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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/Constants.h"
28 #include "llvm/IR/DerivedTypes.h"
29 #include "llvm/IR/Function.h"
30 #include "llvm/IR/InstrTypes.h"
31 #include "llvm/IR/Instruction.h"
32 #include "llvm/IR/Instructions.h"
33 #include "llvm/IR/IntrinsicInst.h"
34 #include "llvm/IR/Intrinsics.h"
35 #include "llvm/IR/Module.h"
36 #include "llvm/IR/PassManager.h"
37 #include "llvm/IR/Type.h"
38 #include "llvm/IR/Use.h"
39 #include "llvm/IR/User.h"
40 #include "llvm/IR/Value.h"
41 #include "llvm/Pass.h"
42 #include "llvm/Support/Casting.h"
43 #include "llvm/Support/Debug.h"
45 #include "llvm/Transforms/IPO.h"
47 #include <cassert>
48 #include <cstdint>
49 #include <utility>
50 #include <vector>
51 
52 using namespace llvm;
53 
54 #define DEBUG_TYPE "deadargelim"
55 
56 STATISTIC(NumArgumentsEliminated, "Number of unread args removed");
57 STATISTIC(NumRetValsEliminated , "Number of unused return values removed");
58 STATISTIC(NumArgumentsReplacedWithUndef,
59  "Number of unread args replaced with undef");
60 
61 namespace {
62 
63  /// DAE - The dead argument elimination pass.
64  class DAE : public ModulePass {
65  protected:
66  // DAH uses this to specify a different ID.
67  explicit DAE(char &ID) : ModulePass(ID) {}
68 
69  public:
70  static char ID; // Pass identification, replacement for typeid
71 
72  DAE() : ModulePass(ID) {
74  }
75 
76  bool runOnModule(Module &M) override {
77  if (skipModule(M))
78  return false;
79  DeadArgumentEliminationPass DAEP(ShouldHackArguments());
80  ModuleAnalysisManager DummyMAM;
81  PreservedAnalyses PA = DAEP.run(M, DummyMAM);
82  return !PA.areAllPreserved();
83  }
84 
85  virtual bool ShouldHackArguments() const { return false; }
86  };
87 
88 } // end anonymous namespace
89 
90 char DAE::ID = 0;
91 
92 INITIALIZE_PASS(DAE, "deadargelim", "Dead Argument Elimination", false, false)
93 
94 namespace {
95 
96  /// DAH - DeadArgumentHacking pass - Same as dead argument elimination, but
97  /// deletes arguments to functions which are external. This is only for use
98  /// by bugpoint.
99  struct DAH : public DAE {
100  static char ID;
101 
102  DAH() : DAE(ID) {}
103 
104  bool ShouldHackArguments() const override { return true; }
105  };
106 
107 } // end anonymous namespace
108 
109 char DAH::ID = 0;
110 
111 INITIALIZE_PASS(DAH, "deadarghaX0r",
112  "Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)",
113  false, false)
114 
115 /// createDeadArgEliminationPass - This pass removes arguments from functions
116 /// which are not used by the body of the function.
117 ModulePass *llvm::createDeadArgEliminationPass() { return new DAE(); }
118 
120 
121 /// DeleteDeadVarargs - If this is an function that takes a ... list, and if
122 /// llvm.vastart is never called, the varargs list is dead for the function.
123 bool DeadArgumentEliminationPass::DeleteDeadVarargs(Function &Fn) {
124  assert(Fn.getFunctionType()->isVarArg() && "Function isn't varargs!");
125  if (Fn.isDeclaration() || !Fn.hasLocalLinkage()) return false;
126 
127  // Ensure that the function is only directly called.
128  if (Fn.hasAddressTaken())
129  return false;
130 
131  // Don't touch naked functions. The assembly might be using an argument, or
132  // otherwise rely on the frame layout in a way that this analysis will not
133  // see.
134  if (Fn.hasFnAttribute(Attribute::Naked)) {
135  return false;
136  }
137 
138  // Okay, we know we can transform this function if safe. Scan its body
139  // looking for calls marked musttail or calls to llvm.vastart.
140  for (BasicBlock &BB : Fn) {
141  for (Instruction &I : BB) {
142  CallInst *CI = dyn_cast<CallInst>(&I);
143  if (!CI)
144  continue;
145  if (CI->isMustTailCall())
146  return false;
147  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI)) {
148  if (II->getIntrinsicID() == Intrinsic::vastart)
149  return false;
150  }
151  }
152  }
153 
154  // If we get here, there are no calls to llvm.vastart in the function body,
155  // remove the "..." and adjust all the calls.
156 
157  // Start by computing a new prototype for the function, which is the same as
158  // the old function, but doesn't have isVarArg set.
159  FunctionType *FTy = Fn.getFunctionType();
160 
161  std::vector<Type *> Params(FTy->param_begin(), FTy->param_end());
163  Params, false);
164  unsigned NumArgs = Params.size();
165 
166  // Create the new function body and insert it into the module...
167  Function *NF = Function::Create(NFTy, Fn.getLinkage(), Fn.getAddressSpace());
168  NF->copyAttributesFrom(&Fn);
169  NF->setComdat(Fn.getComdat());
170  Fn.getParent()->getFunctionList().insert(Fn.getIterator(), NF);
171  NF->takeName(&Fn);
172 
173  // Loop over all of the callers of the function, transforming the call sites
174  // to pass in a smaller number of arguments into the new function.
175  //
176  std::vector<Value *> Args;
177  for (Value::user_iterator I = Fn.user_begin(), E = Fn.user_end(); I != E; ) {
178  CallSite CS(*I++);
179  if (!CS)
180  continue;
181  Instruction *Call = CS.getInstruction();
182 
183  // Pass all the same arguments.
184  Args.assign(CS.arg_begin(), CS.arg_begin() + NumArgs);
185 
186  // Drop any attributes that were on the vararg arguments.
187  AttributeList PAL = CS.getAttributes();
188  if (!PAL.isEmpty()) {
190  for (unsigned ArgNo = 0; ArgNo < NumArgs; ++ArgNo)
191  ArgAttrs.push_back(PAL.getParamAttributes(ArgNo));
192  PAL = AttributeList::get(Fn.getContext(), PAL.getFnAttributes(),
193  PAL.getRetAttributes(), ArgAttrs);
194  }
195 
197  CS.getOperandBundlesAsDefs(OpBundles);
198 
199  CallSite NewCS;
200  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
201  NewCS = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
202  Args, OpBundles, "", Call);
203  } else {
204  NewCS = CallInst::Create(NF, Args, OpBundles, "", Call);
205  cast<CallInst>(NewCS.getInstruction())
206  ->setTailCallKind(cast<CallInst>(Call)->getTailCallKind());
207  }
208  NewCS.setCallingConv(CS.getCallingConv());
209  NewCS.setAttributes(PAL);
210  NewCS->setDebugLoc(Call->getDebugLoc());
211  uint64_t W;
212  if (Call->extractProfTotalWeight(W))
213  NewCS->setProfWeight(W);
214 
215  Args.clear();
216 
217  if (!Call->use_empty())
218  Call->replaceAllUsesWith(NewCS.getInstruction());
219 
220  NewCS->takeName(Call);
221 
222  // Finally, remove the old call from the program, reducing the use-count of
223  // F.
224  Call->eraseFromParent();
225  }
226 
227  // Since we have now created the new function, splice the body of the old
228  // function right into the new function, leaving the old rotting hulk of the
229  // function empty.
230  NF->getBasicBlockList().splice(NF->begin(), Fn.getBasicBlockList());
231 
232  // Loop over the argument list, transferring uses of the old arguments over to
233  // the new arguments, also transferring over the names as well. While we're at
234  // it, remove the dead arguments from the DeadArguments list.
235  for (Function::arg_iterator I = Fn.arg_begin(), E = Fn.arg_end(),
236  I2 = NF->arg_begin(); I != E; ++I, ++I2) {
237  // Move the name and users over to the new version.
238  I->replaceAllUsesWith(&*I2);
239  I2->takeName(&*I);
240  }
241 
242  // Clone metadatas from the old function, including debug info descriptor.
244  Fn.getAllMetadata(MDs);
245  for (auto MD : MDs)
246  NF->addMetadata(MD.first, *MD.second);
247 
248  // Fix up any BlockAddresses that refer to the function.
249  Fn.replaceAllUsesWith(ConstantExpr::getBitCast(NF, Fn.getType()));
250  // Delete the bitcast that we just created, so that NF does not
251  // appear to be address-taken.
253  // Finally, nuke the old function.
254  Fn.eraseFromParent();
255  return true;
256 }
257 
258 /// RemoveDeadArgumentsFromCallers - Checks if the given function has any
259 /// arguments that are unused, and changes the caller parameters to be undefined
260 /// instead.
261 bool DeadArgumentEliminationPass::RemoveDeadArgumentsFromCallers(Function &Fn) {
262  // We cannot change the arguments if this TU does not define the function or
263  // if the linker may choose a function body from another TU, even if the
264  // nominal linkage indicates that other copies of the function have the same
265  // semantics. In the below example, the dead load from %p may not have been
266  // eliminated from the linker-chosen copy of f, so replacing %p with undef
267  // in callers may introduce undefined behavior.
268  //
269  // define linkonce_odr void @f(i32* %p) {
270  // %v = load i32 %p
271  // ret void
272  // }
273  if (!Fn.hasExactDefinition())
274  return false;
275 
276  // Functions with local linkage should already have been handled, except the
277  // fragile (variadic) ones which we can improve here.
278  if (Fn.hasLocalLinkage() && !Fn.getFunctionType()->isVarArg())
279  return false;
280 
281  // Don't touch naked functions. The assembly might be using an argument, or
282  // otherwise rely on the frame layout in a way that this analysis will not
283  // see.
284  if (Fn.hasFnAttribute(Attribute::Naked))
285  return false;
286 
287  if (Fn.use_empty())
288  return false;
289 
290  SmallVector<unsigned, 8> UnusedArgs;
291  bool Changed = false;
292 
293  for (Argument &Arg : Fn.args()) {
294  if (!Arg.hasSwiftErrorAttr() && Arg.use_empty() && !Arg.hasByValOrInAllocaAttr()) {
295  if (Arg.isUsedByMetadata()) {
297  Changed = true;
298  }
299  UnusedArgs.push_back(Arg.getArgNo());
300  }
301  }
302 
303  if (UnusedArgs.empty())
304  return false;
305 
306  for (Use &U : Fn.uses()) {
307  CallSite CS(U.getUser());
308  if (!CS || !CS.isCallee(&U))
309  continue;
310 
311  // Now go through all unused args and replace them with "undef".
312  for (unsigned I = 0, E = UnusedArgs.size(); I != E; ++I) {
313  unsigned ArgNo = UnusedArgs[I];
314 
315  Value *Arg = CS.getArgument(ArgNo);
316  CS.setArgument(ArgNo, UndefValue::get(Arg->getType()));
317  ++NumArgumentsReplacedWithUndef;
318  Changed = true;
319  }
320  }
321 
322  return Changed;
323 }
324 
325 /// Convenience function that returns the number of return values. It returns 0
326 /// for void functions and 1 for functions not returning a struct. It returns
327 /// the number of struct elements for functions returning a struct.
328 static unsigned NumRetVals(const Function *F) {
329  Type *RetTy = F->getReturnType();
330  if (RetTy->isVoidTy())
331  return 0;
332  else if (StructType *STy = dyn_cast<StructType>(RetTy))
333  return STy->getNumElements();
334  else if (ArrayType *ATy = dyn_cast<ArrayType>(RetTy))
335  return ATy->getNumElements();
336  else
337  return 1;
338 }
339 
340 /// Returns the sub-type a function will return at a given Idx. Should
341 /// correspond to the result type of an ExtractValue instruction executed with
342 /// just that one Idx (i.e. only top-level structure is considered).
343 static Type *getRetComponentType(const Function *F, unsigned Idx) {
344  Type *RetTy = F->getReturnType();
345  assert(!RetTy->isVoidTy() && "void type has no subtype");
346 
347  if (StructType *STy = dyn_cast<StructType>(RetTy))
348  return STy->getElementType(Idx);
349  else if (ArrayType *ATy = dyn_cast<ArrayType>(RetTy))
350  return ATy->getElementType();
351  else
352  return RetTy;
353 }
354 
355 /// MarkIfNotLive - This checks Use for liveness in LiveValues. If Use is not
356 /// live, it adds Use to the MaybeLiveUses argument. Returns the determined
357 /// liveness of Use.
359 DeadArgumentEliminationPass::MarkIfNotLive(RetOrArg Use,
360  UseVector &MaybeLiveUses) {
361  // We're live if our use or its Function is already marked as live.
362  if (LiveFunctions.count(Use.F) || LiveValues.count(Use))
363  return Live;
364 
365  // We're maybe live otherwise, but remember that we must become live if
366  // Use becomes live.
367  MaybeLiveUses.push_back(Use);
368  return MaybeLive;
369 }
370 
371 /// SurveyUse - This looks at a single use of an argument or return value
372 /// and determines if it should be alive or not. Adds this use to MaybeLiveUses
373 /// if it causes the used value to become MaybeLive.
374 ///
375 /// RetValNum is the return value number to use when this use is used in a
376 /// return instruction. This is used in the recursion, you should always leave
377 /// it at 0.
379 DeadArgumentEliminationPass::SurveyUse(const Use *U, UseVector &MaybeLiveUses,
380  unsigned RetValNum) {
381  const User *V = U->getUser();
382  if (const ReturnInst *RI = dyn_cast<ReturnInst>(V)) {
383  // The value is returned from a function. It's only live when the
384  // function's return value is live. We use RetValNum here, for the case
385  // that U is really a use of an insertvalue instruction that uses the
386  // original Use.
387  const Function *F = RI->getParent()->getParent();
388  if (RetValNum != -1U) {
389  RetOrArg Use = CreateRet(F, RetValNum);
390  // We might be live, depending on the liveness of Use.
391  return MarkIfNotLive(Use, MaybeLiveUses);
392  } else {
393  DeadArgumentEliminationPass::Liveness Result = MaybeLive;
394  for (unsigned i = 0; i < NumRetVals(F); ++i) {
395  RetOrArg Use = CreateRet(F, i);
396  // We might be live, depending on the liveness of Use. If any
397  // sub-value is live, then the entire value is considered live. This
398  // is a conservative choice, and better tracking is possible.
400  MarkIfNotLive(Use, MaybeLiveUses);
401  if (Result != Live)
402  Result = SubResult;
403  }
404  return Result;
405  }
406  }
407  if (const InsertValueInst *IV = dyn_cast<InsertValueInst>(V)) {
408  if (U->getOperandNo() != InsertValueInst::getAggregateOperandIndex()
409  && IV->hasIndices())
410  // The use we are examining is inserted into an aggregate. Our liveness
411  // depends on all uses of that aggregate, but if it is used as a return
412  // value, only index at which we were inserted counts.
413  RetValNum = *IV->idx_begin();
414 
415  // Note that if we are used as the aggregate operand to the insertvalue,
416  // we don't change RetValNum, but do survey all our uses.
417 
418  Liveness Result = MaybeLive;
419  for (const Use &UU : IV->uses()) {
420  Result = SurveyUse(&UU, MaybeLiveUses, RetValNum);
421  if (Result == Live)
422  break;
423  }
424  return Result;
425  }
426 
427  if (auto CS = ImmutableCallSite(V)) {
428  const Function *F = CS.getCalledFunction();
429  if (F) {
430  // Used in a direct call.
431 
432  // The function argument is live if it is used as a bundle operand.
433  if (CS.isBundleOperand(U))
434  return Live;
435 
436  // Find the argument number. We know for sure that this use is an
437  // argument, since if it was the function argument this would be an
438  // indirect call and the we know can't be looking at a value of the
439  // label type (for the invoke instruction).
440  unsigned ArgNo = CS.getArgumentNo(U);
441 
442  if (ArgNo >= F->getFunctionType()->getNumParams())
443  // The value is passed in through a vararg! Must be live.
444  return Live;
445 
446  assert(CS.getArgument(ArgNo)
447  == CS->getOperand(U->getOperandNo())
448  && "Argument is not where we expected it");
449 
450  // Value passed to a normal call. It's only live when the corresponding
451  // argument to the called function turns out live.
452  RetOrArg Use = CreateArg(F, ArgNo);
453  return MarkIfNotLive(Use, MaybeLiveUses);
454  }
455  }
456  // Used in any other way? Value must be live.
457  return Live;
458 }
459 
460 /// SurveyUses - This looks at all the uses of the given value
461 /// Returns the Liveness deduced from the uses of this value.
462 ///
463 /// Adds all uses that cause the result to be MaybeLive to MaybeLiveRetUses. If
464 /// the result is Live, MaybeLiveUses might be modified but its content should
465 /// be ignored (since it might not be complete).
467 DeadArgumentEliminationPass::SurveyUses(const Value *V,
468  UseVector &MaybeLiveUses) {
469  // Assume it's dead (which will only hold if there are no uses at all..).
470  Liveness Result = MaybeLive;
471  // Check each use.
472  for (const Use &U : V->uses()) {
473  Result = SurveyUse(&U, MaybeLiveUses);
474  if (Result == Live)
475  break;
476  }
477  return Result;
478 }
479 
480 // SurveyFunction - This performs the initial survey of the specified function,
481 // checking out whether or not it uses any of its incoming arguments or whether
482 // any callers use the return value. This fills in the LiveValues set and Uses
483 // map.
484 //
485 // We consider arguments of non-internal functions to be intrinsically alive as
486 // well as arguments to functions which have their "address taken".
487 void DeadArgumentEliminationPass::SurveyFunction(const Function &F) {
488  // Functions with inalloca parameters are expecting args in a particular
489  // register and memory layout.
490  if (F.getAttributes().hasAttrSomewhere(Attribute::InAlloca)) {
491  MarkLive(F);
492  return;
493  }
494 
495  // Don't touch naked functions. The assembly might be using an argument, or
496  // otherwise rely on the frame layout in a way that this analysis will not
497  // see.
498  if (F.hasFnAttribute(Attribute::Naked)) {
499  MarkLive(F);
500  return;
501  }
502 
503  unsigned RetCount = NumRetVals(&F);
504 
505  // Assume all return values are dead
506  using RetVals = SmallVector<Liveness, 5>;
507 
508  RetVals RetValLiveness(RetCount, MaybeLive);
509 
510  using RetUses = SmallVector<UseVector, 5>;
511 
512  // These vectors map each return value to the uses that make it MaybeLive, so
513  // we can add those to the Uses map if the return value really turns out to be
514  // MaybeLive. Initialized to a list of RetCount empty lists.
515  RetUses MaybeLiveRetUses(RetCount);
516 
517  bool HasMustTailCalls = false;
518 
519  for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
520  if (const ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
521  if (RI->getNumOperands() != 0 && RI->getOperand(0)->getType()
522  != F.getFunctionType()->getReturnType()) {
523  // We don't support old style multiple return values.
524  MarkLive(F);
525  return;
526  }
527  }
528 
529  // If we have any returns of `musttail` results - the signature can't
530  // change
531  if (BB->getTerminatingMustTailCall() != nullptr)
532  HasMustTailCalls = true;
533  }
534 
535  if (HasMustTailCalls) {
536  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - " << F.getName()
537  << " has musttail calls\n");
538  }
539 
540  if (!F.hasLocalLinkage() && (!ShouldHackArguments || F.isIntrinsic())) {
541  MarkLive(F);
542  return;
543  }
544 
545  LLVM_DEBUG(
546  dbgs() << "DeadArgumentEliminationPass - Inspecting callers for fn: "
547  << F.getName() << "\n");
548  // Keep track of the number of live retvals, so we can skip checks once all
549  // of them turn out to be live.
550  unsigned NumLiveRetVals = 0;
551 
552  bool HasMustTailCallers = false;
553 
554  // Loop all uses of the function.
555  for (const Use &U : F.uses()) {
556  // If the function is PASSED IN as an argument, its address has been
557  // taken.
558  ImmutableCallSite CS(U.getUser());
559  if (!CS || !CS.isCallee(&U)) {
560  MarkLive(F);
561  return;
562  }
563 
564  // The number of arguments for `musttail` call must match the number of
565  // arguments of the caller
566  if (CS.isMustTailCall())
567  HasMustTailCallers = true;
568 
569  // If this use is anything other than a call site, the function is alive.
570  const Instruction *TheCall = CS.getInstruction();
571  if (!TheCall) { // Not a direct call site?
572  MarkLive(F);
573  return;
574  }
575 
576  // If we end up here, we are looking at a direct call to our function.
577 
578  // Now, check how our return value(s) is/are used in this caller. Don't
579  // bother checking return values if all of them are live already.
580  if (NumLiveRetVals == RetCount)
581  continue;
582 
583  // Check all uses of the return value.
584  for (const Use &U : TheCall->uses()) {
585  if (ExtractValueInst *Ext = dyn_cast<ExtractValueInst>(U.getUser())) {
586  // This use uses a part of our return value, survey the uses of
587  // that part and store the results for this index only.
588  unsigned Idx = *Ext->idx_begin();
589  if (RetValLiveness[Idx] != Live) {
590  RetValLiveness[Idx] = SurveyUses(Ext, MaybeLiveRetUses[Idx]);
591  if (RetValLiveness[Idx] == Live)
592  NumLiveRetVals++;
593  }
594  } else {
595  // Used by something else than extractvalue. Survey, but assume that the
596  // result applies to all sub-values.
597  UseVector MaybeLiveAggregateUses;
598  if (SurveyUse(&U, MaybeLiveAggregateUses) == Live) {
599  NumLiveRetVals = RetCount;
600  RetValLiveness.assign(RetCount, Live);
601  break;
602  } else {
603  for (unsigned i = 0; i != RetCount; ++i) {
604  if (RetValLiveness[i] != Live)
605  MaybeLiveRetUses[i].append(MaybeLiveAggregateUses.begin(),
606  MaybeLiveAggregateUses.end());
607  }
608  }
609  }
610  }
611  }
612 
613  if (HasMustTailCallers) {
614  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - " << F.getName()
615  << " has musttail callers\n");
616  }
617 
618  // Now we've inspected all callers, record the liveness of our return values.
619  for (unsigned i = 0; i != RetCount; ++i)
620  MarkValue(CreateRet(&F, i), RetValLiveness[i], MaybeLiveRetUses[i]);
621 
622  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Inspecting args for fn: "
623  << F.getName() << "\n");
624 
625  // Now, check all of our arguments.
626  unsigned i = 0;
627  UseVector MaybeLiveArgUses;
629  E = F.arg_end(); AI != E; ++AI, ++i) {
630  Liveness Result;
631  if (F.getFunctionType()->isVarArg() || HasMustTailCallers ||
632  HasMustTailCalls) {
633  // Variadic functions will already have a va_arg function expanded inside
634  // them, making them potentially very sensitive to ABI changes resulting
635  // from removing arguments entirely, so don't. For example AArch64 handles
636  // register and stack HFAs very differently, and this is reflected in the
637  // IR which has already been generated.
638  //
639  // `musttail` calls to this function restrict argument removal attempts.
640  // The signature of the caller must match the signature of the function.
641  //
642  // `musttail` calls in this function prevents us from changing its
643  // signature
644  Result = Live;
645  } else {
646  // See what the effect of this use is (recording any uses that cause
647  // MaybeLive in MaybeLiveArgUses).
648  Result = SurveyUses(&*AI, MaybeLiveArgUses);
649  }
650 
651  // Mark the result.
652  MarkValue(CreateArg(&F, i), Result, MaybeLiveArgUses);
653  // Clear the vector again for the next iteration.
654  MaybeLiveArgUses.clear();
655  }
656 }
657 
658 /// MarkValue - This function marks the liveness of RA depending on L. If L is
659 /// MaybeLive, it also takes all uses in MaybeLiveUses and records them in Uses,
660 /// such that RA will be marked live if any use in MaybeLiveUses gets marked
661 /// live later on.
662 void DeadArgumentEliminationPass::MarkValue(const RetOrArg &RA, Liveness L,
663  const UseVector &MaybeLiveUses) {
664  switch (L) {
665  case Live:
666  MarkLive(RA);
667  break;
668  case MaybeLive:
669  // Note any uses of this value, so this return value can be
670  // marked live whenever one of the uses becomes live.
671  for (const auto &MaybeLiveUse : MaybeLiveUses)
672  Uses.insert(std::make_pair(MaybeLiveUse, RA));
673  break;
674  }
675 }
676 
677 /// MarkLive - Mark the given Function as alive, meaning that it cannot be
678 /// changed in any way. Additionally,
679 /// mark any values that are used as this function's parameters or by its return
680 /// values (according to Uses) live as well.
681 void DeadArgumentEliminationPass::MarkLive(const Function &F) {
682  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Intrinsically live fn: "
683  << F.getName() << "\n");
684  // Mark the function as live.
685  LiveFunctions.insert(&F);
686  // Mark all arguments as live.
687  for (unsigned i = 0, e = F.arg_size(); i != e; ++i)
688  PropagateLiveness(CreateArg(&F, i));
689  // Mark all return values as live.
690  for (unsigned i = 0, e = NumRetVals(&F); i != e; ++i)
691  PropagateLiveness(CreateRet(&F, i));
692 }
693 
694 /// MarkLive - Mark the given return value or argument as live. Additionally,
695 /// mark any values that are used by this value (according to Uses) live as
696 /// well.
697 void DeadArgumentEliminationPass::MarkLive(const RetOrArg &RA) {
698  if (LiveFunctions.count(RA.F))
699  return; // Function was already marked Live.
700 
701  if (!LiveValues.insert(RA).second)
702  return; // We were already marked Live.
703 
704  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Marking "
705  << RA.getDescription() << " live\n");
706  PropagateLiveness(RA);
707 }
708 
709 /// PropagateLiveness - Given that RA is a live value, propagate it's liveness
710 /// to any other values it uses (according to Uses).
711 void DeadArgumentEliminationPass::PropagateLiveness(const RetOrArg &RA) {
712  // We don't use upper_bound (or equal_range) here, because our recursive call
713  // to ourselves is likely to cause the upper_bound (which is the first value
714  // not belonging to RA) to become erased and the iterator invalidated.
715  UseMap::iterator Begin = Uses.lower_bound(RA);
716  UseMap::iterator E = Uses.end();
717  UseMap::iterator I;
718  for (I = Begin; I != E && I->first == RA; ++I)
719  MarkLive(I->second);
720 
721  // Erase RA from the Uses map (from the lower bound to wherever we ended up
722  // after the loop).
723  Uses.erase(Begin, I);
724 }
725 
726 // RemoveDeadStuffFromFunction - Remove any arguments and return values from F
727 // that are not in LiveValues. Transform the function and all of the callees of
728 // the function to not have these arguments and return values.
729 //
730 bool DeadArgumentEliminationPass::RemoveDeadStuffFromFunction(Function *F) {
731  // Don't modify fully live functions
732  if (LiveFunctions.count(F))
733  return false;
734 
735  // Start by computing a new prototype for the function, which is the same as
736  // the old function, but has fewer arguments and a different return type.
737  FunctionType *FTy = F->getFunctionType();
738  std::vector<Type*> Params;
739 
740  // Keep track of if we have a live 'returned' argument
741  bool HasLiveReturnedArg = false;
742 
743  // Set up to build a new list of parameter attributes.
744  SmallVector<AttributeSet, 8> ArgAttrVec;
745  const AttributeList &PAL = F->getAttributes();
746 
747  // Remember which arguments are still alive.
748  SmallVector<bool, 10> ArgAlive(FTy->getNumParams(), false);
749  // Construct the new parameter list from non-dead arguments. Also construct
750  // a new set of parameter attributes to correspond. Skip the first parameter
751  // attribute, since that belongs to the return value.
752  unsigned i = 0;
753  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
754  I != E; ++I, ++i) {
755  RetOrArg Arg = CreateArg(F, i);
756  if (LiveValues.erase(Arg)) {
757  Params.push_back(I->getType());
758  ArgAlive[i] = true;
759  ArgAttrVec.push_back(PAL.getParamAttributes(i));
760  HasLiveReturnedArg |= PAL.hasParamAttribute(i, Attribute::Returned);
761  } else {
762  ++NumArgumentsEliminated;
763  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Removing argument "
764  << i << " (" << I->getName() << ") from "
765  << F->getName() << "\n");
766  }
767  }
768 
769  // Find out the new return value.
770  Type *RetTy = FTy->getReturnType();
771  Type *NRetTy = nullptr;
772  unsigned RetCount = NumRetVals(F);
773 
774  // -1 means unused, other numbers are the new index
775  SmallVector<int, 5> NewRetIdxs(RetCount, -1);
776  std::vector<Type*> RetTypes;
777 
778  // If there is a function with a live 'returned' argument but a dead return
779  // value, then there are two possible actions:
780  // 1) Eliminate the return value and take off the 'returned' attribute on the
781  // argument.
782  // 2) Retain the 'returned' attribute and treat the return value (but not the
783  // entire function) as live so that it is not eliminated.
784  //
785  // It's not clear in the general case which option is more profitable because,
786  // even in the absence of explicit uses of the return value, code generation
787  // is free to use the 'returned' attribute to do things like eliding
788  // save/restores of registers across calls. Whether or not this happens is
789  // target and ABI-specific as well as depending on the amount of register
790  // pressure, so there's no good way for an IR-level pass to figure this out.
791  //
792  // Fortunately, the only places where 'returned' is currently generated by
793  // the FE are places where 'returned' is basically free and almost always a
794  // performance win, so the second option can just be used always for now.
795  //
796  // This should be revisited if 'returned' is ever applied more liberally.
797  if (RetTy->isVoidTy() || HasLiveReturnedArg) {
798  NRetTy = RetTy;
799  } else {
800  // Look at each of the original return values individually.
801  for (unsigned i = 0; i != RetCount; ++i) {
802  RetOrArg Ret = CreateRet(F, i);
803  if (LiveValues.erase(Ret)) {
804  RetTypes.push_back(getRetComponentType(F, i));
805  NewRetIdxs[i] = RetTypes.size() - 1;
806  } else {
807  ++NumRetValsEliminated;
808  LLVM_DEBUG(
809  dbgs() << "DeadArgumentEliminationPass - Removing return value "
810  << i << " from " << F->getName() << "\n");
811  }
812  }
813  if (RetTypes.size() > 1) {
814  // More than one return type? Reduce it down to size.
815  if (StructType *STy = dyn_cast<StructType>(RetTy)) {
816  // Make the new struct packed if we used to return a packed struct
817  // already.
818  NRetTy = StructType::get(STy->getContext(), RetTypes, STy->isPacked());
819  } else {
820  assert(isa<ArrayType>(RetTy) && "unexpected multi-value return");
821  NRetTy = ArrayType::get(RetTypes[0], RetTypes.size());
822  }
823  } else if (RetTypes.size() == 1)
824  // One return type? Just a simple value then, but only if we didn't use to
825  // return a struct with that simple value before.
826  NRetTy = RetTypes.front();
827  else if (RetTypes.empty())
828  // No return types? Make it void, but only if we didn't use to return {}.
829  NRetTy = Type::getVoidTy(F->getContext());
830  }
831 
832  assert(NRetTy && "No new return type found?");
833 
834  // The existing function return attributes.
835  AttrBuilder RAttrs(PAL.getRetAttributes());
836 
837  // Remove any incompatible attributes, but only if we removed all return
838  // values. Otherwise, ensure that we don't have any conflicting attributes
839  // here. Currently, this should not be possible, but special handling might be
840  // required when new return value attributes are added.
841  if (NRetTy->isVoidTy())
843  else
844  assert(!RAttrs.overlaps(AttributeFuncs::typeIncompatible(NRetTy)) &&
845  "Return attributes no longer compatible?");
846 
847  AttributeSet RetAttrs = AttributeSet::get(F->getContext(), RAttrs);
848 
849  // Strip allocsize attributes. They might refer to the deleted arguments.
851  F->getContext(), Attribute::AllocSize);
852 
853  // Reconstruct the AttributesList based on the vector we constructed.
854  assert(ArgAttrVec.size() == Params.size());
855  AttributeList NewPAL =
856  AttributeList::get(F->getContext(), FnAttrs, RetAttrs, ArgAttrVec);
857 
858  // Create the new function type based on the recomputed parameters.
859  FunctionType *NFTy = FunctionType::get(NRetTy, Params, FTy->isVarArg());
860 
861  // No change?
862  if (NFTy == FTy)
863  return false;
864 
865  // Create the new function body and insert it into the module...
866  Function *NF = Function::Create(NFTy, F->getLinkage(), F->getAddressSpace());
867  NF->copyAttributesFrom(F);
868  NF->setComdat(F->getComdat());
869  NF->setAttributes(NewPAL);
870  // Insert the new function before the old function, so we won't be processing
871  // it again.
872  F->getParent()->getFunctionList().insert(F->getIterator(), NF);
873  NF->takeName(F);
874 
875  // Loop over all of the callers of the function, transforming the call sites
876  // to pass in a smaller number of arguments into the new function.
877  std::vector<Value*> Args;
878  while (!F->use_empty()) {
879  CallSite CS(F->user_back());
880  Instruction *Call = CS.getInstruction();
881 
882  ArgAttrVec.clear();
883  const AttributeList &CallPAL = CS.getAttributes();
884 
885  // Adjust the call return attributes in case the function was changed to
886  // return void.
887  AttrBuilder RAttrs(CallPAL.getRetAttributes());
889  AttributeSet RetAttrs = AttributeSet::get(F->getContext(), RAttrs);
890 
891  // Declare these outside of the loops, so we can reuse them for the second
892  // loop, which loops the varargs.
893  CallSite::arg_iterator I = CS.arg_begin();
894  unsigned i = 0;
895  // Loop over those operands, corresponding to the normal arguments to the
896  // original function, and add those that are still alive.
897  for (unsigned e = FTy->getNumParams(); i != e; ++I, ++i)
898  if (ArgAlive[i]) {
899  Args.push_back(*I);
900  // Get original parameter attributes, but skip return attributes.
902  if (NRetTy != RetTy && Attrs.hasAttribute(Attribute::Returned)) {
903  // If the return type has changed, then get rid of 'returned' on the
904  // call site. The alternative is to make all 'returned' attributes on
905  // call sites keep the return value alive just like 'returned'
906  // attributes on function declaration but it's less clearly a win and
907  // this is not an expected case anyway
908  ArgAttrVec.push_back(AttributeSet::get(
909  F->getContext(),
910  AttrBuilder(Attrs).removeAttribute(Attribute::Returned)));
911  } else {
912  // Otherwise, use the original attributes.
913  ArgAttrVec.push_back(Attrs);
914  }
915  }
916 
917  // Push any varargs arguments on the list. Don't forget their attributes.
918  for (CallSite::arg_iterator E = CS.arg_end(); I != E; ++I, ++i) {
919  Args.push_back(*I);
920  ArgAttrVec.push_back(CallPAL.getParamAttributes(i));
921  }
922 
923  // Reconstruct the AttributesList based on the vector we constructed.
924  assert(ArgAttrVec.size() == Args.size());
925 
926  // Again, be sure to remove any allocsize attributes, since their indices
927  // may now be incorrect.
928  AttributeSet FnAttrs = CallPAL.getFnAttributes().removeAttribute(
929  F->getContext(), Attribute::AllocSize);
930 
931  AttributeList NewCallPAL = AttributeList::get(
932  F->getContext(), FnAttrs, RetAttrs, ArgAttrVec);
933 
935  CS.getOperandBundlesAsDefs(OpBundles);
936 
937  CallSite NewCS;
938  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
939  NewCS = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
940  Args, OpBundles, "", Call->getParent());
941  } else {
942  NewCS = CallInst::Create(NF, Args, OpBundles, "", Call);
943  cast<CallInst>(NewCS.getInstruction())
944  ->setTailCallKind(cast<CallInst>(Call)->getTailCallKind());
945  }
946  NewCS.setCallingConv(CS.getCallingConv());
947  NewCS.setAttributes(NewCallPAL);
948  NewCS->setDebugLoc(Call->getDebugLoc());
949  uint64_t W;
950  if (Call->extractProfTotalWeight(W))
951  NewCS->setProfWeight(W);
952  Args.clear();
953  ArgAttrVec.clear();
954 
955  Instruction *New = NewCS.getInstruction();
956  if (!Call->use_empty() || Call->isUsedByMetadata()) {
957  if (New->getType() == Call->getType()) {
958  // Return type not changed? Just replace users then.
959  Call->replaceAllUsesWith(New);
960  New->takeName(Call);
961  } else if (New->getType()->isVoidTy()) {
962  // If the return value is dead, replace any uses of it with undef
963  // (any non-debug value uses will get removed later on).
964  if (!Call->getType()->isX86_MMXTy())
965  Call->replaceAllUsesWith(UndefValue::get(Call->getType()));
966  } else {
967  assert((RetTy->isStructTy() || RetTy->isArrayTy()) &&
968  "Return type changed, but not into a void. The old return type"
969  " must have been a struct or an array!");
970  Instruction *InsertPt = Call;
971  if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
972  BasicBlock *NewEdge = SplitEdge(New->getParent(), II->getNormalDest());
973  InsertPt = &*NewEdge->getFirstInsertionPt();
974  }
975 
976  // We used to return a struct or array. Instead of doing smart stuff
977  // with all the uses, we will just rebuild it using extract/insertvalue
978  // chaining and let instcombine clean that up.
979  //
980  // Start out building up our return value from undef
981  Value *RetVal = UndefValue::get(RetTy);
982  for (unsigned i = 0; i != RetCount; ++i)
983  if (NewRetIdxs[i] != -1) {
984  Value *V;
985  if (RetTypes.size() > 1)
986  // We are still returning a struct, so extract the value from our
987  // return value
988  V = ExtractValueInst::Create(New, NewRetIdxs[i], "newret",
989  InsertPt);
990  else
991  // We are now returning a single element, so just insert that
992  V = New;
993  // Insert the value at the old position
994  RetVal = InsertValueInst::Create(RetVal, V, i, "oldret", InsertPt);
995  }
996  // Now, replace all uses of the old call instruction with the return
997  // struct we built
998  Call->replaceAllUsesWith(RetVal);
999  New->takeName(Call);
1000  }
1001  }
1002 
1003  // Finally, remove the old call from the program, reducing the use-count of
1004  // F.
1005  Call->eraseFromParent();
1006  }
1007 
1008  // Since we have now created the new function, splice the body of the old
1009  // function right into the new function, leaving the old rotting hulk of the
1010  // function empty.
1011  NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
1012 
1013  // Loop over the argument list, transferring uses of the old arguments over to
1014  // the new arguments, also transferring over the names as well.
1015  i = 0;
1016  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
1017  I2 = NF->arg_begin(); I != E; ++I, ++i)
1018  if (ArgAlive[i]) {
1019  // If this is a live argument, move the name and users over to the new
1020  // version.
1021  I->replaceAllUsesWith(&*I2);
1022  I2->takeName(&*I);
1023  ++I2;
1024  } else {
1025  // If this argument is dead, replace any uses of it with undef
1026  // (any non-debug value uses will get removed later on).
1027  if (!I->getType()->isX86_MMXTy())
1028  I->replaceAllUsesWith(UndefValue::get(I->getType()));
1029  }
1030 
1031  // If we change the return value of the function we must rewrite any return
1032  // instructions. Check this now.
1033  if (F->getReturnType() != NF->getReturnType())
1034  for (BasicBlock &BB : *NF)
1035  if (ReturnInst *RI = dyn_cast<ReturnInst>(BB.getTerminator())) {
1036  Value *RetVal;
1037 
1038  if (NFTy->getReturnType()->isVoidTy()) {
1039  RetVal = nullptr;
1040  } else {
1041  assert(RetTy->isStructTy() || RetTy->isArrayTy());
1042  // The original return value was a struct or array, insert
1043  // extractvalue/insertvalue chains to extract only the values we need
1044  // to return and insert them into our new result.
1045  // This does generate messy code, but we'll let it to instcombine to
1046  // clean that up.
1047  Value *OldRet = RI->getOperand(0);
1048  // Start out building up our return value from undef
1049  RetVal = UndefValue::get(NRetTy);
1050  for (unsigned i = 0; i != RetCount; ++i)
1051  if (NewRetIdxs[i] != -1) {
1053  "oldret", RI);
1054  if (RetTypes.size() > 1) {
1055  // We're still returning a struct, so reinsert the value into
1056  // our new return value at the new index
1057 
1058  RetVal = InsertValueInst::Create(RetVal, EV, NewRetIdxs[i],
1059  "newret", RI);
1060  } else {
1061  // We are now only returning a simple value, so just return the
1062  // extracted value.
1063  RetVal = EV;
1064  }
1065  }
1066  }
1067  // Replace the return instruction with one returning the new return
1068  // value (possibly 0 if we became void).
1069  ReturnInst::Create(F->getContext(), RetVal, RI);
1070  BB.getInstList().erase(RI);
1071  }
1072 
1073  // Clone metadatas from the old function, including debug info descriptor.
1075  F->getAllMetadata(MDs);
1076  for (auto MD : MDs)
1077  NF->addMetadata(MD.first, *MD.second);
1078 
1079  // Now that the old function is dead, delete it.
1080  F->eraseFromParent();
1081 
1082  return true;
1083 }
1084 
1087  bool Changed = false;
1088 
1089  // First pass: Do a simple check to see if any functions can have their "..."
1090  // removed. We can do this if they never call va_start. This loop cannot be
1091  // fused with the next loop, because deleting a function invalidates
1092  // information computed while surveying other functions.
1093  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Deleting dead varargs\n");
1094  for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
1095  Function &F = *I++;
1096  if (F.getFunctionType()->isVarArg())
1097  Changed |= DeleteDeadVarargs(F);
1098  }
1099 
1100  // Second phase:loop through the module, determining which arguments are live.
1101  // We assume all arguments are dead unless proven otherwise (allowing us to
1102  // determine that dead arguments passed into recursive functions are dead).
1103  //
1104  LLVM_DEBUG(dbgs() << "DeadArgumentEliminationPass - Determining liveness\n");
1105  for (auto &F : M)
1106  SurveyFunction(F);
1107 
1108  // Now, remove all dead arguments and return values from each function in
1109  // turn.
1110  for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
1111  // Increment now, because the function will probably get removed (ie.
1112  // replaced by a new one).
1113  Function *F = &*I++;
1114  Changed |= RemoveDeadStuffFromFunction(F);
1115  }
1116 
1117  // Finally, look for any unused parameters in functions with non-local
1118  // linkage and replace the passed in parameters with undef.
1119  for (auto &F : M)
1120  Changed |= RemoveDeadArgumentsFromCallers(F);
1121 
1122  if (!Changed)
1123  return PreservedAnalyses::all();
1124  return PreservedAnalyses::none();
1125 }
Return a value (possibly void), from a function.
User::op_iterator arg_iterator
The type of iterator to use when looping over actual arguments at this call site. ...
Definition: CallSite.h:213
bool isIntrinsic() const
isIntrinsic - Returns true if the function&#39;s name starts with "llvm.".
Definition: Function.h:199
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:68
iterator_range< use_iterator > uses()
Definition: Value.h:355
bool hasLocalLinkage() const
Definition: GlobalValue.h:436
This instruction extracts a struct member or array element value from an aggregate value...
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
This class represents an incoming formal argument to a Function.
Definition: Argument.h:30
Eliminate dead arguments (and return values) from functions.
CallingConv::ID getCallingConv() const
Get the calling convention of the call.
Definition: CallSite.h:312
This class represents lattice values for constants.
Definition: AllocatorList.h:24
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:65
iterator end()
Definition: Function.h:658
static CallInst * Create(FunctionType *Ty, Value *F, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
This class represents a function call, abstracting a target machine&#39;s calling convention.
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)
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
BasicBlock * SplitEdge(BasicBlock *From, BasicBlock *To, DominatorTree *DT=nullptr, LoopInfo *LI=nullptr, MemorySSAUpdater *MSSAU=nullptr)
Split the edge connecting specified block.
static ReturnInst * Create(LLVMContext &C, Value *retVal=nullptr, Instruction *InsertBefore=nullptr)
SI optimize exec mask operations pre RA
Class to represent struct types.
Definition: DerivedTypes.h:201
ModulePass * createDeadArgHackingPass()
DeadArgHacking pass - Same as DAE, but delete arguments of external functions as well.
A Use represents the edge between a Value definition and its users.
Definition: Use.h:56
This file contains the simple types necessary to represent the attributes associated with functions a...
AttributeSet getRetAttributes() const
The attributes for the ret value are returned.
InstrTy * getInstruction() const
Definition: CallSite.h:92
static StructType * get(LLVMContext &Context, ArrayRef< Type *> Elements, bool isPacked=false)
This static method is the primary way to create a literal StructType.
Definition: Type.cpp:342
User * getUser() const LLVM_READONLY
Returns the User that contains this Use.
Definition: Use.cpp:41
Class to represent function types.
Definition: DerivedTypes.h:103
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
INITIALIZE_PASS(DAH, "deadarghaX0r", "Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)", false, false) ModulePass *llvm
createDeadArgEliminationPass - This pass removes arguments from functions which are not used by the b...
Class to represent array types.
Definition: DerivedTypes.h:369
AttributeSet getParamAttributes(unsigned ArgNo) const
The attributes for the argument or parameter at the given index are returned.
void setComdat(Comdat *C)
Definition: GlobalObject.h:103
bool isVarArg() const
Definition: DerivedTypes.h:123
AttrBuilder & remove(const AttrBuilder &B)
Remove the attributes from the builder.
AttributeList getAttributes() const
Return the attribute list for this Function.
Definition: Function.h:224
bool extractProfTotalWeight(uint64_t &TotalVal) const
Retrieve total raw weight values of a branch.
Definition: Metadata.cpp:1340
LinkageTypes getLinkage() const
Definition: GlobalValue.h:451
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:429
constexpr char Attrs[]
Key for Kernel::Metadata::mAttrs.
void takeName(Value *V)
Transfer the name from V to this value.
Definition: Value.cpp:291
iterator begin()
Definition: Function.h:656
void removeDeadConstantUsers() const
If there are any dead constant users dangling off of this constant, remove them.
Definition: Constants.cpp:537
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:1773
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:217
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:530
LLVM Basic Block Representation.
Definition: BasicBlock.h:58
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
static ExtractValueInst * Create(Value *Agg, ArrayRef< unsigned > Idxs, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
void copyAttributesFrom(const Function *Src)
copyAttributesFrom - copy all additional attributes (those not needed to create a Function) from the ...
Definition: Function.cpp:484
This file contains the declarations for the subclasses of Constant, which represent the different fla...
ModulePass * createDeadArgEliminationPass()
createDeadArgEliminationPass - This pass removes arguments from functions which are not used by the b...
LLVM_NODISCARD AttributeSet removeAttribute(LLVMContext &C, Attribute::AttrKind Kind) const
Remove the specified attribute from this set.
Definition: Attributes.cpp:551
unsigned getNumParams() const
Return the number of fixed parameters this function type requires.
Definition: DerivedTypes.h:139
void initializeDAEPass(PassRegistry &)
param_iterator param_begin() const
Definition: DerivedTypes.h:128
static Type * getVoidTy(LLVMContext &C)
Definition: Type.cpp:161
void splice(iterator where, iplist_impl &L2)
Definition: ilist.h:329
unsigned getAddressSpace() const
Definition: Globals.cpp:111
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:193
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1415
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 unsigned NumRetVals(const Function *F)
Convenience function that returns the number of return values.
Iterator for intrusive lists based on ilist_node.
bool hasParamAttribute(unsigned ArgNo, Attribute::AttrKind Kind) const
Equivalent to hasAttribute(ArgNo + FirstArgIndex, Kind).
AttrBuilder & removeAttribute(Attribute::AttrKind Val)
Remove an attribute from the builder.
IterTy arg_begin() const
Definition: CallSite.h:571
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:847
Module.h This file contains the declarations for the Module class.
static Type * getRetComponentType(const Function *F, unsigned Idx)
Returns the sub-type a function will return at a given Idx.
void addMetadata(unsigned KindID, MDNode &MD)
Add a metadata attachment.
Definition: Metadata.cpp:1394
Type * getReturnType() const
Definition: DerivedTypes.h:124
void setAttributes(AttributeList Attrs)
Set the attribute list for this Function.
Definition: Function.h:227
bool isUsedByMetadata() const
Return true if there is metadata referencing this value.
Definition: Value.h:489
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:133
FunctionType * getFunctionType() const
Returns the FunctionType for me.
Definition: Function.h:164
amdgpu Simplify well known AMD library false Value Value * Arg
const Comdat * getComdat() const
Definition: GlobalObject.h:101
iterator insert(iterator where, pointer New)
Definition: ilist.h:228
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:311
iterator end()
Definition: Module.h:597
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:56
void getOperandBundlesAsDefs(SmallVectorImpl< OperandBundleDef > &Defs) const
Definition: CallSite.h:582
static InvokeInst * Create(FunctionType *Ty, Value *Func, BasicBlock *IfNormal, BasicBlock *IfException, ArrayRef< Value *> Args, const Twine &NameStr, Instruction *InsertBefore=nullptr)
static InsertValueInst * Create(Value *Agg, Value *Val, ArrayRef< unsigned > Idxs, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:214
bool hasExactDefinition() const
Return true if this global has an exact defintion.
Definition: GlobalValue.h:407
Establish a view to a call site for examination.
Definition: CallSite.h:887
#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:595
static ArrayType * get(Type *ElementType, uint64_t NumElements)
This static method is the primary way to construct an ArrayType.
Definition: Type.cpp:581
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:323
const BasicBlockListType & getBasicBlockList() const
Get the underlying elements of the Function...
Definition: Function.h:633
void eraseFromParent()
eraseFromParent - This method unlinks &#39;this&#39; from the containing module and deletes it...
Definition: Function.cpp:214
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:1254
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
Liveness
Liveness enum - During our initial pass over the program, we determine that things are either alive o...
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:566
LLVM Value Representation.
Definition: Value.h:73
AttrBuilder typeIncompatible(Type *Ty)
Which attributes cannot be applied to a type.
AttributeSet getFnAttributes() const
The function attributes are returned.
Invoke instruction.
A container for analyses that lazily runs them and caches their results.
AttributeList getAttributes() const
Get the parameter attributes of the call.
Definition: CallSite.h:329
This header defines various interfaces for pass management in LLVM.
#define LLVM_DEBUG(X)
Definition: Debug.h:123
bool isEmpty() const
Return true if there are no attributes.
Definition: Attributes.h:656
bool use_empty() const
Definition: Value.h:323
constexpr char Args[]
Key for Kernel::Metadata::mArgs.
PointerType * getType() const
Global values are always pointers.
Definition: GlobalValue.h:274
static AttributeList get(LLVMContext &C, ArrayRef< std::pair< unsigned, Attribute >> Attrs)
Create an AttributeList with the specified parameters in it.
Definition: Attributes.cpp:873
iterator_range< arg_iterator > args()
Definition: Function.h:689
User * user_back()
Definition: Value.h:386
A wrapper class for inspecting calls to intrinsic functions.
Definition: IntrinsicInst.h:44
const BasicBlock * getParent() const
Definition: Instruction.h:67
This instruction inserts a struct field of array element value into an aggregate value.
PreservedAnalyses run(Module &M, ModuleAnalysisManager &)