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  for (Argument &Arg : Fn.args()) {
293  if (!Arg.hasSwiftErrorAttr() && Arg.use_empty() && !Arg.hasByValOrInAllocaAttr())
294  UnusedArgs.push_back(Arg.getArgNo());
295  }
296 
297  if (UnusedArgs.empty())
298  return false;
299 
300  bool Changed = false;
301 
302  for (Use &U : Fn.uses()) {
303  CallSite CS(U.getUser());
304  if (!CS || !CS.isCallee(&U))
305  continue;
306 
307  // Now go through all unused args and replace them with "undef".
308  for (unsigned I = 0, E = UnusedArgs.size(); I != E; ++I) {
309  unsigned ArgNo = UnusedArgs[I];
310 
311  Value *Arg = CS.getArgument(ArgNo);
312  CS.setArgument(ArgNo, UndefValue::get(Arg->getType()));
313  ++NumArgumentsReplacedWithUndef;
314  Changed = true;
315  }
316  }
317 
318  return Changed;
319 }
320 
321 /// Convenience function that returns the number of return values. It returns 0
322 /// for void functions and 1 for functions not returning a struct. It returns
323 /// the number of struct elements for functions returning a struct.
324 static unsigned NumRetVals(const Function *F) {
325  Type *RetTy = F->getReturnType();
326  if (RetTy->isVoidTy())
327  return 0;
328  else if (StructType *STy = dyn_cast<StructType>(RetTy))
329  return STy->getNumElements();
330  else if (ArrayType *ATy = dyn_cast<ArrayType>(RetTy))
331  return ATy->getNumElements();
332  else
333  return 1;
334 }
335 
336 /// Returns the sub-type a function will return at a given Idx. Should
337 /// correspond to the result type of an ExtractValue instruction executed with
338 /// just that one Idx (i.e. only top-level structure is considered).
339 static Type *getRetComponentType(const Function *F, unsigned Idx) {
340  Type *RetTy = F->getReturnType();
341  assert(!RetTy->isVoidTy() && "void type has no subtype");
342 
343  if (StructType *STy = dyn_cast<StructType>(RetTy))
344  return STy->getElementType(Idx);
345  else if (ArrayType *ATy = dyn_cast<ArrayType>(RetTy))
346  return ATy->getElementType();
347  else
348  return RetTy;
349 }
350 
351 /// MarkIfNotLive - This checks Use for liveness in LiveValues. If Use is not
352 /// live, it adds Use to the MaybeLiveUses argument. Returns the determined
353 /// liveness of Use.
355 DeadArgumentEliminationPass::MarkIfNotLive(RetOrArg Use,
356  UseVector &MaybeLiveUses) {
357  // We're live if our use or its Function is already marked as live.
358  if (LiveFunctions.count(Use.F) || LiveValues.count(Use))
359  return Live;
360 
361  // We're maybe live otherwise, but remember that we must become live if
362  // Use becomes live.
363  MaybeLiveUses.push_back(Use);
364  return MaybeLive;
365 }
366 
367 /// SurveyUse - This looks at a single use of an argument or return value
368 /// and determines if it should be alive or not. Adds this use to MaybeLiveUses
369 /// if it causes the used value to become MaybeLive.
370 ///
371 /// RetValNum is the return value number to use when this use is used in a
372 /// return instruction. This is used in the recursion, you should always leave
373 /// it at 0.
375 DeadArgumentEliminationPass::SurveyUse(const Use *U, UseVector &MaybeLiveUses,
376  unsigned RetValNum) {
377  const User *V = U->getUser();
378  if (const ReturnInst *RI = dyn_cast<ReturnInst>(V)) {
379  // The value is returned from a function. It's only live when the
380  // function's return value is live. We use RetValNum here, for the case
381  // that U is really a use of an insertvalue instruction that uses the
382  // original Use.
383  const Function *F = RI->getParent()->getParent();
384  if (RetValNum != -1U) {
385  RetOrArg Use = CreateRet(F, RetValNum);
386  // We might be live, depending on the liveness of Use.
387  return MarkIfNotLive(Use, MaybeLiveUses);
388  } else {
390  for (unsigned i = 0; i < NumRetVals(F); ++i) {
391  RetOrArg Use = CreateRet(F, i);
392  // We might be live, depending on the liveness of Use. If any
393  // sub-value is live, then the entire value is considered live. This
394  // is a conservative choice, and better tracking is possible.
396  MarkIfNotLive(Use, MaybeLiveUses);
397  if (Result != Live)
398  Result = SubResult;
399  }
400  return Result;
401  }
402  }
403  if (const InsertValueInst *IV = dyn_cast<InsertValueInst>(V)) {
404  if (U->getOperandNo() != InsertValueInst::getAggregateOperandIndex()
405  && IV->hasIndices())
406  // The use we are examining is inserted into an aggregate. Our liveness
407  // depends on all uses of that aggregate, but if it is used as a return
408  // value, only index at which we were inserted counts.
409  RetValNum = *IV->idx_begin();
410 
411  // Note that if we are used as the aggregate operand to the insertvalue,
412  // we don't change RetValNum, but do survey all our uses.
413 
414  Liveness Result = MaybeLive;
415  for (const Use &UU : IV->uses()) {
416  Result = SurveyUse(&UU, MaybeLiveUses, RetValNum);
417  if (Result == Live)
418  break;
419  }
420  return Result;
421  }
422 
423  if (auto CS = ImmutableCallSite(V)) {
424  const Function *F = CS.getCalledFunction();
425  if (F) {
426  // Used in a direct call.
427 
428  // The function argument is live if it is used as a bundle operand.
429  if (CS.isBundleOperand(U))
430  return Live;
431 
432  // Find the argument number. We know for sure that this use is an
433  // argument, since if it was the function argument this would be an
434  // indirect call and the we know can't be looking at a value of the
435  // label type (for the invoke instruction).
436  unsigned ArgNo = CS.getArgumentNo(U);
437 
438  if (ArgNo >= F->getFunctionType()->getNumParams())
439  // The value is passed in through a vararg! Must be live.
440  return Live;
441 
442  assert(CS.getArgument(ArgNo)
443  == CS->getOperand(U->getOperandNo())
444  && "Argument is not where we expected it");
445 
446  // Value passed to a normal call. It's only live when the corresponding
447  // argument to the called function turns out live.
448  RetOrArg Use = CreateArg(F, ArgNo);
449  return MarkIfNotLive(Use, MaybeLiveUses);
450  }
451  }
452  // Used in any other way? Value must be live.
453  return Live;
454 }
455 
456 /// SurveyUses - This looks at all the uses of the given value
457 /// Returns the Liveness deduced from the uses of this value.
458 ///
459 /// Adds all uses that cause the result to be MaybeLive to MaybeLiveRetUses. If
460 /// the result is Live, MaybeLiveUses might be modified but its content should
461 /// be ignored (since it might not be complete).
463 DeadArgumentEliminationPass::SurveyUses(const Value *V,
464  UseVector &MaybeLiveUses) {
465  // Assume it's dead (which will only hold if there are no uses at all..).
466  Liveness Result = MaybeLive;
467  // Check each use.
468  for (const Use &U : V->uses()) {
469  Result = SurveyUse(&U, MaybeLiveUses);
470  if (Result == Live)
471  break;
472  }
473  return Result;
474 }
475 
476 // SurveyFunction - This performs the initial survey of the specified function,
477 // checking out whether or not it uses any of its incoming arguments or whether
478 // any callers use the return value. This fills in the LiveValues set and Uses
479 // map.
480 //
481 // We consider arguments of non-internal functions to be intrinsically alive as
482 // well as arguments to functions which have their "address taken".
483 void DeadArgumentEliminationPass::SurveyFunction(const Function &F) {
484  // Functions with inalloca parameters are expecting args in a particular
485  // register and memory layout.
486  if (F.getAttributes().hasAttrSomewhere(Attribute::InAlloca)) {
487  MarkLive(F);
488  return;
489  }
490 
491  // Don't touch naked functions. The assembly might be using an argument, or
492  // otherwise rely on the frame layout in a way that this analysis will not
493  // see.
494  if (F.hasFnAttribute(Attribute::Naked)) {
495  MarkLive(F);
496  return;
497  }
498 
499  unsigned RetCount = NumRetVals(&F);
500 
501  // Assume all return values are dead
502  using RetVals = SmallVector<Liveness, 5>;
503 
504  RetVals RetValLiveness(RetCount, MaybeLive);
505 
506  using RetUses = SmallVector<UseVector, 5>;
507 
508  // These vectors map each return value to the uses that make it MaybeLive, so
509  // we can add those to the Uses map if the return value really turns out to be
510  // MaybeLive. Initialized to a list of RetCount empty lists.
511  RetUses MaybeLiveRetUses(RetCount);
512 
513  bool HasMustTailCalls = false;
514 
515  for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
516  if (const ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
517  if (RI->getNumOperands() != 0 && RI->getOperand(0)->getType()
518  != F.getFunctionType()->getReturnType()) {
519  // We don't support old style multiple return values.
520  MarkLive(F);
521  return;
522  }
523  }
524 
525  // If we have any returns of `musttail` results - the signature can't
526  // change
527  if (BB->getTerminatingMustTailCall() != nullptr)
528  HasMustTailCalls = true;
529  }
530 
531  if (HasMustTailCalls) {
532  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - " << F.getName()
533  << " has musttail calls\n");
534  }
535 
536  if (!F.hasLocalLinkage() && (!ShouldHackArguments || F.isIntrinsic())) {
537  MarkLive(F);
538  return;
539  }
540 
541  LLVM_DEBUG(
542  dbgs() << "DeadArgumentEliminationPass - Inspecting callers for fn: "
543  << F.getName() << "\n");
544  // Keep track of the number of live retvals, so we can skip checks once all
545  // of them turn out to be live.
546  unsigned NumLiveRetVals = 0;
547 
548  bool HasMustTailCallers = false;
549 
550  // Loop all uses of the function.
551  for (const Use &U : F.uses()) {
552  // If the function is PASSED IN as an argument, its address has been
553  // taken.
554  ImmutableCallSite CS(U.getUser());
555  if (!CS || !CS.isCallee(&U)) {
556  MarkLive(F);
557  return;
558  }
559 
560  // The number of arguments for `musttail` call must match the number of
561  // arguments of the caller
562  if (CS.isMustTailCall())
563  HasMustTailCallers = true;
564 
565  // If this use is anything other than a call site, the function is alive.
566  const Instruction *TheCall = CS.getInstruction();
567  if (!TheCall) { // Not a direct call site?
568  MarkLive(F);
569  return;
570  }
571 
572  // If we end up here, we are looking at a direct call to our function.
573 
574  // Now, check how our return value(s) is/are used in this caller. Don't
575  // bother checking return values if all of them are live already.
576  if (NumLiveRetVals == RetCount)
577  continue;
578 
579  // Check all uses of the return value.
580  for (const Use &U : TheCall->uses()) {
581  if (ExtractValueInst *Ext = dyn_cast<ExtractValueInst>(U.getUser())) {
582  // This use uses a part of our return value, survey the uses of
583  // that part and store the results for this index only.
584  unsigned Idx = *Ext->idx_begin();
585  if (RetValLiveness[Idx] != Live) {
586  RetValLiveness[Idx] = SurveyUses(Ext, MaybeLiveRetUses[Idx]);
587  if (RetValLiveness[Idx] == Live)
588  NumLiveRetVals++;
589  }
590  } else {
591  // Used by something else than extractvalue. Survey, but assume that the
592  // result applies to all sub-values.
593  UseVector MaybeLiveAggregateUses;
594  if (SurveyUse(&U, MaybeLiveAggregateUses) == Live) {
595  NumLiveRetVals = RetCount;
596  RetValLiveness.assign(RetCount, Live);
597  break;
598  } else {
599  for (unsigned i = 0; i != RetCount; ++i) {
600  if (RetValLiveness[i] != Live)
601  MaybeLiveRetUses[i].append(MaybeLiveAggregateUses.begin(),
602  MaybeLiveAggregateUses.end());
603  }
604  }
605  }
606  }
607  }
608 
609  if (HasMustTailCallers) {
610  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - " << F.getName()
611  << " has musttail callers\n");
612  }
613 
614  // Now we've inspected all callers, record the liveness of our return values.
615  for (unsigned i = 0; i != RetCount; ++i)
616  MarkValue(CreateRet(&F, i), RetValLiveness[i], MaybeLiveRetUses[i]);
617 
618  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Inspecting args for fn: "
619  << F.getName() << "\n");
620 
621  // Now, check all of our arguments.
622  unsigned i = 0;
623  UseVector MaybeLiveArgUses;
625  E = F.arg_end(); AI != E; ++AI, ++i) {
626  Liveness Result;
627  if (F.getFunctionType()->isVarArg() || HasMustTailCallers ||
628  HasMustTailCalls) {
629  // Variadic functions will already have a va_arg function expanded inside
630  // them, making them potentially very sensitive to ABI changes resulting
631  // from removing arguments entirely, so don't. For example AArch64 handles
632  // register and stack HFAs very differently, and this is reflected in the
633  // IR which has already been generated.
634  //
635  // `musttail` calls to this function restrict argument removal attempts.
636  // The signature of the caller must match the signature of the function.
637  //
638  // `musttail` calls in this function prevents us from changing its
639  // signature
640  Result = Live;
641  } else {
642  // See what the effect of this use is (recording any uses that cause
643  // MaybeLive in MaybeLiveArgUses).
644  Result = SurveyUses(&*AI, MaybeLiveArgUses);
645  }
646 
647  // Mark the result.
648  MarkValue(CreateArg(&F, i), Result, MaybeLiveArgUses);
649  // Clear the vector again for the next iteration.
650  MaybeLiveArgUses.clear();
651  }
652 }
653 
654 /// MarkValue - This function marks the liveness of RA depending on L. If L is
655 /// MaybeLive, it also takes all uses in MaybeLiveUses and records them in Uses,
656 /// such that RA will be marked live if any use in MaybeLiveUses gets marked
657 /// live later on.
658 void DeadArgumentEliminationPass::MarkValue(const RetOrArg &RA, Liveness L,
659  const UseVector &MaybeLiveUses) {
660  switch (L) {
661  case Live:
662  MarkLive(RA);
663  break;
664  case MaybeLive:
665  // Note any uses of this value, so this return value can be
666  // marked live whenever one of the uses becomes live.
667  for (const auto &MaybeLiveUse : MaybeLiveUses)
668  Uses.insert(std::make_pair(MaybeLiveUse, RA));
669  break;
670  }
671 }
672 
673 /// MarkLive - Mark the given Function as alive, meaning that it cannot be
674 /// changed in any way. Additionally,
675 /// mark any values that are used as this function's parameters or by its return
676 /// values (according to Uses) live as well.
677 void DeadArgumentEliminationPass::MarkLive(const Function &F) {
678  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Intrinsically live fn: "
679  << F.getName() << "\n");
680  // Mark the function as live.
681  LiveFunctions.insert(&F);
682  // Mark all arguments as live.
683  for (unsigned i = 0, e = F.arg_size(); i != e; ++i)
684  PropagateLiveness(CreateArg(&F, i));
685  // Mark all return values as live.
686  for (unsigned i = 0, e = NumRetVals(&F); i != e; ++i)
687  PropagateLiveness(CreateRet(&F, i));
688 }
689 
690 /// MarkLive - Mark the given return value or argument as live. Additionally,
691 /// mark any values that are used by this value (according to Uses) live as
692 /// well.
693 void DeadArgumentEliminationPass::MarkLive(const RetOrArg &RA) {
694  if (LiveFunctions.count(RA.F))
695  return; // Function was already marked Live.
696 
697  if (!LiveValues.insert(RA).second)
698  return; // We were already marked Live.
699 
700  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Marking "
701  << RA.getDescription() << " live\n");
702  PropagateLiveness(RA);
703 }
704 
705 /// PropagateLiveness - Given that RA is a live value, propagate it's liveness
706 /// to any other values it uses (according to Uses).
707 void DeadArgumentEliminationPass::PropagateLiveness(const RetOrArg &RA) {
708  // We don't use upper_bound (or equal_range) here, because our recursive call
709  // to ourselves is likely to cause the upper_bound (which is the first value
710  // not belonging to RA) to become erased and the iterator invalidated.
711  UseMap::iterator Begin = Uses.lower_bound(RA);
712  UseMap::iterator E = Uses.end();
713  UseMap::iterator I;
714  for (I = Begin; I != E && I->first == RA; ++I)
715  MarkLive(I->second);
716 
717  // Erase RA from the Uses map (from the lower bound to wherever we ended up
718  // after the loop).
719  Uses.erase(Begin, I);
720 }
721 
722 // RemoveDeadStuffFromFunction - Remove any arguments and return values from F
723 // that are not in LiveValues. Transform the function and all of the callees of
724 // the function to not have these arguments and return values.
725 //
726 bool DeadArgumentEliminationPass::RemoveDeadStuffFromFunction(Function *F) {
727  // Don't modify fully live functions
728  if (LiveFunctions.count(F))
729  return false;
730 
731  // Start by computing a new prototype for the function, which is the same as
732  // the old function, but has fewer arguments and a different return type.
733  FunctionType *FTy = F->getFunctionType();
734  std::vector<Type*> Params;
735 
736  // Keep track of if we have a live 'returned' argument
737  bool HasLiveReturnedArg = false;
738 
739  // Set up to build a new list of parameter attributes.
740  SmallVector<AttributeSet, 8> ArgAttrVec;
741  const AttributeList &PAL = F->getAttributes();
742 
743  // Remember which arguments are still alive.
744  SmallVector<bool, 10> ArgAlive(FTy->getNumParams(), false);
745  // Construct the new parameter list from non-dead arguments. Also construct
746  // a new set of parameter attributes to correspond. Skip the first parameter
747  // attribute, since that belongs to the return value.
748  unsigned i = 0;
749  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
750  I != E; ++I, ++i) {
751  RetOrArg Arg = CreateArg(F, i);
752  if (LiveValues.erase(Arg)) {
753  Params.push_back(I->getType());
754  ArgAlive[i] = true;
755  ArgAttrVec.push_back(PAL.getParamAttributes(i));
756  HasLiveReturnedArg |= PAL.hasParamAttribute(i, Attribute::Returned);
757  } else {
758  ++NumArgumentsEliminated;
759  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Removing argument "
760  << i << " (" << I->getName() << ") from "
761  << F->getName() << "\n");
762  }
763  }
764 
765  // Find out the new return value.
766  Type *RetTy = FTy->getReturnType();
767  Type *NRetTy = nullptr;
768  unsigned RetCount = NumRetVals(F);
769 
770  // -1 means unused, other numbers are the new index
771  SmallVector<int, 5> NewRetIdxs(RetCount, -1);
772  std::vector<Type*> RetTypes;
773 
774  // If there is a function with a live 'returned' argument but a dead return
775  // value, then there are two possible actions:
776  // 1) Eliminate the return value and take off the 'returned' attribute on the
777  // argument.
778  // 2) Retain the 'returned' attribute and treat the return value (but not the
779  // entire function) as live so that it is not eliminated.
780  //
781  // It's not clear in the general case which option is more profitable because,
782  // even in the absence of explicit uses of the return value, code generation
783  // is free to use the 'returned' attribute to do things like eliding
784  // save/restores of registers across calls. Whether or not this happens is
785  // target and ABI-specific as well as depending on the amount of register
786  // pressure, so there's no good way for an IR-level pass to figure this out.
787  //
788  // Fortunately, the only places where 'returned' is currently generated by
789  // the FE are places where 'returned' is basically free and almost always a
790  // performance win, so the second option can just be used always for now.
791  //
792  // This should be revisited if 'returned' is ever applied more liberally.
793  if (RetTy->isVoidTy() || HasLiveReturnedArg) {
794  NRetTy = RetTy;
795  } else {
796  // Look at each of the original return values individually.
797  for (unsigned i = 0; i != RetCount; ++i) {
798  RetOrArg Ret = CreateRet(F, i);
799  if (LiveValues.erase(Ret)) {
800  RetTypes.push_back(getRetComponentType(F, i));
801  NewRetIdxs[i] = RetTypes.size() - 1;
802  } else {
803  ++NumRetValsEliminated;
804  LLVM_DEBUG(
805  dbgs() << "DeadArgumentEliminationPass - Removing return value "
806  << i << " from " << F->getName() << "\n");
807  }
808  }
809  if (RetTypes.size() > 1) {
810  // More than one return type? Reduce it down to size.
811  if (StructType *STy = dyn_cast<StructType>(RetTy)) {
812  // Make the new struct packed if we used to return a packed struct
813  // already.
814  NRetTy = StructType::get(STy->getContext(), RetTypes, STy->isPacked());
815  } else {
816  assert(isa<ArrayType>(RetTy) && "unexpected multi-value return");
817  NRetTy = ArrayType::get(RetTypes[0], RetTypes.size());
818  }
819  } else if (RetTypes.size() == 1)
820  // One return type? Just a simple value then, but only if we didn't use to
821  // return a struct with that simple value before.
822  NRetTy = RetTypes.front();
823  else if (RetTypes.empty())
824  // No return types? Make it void, but only if we didn't use to return {}.
825  NRetTy = Type::getVoidTy(F->getContext());
826  }
827 
828  assert(NRetTy && "No new return type found?");
829 
830  // The existing function return attributes.
831  AttrBuilder RAttrs(PAL.getRetAttributes());
832 
833  // Remove any incompatible attributes, but only if we removed all return
834  // values. Otherwise, ensure that we don't have any conflicting attributes
835  // here. Currently, this should not be possible, but special handling might be
836  // required when new return value attributes are added.
837  if (NRetTy->isVoidTy())
839  else
840  assert(!RAttrs.overlaps(AttributeFuncs::typeIncompatible(NRetTy)) &&
841  "Return attributes no longer compatible?");
842 
843  AttributeSet RetAttrs = AttributeSet::get(F->getContext(), RAttrs);
844 
845  // Strip allocsize attributes. They might refer to the deleted arguments.
847  F->getContext(), Attribute::AllocSize);
848 
849  // Reconstruct the AttributesList based on the vector we constructed.
850  assert(ArgAttrVec.size() == Params.size());
851  AttributeList NewPAL =
852  AttributeList::get(F->getContext(), FnAttrs, RetAttrs, ArgAttrVec);
853 
854  // Create the new function type based on the recomputed parameters.
855  FunctionType *NFTy = FunctionType::get(NRetTy, Params, FTy->isVarArg());
856 
857  // No change?
858  if (NFTy == FTy)
859  return false;
860 
861  // Create the new function body and insert it into the module...
862  Function *NF = Function::Create(NFTy, F->getLinkage());
863  NF->copyAttributesFrom(F);
864  NF->setComdat(F->getComdat());
865  NF->setAttributes(NewPAL);
866  // Insert the new function before the old function, so we won't be processing
867  // it again.
868  F->getParent()->getFunctionList().insert(F->getIterator(), NF);
869  NF->takeName(F);
870 
871  // Loop over all of the callers of the function, transforming the call sites
872  // to pass in a smaller number of arguments into the new function.
873  std::vector<Value*> Args;
874  while (!F->use_empty()) {
875  CallSite CS(F->user_back());
876  Instruction *Call = CS.getInstruction();
877 
878  ArgAttrVec.clear();
879  const AttributeList &CallPAL = CS.getAttributes();
880 
881  // Adjust the call return attributes in case the function was changed to
882  // return void.
883  AttrBuilder RAttrs(CallPAL.getRetAttributes());
885  AttributeSet RetAttrs = AttributeSet::get(F->getContext(), RAttrs);
886 
887  // Declare these outside of the loops, so we can reuse them for the second
888  // loop, which loops the varargs.
889  CallSite::arg_iterator I = CS.arg_begin();
890  unsigned i = 0;
891  // Loop over those operands, corresponding to the normal arguments to the
892  // original function, and add those that are still alive.
893  for (unsigned e = FTy->getNumParams(); i != e; ++I, ++i)
894  if (ArgAlive[i]) {
895  Args.push_back(*I);
896  // Get original parameter attributes, but skip return attributes.
898  if (NRetTy != RetTy && Attrs.hasAttribute(Attribute::Returned)) {
899  // If the return type has changed, then get rid of 'returned' on the
900  // call site. The alternative is to make all 'returned' attributes on
901  // call sites keep the return value alive just like 'returned'
902  // attributes on function declaration but it's less clearly a win and
903  // this is not an expected case anyway
904  ArgAttrVec.push_back(AttributeSet::get(
905  F->getContext(),
906  AttrBuilder(Attrs).removeAttribute(Attribute::Returned)));
907  } else {
908  // Otherwise, use the original attributes.
909  ArgAttrVec.push_back(Attrs);
910  }
911  }
912 
913  // Push any varargs arguments on the list. Don't forget their attributes.
914  for (CallSite::arg_iterator E = CS.arg_end(); I != E; ++I, ++i) {
915  Args.push_back(*I);
916  ArgAttrVec.push_back(CallPAL.getParamAttributes(i));
917  }
918 
919  // Reconstruct the AttributesList based on the vector we constructed.
920  assert(ArgAttrVec.size() == Args.size());
921 
922  // Again, be sure to remove any allocsize attributes, since their indices
923  // may now be incorrect.
924  AttributeSet FnAttrs = CallPAL.getFnAttributes().removeAttribute(
925  F->getContext(), Attribute::AllocSize);
926 
927  AttributeList NewCallPAL = AttributeList::get(
928  F->getContext(), FnAttrs, RetAttrs, ArgAttrVec);
929 
931  CS.getOperandBundlesAsDefs(OpBundles);
932 
933  CallSite NewCS;
934  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
935  NewCS = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
936  Args, OpBundles, "", Call->getParent());
937  } else {
938  NewCS = CallInst::Create(NF, Args, OpBundles, "", Call);
939  cast<CallInst>(NewCS.getInstruction())
940  ->setTailCallKind(cast<CallInst>(Call)->getTailCallKind());
941  }
942  NewCS.setCallingConv(CS.getCallingConv());
943  NewCS.setAttributes(NewCallPAL);
944  NewCS->setDebugLoc(Call->getDebugLoc());
945  uint64_t W;
946  if (Call->extractProfTotalWeight(W))
947  NewCS->setProfWeight(W);
948  Args.clear();
949  ArgAttrVec.clear();
950 
951  Instruction *New = NewCS.getInstruction();
952  if (!Call->use_empty()) {
953  if (New->getType() == Call->getType()) {
954  // Return type not changed? Just replace users then.
955  Call->replaceAllUsesWith(New);
956  New->takeName(Call);
957  } else if (New->getType()->isVoidTy()) {
958  // Our return value has uses, but they will get removed later on.
959  // Replace by null for now.
960  if (!Call->getType()->isX86_MMXTy())
961  Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
962  } else {
963  assert((RetTy->isStructTy() || RetTy->isArrayTy()) &&
964  "Return type changed, but not into a void. The old return type"
965  " must have been a struct or an array!");
966  Instruction *InsertPt = Call;
967  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
968  BasicBlock *NewEdge = SplitEdge(New->getParent(), II->getNormalDest());
969  InsertPt = &*NewEdge->getFirstInsertionPt();
970  }
971 
972  // We used to return a struct or array. Instead of doing smart stuff
973  // with all the uses, we will just rebuild it using extract/insertvalue
974  // chaining and let instcombine clean that up.
975  //
976  // Start out building up our return value from undef
977  Value *RetVal = UndefValue::get(RetTy);
978  for (unsigned i = 0; i != RetCount; ++i)
979  if (NewRetIdxs[i] != -1) {
980  Value *V;
981  if (RetTypes.size() > 1)
982  // We are still returning a struct, so extract the value from our
983  // return value
984  V = ExtractValueInst::Create(New, NewRetIdxs[i], "newret",
985  InsertPt);
986  else
987  // We are now returning a single element, so just insert that
988  V = New;
989  // Insert the value at the old position
990  RetVal = InsertValueInst::Create(RetVal, V, i, "oldret", InsertPt);
991  }
992  // Now, replace all uses of the old call instruction with the return
993  // struct we built
994  Call->replaceAllUsesWith(RetVal);
995  New->takeName(Call);
996  }
997  }
998 
999  // Finally, remove the old call from the program, reducing the use-count of
1000  // F.
1001  Call->eraseFromParent();
1002  }
1003 
1004  // Since we have now created the new function, splice the body of the old
1005  // function right into the new function, leaving the old rotting hulk of the
1006  // function empty.
1007  NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
1008 
1009  // Loop over the argument list, transferring uses of the old arguments over to
1010  // the new arguments, also transferring over the names as well.
1011  i = 0;
1012  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
1013  I2 = NF->arg_begin(); I != E; ++I, ++i)
1014  if (ArgAlive[i]) {
1015  // If this is a live argument, move the name and users over to the new
1016  // version.
1017  I->replaceAllUsesWith(&*I2);
1018  I2->takeName(&*I);
1019  ++I2;
1020  } else {
1021  // If this argument is dead, replace any uses of it with null constants
1022  // (these are guaranteed to become unused later on).
1023  if (!I->getType()->isX86_MMXTy())
1024  I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
1025  }
1026 
1027  // If we change the return value of the function we must rewrite any return
1028  // instructions. Check this now.
1029  if (F->getReturnType() != NF->getReturnType())
1030  for (BasicBlock &BB : *NF)
1031  if (ReturnInst *RI = dyn_cast<ReturnInst>(BB.getTerminator())) {
1032  Value *RetVal;
1033 
1034  if (NFTy->getReturnType()->isVoidTy()) {
1035  RetVal = nullptr;
1036  } else {
1037  assert(RetTy->isStructTy() || RetTy->isArrayTy());
1038  // The original return value was a struct or array, insert
1039  // extractvalue/insertvalue chains to extract only the values we need
1040  // to return and insert them into our new result.
1041  // This does generate messy code, but we'll let it to instcombine to
1042  // clean that up.
1043  Value *OldRet = RI->getOperand(0);
1044  // Start out building up our return value from undef
1045  RetVal = UndefValue::get(NRetTy);
1046  for (unsigned i = 0; i != RetCount; ++i)
1047  if (NewRetIdxs[i] != -1) {
1049  "oldret", RI);
1050  if (RetTypes.size() > 1) {
1051  // We're still returning a struct, so reinsert the value into
1052  // our new return value at the new index
1053 
1054  RetVal = InsertValueInst::Create(RetVal, EV, NewRetIdxs[i],
1055  "newret", RI);
1056  } else {
1057  // We are now only returning a simple value, so just return the
1058  // extracted value.
1059  RetVal = EV;
1060  }
1061  }
1062  }
1063  // Replace the return instruction with one returning the new return
1064  // value (possibly 0 if we became void).
1065  ReturnInst::Create(F->getContext(), RetVal, RI);
1066  BB.getInstList().erase(RI);
1067  }
1068 
1069  // Clone metadatas from the old function, including debug info descriptor.
1071  F->getAllMetadata(MDs);
1072  for (auto MD : MDs)
1073  NF->addMetadata(MD.first, *MD.second);
1074 
1075  // Now that the old function is dead, delete it.
1076  F->eraseFromParent();
1077 
1078  return true;
1079 }
1080 
1083  bool Changed = false;
1084 
1085  // First pass: Do a simple check to see if any functions can have their "..."
1086  // removed. We can do this if they never call va_start. This loop cannot be
1087  // fused with the next loop, because deleting a function invalidates
1088  // information computed while surveying other functions.
1089  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Deleting dead varargs\n");
1090  for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
1091  Function &F = *I++;
1092  if (F.getFunctionType()->isVarArg())
1093  Changed |= DeleteDeadVarargs(F);
1094  }
1095 
1096  // Second phase:loop through the module, determining which arguments are live.
1097  // We assume all arguments are dead unless proven otherwise (allowing us to
1098  // determine that dead arguments passed into recursive functions are dead).
1099  //
1100  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Determining liveness\n");
1101  for (auto &F : M)
1102  SurveyFunction(F);
1103 
1104  // Now, remove all dead arguments and return values from each function in
1105  // turn.
1106  for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
1107  // Increment now, because the function will probably get removed (ie.
1108  // replaced by a new one).
1109  Function *F = &*I++;
1110  Changed |= RemoveDeadStuffFromFunction(F);
1111  }
1112 
1113  // Finally, look for any unused parameters in functions with non-local
1114  // linkage and replace the passed in parameters with undef.
1115  for (auto &F : M)
1116  Changed |= RemoveDeadArgumentsFromCallers(F);
1117 
1118  if (!Changed)
1119  return PreservedAnalyses::all();
1120  return PreservedAnalyses::none();
1121 }
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
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:63
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:268
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:336
User * getUser() const LLVM_READONLY
Returns the User that contains this Use.
Definition: Use.cpp:41
Class to represent function types.
Definition: DerivedTypes.h:103
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:439
constexpr char Attrs[]
Key for Kernel::Metadata::mAttrs.
void takeName(Value *V)
Transfer the name from V to this value.
Definition: Value.cpp:301
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:536
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:1750
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:218
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:519
LLVM Basic Block Representation.
Definition: BasicBlock.h:59
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
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...
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:1392
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
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:307
iterator end()
Definition: Module.h:586
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:224
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:714
#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:584
static ArrayType * get(Type *ElementType, uint64_t NumElements)
This static method is the primary way to construct an ArrayType.
Definition: Type.cpp:568
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:323
const BasicBlockListType & getBasicBlockList() const
Get the underlying elements of the Function...
Definition: Function.h: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:645
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 &)