LLVM  8.0.0svn
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/IR/Argument.h"
24 #include "llvm/IR/Attributes.h"
25 #include "llvm/IR/BasicBlock.h"
26 #include "llvm/IR/CallSite.h"
27 #include "llvm/IR/Constant.h"
28 #include "llvm/IR/Constants.h"
29 #include "llvm/IR/DerivedTypes.h"
30 #include "llvm/IR/Function.h"
31 #include "llvm/IR/InstrTypes.h"
32 #include "llvm/IR/Instruction.h"
33 #include "llvm/IR/Instructions.h"
34 #include "llvm/IR/IntrinsicInst.h"
35 #include "llvm/IR/Intrinsics.h"
36 #include "llvm/IR/Module.h"
37 #include "llvm/IR/PassManager.h"
38 #include "llvm/IR/Type.h"
39 #include "llvm/IR/Use.h"
40 #include "llvm/IR/User.h"
41 #include "llvm/IR/Value.h"
42 #include "llvm/Pass.h"
43 #include "llvm/Support/Casting.h"
44 #include "llvm/Support/Debug.h"
46 #include "llvm/Transforms/IPO.h"
48 #include <cassert>
49 #include <cstdint>
50 #include <utility>
51 #include <vector>
52 
53 using namespace llvm;
54 
55 #define DEBUG_TYPE "deadargelim"
56 
57 STATISTIC(NumArgumentsEliminated, "Number of unread args removed");
58 STATISTIC(NumRetValsEliminated , "Number of unused return values removed");
59 STATISTIC(NumArgumentsReplacedWithUndef,
60  "Number of unread args replaced with undef");
61 
62 namespace {
63 
64  /// DAE - The dead argument elimination pass.
65  class DAE : public ModulePass {
66  protected:
67  // DAH uses this to specify a different ID.
68  explicit DAE(char &ID) : ModulePass(ID) {}
69 
70  public:
71  static char ID; // Pass identification, replacement for typeid
72 
73  DAE() : ModulePass(ID) {
75  }
76 
77  bool runOnModule(Module &M) override {
78  if (skipModule(M))
79  return false;
80  DeadArgumentEliminationPass DAEP(ShouldHackArguments());
81  ModuleAnalysisManager DummyMAM;
82  PreservedAnalyses PA = DAEP.run(M, DummyMAM);
83  return !PA.areAllPreserved();
84  }
85 
86  virtual bool ShouldHackArguments() const { return false; }
87  };
88 
89 } // end anonymous namespace
90 
91 char DAE::ID = 0;
92 
93 INITIALIZE_PASS(DAE, "deadargelim", "Dead Argument Elimination", false, false)
94 
95 namespace {
96 
97  /// DAH - DeadArgumentHacking pass - Same as dead argument elimination, but
98  /// deletes arguments to functions which are external. This is only for use
99  /// by bugpoint.
100  struct DAH : public DAE {
101  static char ID;
102 
103  DAH() : DAE(ID) {}
104 
105  bool ShouldHackArguments() const override { return true; }
106  };
107 
108 } // end anonymous namespace
109 
110 char DAH::ID = 0;
111 
112 INITIALIZE_PASS(DAH, "deadarghaX0r",
113  "Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)",
114  false, false)
115 
116 /// createDeadArgEliminationPass - This pass removes arguments from functions
117 /// which are not used by the body of the function.
118 ModulePass *llvm::createDeadArgEliminationPass() { return new DAE(); }
119 
121 
122 /// DeleteDeadVarargs - If this is an function that takes a ... list, and if
123 /// llvm.vastart is never called, the varargs list is dead for the function.
124 bool DeadArgumentEliminationPass::DeleteDeadVarargs(Function &Fn) {
125  assert(Fn.getFunctionType()->isVarArg() && "Function isn't varargs!");
126  if (Fn.isDeclaration() || !Fn.hasLocalLinkage()) return false;
127 
128  // Ensure that the function is only directly called.
129  if (Fn.hasAddressTaken())
130  return false;
131 
132  // Don't touch naked functions. The assembly might be using an argument, or
133  // otherwise rely on the frame layout in a way that this analysis will not
134  // see.
135  if (Fn.hasFnAttribute(Attribute::Naked)) {
136  return false;
137  }
138 
139  // Okay, we know we can transform this function if safe. Scan its body
140  // looking for calls marked musttail or calls to llvm.vastart.
141  for (BasicBlock &BB : Fn) {
142  for (Instruction &I : BB) {
143  CallInst *CI = dyn_cast<CallInst>(&I);
144  if (!CI)
145  continue;
146  if (CI->isMustTailCall())
147  return false;
148  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI)) {
149  if (II->getIntrinsicID() == Intrinsic::vastart)
150  return false;
151  }
152  }
153  }
154 
155  // If we get here, there are no calls to llvm.vastart in the function body,
156  // remove the "..." and adjust all the calls.
157 
158  // Start by computing a new prototype for the function, which is the same as
159  // the old function, but doesn't have isVarArg set.
160  FunctionType *FTy = Fn.getFunctionType();
161 
162  std::vector<Type *> Params(FTy->param_begin(), FTy->param_end());
164  Params, false);
165  unsigned NumArgs = Params.size();
166 
167  // Create the new function body and insert it into the module...
168  Function *NF = Function::Create(NFTy, Fn.getLinkage());
169  NF->copyAttributesFrom(&Fn);
170  NF->setComdat(Fn.getComdat());
171  Fn.getParent()->getFunctionList().insert(Fn.getIterator(), NF);
172  NF->takeName(&Fn);
173 
174  // Loop over all of the callers of the function, transforming the call sites
175  // to pass in a smaller number of arguments into the new function.
176  //
177  std::vector<Value *> Args;
178  for (Value::user_iterator I = Fn.user_begin(), E = Fn.user_end(); I != E; ) {
179  CallSite CS(*I++);
180  if (!CS)
181  continue;
182  Instruction *Call = CS.getInstruction();
183 
184  // Pass all the same arguments.
185  Args.assign(CS.arg_begin(), CS.arg_begin() + NumArgs);
186 
187  // Drop any attributes that were on the vararg arguments.
188  AttributeList PAL = CS.getAttributes();
189  if (!PAL.isEmpty()) {
191  for (unsigned ArgNo = 0; ArgNo < NumArgs; ++ArgNo)
192  ArgAttrs.push_back(PAL.getParamAttributes(ArgNo));
193  PAL = AttributeList::get(Fn.getContext(), PAL.getFnAttributes(),
194  PAL.getRetAttributes(), ArgAttrs);
195  }
196 
198  CS.getOperandBundlesAsDefs(OpBundles);
199 
200  CallSite NewCS;
201  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
202  NewCS = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
203  Args, OpBundles, "", Call);
204  } else {
205  NewCS = CallInst::Create(NF, Args, OpBundles, "", Call);
206  cast<CallInst>(NewCS.getInstruction())
207  ->setTailCallKind(cast<CallInst>(Call)->getTailCallKind());
208  }
209  NewCS.setCallingConv(CS.getCallingConv());
210  NewCS.setAttributes(PAL);
211  NewCS->setDebugLoc(Call->getDebugLoc());
212  uint64_t W;
213  if (Call->extractProfTotalWeight(W))
214  NewCS->setProfWeight(W);
215 
216  Args.clear();
217 
218  if (!Call->use_empty())
219  Call->replaceAllUsesWith(NewCS.getInstruction());
220 
221  NewCS->takeName(Call);
222 
223  // Finally, remove the old call from the program, reducing the use-count of
224  // F.
225  Call->eraseFromParent();
226  }
227 
228  // Since we have now created the new function, splice the body of the old
229  // function right into the new function, leaving the old rotting hulk of the
230  // function empty.
231  NF->getBasicBlockList().splice(NF->begin(), Fn.getBasicBlockList());
232 
233  // Loop over the argument list, transferring uses of the old arguments over to
234  // the new arguments, also transferring over the names as well. While we're at
235  // it, remove the dead arguments from the DeadArguments list.
236  for (Function::arg_iterator I = Fn.arg_begin(), E = Fn.arg_end(),
237  I2 = NF->arg_begin(); I != E; ++I, ++I2) {
238  // Move the name and users over to the new version.
239  I->replaceAllUsesWith(&*I2);
240  I2->takeName(&*I);
241  }
242 
243  // Clone metadatas from the old function, including debug info descriptor.
245  Fn.getAllMetadata(MDs);
246  for (auto MD : MDs)
247  NF->addMetadata(MD.first, *MD.second);
248 
249  // Fix up any BlockAddresses that refer to the function.
250  Fn.replaceAllUsesWith(ConstantExpr::getBitCast(NF, Fn.getType()));
251  // Delete the bitcast that we just created, so that NF does not
252  // appear to be address-taken.
254  // Finally, nuke the old function.
255  Fn.eraseFromParent();
256  return true;
257 }
258 
259 /// RemoveDeadArgumentsFromCallers - Checks if the given function has any
260 /// arguments that are unused, and changes the caller parameters to be undefined
261 /// instead.
262 bool DeadArgumentEliminationPass::RemoveDeadArgumentsFromCallers(Function &Fn) {
263  // We cannot change the arguments if this TU does not define the function or
264  // if the linker may choose a function body from another TU, even if the
265  // nominal linkage indicates that other copies of the function have the same
266  // semantics. In the below example, the dead load from %p may not have been
267  // eliminated from the linker-chosen copy of f, so replacing %p with undef
268  // in callers may introduce undefined behavior.
269  //
270  // define linkonce_odr void @f(i32* %p) {
271  // %v = load i32 %p
272  // ret void
273  // }
274  if (!Fn.hasExactDefinition())
275  return false;
276 
277  // Functions with local linkage should already have been handled, except the
278  // fragile (variadic) ones which we can improve here.
279  if (Fn.hasLocalLinkage() && !Fn.getFunctionType()->isVarArg())
280  return false;
281 
282  // Don't touch naked functions. The assembly might be using an argument, or
283  // otherwise rely on the frame layout in a way that this analysis will not
284  // see.
285  if (Fn.hasFnAttribute(Attribute::Naked))
286  return false;
287 
288  if (Fn.use_empty())
289  return false;
290 
291  SmallVector<unsigned, 8> UnusedArgs;
292  bool Changed = false;
293 
294  for (Argument &Arg : Fn.args()) {
295  if (!Arg.hasSwiftErrorAttr() && Arg.use_empty() && !Arg.hasByValOrInAllocaAttr()) {
296  if (Arg.isUsedByMetadata()) {
298  Changed = true;
299  }
300  UnusedArgs.push_back(Arg.getArgNo());
301  }
302  }
303 
304  if (UnusedArgs.empty())
305  return false;
306 
307  for (Use &U : Fn.uses()) {
308  CallSite CS(U.getUser());
309  if (!CS || !CS.isCallee(&U))
310  continue;
311 
312  // Now go through all unused args and replace them with "undef".
313  for (unsigned I = 0, E = UnusedArgs.size(); I != E; ++I) {
314  unsigned ArgNo = UnusedArgs[I];
315 
316  Value *Arg = CS.getArgument(ArgNo);
317  CS.setArgument(ArgNo, UndefValue::get(Arg->getType()));
318  ++NumArgumentsReplacedWithUndef;
319  Changed = true;
320  }
321  }
322 
323  return Changed;
324 }
325 
326 /// Convenience function that returns the number of return values. It returns 0
327 /// for void functions and 1 for functions not returning a struct. It returns
328 /// the number of struct elements for functions returning a struct.
329 static unsigned NumRetVals(const Function *F) {
330  Type *RetTy = F->getReturnType();
331  if (RetTy->isVoidTy())
332  return 0;
333  else if (StructType *STy = dyn_cast<StructType>(RetTy))
334  return STy->getNumElements();
335  else if (ArrayType *ATy = dyn_cast<ArrayType>(RetTy))
336  return ATy->getNumElements();
337  else
338  return 1;
339 }
340 
341 /// Returns the sub-type a function will return at a given Idx. Should
342 /// correspond to the result type of an ExtractValue instruction executed with
343 /// just that one Idx (i.e. only top-level structure is considered).
344 static Type *getRetComponentType(const Function *F, unsigned Idx) {
345  Type *RetTy = F->getReturnType();
346  assert(!RetTy->isVoidTy() && "void type has no subtype");
347 
348  if (StructType *STy = dyn_cast<StructType>(RetTy))
349  return STy->getElementType(Idx);
350  else if (ArrayType *ATy = dyn_cast<ArrayType>(RetTy))
351  return ATy->getElementType();
352  else
353  return RetTy;
354 }
355 
356 /// MarkIfNotLive - This checks Use for liveness in LiveValues. If Use is not
357 /// live, it adds Use to the MaybeLiveUses argument. Returns the determined
358 /// liveness of Use.
360 DeadArgumentEliminationPass::MarkIfNotLive(RetOrArg Use,
361  UseVector &MaybeLiveUses) {
362  // We're live if our use or its Function is already marked as live.
363  if (LiveFunctions.count(Use.F) || LiveValues.count(Use))
364  return Live;
365 
366  // We're maybe live otherwise, but remember that we must become live if
367  // Use becomes live.
368  MaybeLiveUses.push_back(Use);
369  return MaybeLive;
370 }
371 
372 /// SurveyUse - This looks at a single use of an argument or return value
373 /// and determines if it should be alive or not. Adds this use to MaybeLiveUses
374 /// if it causes the used value to become MaybeLive.
375 ///
376 /// RetValNum is the return value number to use when this use is used in a
377 /// return instruction. This is used in the recursion, you should always leave
378 /// it at 0.
380 DeadArgumentEliminationPass::SurveyUse(const Use *U, UseVector &MaybeLiveUses,
381  unsigned RetValNum) {
382  const User *V = U->getUser();
383  if (const ReturnInst *RI = dyn_cast<ReturnInst>(V)) {
384  // The value is returned from a function. It's only live when the
385  // function's return value is live. We use RetValNum here, for the case
386  // that U is really a use of an insertvalue instruction that uses the
387  // original Use.
388  const Function *F = RI->getParent()->getParent();
389  if (RetValNum != -1U) {
390  RetOrArg Use = CreateRet(F, RetValNum);
391  // We might be live, depending on the liveness of Use.
392  return MarkIfNotLive(Use, MaybeLiveUses);
393  } else {
394  DeadArgumentEliminationPass::Liveness Result = MaybeLive;
395  for (unsigned i = 0; i < NumRetVals(F); ++i) {
396  RetOrArg Use = CreateRet(F, i);
397  // We might be live, depending on the liveness of Use. If any
398  // sub-value is live, then the entire value is considered live. This
399  // is a conservative choice, and better tracking is possible.
401  MarkIfNotLive(Use, MaybeLiveUses);
402  if (Result != Live)
403  Result = SubResult;
404  }
405  return Result;
406  }
407  }
408  if (const InsertValueInst *IV = dyn_cast<InsertValueInst>(V)) {
409  if (U->getOperandNo() != InsertValueInst::getAggregateOperandIndex()
410  && IV->hasIndices())
411  // The use we are examining is inserted into an aggregate. Our liveness
412  // depends on all uses of that aggregate, but if it is used as a return
413  // value, only index at which we were inserted counts.
414  RetValNum = *IV->idx_begin();
415 
416  // Note that if we are used as the aggregate operand to the insertvalue,
417  // we don't change RetValNum, but do survey all our uses.
418 
419  Liveness Result = MaybeLive;
420  for (const Use &UU : IV->uses()) {
421  Result = SurveyUse(&UU, MaybeLiveUses, RetValNum);
422  if (Result == Live)
423  break;
424  }
425  return Result;
426  }
427 
428  if (auto CS = ImmutableCallSite(V)) {
429  const Function *F = CS.getCalledFunction();
430  if (F) {
431  // Used in a direct call.
432 
433  // The function argument is live if it is used as a bundle operand.
434  if (CS.isBundleOperand(U))
435  return Live;
436 
437  // Find the argument number. We know for sure that this use is an
438  // argument, since if it was the function argument this would be an
439  // indirect call and the we know can't be looking at a value of the
440  // label type (for the invoke instruction).
441  unsigned ArgNo = CS.getArgumentNo(U);
442 
443  if (ArgNo >= F->getFunctionType()->getNumParams())
444  // The value is passed in through a vararg! Must be live.
445  return Live;
446 
447  assert(CS.getArgument(ArgNo)
448  == CS->getOperand(U->getOperandNo())
449  && "Argument is not where we expected it");
450 
451  // Value passed to a normal call. It's only live when the corresponding
452  // argument to the called function turns out live.
453  RetOrArg Use = CreateArg(F, ArgNo);
454  return MarkIfNotLive(Use, MaybeLiveUses);
455  }
456  }
457  // Used in any other way? Value must be live.
458  return Live;
459 }
460 
461 /// SurveyUses - This looks at all the uses of the given value
462 /// Returns the Liveness deduced from the uses of this value.
463 ///
464 /// Adds all uses that cause the result to be MaybeLive to MaybeLiveRetUses. If
465 /// the result is Live, MaybeLiveUses might be modified but its content should
466 /// be ignored (since it might not be complete).
468 DeadArgumentEliminationPass::SurveyUses(const Value *V,
469  UseVector &MaybeLiveUses) {
470  // Assume it's dead (which will only hold if there are no uses at all..).
471  Liveness Result = MaybeLive;
472  // Check each use.
473  for (const Use &U : V->uses()) {
474  Result = SurveyUse(&U, MaybeLiveUses);
475  if (Result == Live)
476  break;
477  }
478  return Result;
479 }
480 
481 // SurveyFunction - This performs the initial survey of the specified function,
482 // checking out whether or not it uses any of its incoming arguments or whether
483 // any callers use the return value. This fills in the LiveValues set and Uses
484 // map.
485 //
486 // We consider arguments of non-internal functions to be intrinsically alive as
487 // well as arguments to functions which have their "address taken".
488 void DeadArgumentEliminationPass::SurveyFunction(const Function &F) {
489  // Functions with inalloca parameters are expecting args in a particular
490  // register and memory layout.
491  if (F.getAttributes().hasAttrSomewhere(Attribute::InAlloca)) {
492  MarkLive(F);
493  return;
494  }
495 
496  // Don't touch naked functions. The assembly might be using an argument, or
497  // otherwise rely on the frame layout in a way that this analysis will not
498  // see.
499  if (F.hasFnAttribute(Attribute::Naked)) {
500  MarkLive(F);
501  return;
502  }
503 
504  unsigned RetCount = NumRetVals(&F);
505 
506  // Assume all return values are dead
507  using RetVals = SmallVector<Liveness, 5>;
508 
509  RetVals RetValLiveness(RetCount, MaybeLive);
510 
511  using RetUses = SmallVector<UseVector, 5>;
512 
513  // These vectors map each return value to the uses that make it MaybeLive, so
514  // we can add those to the Uses map if the return value really turns out to be
515  // MaybeLive. Initialized to a list of RetCount empty lists.
516  RetUses MaybeLiveRetUses(RetCount);
517 
518  bool HasMustTailCalls = false;
519 
520  for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
521  if (const ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
522  if (RI->getNumOperands() != 0 && RI->getOperand(0)->getType()
523  != F.getFunctionType()->getReturnType()) {
524  // We don't support old style multiple return values.
525  MarkLive(F);
526  return;
527  }
528  }
529 
530  // If we have any returns of `musttail` results - the signature can't
531  // change
532  if (BB->getTerminatingMustTailCall() != nullptr)
533  HasMustTailCalls = true;
534  }
535 
536  if (HasMustTailCalls) {
537  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - " << F.getName()
538  << " has musttail calls\n");
539  }
540 
541  if (!F.hasLocalLinkage() && (!ShouldHackArguments || F.isIntrinsic())) {
542  MarkLive(F);
543  return;
544  }
545 
546  LLVM_DEBUG(
547  dbgs() << "DeadArgumentEliminationPass - Inspecting callers for fn: "
548  << F.getName() << "\n");
549  // Keep track of the number of live retvals, so we can skip checks once all
550  // of them turn out to be live.
551  unsigned NumLiveRetVals = 0;
552 
553  bool HasMustTailCallers = false;
554 
555  // Loop all uses of the function.
556  for (const Use &U : F.uses()) {
557  // If the function is PASSED IN as an argument, its address has been
558  // taken.
559  ImmutableCallSite CS(U.getUser());
560  if (!CS || !CS.isCallee(&U)) {
561  MarkLive(F);
562  return;
563  }
564 
565  // The number of arguments for `musttail` call must match the number of
566  // arguments of the caller
567  if (CS.isMustTailCall())
568  HasMustTailCallers = true;
569 
570  // If this use is anything other than a call site, the function is alive.
571  const Instruction *TheCall = CS.getInstruction();
572  if (!TheCall) { // Not a direct call site?
573  MarkLive(F);
574  return;
575  }
576 
577  // If we end up here, we are looking at a direct call to our function.
578 
579  // Now, check how our return value(s) is/are used in this caller. Don't
580  // bother checking return values if all of them are live already.
581  if (NumLiveRetVals == RetCount)
582  continue;
583 
584  // Check all uses of the return value.
585  for (const Use &U : TheCall->uses()) {
586  if (ExtractValueInst *Ext = dyn_cast<ExtractValueInst>(U.getUser())) {
587  // This use uses a part of our return value, survey the uses of
588  // that part and store the results for this index only.
589  unsigned Idx = *Ext->idx_begin();
590  if (RetValLiveness[Idx] != Live) {
591  RetValLiveness[Idx] = SurveyUses(Ext, MaybeLiveRetUses[Idx]);
592  if (RetValLiveness[Idx] == Live)
593  NumLiveRetVals++;
594  }
595  } else {
596  // Used by something else than extractvalue. Survey, but assume that the
597  // result applies to all sub-values.
598  UseVector MaybeLiveAggregateUses;
599  if (SurveyUse(&U, MaybeLiveAggregateUses) == Live) {
600  NumLiveRetVals = RetCount;
601  RetValLiveness.assign(RetCount, Live);
602  break;
603  } else {
604  for (unsigned i = 0; i != RetCount; ++i) {
605  if (RetValLiveness[i] != Live)
606  MaybeLiveRetUses[i].append(MaybeLiveAggregateUses.begin(),
607  MaybeLiveAggregateUses.end());
608  }
609  }
610  }
611  }
612  }
613 
614  if (HasMustTailCallers) {
615  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - " << F.getName()
616  << " has musttail callers\n");
617  }
618 
619  // Now we've inspected all callers, record the liveness of our return values.
620  for (unsigned i = 0; i != RetCount; ++i)
621  MarkValue(CreateRet(&F, i), RetValLiveness[i], MaybeLiveRetUses[i]);
622 
623  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Inspecting args for fn: "
624  << F.getName() << "\n");
625 
626  // Now, check all of our arguments.
627  unsigned i = 0;
628  UseVector MaybeLiveArgUses;
630  E = F.arg_end(); AI != E; ++AI, ++i) {
631  Liveness Result;
632  if (F.getFunctionType()->isVarArg() || HasMustTailCallers ||
633  HasMustTailCalls) {
634  // Variadic functions will already have a va_arg function expanded inside
635  // them, making them potentially very sensitive to ABI changes resulting
636  // from removing arguments entirely, so don't. For example AArch64 handles
637  // register and stack HFAs very differently, and this is reflected in the
638  // IR which has already been generated.
639  //
640  // `musttail` calls to this function restrict argument removal attempts.
641  // The signature of the caller must match the signature of the function.
642  //
643  // `musttail` calls in this function prevents us from changing its
644  // signature
645  Result = Live;
646  } else {
647  // See what the effect of this use is (recording any uses that cause
648  // MaybeLive in MaybeLiveArgUses).
649  Result = SurveyUses(&*AI, MaybeLiveArgUses);
650  }
651 
652  // Mark the result.
653  MarkValue(CreateArg(&F, i), Result, MaybeLiveArgUses);
654  // Clear the vector again for the next iteration.
655  MaybeLiveArgUses.clear();
656  }
657 }
658 
659 /// MarkValue - This function marks the liveness of RA depending on L. If L is
660 /// MaybeLive, it also takes all uses in MaybeLiveUses and records them in Uses,
661 /// such that RA will be marked live if any use in MaybeLiveUses gets marked
662 /// live later on.
663 void DeadArgumentEliminationPass::MarkValue(const RetOrArg &RA, Liveness L,
664  const UseVector &MaybeLiveUses) {
665  switch (L) {
666  case Live:
667  MarkLive(RA);
668  break;
669  case MaybeLive:
670  // Note any uses of this value, so this return value can be
671  // marked live whenever one of the uses becomes live.
672  for (const auto &MaybeLiveUse : MaybeLiveUses)
673  Uses.insert(std::make_pair(MaybeLiveUse, RA));
674  break;
675  }
676 }
677 
678 /// MarkLive - Mark the given Function as alive, meaning that it cannot be
679 /// changed in any way. Additionally,
680 /// mark any values that are used as this function's parameters or by its return
681 /// values (according to Uses) live as well.
682 void DeadArgumentEliminationPass::MarkLive(const Function &F) {
683  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Intrinsically live fn: "
684  << F.getName() << "\n");
685  // Mark the function as live.
686  LiveFunctions.insert(&F);
687  // Mark all arguments as live.
688  for (unsigned i = 0, e = F.arg_size(); i != e; ++i)
689  PropagateLiveness(CreateArg(&F, i));
690  // Mark all return values as live.
691  for (unsigned i = 0, e = NumRetVals(&F); i != e; ++i)
692  PropagateLiveness(CreateRet(&F, i));
693 }
694 
695 /// MarkLive - Mark the given return value or argument as live. Additionally,
696 /// mark any values that are used by this value (according to Uses) live as
697 /// well.
698 void DeadArgumentEliminationPass::MarkLive(const RetOrArg &RA) {
699  if (LiveFunctions.count(RA.F))
700  return; // Function was already marked Live.
701 
702  if (!LiveValues.insert(RA).second)
703  return; // We were already marked Live.
704 
705  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Marking "
706  << RA.getDescription() << " live\n");
707  PropagateLiveness(RA);
708 }
709 
710 /// PropagateLiveness - Given that RA is a live value, propagate it's liveness
711 /// to any other values it uses (according to Uses).
712 void DeadArgumentEliminationPass::PropagateLiveness(const RetOrArg &RA) {
713  // We don't use upper_bound (or equal_range) here, because our recursive call
714  // to ourselves is likely to cause the upper_bound (which is the first value
715  // not belonging to RA) to become erased and the iterator invalidated.
716  UseMap::iterator Begin = Uses.lower_bound(RA);
717  UseMap::iterator E = Uses.end();
718  UseMap::iterator I;
719  for (I = Begin; I != E && I->first == RA; ++I)
720  MarkLive(I->second);
721 
722  // Erase RA from the Uses map (from the lower bound to wherever we ended up
723  // after the loop).
724  Uses.erase(Begin, I);
725 }
726 
727 // RemoveDeadStuffFromFunction - Remove any arguments and return values from F
728 // that are not in LiveValues. Transform the function and all of the callees of
729 // the function to not have these arguments and return values.
730 //
731 bool DeadArgumentEliminationPass::RemoveDeadStuffFromFunction(Function *F) {
732  // Don't modify fully live functions
733  if (LiveFunctions.count(F))
734  return false;
735 
736  // Start by computing a new prototype for the function, which is the same as
737  // the old function, but has fewer arguments and a different return type.
738  FunctionType *FTy = F->getFunctionType();
739  std::vector<Type*> Params;
740 
741  // Keep track of if we have a live 'returned' argument
742  bool HasLiveReturnedArg = false;
743 
744  // Set up to build a new list of parameter attributes.
745  SmallVector<AttributeSet, 8> ArgAttrVec;
746  const AttributeList &PAL = F->getAttributes();
747 
748  // Remember which arguments are still alive.
749  SmallVector<bool, 10> ArgAlive(FTy->getNumParams(), false);
750  // Construct the new parameter list from non-dead arguments. Also construct
751  // a new set of parameter attributes to correspond. Skip the first parameter
752  // attribute, since that belongs to the return value.
753  unsigned i = 0;
754  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
755  I != E; ++I, ++i) {
756  RetOrArg Arg = CreateArg(F, i);
757  if (LiveValues.erase(Arg)) {
758  Params.push_back(I->getType());
759  ArgAlive[i] = true;
760  ArgAttrVec.push_back(PAL.getParamAttributes(i));
761  HasLiveReturnedArg |= PAL.hasParamAttribute(i, Attribute::Returned);
762  } else {
763  ++NumArgumentsEliminated;
764  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Removing argument "
765  << i << " (" << I->getName() << ") from "
766  << F->getName() << "\n");
767  }
768  }
769 
770  // Find out the new return value.
771  Type *RetTy = FTy->getReturnType();
772  Type *NRetTy = nullptr;
773  unsigned RetCount = NumRetVals(F);
774 
775  // -1 means unused, other numbers are the new index
776  SmallVector<int, 5> NewRetIdxs(RetCount, -1);
777  std::vector<Type*> RetTypes;
778 
779  // If there is a function with a live 'returned' argument but a dead return
780  // value, then there are two possible actions:
781  // 1) Eliminate the return value and take off the 'returned' attribute on the
782  // argument.
783  // 2) Retain the 'returned' attribute and treat the return value (but not the
784  // entire function) as live so that it is not eliminated.
785  //
786  // It's not clear in the general case which option is more profitable because,
787  // even in the absence of explicit uses of the return value, code generation
788  // is free to use the 'returned' attribute to do things like eliding
789  // save/restores of registers across calls. Whether or not this happens is
790  // target and ABI-specific as well as depending on the amount of register
791  // pressure, so there's no good way for an IR-level pass to figure this out.
792  //
793  // Fortunately, the only places where 'returned' is currently generated by
794  // the FE are places where 'returned' is basically free and almost always a
795  // performance win, so the second option can just be used always for now.
796  //
797  // This should be revisited if 'returned' is ever applied more liberally.
798  if (RetTy->isVoidTy() || HasLiveReturnedArg) {
799  NRetTy = RetTy;
800  } else {
801  // Look at each of the original return values individually.
802  for (unsigned i = 0; i != RetCount; ++i) {
803  RetOrArg Ret = CreateRet(F, i);
804  if (LiveValues.erase(Ret)) {
805  RetTypes.push_back(getRetComponentType(F, i));
806  NewRetIdxs[i] = RetTypes.size() - 1;
807  } else {
808  ++NumRetValsEliminated;
809  LLVM_DEBUG(
810  dbgs() << "DeadArgumentEliminationPass - Removing return value "
811  << i << " from " << F->getName() << "\n");
812  }
813  }
814  if (RetTypes.size() > 1) {
815  // More than one return type? Reduce it down to size.
816  if (StructType *STy = dyn_cast<StructType>(RetTy)) {
817  // Make the new struct packed if we used to return a packed struct
818  // already.
819  NRetTy = StructType::get(STy->getContext(), RetTypes, STy->isPacked());
820  } else {
821  assert(isa<ArrayType>(RetTy) && "unexpected multi-value return");
822  NRetTy = ArrayType::get(RetTypes[0], RetTypes.size());
823  }
824  } else if (RetTypes.size() == 1)
825  // One return type? Just a simple value then, but only if we didn't use to
826  // return a struct with that simple value before.
827  NRetTy = RetTypes.front();
828  else if (RetTypes.empty())
829  // No return types? Make it void, but only if we didn't use to return {}.
830  NRetTy = Type::getVoidTy(F->getContext());
831  }
832 
833  assert(NRetTy && "No new return type found?");
834 
835  // The existing function return attributes.
836  AttrBuilder RAttrs(PAL.getRetAttributes());
837 
838  // Remove any incompatible attributes, but only if we removed all return
839  // values. Otherwise, ensure that we don't have any conflicting attributes
840  // here. Currently, this should not be possible, but special handling might be
841  // required when new return value attributes are added.
842  if (NRetTy->isVoidTy())
844  else
845  assert(!RAttrs.overlaps(AttributeFuncs::typeIncompatible(NRetTy)) &&
846  "Return attributes no longer compatible?");
847 
848  AttributeSet RetAttrs = AttributeSet::get(F->getContext(), RAttrs);
849 
850  // Strip allocsize attributes. They might refer to the deleted arguments.
852  F->getContext(), Attribute::AllocSize);
853 
854  // Reconstruct the AttributesList based on the vector we constructed.
855  assert(ArgAttrVec.size() == Params.size());
856  AttributeList NewPAL =
857  AttributeList::get(F->getContext(), FnAttrs, RetAttrs, ArgAttrVec);
858 
859  // Create the new function type based on the recomputed parameters.
860  FunctionType *NFTy = FunctionType::get(NRetTy, Params, FTy->isVarArg());
861 
862  // No change?
863  if (NFTy == FTy)
864  return false;
865 
866  // Create the new function body and insert it into the module...
867  Function *NF = Function::Create(NFTy, F->getLinkage());
868  NF->copyAttributesFrom(F);
869  NF->setComdat(F->getComdat());
870  NF->setAttributes(NewPAL);
871  // Insert the new function before the old function, so we won't be processing
872  // it again.
873  F->getParent()->getFunctionList().insert(F->getIterator(), NF);
874  NF->takeName(F);
875 
876  // Loop over all of the callers of the function, transforming the call sites
877  // to pass in a smaller number of arguments into the new function.
878  std::vector<Value*> Args;
879  while (!F->use_empty()) {
880  CallSite CS(F->user_back());
881  Instruction *Call = CS.getInstruction();
882 
883  ArgAttrVec.clear();
884  const AttributeList &CallPAL = CS.getAttributes();
885 
886  // Adjust the call return attributes in case the function was changed to
887  // return void.
888  AttrBuilder RAttrs(CallPAL.getRetAttributes());
890  AttributeSet RetAttrs = AttributeSet::get(F->getContext(), RAttrs);
891 
892  // Declare these outside of the loops, so we can reuse them for the second
893  // loop, which loops the varargs.
894  CallSite::arg_iterator I = CS.arg_begin();
895  unsigned i = 0;
896  // Loop over those operands, corresponding to the normal arguments to the
897  // original function, and add those that are still alive.
898  for (unsigned e = FTy->getNumParams(); i != e; ++I, ++i)
899  if (ArgAlive[i]) {
900  Args.push_back(*I);
901  // Get original parameter attributes, but skip return attributes.
903  if (NRetTy != RetTy && Attrs.hasAttribute(Attribute::Returned)) {
904  // If the return type has changed, then get rid of 'returned' on the
905  // call site. The alternative is to make all 'returned' attributes on
906  // call sites keep the return value alive just like 'returned'
907  // attributes on function declaration but it's less clearly a win and
908  // this is not an expected case anyway
909  ArgAttrVec.push_back(AttributeSet::get(
910  F->getContext(),
911  AttrBuilder(Attrs).removeAttribute(Attribute::Returned)));
912  } else {
913  // Otherwise, use the original attributes.
914  ArgAttrVec.push_back(Attrs);
915  }
916  }
917 
918  // Push any varargs arguments on the list. Don't forget their attributes.
919  for (CallSite::arg_iterator E = CS.arg_end(); I != E; ++I, ++i) {
920  Args.push_back(*I);
921  ArgAttrVec.push_back(CallPAL.getParamAttributes(i));
922  }
923 
924  // Reconstruct the AttributesList based on the vector we constructed.
925  assert(ArgAttrVec.size() == Args.size());
926 
927  // Again, be sure to remove any allocsize attributes, since their indices
928  // may now be incorrect.
929  AttributeSet FnAttrs = CallPAL.getFnAttributes().removeAttribute(
930  F->getContext(), Attribute::AllocSize);
931 
932  AttributeList NewCallPAL = AttributeList::get(
933  F->getContext(), FnAttrs, RetAttrs, ArgAttrVec);
934 
936  CS.getOperandBundlesAsDefs(OpBundles);
937 
938  CallSite NewCS;
939  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
940  NewCS = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
941  Args, OpBundles, "", Call->getParent());
942  } else {
943  NewCS = CallInst::Create(NF, Args, OpBundles, "", Call);
944  cast<CallInst>(NewCS.getInstruction())
945  ->setTailCallKind(cast<CallInst>(Call)->getTailCallKind());
946  }
947  NewCS.setCallingConv(CS.getCallingConv());
948  NewCS.setAttributes(NewCallPAL);
949  NewCS->setDebugLoc(Call->getDebugLoc());
950  uint64_t W;
951  if (Call->extractProfTotalWeight(W))
952  NewCS->setProfWeight(W);
953  Args.clear();
954  ArgAttrVec.clear();
955 
956  Instruction *New = NewCS.getInstruction();
957  if (!Call->use_empty()) {
958  if (New->getType() == Call->getType()) {
959  // Return type not changed? Just replace users then.
960  Call->replaceAllUsesWith(New);
961  New->takeName(Call);
962  } else if (New->getType()->isVoidTy()) {
963  // Our return value has uses, but they will get removed later on.
964  // Replace by null for now.
965  if (!Call->getType()->isX86_MMXTy())
966  Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
967  } else {
968  assert((RetTy->isStructTy() || RetTy->isArrayTy()) &&
969  "Return type changed, but not into a void. The old return type"
970  " must have been a struct or an array!");
971  Instruction *InsertPt = Call;
972  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
973  BasicBlock *NewEdge = SplitEdge(New->getParent(), II->getNormalDest());
974  InsertPt = &*NewEdge->getFirstInsertionPt();
975  }
976 
977  // We used to return a struct or array. Instead of doing smart stuff
978  // with all the uses, we will just rebuild it using extract/insertvalue
979  // chaining and let instcombine clean that up.
980  //
981  // Start out building up our return value from undef
982  Value *RetVal = UndefValue::get(RetTy);
983  for (unsigned i = 0; i != RetCount; ++i)
984  if (NewRetIdxs[i] != -1) {
985  Value *V;
986  if (RetTypes.size() > 1)
987  // We are still returning a struct, so extract the value from our
988  // return value
989  V = ExtractValueInst::Create(New, NewRetIdxs[i], "newret",
990  InsertPt);
991  else
992  // We are now returning a single element, so just insert that
993  V = New;
994  // Insert the value at the old position
995  RetVal = InsertValueInst::Create(RetVal, V, i, "oldret", InsertPt);
996  }
997  // Now, replace all uses of the old call instruction with the return
998  // struct we built
999  Call->replaceAllUsesWith(RetVal);
1000  New->takeName(Call);
1001  }
1002  }
1003 
1004  // Finally, remove the old call from the program, reducing the use-count of
1005  // F.
1006  Call->eraseFromParent();
1007  }
1008 
1009  // Since we have now created the new function, splice the body of the old
1010  // function right into the new function, leaving the old rotting hulk of the
1011  // function empty.
1012  NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
1013 
1014  // Loop over the argument list, transferring uses of the old arguments over to
1015  // the new arguments, also transferring over the names as well.
1016  i = 0;
1017  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
1018  I2 = NF->arg_begin(); I != E; ++I, ++i)
1019  if (ArgAlive[i]) {
1020  // If this is a live argument, move the name and users over to the new
1021  // version.
1022  I->replaceAllUsesWith(&*I2);
1023  I2->takeName(&*I);
1024  ++I2;
1025  } else {
1026  // If this argument is dead, replace any uses of it with null constants
1027  // (these are guaranteed to become unused later on).
1028  if (!I->getType()->isX86_MMXTy())
1029  I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
1030  }
1031 
1032  // If we change the return value of the function we must rewrite any return
1033  // instructions. Check this now.
1034  if (F->getReturnType() != NF->getReturnType())
1035  for (BasicBlock &BB : *NF)
1036  if (ReturnInst *RI = dyn_cast<ReturnInst>(BB.getTerminator())) {
1037  Value *RetVal;
1038 
1039  if (NFTy->getReturnType()->isVoidTy()) {
1040  RetVal = nullptr;
1041  } else {
1042  assert(RetTy->isStructTy() || RetTy->isArrayTy());
1043  // The original return value was a struct or array, insert
1044  // extractvalue/insertvalue chains to extract only the values we need
1045  // to return and insert them into our new result.
1046  // This does generate messy code, but we'll let it to instcombine to
1047  // clean that up.
1048  Value *OldRet = RI->getOperand(0);
1049  // Start out building up our return value from undef
1050  RetVal = UndefValue::get(NRetTy);
1051  for (unsigned i = 0; i != RetCount; ++i)
1052  if (NewRetIdxs[i] != -1) {
1054  "oldret", RI);
1055  if (RetTypes.size() > 1) {
1056  // We're still returning a struct, so reinsert the value into
1057  // our new return value at the new index
1058 
1059  RetVal = InsertValueInst::Create(RetVal, EV, NewRetIdxs[i],
1060  "newret", RI);
1061  } else {
1062  // We are now only returning a simple value, so just return the
1063  // extracted value.
1064  RetVal = EV;
1065  }
1066  }
1067  }
1068  // Replace the return instruction with one returning the new return
1069  // value (possibly 0 if we became void).
1070  ReturnInst::Create(F->getContext(), RetVal, RI);
1071  BB.getInstList().erase(RI);
1072  }
1073 
1074  // Clone metadatas from the old function, including debug info descriptor.
1076  F->getAllMetadata(MDs);
1077  for (auto MD : MDs)
1078  NF->addMetadata(MD.first, *MD.second);
1079 
1080  // Now that the old function is dead, delete it.
1081  F->eraseFromParent();
1082 
1083  return true;
1084 }
1085 
1088  bool Changed = false;
1089 
1090  // First pass: Do a simple check to see if any functions can have their "..."
1091  // removed. We can do this if they never call va_start. This loop cannot be
1092  // fused with the next loop, because deleting a function invalidates
1093  // information computed while surveying other functions.
1094  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Deleting dead varargs\n");
1095  for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
1096  Function &F = *I++;
1097  if (F.getFunctionType()->isVarArg())
1098  Changed |= DeleteDeadVarargs(F);
1099  }
1100 
1101  // Second phase:loop through the module, determining which arguments are live.
1102  // We assume all arguments are dead unless proven otherwise (allowing us to
1103  // determine that dead arguments passed into recursive functions are dead).
1104  //
1105  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Determining liveness\n");
1106  for (auto &F : M)
1107  SurveyFunction(F);
1108 
1109  // Now, remove all dead arguments and return values from each function in
1110  // turn.
1111  for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
1112  // Increment now, because the function will probably get removed (ie.
1113  // replaced by a new one).
1114  Function *F = &*I++;
1115  Changed |= RemoveDeadStuffFromFunction(F);
1116  }
1117 
1118  // Finally, look for any unused parameters in functions with non-local
1119  // linkage and replace the passed in parameters with undef.
1120  for (auto &F : M)
1121  Changed |= RemoveDeadArgumentsFromCallers(F);
1122 
1123  if (!Changed)
1124  return PreservedAnalyses::all();
1125  return PreservedAnalyses::none();
1126 }
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:213
bool isIntrinsic() const
isIntrinsic - Returns true if the function&#39;s name starts with "llvm.".
Definition: Function.h:199
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:68
iterator_range< use_iterator > uses()
Definition: Value.h:355
bool hasLocalLinkage() const
Definition: GlobalValue.h:436
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:312
This class represents lattice values for constants.
Definition: AllocatorList.h:24
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:64
iterator end()
Definition: Function.h:658
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:321
arg_iterator arg_end()
Definition: Function.h:680
STATISTIC(NumFunctions, "Total number of functions")
F(f)
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
This defines the Use class.
void getAllMetadata(SmallVectorImpl< std::pair< unsigned, MDNode *>> &MDs) const
Appends all attachments for the global to MDs, sorting by attachment ID.
Definition: Metadata.cpp:1417
bool isMustTailCall() const
static Constant * getNullValue(Type *Ty)
Constructor to create a &#39;0&#39; constant of arbitrary type.
Definition: Constants.cpp:265
BasicBlock * SplitEdge(BasicBlock *From, BasicBlock *To, DominatorTree *DT=nullptr, LoopInfo *LI=nullptr, MemorySSAUpdater *MSSAU=nullptr)
Split the edge connecting specified block.
static ReturnInst * Create(LLVMContext &C, Value *retVal=nullptr, Instruction *InsertBefore=nullptr)
SI optimize exec mask operations pre RA
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
This file contains the simple types necessary to represent the attributes associated with functions a...
AttributeSet getRetAttributes() const
The attributes for the ret value are returned.
InstrTy * getInstruction() const
Definition: CallSite.h:92
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:342
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
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:224
bool extractProfTotalWeight(uint64_t &TotalVal) const
Retrieve total raw weight values of a branch.
Definition: Metadata.cpp:1340
LinkageTypes getLinkage() const
Definition: GlobalValue.h:451
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:430
constexpr char Attrs[]
Key for Kernel::Metadata::mAttrs.
void takeName(Value *V)
Transfer the name from V to this value.
Definition: Value.cpp:292
iterator begin()
Definition: Function.h:656
void removeDeadConstantUsers() const
If there are any dead constant users dangling off of this constant, remove them.
Definition: Constants.cpp:533
static PreservedAnalyses none()
Convenience factory function for the empty preserved set.
Definition: PassManager.h:157
bool hasAttribute(Attribute::AttrKind Kind) const
Return true if the attribute exists in this set.
Definition: Attributes.cpp:578
AttributeSet getAttributes(unsigned Index) const
The attributes for the specified index are returned.
static Constant * getBitCast(Constant *C, Type *Ty, bool OnlyIfReduced=false)
Definition: Constants.cpp:1769
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...
void setAttributes(AttributeList PAL)
Set the parameter attributes of the call.
Definition: CallSite.h:333
Type * getReturnType() const
Returns the type of the ret val.
Definition: Function.h:169
static Function * Create(FunctionType *Ty, LinkageTypes Linkage, unsigned AddrSpace, const Twine &N="", Module *M=nullptr)
Definition: Function.h:136
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:154
static AttributeSet get(LLVMContext &C, const AttrBuilder &B)
Definition: Attributes.cpp:513
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:219
bool areAllPreserved() const
Test whether all analyses are preserved (and none are abandoned).
Definition: PassManager.h:322
static unsigned getAggregateOperandIndex()
const FunctionListType & getFunctionList() const
Get the Module&#39;s list of functions (constant).
Definition: Module.h:520
LLVM Basic Block Representation.
Definition: BasicBlock.h:58
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
static ExtractValueInst * Create(Value *Agg, ArrayRef< unsigned > Idxs, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
void copyAttributesFrom(const Function *Src)
copyAttributesFrom - copy all additional attributes (those not needed to create a Function) from the ...
Definition: Function.cpp:485
This file contains the declarations for the subclasses of Constant, which represent the different fla...
ModulePass * createDeadArgEliminationPass()
createDeadArgEliminationPass - This pass removes arguments from functions which are not used by the b...
LLVM_NODISCARD AttributeSet removeAttribute(LLVMContext &C, Attribute::AttrKind Kind) const
Remove the specified attribute from this set.
Definition: Attributes.cpp:551
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:329
void setCallingConv(CallingConv::ID CC)
Set the calling convention of the call.
Definition: CallSite.h:316
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:698
arg_iterator arg_begin()
Definition: Function.h:671
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:1411
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:160
size_t size() const
Definition: SmallVector.h:53
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).
AttrBuilder & removeAttribute(Attribute::AttrKind Val)
Remove an attribute from the builder.
IterTy arg_begin() const
Definition: CallSite.h:571
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:847
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.
void addMetadata(unsigned KindID, MDNode &MD)
Add a metadata attachment.
Definition: Metadata.cpp:1394
Type * getReturnType() const
Definition: DerivedTypes.h:124
void setAttributes(AttributeList Attrs)
Set the attribute list for this Function.
Definition: Function.h:227
bool isUsedByMetadata() const
Return true if there is metadata referencing this value.
Definition: Value.h:489
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:133
FunctionType * getFunctionType() const
Returns the FunctionType for me.
Definition: Function.h:164
amdgpu Simplify well known AMD library false Value Value * Arg
const Comdat * getComdat() const
Definition: GlobalObject.h:101
iterator insert(iterator where, pointer New)
Definition: ilist.h:228
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:311
iterator end()
Definition: Module.h:587
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:56
void getOperandBundlesAsDefs(SmallVectorImpl< OperandBundleDef > &Defs) const
Definition: CallSite.h:582
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:215
bool hasExactDefinition() const
Return true if this global has an exact defintion.
Definition: GlobalValue.h:407
Establish a view to a call site for examination.
Definition: CallSite.h:711
#define I(x, y, z)
Definition: MD5.cpp:58
user_iterator_impl< User > user_iterator
Definition: Value.h:369
ModulePass class - This class is used to implement unstructured interprocedural optimizations and ana...
Definition: Pass.h:225
iterator begin()
Definition: Module.h:585
static ArrayType * get(Type *ElementType, uint64_t NumElements)
This static method is the primary way to construct an ArrayType.
Definition: Type.cpp:581
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:633
void eraseFromParent()
eraseFromParent - This method unlinks &#39;this&#39; from the containing module and deletes it...
Definition: Function.cpp:215
bool isDeclaration() const
Return true if the primary definition of this global value is outside of the current translation unit...
Definition: Globals.cpp:206
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:1255
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:566
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.
A container for analyses that lazily runs them and caches their results.
AttributeList getAttributes() const
Get the parameter attributes of the call.
Definition: CallSite.h:329
This header defines various interfaces for pass management in LLVM.
#define LLVM_DEBUG(X)
Definition: Debug.h:123
bool isEmpty() const
Return true if there are no attributes.
Definition: Attributes.h:656
bool use_empty() const
Definition: Value.h:323
constexpr char Args[]
Key for Kernel::Metadata::mArgs.
PointerType * getType() const
Global values are always pointers.
Definition: GlobalValue.h:274
static AttributeList get(LLVMContext &C, ArrayRef< std::pair< unsigned, Attribute >> Attrs)
Create an AttributeList with the specified parameters in it.
Definition: Attributes.cpp:873
iterator_range< arg_iterator > args()
Definition: Function.h:689
User * user_back()
Definition: Value.h:386
A wrapper class for inspecting calls to intrinsic functions.
Definition: IntrinsicInst.h:44
const BasicBlock * getParent() const
Definition: Instruction.h:67
This instruction inserts a struct field of array element value into an aggregate value.
PreservedAnalyses run(Module &M, ModuleAnalysisManager &)