LLVM  6.0.0svn
DeadArgumentElimination.cpp
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1 //===- DeadArgumentElimination.cpp - Eliminate dead arguments -------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This pass deletes dead arguments from internal functions. Dead argument
11 // elimination removes arguments which are directly dead, as well as arguments
12 // only passed into function calls as dead arguments of other functions. This
13 // pass also deletes dead return values in a similar way.
14 //
15 // This pass is often useful as a cleanup pass to run after aggressive
16 // interprocedural passes, which add possibly-dead arguments or return values.
17 //
18 //===----------------------------------------------------------------------===//
19 
21 #include "llvm/ADT/SmallVector.h"
22 #include "llvm/ADT/Statistic.h"
23 #include "llvm/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  // Patch the pointer to LLVM function in debug info descriptor.
244  NF->setSubprogram(Fn.getSubprogram());
245 
246  // Fix up any BlockAddresses that refer to the function.
247  Fn.replaceAllUsesWith(ConstantExpr::getBitCast(NF, Fn.getType()));
248  // Delete the bitcast that we just created, so that NF does not
249  // appear to be address-taken.
251  // Finally, nuke the old function.
252  Fn.eraseFromParent();
253  return true;
254 }
255 
256 /// RemoveDeadArgumentsFromCallers - Checks if the given function has any
257 /// arguments that are unused, and changes the caller parameters to be undefined
258 /// instead.
259 bool DeadArgumentEliminationPass::RemoveDeadArgumentsFromCallers(Function &Fn) {
260  // We cannot change the arguments if this TU does not define the function or
261  // if the linker may choose a function body from another TU, even if the
262  // nominal linkage indicates that other copies of the function have the same
263  // semantics. In the below example, the dead load from %p may not have been
264  // eliminated from the linker-chosen copy of f, so replacing %p with undef
265  // in callers may introduce undefined behavior.
266  //
267  // define linkonce_odr void @f(i32* %p) {
268  // %v = load i32 %p
269  // ret void
270  // }
271  if (!Fn.hasExactDefinition())
272  return false;
273 
274  // Functions with local linkage should already have been handled, except the
275  // fragile (variadic) ones which we can improve here.
276  if (Fn.hasLocalLinkage() && !Fn.getFunctionType()->isVarArg())
277  return false;
278 
279  // Don't touch naked functions. The assembly might be using an argument, or
280  // otherwise rely on the frame layout in a way that this analysis will not
281  // see.
282  if (Fn.hasFnAttribute(Attribute::Naked))
283  return false;
284 
285  if (Fn.use_empty())
286  return false;
287 
288  SmallVector<unsigned, 8> UnusedArgs;
289  for (Argument &Arg : Fn.args()) {
290  if (!Arg.hasSwiftErrorAttr() && Arg.use_empty() && !Arg.hasByValOrInAllocaAttr())
291  UnusedArgs.push_back(Arg.getArgNo());
292  }
293 
294  if (UnusedArgs.empty())
295  return false;
296 
297  bool Changed = false;
298 
299  for (Use &U : Fn.uses()) {
300  CallSite CS(U.getUser());
301  if (!CS || !CS.isCallee(&U))
302  continue;
303 
304  // Now go through all unused args and replace them with "undef".
305  for (unsigned I = 0, E = UnusedArgs.size(); I != E; ++I) {
306  unsigned ArgNo = UnusedArgs[I];
307 
308  Value *Arg = CS.getArgument(ArgNo);
309  CS.setArgument(ArgNo, UndefValue::get(Arg->getType()));
310  ++NumArgumentsReplacedWithUndef;
311  Changed = true;
312  }
313  }
314 
315  return Changed;
316 }
317 
318 /// Convenience function that returns the number of return values. It returns 0
319 /// for void functions and 1 for functions not returning a struct. It returns
320 /// the number of struct elements for functions returning a struct.
321 static unsigned NumRetVals(const Function *F) {
322  Type *RetTy = F->getReturnType();
323  if (RetTy->isVoidTy())
324  return 0;
325  else if (StructType *STy = dyn_cast<StructType>(RetTy))
326  return STy->getNumElements();
327  else if (ArrayType *ATy = dyn_cast<ArrayType>(RetTy))
328  return ATy->getNumElements();
329  else
330  return 1;
331 }
332 
333 /// Returns the sub-type a function will return at a given Idx. Should
334 /// correspond to the result type of an ExtractValue instruction executed with
335 /// just that one Idx (i.e. only top-level structure is considered).
336 static Type *getRetComponentType(const Function *F, unsigned Idx) {
337  Type *RetTy = F->getReturnType();
338  assert(!RetTy->isVoidTy() && "void type has no subtype");
339 
340  if (StructType *STy = dyn_cast<StructType>(RetTy))
341  return STy->getElementType(Idx);
342  else if (ArrayType *ATy = dyn_cast<ArrayType>(RetTy))
343  return ATy->getElementType();
344  else
345  return RetTy;
346 }
347 
348 /// MarkIfNotLive - This checks Use for liveness in LiveValues. If Use is not
349 /// live, it adds Use to the MaybeLiveUses argument. Returns the determined
350 /// liveness of Use.
352 DeadArgumentEliminationPass::MarkIfNotLive(RetOrArg Use,
353  UseVector &MaybeLiveUses) {
354  // We're live if our use or its Function is already marked as live.
355  if (LiveFunctions.count(Use.F) || LiveValues.count(Use))
356  return Live;
357 
358  // We're maybe live otherwise, but remember that we must become live if
359  // Use becomes live.
360  MaybeLiveUses.push_back(Use);
361  return MaybeLive;
362 }
363 
364 /// SurveyUse - This looks at a single use of an argument or return value
365 /// and determines if it should be alive or not. Adds this use to MaybeLiveUses
366 /// if it causes the used value to become MaybeLive.
367 ///
368 /// RetValNum is the return value number to use when this use is used in a
369 /// return instruction. This is used in the recursion, you should always leave
370 /// it at 0.
372 DeadArgumentEliminationPass::SurveyUse(const Use *U, UseVector &MaybeLiveUses,
373  unsigned RetValNum) {
374  const User *V = U->getUser();
375  if (const ReturnInst *RI = dyn_cast<ReturnInst>(V)) {
376  // The value is returned from a function. It's only live when the
377  // function's return value is live. We use RetValNum here, for the case
378  // that U is really a use of an insertvalue instruction that uses the
379  // original Use.
380  const Function *F = RI->getParent()->getParent();
381  if (RetValNum != -1U) {
382  RetOrArg Use = CreateRet(F, RetValNum);
383  // We might be live, depending on the liveness of Use.
384  return MarkIfNotLive(Use, MaybeLiveUses);
385  } else {
386  DeadArgumentEliminationPass::Liveness Result = MaybeLive;
387  for (unsigned i = 0; i < NumRetVals(F); ++i) {
388  RetOrArg Use = CreateRet(F, i);
389  // We might be live, depending on the liveness of Use. If any
390  // sub-value is live, then the entire value is considered live. This
391  // is a conservative choice, and better tracking is possible.
393  MarkIfNotLive(Use, MaybeLiveUses);
394  if (Result != Live)
395  Result = SubResult;
396  }
397  return Result;
398  }
399  }
400  if (const InsertValueInst *IV = dyn_cast<InsertValueInst>(V)) {
401  if (U->getOperandNo() != InsertValueInst::getAggregateOperandIndex()
402  && IV->hasIndices())
403  // The use we are examining is inserted into an aggregate. Our liveness
404  // depends on all uses of that aggregate, but if it is used as a return
405  // value, only index at which we were inserted counts.
406  RetValNum = *IV->idx_begin();
407 
408  // Note that if we are used as the aggregate operand to the insertvalue,
409  // we don't change RetValNum, but do survey all our uses.
410 
411  Liveness Result = MaybeLive;
412  for (const Use &UU : IV->uses()) {
413  Result = SurveyUse(&UU, MaybeLiveUses, RetValNum);
414  if (Result == Live)
415  break;
416  }
417  return Result;
418  }
419 
420  if (auto CS = ImmutableCallSite(V)) {
421  const Function *F = CS.getCalledFunction();
422  if (F) {
423  // Used in a direct call.
424 
425  // The function argument is live if it is used as a bundle operand.
426  if (CS.isBundleOperand(U))
427  return Live;
428 
429  // Find the argument number. We know for sure that this use is an
430  // argument, since if it was the function argument this would be an
431  // indirect call and the we know can't be looking at a value of the
432  // label type (for the invoke instruction).
433  unsigned ArgNo = CS.getArgumentNo(U);
434 
435  if (ArgNo >= F->getFunctionType()->getNumParams())
436  // The value is passed in through a vararg! Must be live.
437  return Live;
438 
439  assert(CS.getArgument(ArgNo)
440  == CS->getOperand(U->getOperandNo())
441  && "Argument is not where we expected it");
442 
443  // Value passed to a normal call. It's only live when the corresponding
444  // argument to the called function turns out live.
445  RetOrArg Use = CreateArg(F, ArgNo);
446  return MarkIfNotLive(Use, MaybeLiveUses);
447  }
448  }
449  // Used in any other way? Value must be live.
450  return Live;
451 }
452 
453 /// SurveyUses - This looks at all the uses of the given value
454 /// Returns the Liveness deduced from the uses of this value.
455 ///
456 /// Adds all uses that cause the result to be MaybeLive to MaybeLiveRetUses. If
457 /// the result is Live, MaybeLiveUses might be modified but its content should
458 /// be ignored (since it might not be complete).
460 DeadArgumentEliminationPass::SurveyUses(const Value *V,
461  UseVector &MaybeLiveUses) {
462  // Assume it's dead (which will only hold if there are no uses at all..).
463  Liveness Result = MaybeLive;
464  // Check each use.
465  for (const Use &U : V->uses()) {
466  Result = SurveyUse(&U, MaybeLiveUses);
467  if (Result == Live)
468  break;
469  }
470  return Result;
471 }
472 
473 // SurveyFunction - This performs the initial survey of the specified function,
474 // checking out whether or not it uses any of its incoming arguments or whether
475 // any callers use the return value. This fills in the LiveValues set and Uses
476 // map.
477 //
478 // We consider arguments of non-internal functions to be intrinsically alive as
479 // well as arguments to functions which have their "address taken".
480 void DeadArgumentEliminationPass::SurveyFunction(const Function &F) {
481  // Functions with inalloca parameters are expecting args in a particular
482  // register and memory layout.
483  if (F.getAttributes().hasAttrSomewhere(Attribute::InAlloca)) {
484  MarkLive(F);
485  return;
486  }
487 
488  // Don't touch naked functions. The assembly might be using an argument, or
489  // otherwise rely on the frame layout in a way that this analysis will not
490  // see.
491  if (F.hasFnAttribute(Attribute::Naked)) {
492  MarkLive(F);
493  return;
494  }
495 
496  unsigned RetCount = NumRetVals(&F);
497 
498  // Assume all return values are dead
499  using RetVals = SmallVector<Liveness, 5>;
500 
501  RetVals RetValLiveness(RetCount, MaybeLive);
502 
503  using RetUses = SmallVector<UseVector, 5>;
504 
505  // These vectors map each return value to the uses that make it MaybeLive, so
506  // we can add those to the Uses map if the return value really turns out to be
507  // MaybeLive. Initialized to a list of RetCount empty lists.
508  RetUses MaybeLiveRetUses(RetCount);
509 
510  for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
511  if (const ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
512  if (RI->getNumOperands() != 0 && RI->getOperand(0)->getType()
513  != F.getFunctionType()->getReturnType()) {
514  // We don't support old style multiple return values.
515  MarkLive(F);
516  return;
517  }
518 
519  if (!F.hasLocalLinkage() && (!ShouldHackArguments || F.isIntrinsic())) {
520  MarkLive(F);
521  return;
522  }
523 
524  DEBUG(dbgs() << "DeadArgumentEliminationPass - Inspecting callers for fn: "
525  << F.getName() << "\n");
526  // Keep track of the number of live retvals, so we can skip checks once all
527  // of them turn out to be live.
528  unsigned NumLiveRetVals = 0;
529  // Loop all uses of the function.
530  for (const Use &U : F.uses()) {
531  // If the function is PASSED IN as an argument, its address has been
532  // taken.
533  ImmutableCallSite CS(U.getUser());
534  if (!CS || !CS.isCallee(&U)) {
535  MarkLive(F);
536  return;
537  }
538 
539  // If this use is anything other than a call site, the function is alive.
540  const Instruction *TheCall = CS.getInstruction();
541  if (!TheCall) { // Not a direct call site?
542  MarkLive(F);
543  return;
544  }
545 
546  // If we end up here, we are looking at a direct call to our function.
547 
548  // Now, check how our return value(s) is/are used in this caller. Don't
549  // bother checking return values if all of them are live already.
550  if (NumLiveRetVals == RetCount)
551  continue;
552 
553  // Check all uses of the return value.
554  for (const Use &U : TheCall->uses()) {
555  if (ExtractValueInst *Ext = dyn_cast<ExtractValueInst>(U.getUser())) {
556  // This use uses a part of our return value, survey the uses of
557  // that part and store the results for this index only.
558  unsigned Idx = *Ext->idx_begin();
559  if (RetValLiveness[Idx] != Live) {
560  RetValLiveness[Idx] = SurveyUses(Ext, MaybeLiveRetUses[Idx]);
561  if (RetValLiveness[Idx] == Live)
562  NumLiveRetVals++;
563  }
564  } else {
565  // Used by something else than extractvalue. Survey, but assume that the
566  // result applies to all sub-values.
567  UseVector MaybeLiveAggregateUses;
568  if (SurveyUse(&U, MaybeLiveAggregateUses) == Live) {
569  NumLiveRetVals = RetCount;
570  RetValLiveness.assign(RetCount, Live);
571  break;
572  } else {
573  for (unsigned i = 0; i != RetCount; ++i) {
574  if (RetValLiveness[i] != Live)
575  MaybeLiveRetUses[i].append(MaybeLiveAggregateUses.begin(),
576  MaybeLiveAggregateUses.end());
577  }
578  }
579  }
580  }
581  }
582 
583  // Now we've inspected all callers, record the liveness of our return values.
584  for (unsigned i = 0; i != RetCount; ++i)
585  MarkValue(CreateRet(&F, i), RetValLiveness[i], MaybeLiveRetUses[i]);
586 
587  DEBUG(dbgs() << "DeadArgumentEliminationPass - Inspecting args for fn: "
588  << F.getName() << "\n");
589 
590  // Now, check all of our arguments.
591  unsigned i = 0;
592  UseVector MaybeLiveArgUses;
594  E = F.arg_end(); AI != E; ++AI, ++i) {
595  Liveness Result;
596  if (F.getFunctionType()->isVarArg()) {
597  // Variadic functions will already have a va_arg function expanded inside
598  // them, making them potentially very sensitive to ABI changes resulting
599  // from removing arguments entirely, so don't. For example AArch64 handles
600  // register and stack HFAs very differently, and this is reflected in the
601  // IR which has already been generated.
602  Result = Live;
603  } else {
604  // See what the effect of this use is (recording any uses that cause
605  // MaybeLive in MaybeLiveArgUses).
606  Result = SurveyUses(&*AI, MaybeLiveArgUses);
607  }
608 
609  // Mark the result.
610  MarkValue(CreateArg(&F, i), Result, MaybeLiveArgUses);
611  // Clear the vector again for the next iteration.
612  MaybeLiveArgUses.clear();
613  }
614 }
615 
616 /// MarkValue - This function marks the liveness of RA depending on L. If L is
617 /// MaybeLive, it also takes all uses in MaybeLiveUses and records them in Uses,
618 /// such that RA will be marked live if any use in MaybeLiveUses gets marked
619 /// live later on.
620 void DeadArgumentEliminationPass::MarkValue(const RetOrArg &RA, Liveness L,
621  const UseVector &MaybeLiveUses) {
622  switch (L) {
623  case Live:
624  MarkLive(RA);
625  break;
626  case MaybeLive:
627  // Note any uses of this value, so this return value can be
628  // marked live whenever one of the uses becomes live.
629  for (const auto &MaybeLiveUse : MaybeLiveUses)
630  Uses.insert(std::make_pair(MaybeLiveUse, RA));
631  break;
632  }
633 }
634 
635 /// MarkLive - Mark the given Function as alive, meaning that it cannot be
636 /// changed in any way. Additionally,
637 /// mark any values that are used as this function's parameters or by its return
638 /// values (according to Uses) live as well.
639 void DeadArgumentEliminationPass::MarkLive(const Function &F) {
640  DEBUG(dbgs() << "DeadArgumentEliminationPass - Intrinsically live fn: "
641  << F.getName() << "\n");
642  // Mark the function as live.
643  LiveFunctions.insert(&F);
644  // Mark all arguments as live.
645  for (unsigned i = 0, e = F.arg_size(); i != e; ++i)
646  PropagateLiveness(CreateArg(&F, i));
647  // Mark all return values as live.
648  for (unsigned i = 0, e = NumRetVals(&F); i != e; ++i)
649  PropagateLiveness(CreateRet(&F, i));
650 }
651 
652 /// MarkLive - Mark the given return value or argument as live. Additionally,
653 /// mark any values that are used by this value (according to Uses) live as
654 /// well.
655 void DeadArgumentEliminationPass::MarkLive(const RetOrArg &RA) {
656  if (LiveFunctions.count(RA.F))
657  return; // Function was already marked Live.
658 
659  if (!LiveValues.insert(RA).second)
660  return; // We were already marked Live.
661 
662  DEBUG(dbgs() << "DeadArgumentEliminationPass - Marking "
663  << RA.getDescription() << " live\n");
664  PropagateLiveness(RA);
665 }
666 
667 /// PropagateLiveness - Given that RA is a live value, propagate it's liveness
668 /// to any other values it uses (according to Uses).
669 void DeadArgumentEliminationPass::PropagateLiveness(const RetOrArg &RA) {
670  // We don't use upper_bound (or equal_range) here, because our recursive call
671  // to ourselves is likely to cause the upper_bound (which is the first value
672  // not belonging to RA) to become erased and the iterator invalidated.
673  UseMap::iterator Begin = Uses.lower_bound(RA);
674  UseMap::iterator E = Uses.end();
675  UseMap::iterator I;
676  for (I = Begin; I != E && I->first == RA; ++I)
677  MarkLive(I->second);
678 
679  // Erase RA from the Uses map (from the lower bound to wherever we ended up
680  // after the loop).
681  Uses.erase(Begin, I);
682 }
683 
684 // RemoveDeadStuffFromFunction - Remove any arguments and return values from F
685 // that are not in LiveValues. Transform the function and all of the callees of
686 // the function to not have these arguments and return values.
687 //
688 bool DeadArgumentEliminationPass::RemoveDeadStuffFromFunction(Function *F) {
689  // Don't modify fully live functions
690  if (LiveFunctions.count(F))
691  return false;
692 
693  // Start by computing a new prototype for the function, which is the same as
694  // the old function, but has fewer arguments and a different return type.
695  FunctionType *FTy = F->getFunctionType();
696  std::vector<Type*> Params;
697 
698  // Keep track of if we have a live 'returned' argument
699  bool HasLiveReturnedArg = false;
700 
701  // Set up to build a new list of parameter attributes.
702  SmallVector<AttributeSet, 8> ArgAttrVec;
703  const AttributeList &PAL = F->getAttributes();
704 
705  // Remember which arguments are still alive.
706  SmallVector<bool, 10> ArgAlive(FTy->getNumParams(), false);
707  // Construct the new parameter list from non-dead arguments. Also construct
708  // a new set of parameter attributes to correspond. Skip the first parameter
709  // attribute, since that belongs to the return value.
710  unsigned i = 0;
711  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
712  I != E; ++I, ++i) {
713  RetOrArg Arg = CreateArg(F, i);
714  if (LiveValues.erase(Arg)) {
715  Params.push_back(I->getType());
716  ArgAlive[i] = true;
717  ArgAttrVec.push_back(PAL.getParamAttributes(i));
718  HasLiveReturnedArg |= PAL.hasParamAttribute(i, Attribute::Returned);
719  } else {
720  ++NumArgumentsEliminated;
721  DEBUG(dbgs() << "DeadArgumentEliminationPass - Removing argument " << i
722  << " (" << I->getName() << ") from " << F->getName()
723  << "\n");
724  }
725  }
726 
727  // Find out the new return value.
728  Type *RetTy = FTy->getReturnType();
729  Type *NRetTy = nullptr;
730  unsigned RetCount = NumRetVals(F);
731 
732  // -1 means unused, other numbers are the new index
733  SmallVector<int, 5> NewRetIdxs(RetCount, -1);
734  std::vector<Type*> RetTypes;
735 
736  // If there is a function with a live 'returned' argument but a dead return
737  // value, then there are two possible actions:
738  // 1) Eliminate the return value and take off the 'returned' attribute on the
739  // argument.
740  // 2) Retain the 'returned' attribute and treat the return value (but not the
741  // entire function) as live so that it is not eliminated.
742  //
743  // It's not clear in the general case which option is more profitable because,
744  // even in the absence of explicit uses of the return value, code generation
745  // is free to use the 'returned' attribute to do things like eliding
746  // save/restores of registers across calls. Whether or not this happens is
747  // target and ABI-specific as well as depending on the amount of register
748  // pressure, so there's no good way for an IR-level pass to figure this out.
749  //
750  // Fortunately, the only places where 'returned' is currently generated by
751  // the FE are places where 'returned' is basically free and almost always a
752  // performance win, so the second option can just be used always for now.
753  //
754  // This should be revisited if 'returned' is ever applied more liberally.
755  if (RetTy->isVoidTy() || HasLiveReturnedArg) {
756  NRetTy = RetTy;
757  } else {
758  // Look at each of the original return values individually.
759  for (unsigned i = 0; i != RetCount; ++i) {
760  RetOrArg Ret = CreateRet(F, i);
761  if (LiveValues.erase(Ret)) {
762  RetTypes.push_back(getRetComponentType(F, i));
763  NewRetIdxs[i] = RetTypes.size() - 1;
764  } else {
765  ++NumRetValsEliminated;
766  DEBUG(dbgs() << "DeadArgumentEliminationPass - Removing return value "
767  << i << " from " << F->getName() << "\n");
768  }
769  }
770  if (RetTypes.size() > 1) {
771  // More than one return type? Reduce it down to size.
772  if (StructType *STy = dyn_cast<StructType>(RetTy)) {
773  // Make the new struct packed if we used to return a packed struct
774  // already.
775  NRetTy = StructType::get(STy->getContext(), RetTypes, STy->isPacked());
776  } else {
777  assert(isa<ArrayType>(RetTy) && "unexpected multi-value return");
778  NRetTy = ArrayType::get(RetTypes[0], RetTypes.size());
779  }
780  } else if (RetTypes.size() == 1)
781  // One return type? Just a simple value then, but only if we didn't use to
782  // return a struct with that simple value before.
783  NRetTy = RetTypes.front();
784  else if (RetTypes.empty())
785  // No return types? Make it void, but only if we didn't use to return {}.
786  NRetTy = Type::getVoidTy(F->getContext());
787  }
788 
789  assert(NRetTy && "No new return type found?");
790 
791  // The existing function return attributes.
792  AttrBuilder RAttrs(PAL.getRetAttributes());
793 
794  // Remove any incompatible attributes, but only if we removed all return
795  // values. Otherwise, ensure that we don't have any conflicting attributes
796  // here. Currently, this should not be possible, but special handling might be
797  // required when new return value attributes are added.
798  if (NRetTy->isVoidTy())
800  else
801  assert(!RAttrs.overlaps(AttributeFuncs::typeIncompatible(NRetTy)) &&
802  "Return attributes no longer compatible?");
803 
804  AttributeSet RetAttrs = AttributeSet::get(F->getContext(), RAttrs);
805 
806  // Reconstruct the AttributesList based on the vector we constructed.
807  assert(ArgAttrVec.size() == Params.size());
809  F->getContext(), PAL.getFnAttributes(), RetAttrs, ArgAttrVec);
810 
811  // Create the new function type based on the recomputed parameters.
812  FunctionType *NFTy = FunctionType::get(NRetTy, Params, FTy->isVarArg());
813 
814  // No change?
815  if (NFTy == FTy)
816  return false;
817 
818  // Create the new function body and insert it into the module...
819  Function *NF = Function::Create(NFTy, F->getLinkage());
820  NF->copyAttributesFrom(F);
821  NF->setComdat(F->getComdat());
822  NF->setAttributes(NewPAL);
823  // Insert the new function before the old function, so we won't be processing
824  // it again.
825  F->getParent()->getFunctionList().insert(F->getIterator(), NF);
826  NF->takeName(F);
827 
828  // Loop over all of the callers of the function, transforming the call sites
829  // to pass in a smaller number of arguments into the new function.
830  std::vector<Value*> Args;
831  while (!F->use_empty()) {
832  CallSite CS(F->user_back());
833  Instruction *Call = CS.getInstruction();
834 
835  ArgAttrVec.clear();
836  const AttributeList &CallPAL = CS.getAttributes();
837 
838  // Adjust the call return attributes in case the function was changed to
839  // return void.
840  AttrBuilder RAttrs(CallPAL.getRetAttributes());
842  AttributeSet RetAttrs = AttributeSet::get(F->getContext(), RAttrs);
843 
844  // Declare these outside of the loops, so we can reuse them for the second
845  // loop, which loops the varargs.
846  CallSite::arg_iterator I = CS.arg_begin();
847  unsigned i = 0;
848  // Loop over those operands, corresponding to the normal arguments to the
849  // original function, and add those that are still alive.
850  for (unsigned e = FTy->getNumParams(); i != e; ++I, ++i)
851  if (ArgAlive[i]) {
852  Args.push_back(*I);
853  // Get original parameter attributes, but skip return attributes.
855  if (NRetTy != RetTy && Attrs.hasAttribute(Attribute::Returned)) {
856  // If the return type has changed, then get rid of 'returned' on the
857  // call site. The alternative is to make all 'returned' attributes on
858  // call sites keep the return value alive just like 'returned'
859  // attributes on function declaration but it's less clearly a win and
860  // this is not an expected case anyway
861  ArgAttrVec.push_back(AttributeSet::get(
862  F->getContext(),
863  AttrBuilder(Attrs).removeAttribute(Attribute::Returned)));
864  } else {
865  // Otherwise, use the original attributes.
866  ArgAttrVec.push_back(Attrs);
867  }
868  }
869 
870  // Push any varargs arguments on the list. Don't forget their attributes.
871  for (CallSite::arg_iterator E = CS.arg_end(); I != E; ++I, ++i) {
872  Args.push_back(*I);
873  ArgAttrVec.push_back(CallPAL.getParamAttributes(i));
874  }
875 
876  // Reconstruct the AttributesList based on the vector we constructed.
877  assert(ArgAttrVec.size() == Args.size());
878  AttributeList NewCallPAL = AttributeList::get(
879  F->getContext(), CallPAL.getFnAttributes(), RetAttrs, ArgAttrVec);
880 
882  CS.getOperandBundlesAsDefs(OpBundles);
883 
884  CallSite NewCS;
885  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
886  NewCS = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
887  Args, OpBundles, "", Call->getParent());
888  } else {
889  NewCS = CallInst::Create(NF, Args, OpBundles, "", Call);
890  cast<CallInst>(NewCS.getInstruction())
891  ->setTailCallKind(cast<CallInst>(Call)->getTailCallKind());
892  }
893  NewCS.setCallingConv(CS.getCallingConv());
894  NewCS.setAttributes(NewCallPAL);
895  NewCS->setDebugLoc(Call->getDebugLoc());
896  uint64_t W;
897  if (Call->extractProfTotalWeight(W))
898  NewCS->setProfWeight(W);
899  Args.clear();
900  ArgAttrVec.clear();
901 
902  Instruction *New = NewCS.getInstruction();
903  if (!Call->use_empty()) {
904  if (New->getType() == Call->getType()) {
905  // Return type not changed? Just replace users then.
906  Call->replaceAllUsesWith(New);
907  New->takeName(Call);
908  } else if (New->getType()->isVoidTy()) {
909  // Our return value has uses, but they will get removed later on.
910  // Replace by null for now.
911  if (!Call->getType()->isX86_MMXTy())
912  Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
913  } else {
914  assert((RetTy->isStructTy() || RetTy->isArrayTy()) &&
915  "Return type changed, but not into a void. The old return type"
916  " must have been a struct or an array!");
917  Instruction *InsertPt = Call;
918  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
919  BasicBlock *NewEdge = SplitEdge(New->getParent(), II->getNormalDest());
920  InsertPt = &*NewEdge->getFirstInsertionPt();
921  }
922 
923  // We used to return a struct or array. Instead of doing smart stuff
924  // with all the uses, we will just rebuild it using extract/insertvalue
925  // chaining and let instcombine clean that up.
926  //
927  // Start out building up our return value from undef
928  Value *RetVal = UndefValue::get(RetTy);
929  for (unsigned i = 0; i != RetCount; ++i)
930  if (NewRetIdxs[i] != -1) {
931  Value *V;
932  if (RetTypes.size() > 1)
933  // We are still returning a struct, so extract the value from our
934  // return value
935  V = ExtractValueInst::Create(New, NewRetIdxs[i], "newret",
936  InsertPt);
937  else
938  // We are now returning a single element, so just insert that
939  V = New;
940  // Insert the value at the old position
941  RetVal = InsertValueInst::Create(RetVal, V, i, "oldret", InsertPt);
942  }
943  // Now, replace all uses of the old call instruction with the return
944  // struct we built
945  Call->replaceAllUsesWith(RetVal);
946  New->takeName(Call);
947  }
948  }
949 
950  // Finally, remove the old call from the program, reducing the use-count of
951  // F.
952  Call->eraseFromParent();
953  }
954 
955  // Since we have now created the new function, splice the body of the old
956  // function right into the new function, leaving the old rotting hulk of the
957  // function empty.
958  NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
959 
960  // Loop over the argument list, transferring uses of the old arguments over to
961  // the new arguments, also transferring over the names as well.
962  i = 0;
963  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
964  I2 = NF->arg_begin(); I != E; ++I, ++i)
965  if (ArgAlive[i]) {
966  // If this is a live argument, move the name and users over to the new
967  // version.
968  I->replaceAllUsesWith(&*I2);
969  I2->takeName(&*I);
970  ++I2;
971  } else {
972  // If this argument is dead, replace any uses of it with null constants
973  // (these are guaranteed to become unused later on).
974  if (!I->getType()->isX86_MMXTy())
975  I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
976  }
977 
978  // If we change the return value of the function we must rewrite any return
979  // instructions. Check this now.
980  if (F->getReturnType() != NF->getReturnType())
981  for (BasicBlock &BB : *NF)
982  if (ReturnInst *RI = dyn_cast<ReturnInst>(BB.getTerminator())) {
983  Value *RetVal;
984 
985  if (NFTy->getReturnType()->isVoidTy()) {
986  RetVal = nullptr;
987  } else {
988  assert(RetTy->isStructTy() || RetTy->isArrayTy());
989  // The original return value was a struct or array, insert
990  // extractvalue/insertvalue chains to extract only the values we need
991  // to return and insert them into our new result.
992  // This does generate messy code, but we'll let it to instcombine to
993  // clean that up.
994  Value *OldRet = RI->getOperand(0);
995  // Start out building up our return value from undef
996  RetVal = UndefValue::get(NRetTy);
997  for (unsigned i = 0; i != RetCount; ++i)
998  if (NewRetIdxs[i] != -1) {
1000  "oldret", RI);
1001  if (RetTypes.size() > 1) {
1002  // We're still returning a struct, so reinsert the value into
1003  // our new return value at the new index
1004 
1005  RetVal = InsertValueInst::Create(RetVal, EV, NewRetIdxs[i],
1006  "newret", RI);
1007  } else {
1008  // We are now only returning a simple value, so just return the
1009  // extracted value.
1010  RetVal = EV;
1011  }
1012  }
1013  }
1014  // Replace the return instruction with one returning the new return
1015  // value (possibly 0 if we became void).
1016  ReturnInst::Create(F->getContext(), RetVal, RI);
1017  BB.getInstList().erase(RI);
1018  }
1019 
1020  // Patch the pointer to LLVM function in debug info descriptor.
1021  NF->setSubprogram(F->getSubprogram());
1022 
1023  // Now that the old function is dead, delete it.
1024  F->eraseFromParent();
1025 
1026  return true;
1027 }
1028 
1031  bool Changed = false;
1032 
1033  // First pass: Do a simple check to see if any functions can have their "..."
1034  // removed. We can do this if they never call va_start. This loop cannot be
1035  // fused with the next loop, because deleting a function invalidates
1036  // information computed while surveying other functions.
1037  DEBUG(dbgs() << "DeadArgumentEliminationPass - Deleting dead varargs\n");
1038  for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
1039  Function &F = *I++;
1040  if (F.getFunctionType()->isVarArg())
1041  Changed |= DeleteDeadVarargs(F);
1042  }
1043 
1044  // Second phase:loop through the module, determining which arguments are live.
1045  // We assume all arguments are dead unless proven otherwise (allowing us to
1046  // determine that dead arguments passed into recursive functions are dead).
1047  //
1048  DEBUG(dbgs() << "DeadArgumentEliminationPass - Determining liveness\n");
1049  for (auto &F : M)
1050  SurveyFunction(F);
1051 
1052  // Now, remove all dead arguments and return values from each function in
1053  // turn.
1054  for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
1055  // Increment now, because the function will probably get removed (ie.
1056  // replaced by a new one).
1057  Function *F = &*I++;
1058  Changed |= RemoveDeadStuffFromFunction(F);
1059  }
1060 
1061  // Finally, look for any unused parameters in functions with non-local
1062  // linkage and replace the passed in parameters with undef.
1063  for (auto &F : M)
1064  Changed |= RemoveDeadArgumentsFromCallers(F);
1065 
1066  if (!Changed)
1067  return PreservedAnalyses::all();
1068  return PreservedAnalyses::none();
1069 }
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:180
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:69
iterator_range< use_iterator > uses()
Definition: Value.h:356
bool hasLocalLinkage() const
Definition: GlobalValue.h:427
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
LLVM_ATTRIBUTE_ALWAYS_INLINE size_type size() const
Definition: SmallVector.h:136
iterator end()
Definition: Function.h:590
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:262
arg_iterator arg_end()
Definition: Function.h:612
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.
bool isMustTailCall() const
static Constant * getNullValue(Type *Ty)
Constructor to create a &#39;0&#39; constant of arbitrary type.
Definition: Constants.cpp:207
static ReturnInst * Create(LLVMContext &C, Value *retVal=nullptr, Instruction *InsertBefore=nullptr)
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:205
bool extractProfTotalWeight(uint64_t &TotalVal) const
Retrieve total raw weight values of a branch.
Definition: Metadata.cpp:1328
LinkageTypes getLinkage() const
Definition: GlobalValue.h:441
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:430
constexpr char Attrs[]
Key for Kernel::Metadata::mAttrs.
void takeName(Value *V)
Transfer the name from V to this value.
Definition: Value.cpp:292
iterator begin()
Definition: Function.h:588
void removeDeadConstantUsers() const
If there are any dead constant users dangling off of this constant, remove them.
Definition: Constants.cpp:475
static PreservedAnalyses none()
Convenience factory function for the empty preserved set.
Definition: PassManager.h:156
bool hasAttribute(Attribute::AttrKind Kind) const
Return true if the attribute exists in this set.
Definition: Attributes.cpp:573
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:1678
bool isVoidTy() const
Return true if this is &#39;void&#39;.
Definition: Type.h:141
bool hasAttrSomewhere(Attribute::AttrKind Kind, unsigned *Index=nullptr) const
Return true if the specified attribute is set for at least one parameter or for the return value...
void setAttributes(AttributeList PAL)
Set the parameter attributes of the call.
Definition: CallSite.h:333
void setSubprogram(DISubprogram *SP)
Set the attached subprogram.
Definition: Metadata.cpp:1493
Type * getReturnType() const
Returns the type of the ret val.
Definition: Function.h:150
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:503
const_iterator getFirstInsertionPt() const
Returns an iterator to the first instruction in this block that is suitable for inserting a non-PHI i...
Definition: BasicBlock.cpp:200
bool areAllPreserved() const
Test whether all analyses are preserved (and none are abandoned).
Definition: PassManager.h:321
static unsigned getAggregateOperandIndex()
const FunctionListType & getFunctionList() const
Get the Module&#39;s list of functions (constant).
Definition: Module.h:507
LLVM Basic Block Representation.
Definition: BasicBlock.h:59
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
DISubprogram * getSubprogram() const
Get the attached subprogram.
Definition: Metadata.cpp:1497
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:463
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...
unsigned getNumParams() const
Return the number of fixed parameters this function type requires.
Definition: DerivedTypes.h:139
void initializeDAEPass(PassRegistry &)
param_iterator param_begin() const
Definition: DerivedTypes.h:128
static Type * getVoidTy(LLVMContext &C)
Definition: Type.cpp:161
void splice(iterator where, iplist_impl &L2)
Definition: ilist.h:342
void setCallingConv(CallingConv::ID CC)
Set the calling convention of the call.
Definition: CallSite.h: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:630
arg_iterator arg_begin()
Definition: Function.h:603
self_iterator getIterator()
Definition: ilist_node.h:82
LLVMContext & getContext() const
getContext - Return a reference to the LLVMContext associated with this function. ...
Definition: Function.cpp:194
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1320
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:159
static InvokeInst * Create(Value *Func, BasicBlock *IfNormal, BasicBlock *IfException, ArrayRef< Value *> Args, const Twine &NameStr, Instruction *InsertBefore=nullptr)
static unsigned NumRetVals(const Function *F)
Convenience function that returns the number of return values.
Iterator for intrusive lists based on ilist_node.
bool hasParamAttribute(unsigned ArgNo, Attribute::AttrKind Kind) const
Equivalent to hasAttribute(ArgNo + FirstArgIndex, Kind).
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:864
Module.h This file contains the declarations for the Module class.
static Type * getRetComponentType(const Function *F, unsigned Idx)
Returns the sub-type a function will return at a given Idx.
Type * getReturnType() const
Definition: DerivedTypes.h:124
void setAttributes(AttributeList Attrs)
Set the attribute list for this Function.
Definition: Function.h:208
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:145
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:241
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:284
iterator end()
Definition: Module.h:574
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:61
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:220
bool hasExactDefinition() const
Return true if this global has an exact defintion.
Definition: GlobalValue.h:398
Establish a view to a call site for examination.
Definition: CallSite.h:713
#define I(x, y, z)
Definition: MD5.cpp:58
user_iterator_impl< User > user_iterator
Definition: Value.h:370
ModulePass class - This class is used to implement unstructured interprocedural optimizations and ana...
Definition: Pass.h:225
iterator begin()
Definition: Module.h:572
static ArrayType * get(Type *ElementType, uint64_t NumElements)
This static method is the primary way to construct an ArrayType.
Definition: Type.cpp:568
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:323
const BasicBlockListType & getBasicBlockList() const
Get the underlying elements of the Function...
Definition: Function.h:565
void eraseFromParent()
eraseFromParent - This method unlinks &#39;this&#39; from the containing module and deletes it...
Definition: Function.cpp:202
bool isDeclaration() const
Return true if the primary definition of this global value is outside of the current translation unit...
Definition: Globals.cpp:201
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:1213
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:556
LLVM Value Representation.
Definition: Value.h:73
AttrBuilder typeIncompatible(Type *Ty)
Which attributes cannot be applied to a type.
AttributeSet getFnAttributes() const
The function attributes are returned.
Invoke instruction.
#define DEBUG(X)
Definition: Debug.h:118
BasicBlock * SplitEdge(BasicBlock *From, BasicBlock *To, DominatorTree *DT=nullptr, LoopInfo *LI=nullptr)
Split the edge connecting specified block.
A container for analyses that lazily runs them and caches their results.
static Function * Create(FunctionType *Ty, LinkageTypes Linkage, const Twine &N="", Module *M=nullptr)
Definition: Function.h:136
AttributeList getAttributes() const
Get the parameter attributes of the call.
Definition: CallSite.h:329
This header defines various interfaces for pass management in LLVM.
bool isEmpty() const
Return true if there are no attributes.
Definition: Attributes.h:646
bool use_empty() const
Definition: Value.h:328
constexpr char Args[]
Key for Kernel::Metadata::mArgs.
PointerType * getType() const
Global values are always pointers.
Definition: GlobalValue.h:265
static AttributeList get(LLVMContext &C, ArrayRef< std::pair< unsigned, Attribute >> Attrs)
Create an AttributeList with the specified parameters in it.
Definition: Attributes.cpp:868
iterator_range< arg_iterator > args()
Definition: Function.h:621
User * user_back()
Definition: Value.h:387
A wrapper class for inspecting calls to intrinsic functions.
Definition: IntrinsicInst.h:44
const BasicBlock * getParent() const
Definition: Instruction.h:66
This instruction inserts a struct field of array element value into an aggregate value.
PreservedAnalyses run(Module &M, ModuleAnalysisManager &)