LLVM  6.0.0svn
AlwaysInliner.cpp
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1 //===- InlineAlways.cpp - Code to inline always_inline functions ----------===//
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 file implements a custom inliner that handles only functions that
11 // are marked as "always inline".
12 //
13 //===----------------------------------------------------------------------===//
14 
16 #include "llvm/ADT/SetVector.h"
22 #include "llvm/IR/CallSite.h"
23 #include "llvm/IR/CallingConv.h"
24 #include "llvm/IR/DataLayout.h"
25 #include "llvm/IR/Instructions.h"
26 #include "llvm/IR/IntrinsicInst.h"
27 #include "llvm/IR/Module.h"
28 #include "llvm/IR/Type.h"
29 #include "llvm/Transforms/IPO.h"
33 
34 using namespace llvm;
35 
36 #define DEBUG_TYPE "inline"
37 
41  bool Changed = false;
42  SmallVector<Function *, 16> InlinedFunctions;
43  for (Function &F : M)
44  if (!F.isDeclaration() && F.hasFnAttribute(Attribute::AlwaysInline) &&
45  isInlineViable(F)) {
46  Calls.clear();
47 
48  for (User *U : F.users())
49  if (auto CS = CallSite(U))
50  if (CS.getCalledFunction() == &F)
51  Calls.insert(CS);
52 
53  for (CallSite CS : Calls)
54  // FIXME: We really shouldn't be able to fail to inline at this point!
55  // We should do something to log or check the inline failures here.
56  Changed |= InlineFunction(CS, IFI);
57 
58  // Remember to try and delete this function afterward. This both avoids
59  // re-walking the rest of the module and avoids dealing with any iterator
60  // invalidation issues while deleting functions.
61  InlinedFunctions.push_back(&F);
62  }
63 
64  // Remove any live functions.
65  erase_if(InlinedFunctions, [&](Function *F) {
67  return !F->isDefTriviallyDead();
68  });
69 
70  // Delete the non-comdat ones from the module and also from our vector.
71  auto NonComdatBegin = partition(
72  InlinedFunctions, [&](Function *F) { return F->hasComdat(); });
73  for (Function *F : make_range(NonComdatBegin, InlinedFunctions.end()))
74  M.getFunctionList().erase(F);
75  InlinedFunctions.erase(NonComdatBegin, InlinedFunctions.end());
76 
77  if (!InlinedFunctions.empty()) {
78  // Now we just have the comdat functions. Filter out the ones whose comdats
79  // are not actually dead.
80  filterDeadComdatFunctions(M, InlinedFunctions);
81  // The remaining functions are actually dead.
82  for (Function *F : InlinedFunctions)
83  M.getFunctionList().erase(F);
84  }
85 
86  return Changed ? PreservedAnalyses::none() : PreservedAnalyses::all();
87 }
88 
89 namespace {
90 
91 /// Inliner pass which only handles "always inline" functions.
92 ///
93 /// Unlike the \c AlwaysInlinerPass, this uses the more heavyweight \c Inliner
94 /// base class to provide several facilities such as array alloca merging.
95 class AlwaysInlinerLegacyPass : public LegacyInlinerBase {
96 
97 public:
98  AlwaysInlinerLegacyPass() : LegacyInlinerBase(ID, /*InsertLifetime*/ true) {
100  }
101 
102  AlwaysInlinerLegacyPass(bool InsertLifetime)
103  : LegacyInlinerBase(ID, InsertLifetime) {
105  }
106 
107  /// Main run interface method. We override here to avoid calling skipSCC().
108  bool runOnSCC(CallGraphSCC &SCC) override { return inlineCalls(SCC); }
109 
110  static char ID; // Pass identification, replacement for typeid
111 
112  InlineCost getInlineCost(CallSite CS) override;
113 
115  bool doFinalization(CallGraph &CG) override {
116  return removeDeadFunctions(CG, /*AlwaysInlineOnly=*/true);
117  }
118 };
119 }
120 
122 INITIALIZE_PASS_BEGIN(AlwaysInlinerLegacyPass, "always-inline",
123  "Inliner for always_inline functions", false, false)
128 INITIALIZE_PASS_END(AlwaysInlinerLegacyPass, "always-inline",
129  "Inliner for always_inline functions", false, false)
130 
131 Pass *llvm::createAlwaysInlinerLegacyPass(bool InsertLifetime) {
132  return new AlwaysInlinerLegacyPass(InsertLifetime);
133 }
134 
135 /// \brief Get the inline cost for the always-inliner.
136 ///
137 /// The always inliner *only* handles functions which are marked with the
138 /// attribute to force inlining. As such, it is dramatically simpler and avoids
139 /// using the powerful (but expensive) inline cost analysis. Instead it uses
140 /// a very simple and boring direct walk of the instructions looking for
141 /// impossible-to-inline constructs.
142 ///
143 /// Note, it would be possible to go to some lengths to cache the information
144 /// computed here, but as we only expect to do this for relatively few and
145 /// small functions which have the explicit attribute to force inlining, it is
146 /// likely not worth it in practice.
149 
150  // Only inline direct calls to functions with always-inline attributes
151  // that are viable for inlining. FIXME: We shouldn't even get here for
152  // declarations.
153  if (Callee && !Callee->isDeclaration() &&
154  CS.hasFnAttr(Attribute::AlwaysInline) && isInlineViable(*Callee))
155  return InlineCost::getAlways();
156 
157  return InlineCost::getNever();
158 }
Pass interface - Implemented by all &#39;passes&#39;.
Definition: Pass.h:81
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
partial Partial Inliner
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
INITIALIZE_PASS_BEGIN(AlwaysInlinerLegacyPass, "always-inline", "Inliner for always_inline functions", false, false) INITIALIZE_PASS_END(AlwaysInlinerLegacyPass
An immutable pass that tracks lazily created AssumptionCache objects.
F(f)
InlineFunctionInfo - This class captures the data input to the InlineFunction call, and records the auxiliary results produced by it.
Definition: Cloning.h:176
Represents the cost of inlining a function.
Definition: InlineCost.h:65
bool InlineFunction(CallInst *C, InlineFunctionInfo &IFI, AAResults *CalleeAAR=nullptr, bool InsertLifetime=true)
InlineFunction - This function inlines the called function into the basic block of the caller...
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:51
An analysis pass based on legacy pass manager to deliver ProfileSummaryInfo.
This class contains all of the helper code which is used to perform the inlining operations that do n...
Definition: Inliner.h:31
bool isInlineViable(Function &Callee)
Minimal filter to detect invalid constructs for inlining.
virtual bool doFinalization(Module &)
doFinalization - Virtual method overriden by subclasses to do any necessary clean up after all passes...
Definition: Pass.h:110
always Inliner for always_inline functions
This file provides interfaces used to build and manipulate a call graph, which is a very useful tool ...
bool insert(const value_type &X)
Insert a new element into the SetVector.
Definition: SetVector.h:142
amdgpu Simplify well known AMD library false Value * Callee
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
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:153
The ModulePass which wraps up a CallGraph and the logic to build it.
Definition: CallGraph.h:324
bool hasFnAttr(Attribute::AttrKind Kind) const
Return true if this function has the given attribute.
Definition: CallSite.h:362
static InlineCost getNever()
Definition: InlineCost.h:89
Pass * createAlwaysInlinerLegacyPass(bool InsertLifetime=true)
Create a legacy pass manager instance of a pass to inline and remove functions marked as "always_inli...
void initializeAlwaysInlinerLegacyPassPass(PassRegistry &)
iterator erase(const_iterator CI)
Definition: SmallVector.h:449
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:159
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
InlineCost getInlineCost(CallSite CS, const InlineParams &Params, TargetTransformInfo &CalleeTTI, std::function< AssumptionCache &(Function &)> &GetAssumptionCache, Optional< function_ref< BlockFrequencyInfo &(Function &)>> GetBFI, ProfileSummaryInfo *PSI, OptimizationRemarkEmitter *ORE=nullptr)
Get an InlineCost object representing the cost of inlining this callsite.
Provides passes to inlining "always_inline" functions.
iterator_range< T > make_range(T x, T y)
Convenience function for iterating over sub-ranges.
A SetVector that performs no allocations if smaller than a certain size.
Definition: SetVector.h:298
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.
PreservedAnalyses run(Module &M, ModuleAnalysisManager &)
always inline
void erase_if(Container &C, UnaryPredicate P)
Provide a container algorithm similar to C++ Library Fundamentals v2&#39;s erase_if which is equivalent t...
Definition: STLExtras.h:880
bool hasComdat() const
Definition: GlobalObject.h:100
void filterDeadComdatFunctions(Module &M, SmallVectorImpl< Function *> &DeadComdatFunctions)
Filter out potentially dead comdat functions where other entries keep the entire comdat group alive...
The basic data container for the call graph of a Module of IR.
Definition: CallGraph.h:74
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator end()
Definition: SmallVector.h:120
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:61
auto partition(R &&Range, UnaryPredicate P) -> decltype(std::begin(Range))
Provide wrappers to std::partition which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:852
bool isDeclaration() const
Return true if the primary definition of this global value is outside of the current translation unit...
Definition: Globals.cpp:201
FunTy * getCalledFunction() const
Return the function being called if this is a direct call, otherwise return null (if it&#39;s an indirect...
Definition: CallSite.h:107
CallGraphSCC - This is a single SCC that a CallGraphSCCPass is run on.
A container for analyses that lazily runs them and caches their results.
for(unsigned i=Desc.getNumOperands(), e=OldMI.getNumOperands();i !=e;++i)
static InlineCost getAlways()
Definition: InlineCost.h:86
bool isDefTriviallyDead() const
isDefTriviallyDead - Return true if it is trivially safe to remove this function definition from the ...
Definition: Function.cpp:1233