComdat(Comdat *C)
Definition: GlobalObject.h:103
bool isVarArg() const
Definition: DerivedTypes.h:123
AttrBuilder & remove(const AttrBuilder &B)
Remove the attributes from the builder.
AttributeList getAttributes() const
Return the attribute list for this Function.
Definition: Function.h:197
bool extractProfTotalWeight(uint64_t &TotalVal) const
Retrieve total raw weight values of a branch.
Definition: Metadata.cpp:1328
LinkageTypes getLinkage() const
Definition: GlobalValue.h:430
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:428
void takeName(Value *V)
Transfer the name from V to this value.
Definition: Value.cpp:290
iterator begin()
Definition: Function.h:580
void removeDeadConstantUsers() const
If there are any dead constant users dangling off of this constant, remove them.
Definition: Constants.cpp:475
static PreservedAnalyses none()
Convenience factory function for the empty preserved set.
Definition: PassManager.h:156
bool hasAttribute(Attribute::AttrKind Kind) const
Return true if the attribute exists in this set.
Definition: Attributes.cpp:571
static Constant * getBitCast(Constant *C, Type *Ty, bool OnlyIfReduced=false)
Definition: Constants.cpp:1678
bool isVoidTy() const
Return true if this is &#39;void&#39;.
Definition: Type.h:141
bool hasAttrSomewhere(Attribute::AttrKind Kind, unsigned *Index=nullptr) const
Return true if the specified attribute is set for at least one parameter or for the return value...
constexpr char Attrs[]
Key for Kernel::Metadata::mAttrs.
void setAttributes(AttributeList PAL)
Set the parameter attributes of the call.
Definition: CallSite.h:330
void setSubprogram(DISubprogram *SP)
Set the attached subprogram.
Definition: Metadata.cpp:1494
Type * getReturnType() const
Returns the type of the ret val.
Definition: Function.h:142
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:153
static AttributeSet get(LLVMContext &C, const AttrBuilder &B)
Definition: Attributes.cpp:501
const_iterator getFirstInsertionPt() const
Returns an iterator to the first instruction in this block that is suitable for inserting a non-PHI i...
Definition: BasicBlock.cpp:200
bool areAllPreserved() const
Test whether all analyses are preserved (and none are abandoned).
Definition: PassManager.h:321
static unsigned getAggregateOperandIndex()
const FunctionListType & getFunctionList() const
Get the Module&#39;s list of functions (constant).
Definition: Module.h:507
LLVM Basic Block Representation.
Definition: BasicBlock.h:59
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
DISubprogram * getSubprogram() const
Get the attached subprogram.
Definition: Metadata.cpp:1498
static ExtractValueInst * Create(Value *Agg, ArrayRef< unsigned > Idxs, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
void copyAttributesFrom(const Function *Src)
copyAttributesFrom - copy all additional attributes (those not needed to create a Function) from the ...
Definition: Function.cpp:463
constexpr char Args[]
Key for Kernel::Metadata::mArgs.
ModulePass * createDeadArgEliminationPass()
createDeadArgEliminationPass - This pass removes arguments from functions which are not used by the b...
unsigned getNumParams() const
Return the number of fixed parameters this function type requires.
Definition: DerivedTypes.h:139
void initializeDAEPass(PassRegistry &)
param_iterator param_begin() const
Definition: DerivedTypes.h:128
static Type * getVoidTy(LLVMContext &C)
Definition: Type.cpp:161
void splice(iterator where, iplist_impl &L2)
Definition: ilist.h:342
void setCallingConv(CallingConv::ID CC)
Set the calling convention of the call.
Definition: CallSite.h:313
static FunctionType * get(Type *Result, ArrayRef< Type *> Params, bool isVarArg)
This static method is the primary way of constructing a FunctionType.
Definition: Type.cpp:297
size_t arg_size() const
Definition: Function.h:622
arg_iterator arg_begin()
Definition: Function.h:595
self_iterator getIterator()
Definition: ilist_node.h:82
LLVMContext & getContext() const
getContext - Return a reference to the LLVMContext associated with this function. ...
Definition: Function.cpp:194
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1320
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:159
static InvokeInst * Create(Value *Func, BasicBlock *IfNormal, BasicBlock *IfException, ArrayRef< Value *> Args, const Twine &NameStr, Instruction *InsertBefore=nullptr)
static unsigned NumRetVals(const Function *F)
Convenience function that returns the number of return values.
Iterator for intrusive lists based on ilist_node.
bool hasParamAttribute(unsigned ArgNo, Attribute::AttrKind Kind) const
Equivalent to hasAttribute(ArgNo + FirstArgIndex, Kind).
#define E
Definition: LargeTest.cpp:27
AttrBuilder & removeAttribute(Attribute::AttrKind Val)
Remove an attribute from the builder.
IterTy arg_begin() const
Definition: CallSite.h:545
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:864
Module.h This file contains the declarations for the Module class.
static Type * getRetComponentType(const Function *F, unsigned Idx)
Returns the sub-type a function will return at a given Idx.
Type * getReturnType() const
Definition: DerivedTypes.h:124
void setAttributes(AttributeList Attrs)
Set the attribute list for this Function.
Definition: Function.h:200
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
FunctionType * getFunctionType() const
Returns the FunctionType for me.
Definition: Function.h:137
const Comdat * getComdat() const
Definition: GlobalObject.h:101
iterator insert(iterator where, pointer New)
Definition: ilist.h:241
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:280
iterator end()
Definition: Module.h:574
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:61
void getOperandBundlesAsDefs(SmallVectorImpl< OperandBundleDef > &Defs) const
Definition: CallSite.h:556
static InsertValueInst * Create(Value *Agg, Value *Val, ArrayRef< unsigned > Idxs, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:218
bool hasExactDefinition() const
Return true if this global has an exact defintion.
Definition: GlobalValue.h:387
Establish a view to a call site for examination.
Definition: CallSite.h:687
#define I(x, y, z)
Definition: MD5.cpp:58
user_iterator_impl< User > user_iterator
Definition: Value.h:364
ModulePass class - This class is used to implement unstructured interprocedural optimizations and ana...
Definition: Pass.h:235
iterator begin()
Definition: Module.h:572
static ArrayType * get(Type *ElementType, uint64_t NumElements)
This static method is the primary way to construct an ArrayType.
Definition: Type.cpp:568
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:323
const BasicBlockListType & getBasicBlockList() const
Get the underlying elements of the Function...
Definition: Function.h:557
void eraseFromParent()
eraseFromParent - This method unlinks &#39;this&#39; from the containing module and deletes it...
Definition: Function.cpp:202
bool isDeclaration() const
Return true if the primary definition of this global value is outside of the current translation unit...
Definition: Globals.cpp:200
bool hasAddressTaken(const User **=nullptr) const
hasAddressTaken - returns true if there are any uses of this function other than direct calls or invo...
Definition: Function.cpp:1208
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
Liveness
Liveness enum - During our initial pass over the program, we determine that things are either alive o...
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:545
LLVM Value Representation.
Definition: Value.h:73
AttrBuilder typeIncompatible(Type *Ty)
Which attributes cannot be applied to a type.
AttributeSet getFnAttributes() const
The function attributes are returned.
Invoke instruction.
#define DEBUG(X)
Definition: Debug.h:118
BasicBlock * SplitEdge(BasicBlock *From, BasicBlock *To, DominatorTree *DT=nullptr, LoopInfo *LI=nullptr)
Split the edge connecting specified block.
A container for analyses that lazily runs them and caches their results.
static Function * Create(FunctionType *Ty, LinkageTypes Linkage, const Twine &N="", Module *M=nullptr)
Definition: Function.h:128
AttributeList getAttributes() const
Get the parameter attributes of the call.
Definition: CallSite.h:326
bool isEmpty() const
Return true if there are no attributes.
Definition: Attributes.h:646
bool use_empty() const
Definition: Value.h:322
PointerType * getType() const
Global values are always pointers.
Definition: GlobalValue.h:260
static AttributeList get(LLVMContext &C, ArrayRef< std::pair< unsigned, Attribute >> Attrs)
Create an AttributeList with the specified parameters in it.
Definition: Attributes.cpp:868
iterator_range< arg_iterator > args()
Definition: Function.h:613
User * user_back()
Definition: Value.h:381
A wrapper class for inspecting calls to intrinsic functions.
Definition: IntrinsicInst.h:44
const BasicBlock * getParent() const
Definition: Instruction.h:66
This instruction inserts a struct field of array element value into an aggregate value.
PreservedAnalyses run(Module &M, ModuleAnalysisManager &)