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 <cassert> 18 #include <climits> 19 #include <vector> 20 #include "llvm/ADT/DenseMap.h" 21 #include "llvm/ADT/ValueMap.h" 22 #include "llvm/Analysis/CodeMetrics.h" 23 24 namespace llvm { 25 26 class Value; 27 class Function; 28 class BasicBlock; 29 class CallSite; 30 template<class PtrType, unsigned SmallSize> 31 class SmallPtrSet; 32 33 namespace InlineConstants { 34 // Various magic constants used to adjust heuristics. 35 const int InstrCost = 5; 36 const int IndirectCallBonus = -100; 37 const int CallPenalty = 25; 38 const int LastCallToStaticBonus = -15000; 39 const int ColdccPenalty = 2000; 40 const int NoreturnPenalty = 10000; 41 } 42 43 /// InlineCost - Represent the cost of inlining a function. This 44 /// supports special values for functions which should "always" or 45 /// "never" be inlined. Otherwise, the cost represents a unitless 46 /// amount; smaller values increase the likelihood of the function 47 /// being inlined. 48 class InlineCost { 49 enum Kind { 50 Value, 51 Always, 52 Never 53 }; 54 55 // This is a do-it-yourself implementation of 56 // int Cost : 30; 57 // unsigned Type : 2; 58 // We used to use bitfields, but they were sometimes miscompiled (PR3822). 59 enum { TYPE_BITS = 2 }; 60 enum { COST_BITS = unsigned(sizeof(unsigned)) * CHAR_BIT - TYPE_BITS }; 61 unsigned TypedCost; // int Cost : COST_BITS; unsigned Type : TYPE_BITS; 62 63 Kind getType() const { 64 return Kind(TypedCost >> COST_BITS); 65 } 66 67 int getCost() const { 68 // Sign-extend the bottom COST_BITS bits. 69 return (int(TypedCost << TYPE_BITS)) >> TYPE_BITS; 70 } 71 72 InlineCost(int C, int T) { 73 TypedCost = (unsigned(C << TYPE_BITS) >> TYPE_BITS) | (T << COST_BITS); 74 assert(getCost() == C && "Cost exceeds InlineCost precision"); 75 } 76 public: 77 static InlineCost get(int Cost) { return InlineCost(Cost, Value); } 78 static InlineCost getAlways() { return InlineCost(0, Always); } 79 static InlineCost getNever() { return InlineCost(0, Never); } 80 81 bool isVariable() const { return getType() == Value; } 82 bool isAlways() const { return getType() == Always; } 83 bool isNever() const { return getType() == Never; } 84 85 /// getValue() - Return a "variable" inline cost's amount. It is 86 /// an error to call this on an "always" or "never" InlineCost. 87 int getValue() const { 88 assert(getType() == Value && "Invalid access of InlineCost"); 89 return getCost(); 90 } 91 }; 92 93 /// InlineCostAnalyzer - Cost analyzer used by inliner. 94 class InlineCostAnalyzer { 95 struct ArgInfo { 96 public: 97 unsigned ConstantWeight; 98 unsigned AllocaWeight; 99 100 ArgInfo(unsigned CWeight, unsigned AWeight) 101 : ConstantWeight(CWeight), AllocaWeight(AWeight) 102 {} 103 }; 104 105 struct FunctionInfo { 106 CodeMetrics Metrics; 107 108 /// ArgumentWeights - Each formal argument of the function is inspected to 109 /// see if it is used in any contexts where making it a constant or alloca 110 /// would reduce the code size. If so, we add some value to the argument 111 /// entry here. 112 std::vector<ArgInfo> ArgumentWeights; 113 114 /// analyzeFunction - Add information about the specified function 115 /// to the current structure. 116 void analyzeFunction(Function *F); 117 118 /// NeverInline - Returns true if the function should never be 119 /// inlined into any caller. 120 bool NeverInline(); 121 }; 122 123 // The Function* for a function can be changed (by ArgumentPromotion); 124 // the ValueMap will update itself when this happens. 125 ValueMap<const Function *, FunctionInfo> CachedFunctionInfo; 126 127 int CountBonusForConstant(Value *V, Constant *C = NULL); 128 int ConstantFunctionBonus(CallSite CS, Constant *C); 129 int getInlineSize(CallSite CS, Function *Callee); 130 int getInlineBonuses(CallSite CS, Function *Callee); 131 public: 132 133 /// getInlineCost - The heuristic used to determine if we should inline the 134 /// function call or not. 135 /// 136 InlineCost getInlineCost(CallSite CS, 137 SmallPtrSet<const Function *, 16> &NeverInline); 138 /// getCalledFunction - The heuristic used to determine if we should inline 139 /// the function call or not. The callee is explicitly specified, to allow 140 /// you to calculate the cost of inlining a function via a pointer. The 141 /// result assumes that the inlined version will always be used. You should 142 /// weight it yourself in cases where this callee will not always be called. 143 InlineCost getInlineCost(CallSite CS, 144 Function *Callee, 145 SmallPtrSet<const Function *, 16> &NeverInline); 146 147 /// getSpecializationBonus - The heuristic used to determine the per-call 148 /// performance boost for using a specialization of Callee with argument 149 /// SpecializedArgNos replaced by a constant. 150 int getSpecializationBonus(Function *Callee, 151 SmallVectorImpl<unsigned> &SpecializedArgNo); 152 153 /// getSpecializationCost - The heuristic used to determine the code-size 154 /// impact of creating a specialized version of Callee with argument 155 /// SpecializedArgNo replaced by a constant. 156 InlineCost getSpecializationCost(Function *Callee, 157 SmallVectorImpl<unsigned> &SpecializedArgNo); 158 159 /// getInlineFudgeFactor - Return a > 1.0 factor if the inliner should use a 160 /// higher threshold to determine if the function call should be inlined. 161 float getInlineFudgeFactor(CallSite CS); 162 163 /// resetCachedFunctionInfo - erase any cached cost info for this function. 164 void resetCachedCostInfo(Function* Caller) { 165 CachedFunctionInfo[Caller] = FunctionInfo(); 166 } 167 168 /// growCachedCostInfo - update the cached cost info for Caller after Callee 169 /// has been inlined. If Callee is NULL it means a dead call has been 170 /// eliminated. 171 void growCachedCostInfo(Function* Caller, Function* Callee); 172 173 /// clear - empty the cache of inline costs 174 void clear(); 175 }; 176 177 /// callIsSmall - If a call is likely to lower to a single target instruction, 178 /// or is otherwise deemed small return true. 179 bool callIsSmall(const Function *Callee); 180 } 181 182 #endif 183
