LLVM  3.7.0
InlineAlways.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 
15 #include "llvm/Transforms/IPO.h"
16 #include "llvm/ADT/SmallPtrSet.h"
21 #include "llvm/IR/CallSite.h"
22 #include "llvm/IR/CallingConv.h"
23 #include "llvm/IR/DataLayout.h"
24 #include "llvm/IR/Instructions.h"
25 #include "llvm/IR/IntrinsicInst.h"
26 #include "llvm/IR/Module.h"
27 #include "llvm/IR/Type.h"
29 
30 using namespace llvm;
31 
32 #define DEBUG_TYPE "inline"
33 
34 namespace {
35 
36 /// \brief Inliner pass which only handles "always inline" functions.
37 class AlwaysInliner : public Inliner {
38  InlineCostAnalysis *ICA;
39 
40 public:
41  // Use extremely low threshold.
42  AlwaysInliner() : Inliner(ID, -2000000000, /*InsertLifetime*/ true),
43  ICA(nullptr) {
45  }
46 
47  AlwaysInliner(bool InsertLifetime)
48  : Inliner(ID, -2000000000, InsertLifetime), ICA(nullptr) {
50  }
51 
52  static char ID; // Pass identification, replacement for typeid
53 
54  InlineCost getInlineCost(CallSite CS) override;
55 
56  void getAnalysisUsage(AnalysisUsage &AU) const override;
57  bool runOnSCC(CallGraphSCC &SCC) override;
58 
60  bool doFinalization(CallGraph &CG) override {
61  return removeDeadFunctions(CG, /*AlwaysInlineOnly=*/ true);
62  }
63 };
64 
65 }
66 
67 char AlwaysInliner::ID = 0;
68 INITIALIZE_PASS_BEGIN(AlwaysInliner, "always-inline",
69  "Inliner for always_inline functions", false, false)
74 INITIALIZE_PASS_END(AlwaysInliner, "always-inline",
75  "Inliner for always_inline functions", false, false)
76 
77 Pass *llvm::createAlwaysInlinerPass() { return new AlwaysInliner(); }
78 
79 Pass *llvm::createAlwaysInlinerPass(bool InsertLifetime) {
80  return new AlwaysInliner(InsertLifetime);
81 }
82 
83 /// \brief Get the inline cost for the always-inliner.
84 ///
85 /// The always inliner *only* handles functions which are marked with the
86 /// attribute to force inlining. As such, it is dramatically simpler and avoids
87 /// using the powerful (but expensive) inline cost analysis. Instead it uses
88 /// a very simple and boring direct walk of the instructions looking for
89 /// impossible-to-inline constructs.
90 ///
91 /// Note, it would be possible to go to some lengths to cache the information
92 /// computed here, but as we only expect to do this for relatively few and
93 /// small functions which have the explicit attribute to force inlining, it is
94 /// likely not worth it in practice.
95 InlineCost AlwaysInliner::getInlineCost(CallSite CS) {
96  Function *Callee = CS.getCalledFunction();
97 
98  // Only inline direct calls to functions with always-inline attributes
99  // that are viable for inlining. FIXME: We shouldn't even get here for
100  // declarations.
101  if (Callee && !Callee->isDeclaration() &&
103  ICA->isInlineViable(*Callee))
104  return InlineCost::getAlways();
105 
106  return InlineCost::getNever();
107 }
108 
109 bool AlwaysInliner::runOnSCC(CallGraphSCC &SCC) {
110  ICA = &getAnalysis<InlineCostAnalysis>();
111  return Inliner::runOnSCC(SCC);
112 }
113 
114 void AlwaysInliner::getAnalysisUsage(AnalysisUsage &AU) const {
117 }
Pass interface - Implemented by all 'passes'.
Definition: Pass.h:82
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
An immutable pass that tracks lazily created AssumptionCache objects.
Pass * createAlwaysInlinerPass()
createAlwaysInlinerPass - Return a new pass object that inlines only functions that are marked as "al...
Represents the cost of inlining a function.
Definition: InlineCost.h:51
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:70
virtual bool doFinalization(Module &)
doFinalization - Virtual method overriden by subclasses to do any necessary clean up after all passes...
Definition: Pass.h:116
#define INITIALIZE_PASS_END(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:75
bool hasFnAttr(Attribute::AttrKind A) const
Return true if this function has the given attribute.
Definition: CallSite.h:237
This file provides interfaces used to build and manipulate a call graph, which is a very useful tool ...
void getAnalysisUsage(AnalysisUsage &Info) const override
getAnalysisUsage - For this class, we declare that we require and preserve the call graph...
Definition: Inliner.cpp:78
Inliner - This class contains all of the helper code which is used to perform the inlining operations...
Definition: InlinerPass.h:32
always inline
The ModulePass which wraps up a CallGraph and the logic to build it.
Definition: CallGraph.h:316
FunTy * getCalledFunction() const
getCalledFunction - Return the function being called if this is a direct call, otherwise return null ...
Definition: CallSite.h:99
Cost analyzer used by inliner.
Definition: InlineCost.h:102
always Inliner for always_inline false
Represent the analysis usage information of a pass.
static InlineCost getNever()
Definition: InlineCost.h:75
for(unsigned i=0, e=MI->getNumOperands();i!=e;++i)
#define INITIALIZE_AG_DEPENDENCY(depName)
Definition: PassSupport.h:72
bool runOnSCC(CallGraphSCC &SCC) override
runOnSCC - This method should be implemented by the subclass to perform whatever action is necessary ...
Definition: Inliner.cpp:431
void initializeAlwaysInlinerPass(PassRegistry &)
Module.h This file contains the declarations for the Module class.
The basic data container for the call graph of a Module of IR.
Definition: CallGraph.h:75
bool isDeclaration() const
Return true if the primary definition of this global value is outside of the current translation unit...
Definition: Globals.cpp:128
INITIALIZE_PASS_BEGIN(AlwaysInliner,"always-inline","Inliner for always_inline functions", false, false) INITIALIZE_PASS_END(AlwaysInliner
CallGraphSCC - This is a single SCC that a CallGraphSCCPass is run on.
always Inliner for always_inline functions
static InlineCost getAlways()
Definition: InlineCost.h:72