InlineCost.h revision 593423f7461fbbbf752ff013bf20c19ef95d3435
1//===- InlineCost.h - Cost analysis for inliner -----------------*- C++ -*-===// 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 heuristics for inlining decisions. 11// 12//===----------------------------------------------------------------------===// 13 14#ifndef LLVM_ANALYSIS_INLINECOST_H 15#define LLVM_ANALYSIS_INLINECOST_H 16 17#include "llvm/Function.h" 18#include "llvm/ADT/DenseMap.h" 19#include "llvm/ADT/SmallPtrSet.h" 20#include "llvm/ADT/ValueMap.h" 21#include "llvm/Analysis/CodeMetrics.h" 22#include <cassert> 23#include <climits> 24#include <vector> 25 26namespace llvm { 27 28 class CallSite; 29 class DataLayout; 30 31 namespace InlineConstants { 32 // Various magic constants used to adjust heuristics. 33 const int InstrCost = 5; 34 const int IndirectCallThreshold = 100; 35 const int CallPenalty = 25; 36 const int LastCallToStaticBonus = -15000; 37 const int ColdccPenalty = 2000; 38 const int NoreturnPenalty = 10000; 39 /// Do not inline functions which allocate this many bytes on the stack 40 /// when the caller is recursive. 41 const unsigned TotalAllocaSizeRecursiveCaller = 1024; 42 } 43 44 /// \brief Represents the cost of inlining a function. 45 /// 46 /// This supports special values for functions which should "always" or 47 /// "never" be inlined. Otherwise, the cost represents a unitless amount; 48 /// smaller values increase the likelihood of the function being inlined. 49 /// 50 /// Objects of this type also provide the adjusted threshold for inlining 51 /// based on the information available for a particular callsite. They can be 52 /// directly tested to determine if inlining should occur given the cost and 53 /// threshold for this cost metric. 54 class InlineCost { 55 enum SentinelValues { 56 AlwaysInlineCost = INT_MIN, 57 NeverInlineCost = INT_MAX 58 }; 59 60 /// \brief The estimated cost of inlining this callsite. 61 const int Cost; 62 63 /// \brief The adjusted threshold against which this cost was computed. 64 const int Threshold; 65 66 // Trivial constructor, interesting logic in the factory functions below. 67 InlineCost(int Cost, int Threshold) 68 : Cost(Cost), Threshold(Threshold) {} 69 70 public: 71 static InlineCost get(int Cost, int Threshold) { 72 assert(Cost > AlwaysInlineCost && "Cost crosses sentinel value"); 73 assert(Cost < NeverInlineCost && "Cost crosses sentinel value"); 74 return InlineCost(Cost, Threshold); 75 } 76 static InlineCost getAlways() { 77 return InlineCost(AlwaysInlineCost, 0); 78 } 79 static InlineCost getNever() { 80 return InlineCost(NeverInlineCost, 0); 81 } 82 83 /// \brief Test whether the inline cost is low enough for inlining. 84 operator bool() const { 85 return Cost < Threshold; 86 } 87 88 bool isAlways() const { return Cost == AlwaysInlineCost; } 89 bool isNever() const { return Cost == NeverInlineCost; } 90 bool isVariable() const { return !isAlways() && !isNever(); } 91 92 /// \brief Get the inline cost estimate. 93 /// It is an error to call this on an "always" or "never" InlineCost. 94 int getCost() const { 95 assert(isVariable() && "Invalid access of InlineCost"); 96 return Cost; 97 } 98 99 /// \brief Get the cost delta from the threshold for inlining. 100 /// Only valid if the cost is of the variable kind. Returns a negative 101 /// value if the cost is too high to inline. 102 int getCostDelta() const { return Threshold - getCost(); } 103 }; 104 105 /// InlineCostAnalyzer - Cost analyzer used by inliner. 106 class InlineCostAnalyzer { 107 // DataLayout if available, or null. 108 const DataLayout *TD; 109 110 public: 111 InlineCostAnalyzer(): TD(0) {} 112 113 void setDataLayout(const DataLayout *TData) { TD = TData; } 114 115 /// \brief Get an InlineCost object representing the cost of inlining this 116 /// callsite. 117 /// 118 /// Note that threshold is passed into this function. Only costs below the 119 /// threshold are computed with any accuracy. The threshold can be used to 120 /// bound the computation necessary to determine whether the cost is 121 /// sufficiently low to warrant inlining. 122 InlineCost getInlineCost(CallSite CS, int Threshold); 123 124 /// \brief Get an InlineCost with the callee explicitly specified. 125 /// This allows you to calculate the cost of inlining a function via a 126 /// pointer. This behaves exactly as the version with no explicit callee 127 /// parameter in all other respects. 128 // 129 // Note: This is used by out-of-tree passes, please do not remove without 130 // adding a replacement API. 131 InlineCost getInlineCost(CallSite CS, Function *Callee, int Threshold); 132 }; 133} 134 135#endif 136