LLVM  10.0.0svn
DeadArgumentElimination.cpp
Go to the documentation of this file.
1 //===- DeadArgumentElimination.cpp - Eliminate dead arguments -------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This pass deletes dead arguments from internal functions. Dead argument
10 // elimination removes arguments which are directly dead, as well as arguments
11 // only passed into function calls as dead arguments of other functions. This
12 // pass also deletes dead return values in a similar way.
13 //
14 // This pass is often useful as a cleanup pass to run after aggressive
15 // interprocedural passes, which add possibly-dead arguments or return values.
16 //
17 //===----------------------------------------------------------------------===//
18 
20 #include "llvm/ADT/SmallVector.h"
21 #include "llvm/ADT/Statistic.h"
22 #include "llvm/IR/Argument.h"
23 #include "llvm/IR/Attributes.h"
24 #include "llvm/IR/BasicBlock.h"
25 #include "llvm/IR/CallSite.h"
26 #include "llvm/IR/Constants.h"
27 #include "llvm/IR/DerivedTypes.h"
28 #include "llvm/IR/Function.h"
29 #include "llvm/IR/InstrTypes.h"
30 #include "llvm/IR/Instruction.h"
31 #include "llvm/IR/Instructions.h"
32 #include "llvm/IR/IntrinsicInst.h"
33 #include "llvm/IR/Intrinsics.h"
34 #include "llvm/IR/Module.h"
35 #include "llvm/IR/PassManager.h"
36 #include "llvm/IR/Type.h"
37 #include "llvm/IR/Use.h"
38 #include "llvm/IR/User.h"
39 #include "llvm/IR/Value.h"
40 #include "llvm/Pass.h"
41 #include "llvm/Support/Casting.h"
42 #include "llvm/Support/Debug.h"
44 #include "llvm/Transforms/IPO.h"
46 #include <cassert>
47 #include <cstdint>
48 #include <utility>
49 #include <vector>
50 
51 using namespace llvm;
52 
53 #define DEBUG_TYPE "deadargelim"
54 
55 STATISTIC(NumArgumentsEliminated, "Number of unread args removed");
56 STATISTIC(NumRetValsEliminated , "Number of unused return values removed");
57 STATISTIC(NumArgumentsReplacedWithUndef,
58  "Number of unread args replaced with undef");
59 
60 namespace {
61 
62  /// DAE - The dead argument elimination pass.
63  class DAE : public ModulePass {
64  protected:
65  // DAH uses this to specify a different ID.
66  explicit DAE(char &ID) : ModulePass(ID) {}
67 
68  public:
69  static char ID; // Pass identification, replacement for typeid
70 
71  DAE() : ModulePass(ID) {
73  }
74 
75  bool runOnModule(Module &M) override {
76  if (skipModule(M))
77  return false;
78  DeadArgumentEliminationPass DAEP(ShouldHackArguments());
79  ModuleAnalysisManager DummyMAM;
80  PreservedAnalyses PA = DAEP.run(M, DummyMAM);
81  return !PA.areAllPreserved();
82  }
83 
84  virtual bool ShouldHackArguments() const { return false; }
85  };
86 
87 } // end anonymous namespace
88 
89 char DAE::ID = 0;
90 
91 INITIALIZE_PASS(DAE, "deadargelim", "Dead Argument Elimination", false, false)
92 
93 namespace {
94 
95  /// DAH - DeadArgumentHacking pass - Same as dead argument elimination, but
96  /// deletes arguments to functions which are external. This is only for use
97  /// by bugpoint.
98  struct DAH : public DAE {
99  static char ID;
100 
101  DAH() : DAE(ID) {}
102 
103  bool ShouldHackArguments() const override { return true; }
104  };
105 
106 } // end anonymous namespace
107 
108 char DAH::ID = 0;
109 
110 INITIALIZE_PASS(DAH, "deadarghaX0r",
111  "Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)",
112  false, false)
113 
114 /// createDeadArgEliminationPass - This pass removes arguments from functions
115 /// which are not used by the body of the function.
116 ModulePass *llvm::createDeadArgEliminationPass() { return new DAE(); }
117 
119 
120 /// DeleteDeadVarargs - If this is an function that takes a ... list, and if
121 /// llvm.vastart is never called, the varargs list is dead for the function.
122 bool DeadArgumentEliminationPass::DeleteDeadVarargs(Function &Fn) {
123  assert(Fn.getFunctionType()->isVarArg() && "Function isn't varargs!");
124  if (Fn.isDeclaration() || !Fn.hasLocalLinkage()) return false;
125 
126  // Ensure that the function is only directly called.
127  if (Fn.hasAddressTaken())
128  return false;
129 
130  // Don't touch naked functions. The assembly might be using an argument, or
131  // otherwise rely on the frame layout in a way that this analysis will not
132  // see.
133  if (Fn.hasFnAttribute(Attribute::Naked)) {
134  return false;
135  }
136 
137  // Okay, we know we can transform this function if safe. Scan its body
138  // looking for calls marked musttail or calls to llvm.vastart.
139  for (BasicBlock &BB : Fn) {
140  for (Instruction &I : BB) {
141  CallInst *CI = dyn_cast<CallInst>(&I);
142  if (!CI)
143  continue;
144  if (CI->isMustTailCall())
145  return false;
146  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI)) {
147  if (II->getIntrinsicID() == Intrinsic::vastart)
148  return false;
149  }
150  }
151  }
152 
153  // If we get here, there are no calls to llvm.vastart in the function body,
154  // remove the "..." and adjust all the calls.
155 
156  // Start by computing a new prototype for the function, which is the same as
157  // the old function, but doesn't have isVarArg set.
158  FunctionType *FTy = Fn.getFunctionType();
159 
160  std::vector<Type *> Params(FTy->param_begin(), FTy->param_end());
162  Params, false);
163  unsigned NumArgs = Params.size();
164 
165  // Create the new function body and insert it into the module...
166  Function *NF = Function::Create(NFTy, Fn.getLinkage(), Fn.getAddressSpace());
167  NF->copyAttributesFrom(&Fn);
168  NF->setComdat(Fn.getComdat());
169  Fn.getParent()->getFunctionList().insert(Fn.getIterator(), NF);
170  NF->takeName(&Fn);
171 
172  // Loop over all of the callers of the function, transforming the call sites
173  // to pass in a smaller number of arguments into the new function.
174  //
175  std::vector<Value *> Args;
176  for (Value::user_iterator I = Fn.user_begin(), E = Fn.user_end(); I != E; ) {
177  CallSite CS(*I++);
178  if (!CS)
179  continue;
180  Instruction *Call = CS.getInstruction();
181 
182  // Pass all the same arguments.
183  Args.assign(CS.arg_begin(), CS.arg_begin() + NumArgs);
184 
185  // Drop any attributes that were on the vararg arguments.
186  AttributeList PAL = CS.getAttributes();
187  if (!PAL.isEmpty()) {
189  for (unsigned ArgNo = 0; ArgNo < NumArgs; ++ArgNo)
190  ArgAttrs.push_back(PAL.getParamAttributes(ArgNo));
191  PAL = AttributeList::get(Fn.getContext(), PAL.getFnAttributes(),
192  PAL.getRetAttributes(), ArgAttrs);
193  }
194 
196  CS.getOperandBundlesAsDefs(OpBundles);
197 
198  CallSite NewCS;
199  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
200  NewCS = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
201  Args, OpBundles, "", Call);
202  } else {
203  NewCS = CallInst::Create(NF, Args, OpBundles, "", Call);
204  cast<CallInst>(NewCS.getInstruction())
205  ->setTailCallKind(cast<CallInst>(Call)->getTailCallKind());
206  }
207  NewCS.setCallingConv(CS.getCallingConv());
208  NewCS.setAttributes(PAL);
209  NewCS->setDebugLoc(Call->getDebugLoc());
210  uint64_t W;
211  if (Call->extractProfTotalWeight(W))
212  NewCS->setProfWeight(W);
213 
214  Args.clear();
215 
216  if (!Call->use_empty())
217  Call->replaceAllUsesWith(NewCS.getInstruction());
218 
219  NewCS->takeName(Call);
220 
221  // Finally, remove the old call from the program, reducing the use-count of
222  // F.
223  Call->eraseFromParent();
224  }
225 
226  // Since we have now created the new function, splice the body of the old
227  // function right into the new function, leaving the old rotting hulk of the
228  // function empty.
229  NF->getBasicBlockList().splice(NF->begin(), Fn.getBasicBlockList());
230 
231  // Loop over the argument list, transferring uses of the old arguments over to
232  // the new arguments, also transferring over the names as well. While we're at
233  // it, remove the dead arguments from the DeadArguments list.
234  for (Function::arg_iterator I = Fn.arg_begin(), E = Fn.arg_end(),
235  I2 = NF->arg_begin(); I != E; ++I, ++I2) {
236  // Move the name and users over to the new version.
237  I->replaceAllUsesWith(&*I2);
238  I2->takeName(&*I);
239  }
240 
241  // Clone metadatas from the old function, including debug info descriptor.
243  Fn.getAllMetadata(MDs);
244  for (auto MD : MDs)
245  NF->addMetadata(MD.first, *MD.second);
246 
247  // Fix up any BlockAddresses that refer to the function.
248  Fn.replaceAllUsesWith(ConstantExpr::getBitCast(NF, Fn.getType()));
249  // Delete the bitcast that we just created, so that NF does not
250  // appear to be address-taken.
252  // Finally, nuke the old function.
253  Fn.eraseFromParent();
254  return true;
255 }
256 
257 /// RemoveDeadArgumentsFromCallers - Checks if the given function has any
258 /// arguments that are unused, and changes the caller parameters to be undefined
259 /// instead.
260 bool DeadArgumentEliminationPass::RemoveDeadArgumentsFromCallers(Function &Fn) {
261  // We cannot change the arguments if this TU does not define the function or
262  // if the linker may choose a function body from another TU, even if the
263  // nominal linkage indicates that other copies of the function have the same
264  // semantics. In the below example, the dead load from %p may not have been
265  // eliminated from the linker-chosen copy of f, so replacing %p with undef
266  // in callers may introduce undefined behavior.
267  //
268  // define linkonce_odr void @f(i32* %p) {
269  // %v = load i32 %p
270  // ret void
271  // }
272  if (!Fn.hasExactDefinition())
273  return false;
274 
275  // Functions with local linkage should already have been handled, except the
276  // fragile (variadic) ones which we can improve here.
277  if (Fn.hasLocalLinkage() && !Fn.getFunctionType()->isVarArg())
278  return false;
279 
280  // Don't touch naked functions. The assembly might be using an argument, or
281  // otherwise rely on the frame layout in a way that this analysis will not
282  // see.
283  if (Fn.hasFnAttribute(Attribute::Naked))
284  return false;
285 
286  if (Fn.use_empty())
287  return false;
288 
289  SmallVector<unsigned, 8> UnusedArgs;
290  bool Changed = false;
291 
292  for (Argument &Arg : Fn.args()) {
293  if (!Arg.hasSwiftErrorAttr() && Arg.use_empty() && !Arg.hasByValOrInAllocaAttr()) {
294  if (Arg.isUsedByMetadata()) {
295  Arg.replaceAllUsesWith(UndefValue::get(Arg.getType()));
296  Changed = true;
297  }
298  UnusedArgs.push_back(Arg.getArgNo());
299  }
300  }
301 
302  if (UnusedArgs.empty())
303  return false;
304 
305  for (Use &U : Fn.uses()) {
306  CallSite CS(U.getUser());
307  if (!CS || !CS.isCallee(&U))
308  continue;
309 
310  // Now go through all unused args and replace them with "undef".
311  for (unsigned I = 0, E = UnusedArgs.size(); I != E; ++I) {
312  unsigned ArgNo = UnusedArgs[I];
313 
314  Value *Arg = CS.getArgument(ArgNo);
315  CS.setArgument(ArgNo, UndefValue::get(Arg->getType()));
316  ++NumArgumentsReplacedWithUndef;
317  Changed = true;
318  }
319  }
320 
321  return Changed;
322 }
323 
324 /// Convenience function that returns the number of return values. It returns 0
325 /// for void functions and 1 for functions not returning a struct. It returns
326 /// the number of struct elements for functions returning a struct.
327 static unsigned NumRetVals(const Function *F) {
328  Type *RetTy = F->getReturnType();
329  if (RetTy->isVoidTy())
330  return 0;
331  else if (StructType *STy = dyn_cast<StructType>(RetTy))
332  return STy->getNumElements();
333  else if (ArrayType *ATy = dyn_cast<ArrayType>(RetTy))
334  return ATy->getNumElements();
335  else
336  return 1;
337 }
338 
339 /// Returns the sub-type a function will return at a given Idx. Should
340 /// correspond to the result type of an ExtractValue instruction executed with
341 /// just that one Idx (i.e. only top-level structure is considered).
342 static Type *getRetComponentType(const Function *F, unsigned Idx) {
343  Type *RetTy = F->getReturnType();
344  assert(!RetTy->isVoidTy() && "void type has no subtype");
345 
346  if (StructType *STy = dyn_cast<StructType>(RetTy))
347  return STy->getElementType(Idx);
348  else if (ArrayType *ATy = dyn_cast<ArrayType>(RetTy))
349  return ATy->getElementType();
350  else
351  return RetTy;
352 }
353 
354 /// MarkIfNotLive - This checks Use for liveness in LiveValues. If Use is not
355 /// live, it adds Use to the MaybeLiveUses argument. Returns the determined
356 /// liveness of Use.
358 DeadArgumentEliminationPass::MarkIfNotLive(RetOrArg Use,
359  UseVector &MaybeLiveUses) {
360  // We're live if our use or its Function is already marked as live.
361  if (LiveFunctions.count(Use.F) || LiveValues.count(Use))
362  return Live;
363 
364  // We're maybe live otherwise, but remember that we must become live if
365  // Use becomes live.
366  MaybeLiveUses.push_back(Use);
367  return MaybeLive;
368 }
369 
370 /// SurveyUse - This looks at a single use of an argument or return value
371 /// and determines if it should be alive or not. Adds this use to MaybeLiveUses
372 /// if it causes the used value to become MaybeLive.
373 ///
374 /// RetValNum is the return value number to use when this use is used in a
375 /// return instruction. This is used in the recursion, you should always leave
376 /// it at 0.
378 DeadArgumentEliminationPass::SurveyUse(const Use *U, UseVector &MaybeLiveUses,
379  unsigned RetValNum) {
380  const User *V = U->getUser();
381  if (const ReturnInst *RI = dyn_cast<ReturnInst>(V)) {
382  // The value is returned from a function. It's only live when the
383  // function's return value is live. We use RetValNum here, for the case
384  // that U is really a use of an insertvalue instruction that uses the
385  // original Use.
386  const Function *F = RI->getParent()->getParent();
387  if (RetValNum != -1U) {
388  RetOrArg Use = CreateRet(F, RetValNum);
389  // We might be live, depending on the liveness of Use.
390  return MarkIfNotLive(Use, MaybeLiveUses);
391  } else {
392  DeadArgumentEliminationPass::Liveness Result = MaybeLive;
393  for (unsigned i = 0; i < NumRetVals(F); ++i) {
394  RetOrArg Use = CreateRet(F, i);
395  // We might be live, depending on the liveness of Use. If any
396  // sub-value is live, then the entire value is considered live. This
397  // is a conservative choice, and better tracking is possible.
399  MarkIfNotLive(Use, MaybeLiveUses);
400  if (Result != Live)
401  Result = SubResult;
402  }
403  return Result;
404  }
405  }
406  if (const InsertValueInst *IV = dyn_cast<InsertValueInst>(V)) {
407  if (U->getOperandNo() != InsertValueInst::getAggregateOperandIndex()
408  && IV->hasIndices())
409  // The use we are examining is inserted into an aggregate. Our liveness
410  // depends on all uses of that aggregate, but if it is used as a return
411  // value, only index at which we were inserted counts.
412  RetValNum = *IV->idx_begin();
413 
414  // Note that if we are used as the aggregate operand to the insertvalue,
415  // we don't change RetValNum, but do survey all our uses.
416 
417  Liveness Result = MaybeLive;
418  for (const Use &UU : IV->uses()) {
419  Result = SurveyUse(&UU, MaybeLiveUses, RetValNum);
420  if (Result == Live)
421  break;
422  }
423  return Result;
424  }
425 
426  if (auto CS = ImmutableCallSite(V)) {
427  const Function *F = CS.getCalledFunction();
428  if (F) {
429  // Used in a direct call.
430 
431  // The function argument is live if it is used as a bundle operand.
432  if (CS.isBundleOperand(U))
433  return Live;
434 
435  // Find the argument number. We know for sure that this use is an
436  // argument, since if it was the function argument this would be an
437  // indirect call and the we know can't be looking at a value of the
438  // label type (for the invoke instruction).
439  unsigned ArgNo = CS.getArgumentNo(U);
440 
441  if (ArgNo >= F->getFunctionType()->getNumParams())
442  // The value is passed in through a vararg! Must be live.
443  return Live;
444 
445  assert(CS.getArgument(ArgNo)
446  == CS->getOperand(U->getOperandNo())
447  && "Argument is not where we expected it");
448 
449  // Value passed to a normal call. It's only live when the corresponding
450  // argument to the called function turns out live.
451  RetOrArg Use = CreateArg(F, ArgNo);
452  return MarkIfNotLive(Use, MaybeLiveUses);
453  }
454  }
455  // Used in any other way? Value must be live.
456  return Live;
457 }
458 
459 /// SurveyUses - This looks at all the uses of the given value
460 /// Returns the Liveness deduced from the uses of this value.
461 ///
462 /// Adds all uses that cause the result to be MaybeLive to MaybeLiveRetUses. If
463 /// the result is Live, MaybeLiveUses might be modified but its content should
464 /// be ignored (since it might not be complete).
466 DeadArgumentEliminationPass::SurveyUses(const Value *V,
467  UseVector &MaybeLiveUses) {
468  // Assume it's dead (which will only hold if there are no uses at all..).
469  Liveness Result = MaybeLive;
470  // Check each use.
471  for (const Use &U : V->uses()) {
472  Result = SurveyUse(&U, MaybeLiveUses);
473  if (Result == Live)
474  break;
475  }
476  return Result;
477 }
478 
479 // SurveyFunction - This performs the initial survey of the specified function,
480 // checking out whether or not it uses any of its incoming arguments or whether
481 // any callers use the return value. This fills in the LiveValues set and Uses
482 // map.
483 //
484 // We consider arguments of non-internal functions to be intrinsically alive as
485 // well as arguments to functions which have their "address taken".
486 void DeadArgumentEliminationPass::SurveyFunction(const Function &F) {
487  // Functions with inalloca parameters are expecting args in a particular
488  // register and memory layout.
489  if (F.getAttributes().hasAttrSomewhere(Attribute::InAlloca)) {
490  MarkLive(F);
491  return;
492  }
493 
494  // Don't touch naked functions. The assembly might be using an argument, or
495  // otherwise rely on the frame layout in a way that this analysis will not
496  // see.
497  if (F.hasFnAttribute(Attribute::Naked)) {
498  MarkLive(F);
499  return;
500  }
501 
502  unsigned RetCount = NumRetVals(&F);
503 
504  // Assume all return values are dead
505  using RetVals = SmallVector<Liveness, 5>;
506 
507  RetVals RetValLiveness(RetCount, MaybeLive);
508 
509  using RetUses = SmallVector<UseVector, 5>;
510 
511  // These vectors map each return value to the uses that make it MaybeLive, so
512  // we can add those to the Uses map if the return value really turns out to be
513  // MaybeLive. Initialized to a list of RetCount empty lists.
514  RetUses MaybeLiveRetUses(RetCount);
515 
516  bool HasMustTailCalls = false;
517 
518  for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
519  if (const ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
520  if (RI->getNumOperands() != 0 && RI->getOperand(0)->getType()
521  != F.getFunctionType()->getReturnType()) {
522  // We don't support old style multiple return values.
523  MarkLive(F);
524  return;
525  }
526  }
527 
528  // If we have any returns of `musttail` results - the signature can't
529  // change
530  if (BB->getTerminatingMustTailCall() != nullptr)
531  HasMustTailCalls = true;
532  }
533 
534  if (HasMustTailCalls) {
535  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - " << F.getName()
536  << " has musttail calls\n");
537  }
538 
539  if (!F.hasLocalLinkage() && (!ShouldHackArguments || F.isIntrinsic())) {
540  MarkLive(F);
541  return;
542  }
543 
544  LLVM_DEBUG(
545  dbgs() << "DeadArgumentEliminationPass - Inspecting callers for fn: "
546  << F.getName() << "\n");
547  // Keep track of the number of live retvals, so we can skip checks once all
548  // of them turn out to be live.
549  unsigned NumLiveRetVals = 0;
550 
551  bool HasMustTailCallers = false;
552 
553  // Loop all uses of the function.
554  for (const Use &U : F.uses()) {
555  // If the function is PASSED IN as an argument, its address has been
556  // taken.
557  ImmutableCallSite CS(U.getUser());
558  if (!CS || !CS.isCallee(&U)) {
559  MarkLive(F);
560  return;
561  }
562 
563  // The number of arguments for `musttail` call must match the number of
564  // arguments of the caller
565  if (CS.isMustTailCall())
566  HasMustTailCallers = true;
567 
568  // If this use is anything other than a call site, the function is alive.
569  const Instruction *TheCall = CS.getInstruction();
570  if (!TheCall) { // Not a direct call site?
571  MarkLive(F);
572  return;
573  }
574 
575  // If we end up here, we are looking at a direct call to our function.
576 
577  // Now, check how our return value(s) is/are used in this caller. Don't
578  // bother checking return values if all of them are live already.
579  if (NumLiveRetVals == RetCount)
580  continue;
581 
582  // Check all uses of the return value.
583  for (const Use &U : TheCall->uses()) {
584  if (ExtractValueInst *Ext = dyn_cast<ExtractValueInst>(U.getUser())) {
585  // This use uses a part of our return value, survey the uses of
586  // that part and store the results for this index only.
587  unsigned Idx = *Ext->idx_begin();
588  if (RetValLiveness[Idx] != Live) {
589  RetValLiveness[Idx] = SurveyUses(Ext, MaybeLiveRetUses[Idx]);
590  if (RetValLiveness[Idx] == Live)
591  NumLiveRetVals++;
592  }
593  } else {
594  // Used by something else than extractvalue. Survey, but assume that the
595  // result applies to all sub-values.
596  UseVector MaybeLiveAggregateUses;
597  if (SurveyUse(&U, MaybeLiveAggregateUses) == Live) {
598  NumLiveRetVals = RetCount;
599  RetValLiveness.assign(RetCount, Live);
600  break;
601  } else {
602  for (unsigned i = 0; i != RetCount; ++i) {
603  if (RetValLiveness[i] != Live)
604  MaybeLiveRetUses[i].append(MaybeLiveAggregateUses.begin(),
605  MaybeLiveAggregateUses.end());
606  }
607  }
608  }
609  }
610  }
611 
612  if (HasMustTailCallers) {
613  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - " << F.getName()
614  << " has musttail callers\n");
615  }
616 
617  // Now we've inspected all callers, record the liveness of our return values.
618  for (unsigned i = 0; i != RetCount; ++i)
619  MarkValue(CreateRet(&F, i), RetValLiveness[i], MaybeLiveRetUses[i]);
620 
621  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Inspecting args for fn: "
622  << F.getName() << "\n");
623 
624  // Now, check all of our arguments.
625  unsigned i = 0;
626  UseVector MaybeLiveArgUses;
628  E = F.arg_end(); AI != E; ++AI, ++i) {
629  Liveness Result;
630  if (F.getFunctionType()->isVarArg() || HasMustTailCallers ||
631  HasMustTailCalls) {
632  // Variadic functions will already have a va_arg function expanded inside
633  // them, making them potentially very sensitive to ABI changes resulting
634  // from removing arguments entirely, so don't. For example AArch64 handles
635  // register and stack HFAs very differently, and this is reflected in the
636  // IR which has already been generated.
637  //
638  // `musttail` calls to this function restrict argument removal attempts.
639  // The signature of the caller must match the signature of the function.
640  //
641  // `musttail` calls in this function prevents us from changing its
642  // signature
643  Result = Live;
644  } else {
645  // See what the effect of this use is (recording any uses that cause
646  // MaybeLive in MaybeLiveArgUses).
647  Result = SurveyUses(&*AI, MaybeLiveArgUses);
648  }
649 
650  // Mark the result.
651  MarkValue(CreateArg(&F, i), Result, MaybeLiveArgUses);
652  // Clear the vector again for the next iteration.
653  MaybeLiveArgUses.clear();
654  }
655 }
656 
657 /// MarkValue - This function marks the liveness of RA depending on L. If L is
658 /// MaybeLive, it also takes all uses in MaybeLiveUses and records them in Uses,
659 /// such that RA will be marked live if any use in MaybeLiveUses gets marked
660 /// live later on.
661 void DeadArgumentEliminationPass::MarkValue(const RetOrArg &RA, Liveness L,
662  const UseVector &MaybeLiveUses) {
663  switch (L) {
664  case Live:
665  MarkLive(RA);
666  break;
667  case MaybeLive:
668  // Note any uses of this value, so this return value can be
669  // marked live whenever one of the uses becomes live.
670  for (const auto &MaybeLiveUse : MaybeLiveUses)
671  Uses.insert(std::make_pair(MaybeLiveUse, RA));
672  break;
673  }
674 }
675 
676 /// MarkLive - Mark the given Function as alive, meaning that it cannot be
677 /// changed in any way. Additionally,
678 /// mark any values that are used as this function's parameters or by its return
679 /// values (according to Uses) live as well.
680 void DeadArgumentEliminationPass::MarkLive(const Function &F) {
681  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Intrinsically live fn: "
682  << F.getName() << "\n");
683  // Mark the function as live.
684  LiveFunctions.insert(&F);
685  // Mark all arguments as live.
686  for (unsigned i = 0, e = F.arg_size(); i != e; ++i)
687  PropagateLiveness(CreateArg(&F, i));
688  // Mark all return values as live.
689  for (unsigned i = 0, e = NumRetVals(&F); i != e; ++i)
690  PropagateLiveness(CreateRet(&F, i));
691 }
692 
693 /// MarkLive - Mark the given return value or argument as live. Additionally,
694 /// mark any values that are used by this value (according to Uses) live as
695 /// well.
696 void DeadArgumentEliminationPass::MarkLive(const RetOrArg &RA) {
697  if (LiveFunctions.count(RA.F))
698  return; // Function was already marked Live.
699 
700  if (!LiveValues.insert(RA).second)
701  return; // We were already marked Live.
702 
703  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Marking "
704  << RA.getDescription() << " live\n");
705  PropagateLiveness(RA);
706 }
707 
708 /// PropagateLiveness - Given that RA is a live value, propagate it's liveness
709 /// to any other values it uses (according to Uses).
710 void DeadArgumentEliminationPass::PropagateLiveness(const RetOrArg &RA) {
711  // We don't use upper_bound (or equal_range) here, because our recursive call
712  // to ourselves is likely to cause the upper_bound (which is the first value
713  // not belonging to RA) to become erased and the iterator invalidated.
714  UseMap::iterator Begin = Uses.lower_bound(RA);
715  UseMap::iterator E = Uses.end();
716  UseMap::iterator I;
717  for (I = Begin; I != E && I->first == RA; ++I)
718  MarkLive(I->second);
719 
720  // Erase RA from the Uses map (from the lower bound to wherever we ended up
721  // after the loop).
722  Uses.erase(Begin, I);
723 }
724 
725 // RemoveDeadStuffFromFunction - Remove any arguments and return values from F
726 // that are not in LiveValues. Transform the function and all of the callees of
727 // the function to not have these arguments and return values.
728 //
729 bool DeadArgumentEliminationPass::RemoveDeadStuffFromFunction(Function *F) {
730  // Don't modify fully live functions
731  if (LiveFunctions.count(F))
732  return false;
733 
734  // Start by computing a new prototype for the function, which is the same as
735  // the old function, but has fewer arguments and a different return type.
736  FunctionType *FTy = F->getFunctionType();
737  std::vector<Type*> Params;
738 
739  // Keep track of if we have a live 'returned' argument
740  bool HasLiveReturnedArg = false;
741 
742  // Set up to build a new list of parameter attributes.
743  SmallVector<AttributeSet, 8> ArgAttrVec;
744  const AttributeList &PAL = F->getAttributes();
745 
746  // Remember which arguments are still alive.
747  SmallVector<bool, 10> ArgAlive(FTy->getNumParams(), false);
748  // Construct the new parameter list from non-dead arguments. Also construct
749  // a new set of parameter attributes to correspond. Skip the first parameter
750  // attribute, since that belongs to the return value.
751  unsigned i = 0;
752  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
753  I != E; ++I, ++i) {
754  RetOrArg Arg = CreateArg(F, i);
755  if (LiveValues.erase(Arg)) {
756  Params.push_back(I->getType());
757  ArgAlive[i] = true;
758  ArgAttrVec.push_back(PAL.getParamAttributes(i));
759  HasLiveReturnedArg |= PAL.hasParamAttribute(i, Attribute::Returned);
760  } else {
761  ++NumArgumentsEliminated;
762  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Removing argument "
763  << i << " (" << I->getName() << ") from "
764  << F->getName() << "\n");
765  }
766  }
767 
768  // Find out the new return value.
769  Type *RetTy = FTy->getReturnType();
770  Type *NRetTy = nullptr;
771  unsigned RetCount = NumRetVals(F);
772 
773  // -1 means unused, other numbers are the new index
774  SmallVector<int, 5> NewRetIdxs(RetCount, -1);
775  std::vector<Type*> RetTypes;
776 
777  // If there is a function with a live 'returned' argument but a dead return
778  // value, then there are two possible actions:
779  // 1) Eliminate the return value and take off the 'returned' attribute on the
780  // argument.
781  // 2) Retain the 'returned' attribute and treat the return value (but not the
782  // entire function) as live so that it is not eliminated.
783  //
784  // It's not clear in the general case which option is more profitable because,
785  // even in the absence of explicit uses of the return value, code generation
786  // is free to use the 'returned' attribute to do things like eliding
787  // save/restores of registers across calls. Whether or not this happens is
788  // target and ABI-specific as well as depending on the amount of register
789  // pressure, so there's no good way for an IR-level pass to figure this out.
790  //
791  // Fortunately, the only places where 'returned' is currently generated by
792  // the FE are places where 'returned' is basically free and almost always a
793  // performance win, so the second option can just be used always for now.
794  //
795  // This should be revisited if 'returned' is ever applied more liberally.
796  if (RetTy->isVoidTy() || HasLiveReturnedArg) {
797  NRetTy = RetTy;
798  } else {
799  // Look at each of the original return values individually.
800  for (unsigned i = 0; i != RetCount; ++i) {
801  RetOrArg Ret = CreateRet(F, i);
802  if (LiveValues.erase(Ret)) {
803  RetTypes.push_back(getRetComponentType(F, i));
804  NewRetIdxs[i] = RetTypes.size() - 1;
805  } else {
806  ++NumRetValsEliminated;
807  LLVM_DEBUG(
808  dbgs() << "DeadArgumentEliminationPass - Removing return value "
809  << i << " from " << F->getName() << "\n");
810  }
811  }
812  if (RetTypes.size() > 1) {
813  // More than one return type? Reduce it down to size.
814  if (StructType *STy = dyn_cast<StructType>(RetTy)) {
815  // Make the new struct packed if we used to return a packed struct
816  // already.
817  NRetTy = StructType::get(STy->getContext(), RetTypes, STy->isPacked());
818  } else {
819  assert(isa<ArrayType>(RetTy) && "unexpected multi-value return");
820  NRetTy = ArrayType::get(RetTypes[0], RetTypes.size());
821  }
822  } else if (RetTypes.size() == 1)
823  // One return type? Just a simple value then, but only if we didn't use to
824  // return a struct with that simple value before.
825  NRetTy = RetTypes.front();
826  else if (RetTypes.empty())
827  // No return types? Make it void, but only if we didn't use to return {}.
828  NRetTy = Type::getVoidTy(F->getContext());
829  }
830 
831  assert(NRetTy && "No new return type found?");
832 
833  // The existing function return attributes.
834  AttrBuilder RAttrs(PAL.getRetAttributes());
835 
836  // Remove any incompatible attributes, but only if we removed all return
837  // values. Otherwise, ensure that we don't have any conflicting attributes
838  // here. Currently, this should not be possible, but special handling might be
839  // required when new return value attributes are added.
840  if (NRetTy->isVoidTy())
842  else
843  assert(!RAttrs.overlaps(AttributeFuncs::typeIncompatible(NRetTy)) &&
844  "Return attributes no longer compatible?");
845 
846  AttributeSet RetAttrs = AttributeSet::get(F->getContext(), RAttrs);
847 
848  // Strip allocsize attributes. They might refer to the deleted arguments.
850  F->getContext(), Attribute::AllocSize);
851 
852  // Reconstruct the AttributesList based on the vector we constructed.
853  assert(ArgAttrVec.size() == Params.size());
854  AttributeList NewPAL =
855  AttributeList::get(F->getContext(), FnAttrs, RetAttrs, ArgAttrVec);
856 
857  // Create the new function type based on the recomputed parameters.
858  FunctionType *NFTy = FunctionType::get(NRetTy, Params, FTy->isVarArg());
859 
860  // No change?
861  if (NFTy == FTy)
862  return false;
863 
864  // Create the new function body and insert it into the module...
865  Function *NF = Function::Create(NFTy, F->getLinkage(), F->getAddressSpace());
866  NF->copyAttributesFrom(F);
867  NF->setComdat(F->getComdat());
868  NF->setAttributes(NewPAL);
869  // Insert the new function before the old function, so we won't be processing
870  // it again.
871  F->getParent()->getFunctionList().insert(F->getIterator(), NF);
872  NF->takeName(F);
873 
874  // Loop over all of the callers of the function, transforming the call sites
875  // to pass in a smaller number of arguments into the new function.
876  std::vector<Value*> Args;
877  while (!F->use_empty()) {
878  CallSite CS(F->user_back());
879  Instruction *Call = CS.getInstruction();
880 
881  ArgAttrVec.clear();
882  const AttributeList &CallPAL = CS.getAttributes();
883 
884  // Adjust the call return attributes in case the function was changed to
885  // return void.
886  AttrBuilder RAttrs(CallPAL.getRetAttributes());
888  AttributeSet RetAttrs = AttributeSet::get(F->getContext(), RAttrs);
889 
890  // Declare these outside of the loops, so we can reuse them for the second
891  // loop, which loops the varargs.
892  CallSite::arg_iterator I = CS.arg_begin();
893  unsigned i = 0;
894  // Loop over those operands, corresponding to the normal arguments to the
895  // original function, and add those that are still alive.
896  for (unsigned e = FTy->getNumParams(); i != e; ++I, ++i)
897  if (ArgAlive[i]) {
898  Args.push_back(*I);
899  // Get original parameter attributes, but skip return attributes.
901  if (NRetTy != RetTy && Attrs.hasAttribute(Attribute::Returned)) {
902  // If the return type has changed, then get rid of 'returned' on the
903  // call site. The alternative is to make all 'returned' attributes on
904  // call sites keep the return value alive just like 'returned'
905  // attributes on function declaration but it's less clearly a win and
906  // this is not an expected case anyway
907  ArgAttrVec.push_back(AttributeSet::get(
908  F->getContext(),
909  AttrBuilder(Attrs).removeAttribute(Attribute::Returned)));
910  } else {
911  // Otherwise, use the original attributes.
912  ArgAttrVec.push_back(Attrs);
913  }
914  }
915 
916  // Push any varargs arguments on the list. Don't forget their attributes.
917  for (CallSite::arg_iterator E = CS.arg_end(); I != E; ++I, ++i) {
918  Args.push_back(*I);
919  ArgAttrVec.push_back(CallPAL.getParamAttributes(i));
920  }
921 
922  // Reconstruct the AttributesList based on the vector we constructed.
923  assert(ArgAttrVec.size() == Args.size());
924 
925  // Again, be sure to remove any allocsize attributes, since their indices
926  // may now be incorrect.
927  AttributeSet FnAttrs = CallPAL.getFnAttributes().removeAttribute(
928  F->getContext(), Attribute::AllocSize);
929 
930  AttributeList NewCallPAL = AttributeList::get(
931  F->getContext(), FnAttrs, RetAttrs, ArgAttrVec);
932 
934  CS.getOperandBundlesAsDefs(OpBundles);
935 
936  CallSite NewCS;
937  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
938  NewCS = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
939  Args, OpBundles, "", Call->getParent());
940  } else {
941  NewCS = CallInst::Create(NFTy, NF, Args, OpBundles, "", Call);
942  cast<CallInst>(NewCS.getInstruction())
943  ->setTailCallKind(cast<CallInst>(Call)->getTailCallKind());
944  }
945  NewCS.setCallingConv(CS.getCallingConv());
946  NewCS.setAttributes(NewCallPAL);
947  NewCS->setDebugLoc(Call->getDebugLoc());
948  uint64_t W;
949  if (Call->extractProfTotalWeight(W))
950  NewCS->setProfWeight(W);
951  Args.clear();
952  ArgAttrVec.clear();
953 
954  Instruction *New = NewCS.getInstruction();
955  if (!Call->use_empty() || Call->isUsedByMetadata()) {
956  if (New->getType() == Call->getType()) {
957  // Return type not changed? Just replace users then.
958  Call->replaceAllUsesWith(New);
959  New->takeName(Call);
960  } else if (New->getType()->isVoidTy()) {
961  // If the return value is dead, replace any uses of it with undef
962  // (any non-debug value uses will get removed later on).
963  if (!Call->getType()->isX86_MMXTy())
964  Call->replaceAllUsesWith(UndefValue::get(Call->getType()));
965  } else {
966  assert((RetTy->isStructTy() || RetTy->isArrayTy()) &&
967  "Return type changed, but not into a void. The old return type"
968  " must have been a struct or an array!");
969  Instruction *InsertPt = Call;
970  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
971  BasicBlock *NewEdge = SplitEdge(New->getParent(), II->getNormalDest());
972  InsertPt = &*NewEdge->getFirstInsertionPt();
973  }
974 
975  // We used to return a struct or array. Instead of doing smart stuff
976  // with all the uses, we will just rebuild it using extract/insertvalue
977  // chaining and let instcombine clean that up.
978  //
979  // Start out building up our return value from undef
980  Value *RetVal = UndefValue::get(RetTy);
981  for (unsigned i = 0; i != RetCount; ++i)
982  if (NewRetIdxs[i] != -1) {
983  Value *V;
984  if (RetTypes.size() > 1)
985  // We are still returning a struct, so extract the value from our
986  // return value
987  V = ExtractValueInst::Create(New, NewRetIdxs[i], "newret",
988  InsertPt);
989  else
990  // We are now returning a single element, so just insert that
991  V = New;
992  // Insert the value at the old position
993  RetVal = InsertValueInst::Create(RetVal, V, i, "oldret", InsertPt);
994  }
995  // Now, replace all uses of the old call instruction with the return
996  // struct we built
997  Call->replaceAllUsesWith(RetVal);
998  New->takeName(Call);
999  }
1000  }
1001 
1002  // Finally, remove the old call from the program, reducing the use-count of
1003  // F.
1004  Call->eraseFromParent();
1005  }
1006 
1007  // Since we have now created the new function, splice the body of the old
1008  // function right into the new function, leaving the old rotting hulk of the
1009  // function empty.
1010  NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
1011 
1012  // Loop over the argument list, transferring uses of the old arguments over to
1013  // the new arguments, also transferring over the names as well.
1014  i = 0;
1015  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
1016  I2 = NF->arg_begin(); I != E; ++I, ++i)
1017  if (ArgAlive[i]) {
1018  // If this is a live argument, move the name and users over to the new
1019  // version.
1020  I->replaceAllUsesWith(&*I2);
1021  I2->takeName(&*I);
1022  ++I2;
1023  } else {
1024  // If this argument is dead, replace any uses of it with undef
1025  // (any non-debug value uses will get removed later on).
1026  if (!I->getType()->isX86_MMXTy())
1027  I->replaceAllUsesWith(UndefValue::get(I->getType()));
1028  }
1029 
1030  // If we change the return value of the function we must rewrite any return
1031  // instructions. Check this now.
1032  if (F->getReturnType() != NF->getReturnType())
1033  for (BasicBlock &BB : *NF)
1034  if (ReturnInst *RI = dyn_cast<ReturnInst>(BB.getTerminator())) {
1035  Value *RetVal;
1036 
1037  if (NFTy->getReturnType()->isVoidTy()) {
1038  RetVal = nullptr;
1039  } else {
1040  assert(RetTy->isStructTy() || RetTy->isArrayTy());
1041  // The original return value was a struct or array, insert
1042  // extractvalue/insertvalue chains to extract only the values we need
1043  // to return and insert them into our new result.
1044  // This does generate messy code, but we'll let it to instcombine to
1045  // clean that up.
1046  Value *OldRet = RI->getOperand(0);
1047  // Start out building up our return value from undef
1048  RetVal = UndefValue::get(NRetTy);
1049  for (unsigned i = 0; i != RetCount; ++i)
1050  if (NewRetIdxs[i] != -1) {
1052  "oldret", RI);
1053  if (RetTypes.size() > 1) {
1054  // We're still returning a struct, so reinsert the value into
1055  // our new return value at the new index
1056 
1057  RetVal = InsertValueInst::Create(RetVal, EV, NewRetIdxs[i],
1058  "newret", RI);
1059  } else {
1060  // We are now only returning a simple value, so just return the
1061  // extracted value.
1062  RetVal = EV;
1063  }
1064  }
1065  }
1066  // Replace the return instruction with one returning the new return
1067  // value (possibly 0 if we became void).
1068  ReturnInst::Create(F->getContext(), RetVal, RI);
1069  BB.getInstList().erase(RI);
1070  }
1071 
1072  // Clone metadatas from the old function, including debug info descriptor.
1074  F->getAllMetadata(MDs);
1075  for (auto MD : MDs)
1076  NF->addMetadata(MD.first, *MD.second);
1077 
1078  // Now that the old function is dead, delete it.
1079  F->eraseFromParent();
1080 
1081  return true;
1082 }
1083 
1086  bool Changed = false;
1087 
1088  // First pass: Do a simple check to see if any functions can have their "..."
1089  // removed. We can do this if they never call va_start. This loop cannot be
1090  // fused with the next loop, because deleting a function invalidates
1091  // information computed while surveying other functions.
1092  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Deleting dead varargs\n");
1093  for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
1094  Function &F = *I++;
1095  if (F.getFunctionType()->isVarArg())
1096  Changed |= DeleteDeadVarargs(F);
1097  }
1098 
1099  // Second phase:loop through the module, determining which arguments are live.
1100  // We assume all arguments are dead unless proven otherwise (allowing us to
1101  // determine that dead arguments passed into recursive functions are dead).
1102  //
1103  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Determining liveness\n");
1104  for (auto &F : M)
1105  SurveyFunction(F);
1106 
1107  // Now, remove all dead arguments and return values from each function in
1108  // turn.
1109  for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
1110  // Increment now, because the function will probably get removed (ie.
1111  // replaced by a new one).
1112  Function *F = &*I++;
1113  Changed |= RemoveDeadStuffFromFunction(F);
1114  }
1115 
1116  // Finally, look for any unused parameters in functions with non-local
1117  // linkage and replace the passed in parameters with undef.
1118  for (auto &F : M)
1119  Changed |= RemoveDeadArgumentsFromCallers(F);
1120 
1121  if (!Changed)
1122  return PreservedAnalyses::all();
1123  return PreservedAnalyses::none();
1124 }
Return a value (possibly void), from a function.
bool isIntrinsic() const
isIntrinsic - Returns true if the function&#39;s name starts with "llvm.".
Definition: Function.h:198
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:67
iterator_range< use_iterator > uses()
Definition: Value.h:374
bool hasLocalLinkage() const
Definition: GlobalValue.h:445
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:29
Eliminate dead arguments (and return values) from functions.
IterTy arg_begin() const
Definition: CallSite.h:584
This class represents lattice values for constants.
Definition: AllocatorList.h:23
void setAttributes(AttributeList PAL)
Set the parameter attributes of the call.
Definition: CallSite.h:341
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:65
iterator end()
Definition: Function.h:682
static CallInst * Create(FunctionType *Ty, Value *F, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
This class represents a function call, abstracting a target machine&#39;s calling convention.
void setCallingConv(CallingConv::ID CC)
Set the calling convention of the call.
Definition: CallSite.h:324
bool hasFnAttribute(Attribute::AttrKind Kind) const
Return true if the function has the attribute.
Definition: Function.h:323
void getOperandBundlesAsDefs(SmallVectorImpl< OperandBundleDef > &Defs) const
Definition: CallSite.h:595
arg_iterator arg_end()
Definition: Function.h:704
STATISTIC(NumFunctions, "Total number of functions")
F(f)
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:1413
bool isMustTailCall() const
CallingConv::ID getCallingConv() const
Get the calling convention of the call.
Definition: CallSite.h:320
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:233
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:55
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.
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:341
InstrTy * getInstruction() const
Definition: CallSite.h:96
User * getUser() const LLVM_READONLY
Returns the User that contains this Use.
Definition: Use.cpp:40
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:403
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:107
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:223
bool extractProfTotalWeight(uint64_t &TotalVal) const
Retrieve total raw weight values of a branch.
Definition: Metadata.cpp:1336
LinkageTypes getLinkage() const
Definition: GlobalValue.h:460
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:429
constexpr char Attrs[]
Key for Kernel::Metadata::mAttrs.
void takeName(Value *V)
Transfer the name from V to this value.
Definition: Value.cpp:291
iterator begin()
Definition: Function.h:680
void removeDeadConstantUsers() const
If there are any dead constant users dangling off of this constant, remove them.
Definition: Constants.cpp:571
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:657
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:1804
bool isVoidTy() const
Return true if this is &#39;void&#39;.
Definition: Type.h:140
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...
Type * getReturnType() const
Returns the type of the ret val.
Definition: Function.h:168
static Function * Create(FunctionType *Ty, LinkageTypes Linkage, unsigned AddrSpace, const Twine &N="", Module *M=nullptr)
Definition: Function.h:135
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:592
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:216
bool areAllPreserved() const
Test whether all analyses are preserved (and none are abandoned).
Definition: PassManager.h:328
static unsigned getAggregateOperandIndex()
const FunctionListType & getFunctionList() const
Get the Module&#39;s list of functions (constant).
Definition: Module.h:533
LLVM Basic Block Representation.
Definition: BasicBlock.h:57
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
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:496
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...
AttributeList getAttributes() const
Get the parameter attributes of the call.
Definition: CallSite.h:337
LLVM_NODISCARD AttributeSet removeAttribute(LLVMContext &C, Attribute::AttrKind Kind) const
Remove the specified attribute from this set.
Definition: Attributes.cpp:630
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:160
void splice(iterator where, iplist_impl &L2)
Definition: ilist.h:327
unsigned getAddressSpace() const
Definition: Globals.cpp:111
amdgpu Simplify well known AMD library false FunctionCallee Value * Arg
static FunctionType * get(Type *Result, ArrayRef< Type *> Params, bool isVarArg)
This static method is the primary way of constructing a FunctionType.
Definition: Type.cpp:296
size_t arg_size() const
Definition: Function.h:728
arg_iterator arg_begin()
Definition: Function.h:695
self_iterator getIterator()
Definition: ilist_node.h:81
LLVMContext & getContext() const
getContext - Return a reference to the LLVMContext associated with this function. ...
Definition: Function.cpp:205
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1446
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:159
size_t size() const
Definition: SmallVector.h:52
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.
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:837
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:1390
Type * getReturnType() const
Definition: DerivedTypes.h:124
User::op_iterator arg_iterator
The type of iterator to use when looping over actual arguments at this call site. ...
Definition: CallSite.h:220
void setAttributes(AttributeList Attrs)
Set the attribute list for this Function.
Definition: Function.h:226
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:163
const Comdat * getComdat() const
Definition: GlobalObject.h:105
iterator insert(iterator where, pointer New)
Definition: ilist.h:226
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:331
iterator end()
Definition: Module.h:600
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:55
static InvokeInst * Create(FunctionType *Ty, Value *Func, BasicBlock *IfNormal, BasicBlock *IfException, ArrayRef< Value *> Args, const Twine &NameStr, Instruction *InsertBefore=nullptr)
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:214
bool hasExactDefinition() const
Return true if this global has an exact defintion.
Definition: GlobalValue.h:416
Establish a view to a call site for examination.
Definition: CallSite.h:897
#define I(x, y, z)
Definition: MD5.cpp:58
user_iterator_impl< User > user_iterator
Definition: Value.h:388
ModulePass class - This class is used to implement unstructured interprocedural optimizations and ana...
Definition: Pass.h:224
iterator begin()
Definition: Module.h:598
static ArrayType * get(Type *ElementType, uint64_t NumElements)
This static method is the primary way to construct an ArrayType.
Definition: Type.cpp:582
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:332
const BasicBlockListType & getBasicBlockList() const
Get the underlying elements of the Function...
Definition: Function.h:657
void eraseFromParent()
eraseFromParent - This method unlinks &#39;this&#39; from the containing module and deletes it...
Definition: Function.cpp:226
bool isDeclaration() const
Return true if the primary definition of this global value is outside of the current translation unit...
Definition: Globals.cpp:231
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:1360
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:575
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.
This header defines various interfaces for pass management in LLVM.
#define LLVM_DEBUG(X)
Definition: Debug.h:122
bool isEmpty() const
Return true if there are no attributes.
Definition: Attributes.h:669
bool use_empty() const
Definition: Value.h:342
constexpr char Args[]
Key for Kernel::Metadata::mArgs.
PointerType * getType() const
Global values are always pointers.
Definition: GlobalValue.h:277
static AttributeList get(LLVMContext &C, ArrayRef< std::pair< unsigned, Attribute >> Attrs)
Create an AttributeList with the specified parameters in it.
Definition: Attributes.cpp:973
iterator_range< arg_iterator > args()
Definition: Function.h:719
User * user_back()
Definition: Value.h:405
A wrapper class for inspecting calls to intrinsic functions.
Definition: IntrinsicInst.h:43
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 &)