InlineCost.h revision f96769bed208b8a3f82b53771350dc0a743db85a
1ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru//===- InlineCost.cpp - Cost analysis for inliner ---------------*- C++ -*-===// 2ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru// 3ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru// The LLVM Compiler Infrastructure 4ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru// 5ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru// This file is distributed under the University of Illinois Open Source 6ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru// License. See LICENSE.TXT for details. 7ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru// 8ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru//===----------------------------------------------------------------------===// 9ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru// 10ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru// This file implements heuristics for inlining decisions. 11ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru// 12ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru//===----------------------------------------------------------------------===// 13ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 14ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru#ifndef LLVM_ANALYSIS_INLINECOST_H 15ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru#define LLVM_ANALYSIS_INLINECOST_H 16ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 17ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru#include <cassert> 18ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru#include <climits> 19ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru#include <map> 20ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru#include <vector> 21ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru#include "llvm/ADT/DenseMap.h" 22ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 23ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Querunamespace llvm { 24ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 25ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru class Value; 26ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru class Function; 27ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru class BasicBlock; 28ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru class CallSite; 29ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru template<class PtrType, unsigned SmallSize> 30ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru class SmallPtrSet; 31ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 32ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru // CodeMetrics - Calculate size and a few similar metrics for a set of 33ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru // basic blocks. 34ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru struct CodeMetrics { 35ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// NeverInline - True if this callee should never be inlined into a 36ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// caller. 37ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru bool NeverInline; 38ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 39ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// usesDynamicAlloca - True if this function calls alloca (in the C sense). 40ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru bool usesDynamicAlloca; 41ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 42ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// NumInsts, NumBlocks - Keep track of how large each function is, which 43ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// is used to estimate the code size cost of inlining it. 44ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru unsigned NumInsts, NumBlocks; 45ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 46ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// NumBBInsts - Keeps track of basic block code size estimates. 47ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru DenseMap<const BasicBlock *, unsigned> NumBBInsts; 48ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 49ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// NumCalls - Keep track of the number of calls to 'big' functions. 50ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru unsigned NumCalls; 51ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 52ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// NumVectorInsts - Keep track of how many instructions produce vector 53ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// values. The inliner is being more aggressive with inlining vector 54ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// kernels. 55ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru unsigned NumVectorInsts; 56ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 57ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// NumRets - Keep track of how many Ret instructions the block contains. 58ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru unsigned NumRets; 59ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 60ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru CodeMetrics() : NeverInline(false), usesDynamicAlloca(false), NumInsts(0), 61ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru NumBlocks(0), NumCalls(0), NumVectorInsts(0), NumRets(0) {} 62ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 63ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// analyzeBasicBlock - Add information about the specified basic block 64ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// to the current structure. 65ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru void analyzeBasicBlock(const BasicBlock *BB); 66ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 67ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// analyzeFunction - Add information about the specified function 68ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// to the current structure. 69ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru void analyzeFunction(Function *F); 70ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru }; 71ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 72ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru namespace InlineConstants { 73ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru // Various magic constants used to adjust heuristics. 74ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru const int InstrCost = 5; 75ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru const int IndirectCallBonus = 500; 76ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru const int CallPenalty = 25; 77ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru const int LastCallToStaticBonus = -15000; 78ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru const int ColdccPenalty = 2000; 79ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru const int NoreturnPenalty = 10000; 80ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru } 81ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 82ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// InlineCost - Represent the cost of inlining a function. This 83ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// supports special values for functions which should "always" or 84ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// "never" be inlined. Otherwise, the cost represents a unitless 85ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// amount; smaller values increase the likelyhood of the function 86ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru /// being inlined. 87ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru class InlineCost { 88ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru enum Kind { 89ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru Value, 90ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru Always, 91ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru Never 92ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru }; 93ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 94ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru // This is a do-it-yourself implementation of 95ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru // int Cost : 30; 96ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru // unsigned Type : 2; 97ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru // We used to use bitfields, but they were sometimes miscompiled (PR3822). 98ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru enum { TYPE_BITS = 2 }; 99ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru enum { COST_BITS = unsigned(sizeof(unsigned)) * CHAR_BIT - TYPE_BITS }; 100ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru unsigned TypedCost; // int Cost : COST_BITS; unsigned Type : TYPE_BITS; 101ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 102ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru Kind getType() const { 103ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru return Kind(TypedCost >> COST_BITS); 104ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru } 105ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 106ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru int getCost() const { 107ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru // Sign-extend the bottom COST_BITS bits. 108ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru return (int(TypedCost << TYPE_BITS)) >> TYPE_BITS; 109ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru } 110ac04d0bbe12b3ef54518635711412f178cb4d16Jean-Baptiste Queru 111 InlineCost(int C, int T) { 112 TypedCost = (unsigned(C << TYPE_BITS) >> TYPE_BITS) | (T << COST_BITS); 113 assert(getCost() == C && "Cost exceeds InlineCost precision"); 114 } 115 public: 116 static InlineCost get(int Cost) { return InlineCost(Cost, Value); } 117 static InlineCost getAlways() { return InlineCost(0, Always); } 118 static InlineCost getNever() { return InlineCost(0, Never); } 119 120 bool isVariable() const { return getType() == Value; } 121 bool isAlways() const { return getType() == Always; } 122 bool isNever() const { return getType() == Never; } 123 124 /// getValue() - Return a "variable" inline cost's amount. It is 125 /// an error to call this on an "always" or "never" InlineCost. 126 int getValue() const { 127 assert(getType() == Value && "Invalid access of InlineCost"); 128 return getCost(); 129 } 130 }; 131 132 /// InlineCostAnalyzer - Cost analyzer used by inliner. 133 class InlineCostAnalyzer { 134 struct ArgInfo { 135 public: 136 unsigned ConstantWeight; 137 unsigned AllocaWeight; 138 139 ArgInfo(unsigned CWeight, unsigned AWeight) 140 : ConstantWeight(CWeight), AllocaWeight(AWeight) {} 141 }; 142 143 struct FunctionInfo { 144 CodeMetrics Metrics; 145 146 /// ArgumentWeights - Each formal argument of the function is inspected to 147 /// see if it is used in any contexts where making it a constant or alloca 148 /// would reduce the code size. If so, we add some value to the argument 149 /// entry here. 150 std::vector<ArgInfo> ArgumentWeights; 151 152 /// CountCodeReductionForConstant - Figure out an approximation for how 153 /// many instructions will be constant folded if the specified value is 154 /// constant. 155 unsigned CountCodeReductionForConstant(Value *V); 156 157 /// CountCodeReductionForAlloca - Figure out an approximation of how much 158 /// smaller the function will be if it is inlined into a context where an 159 /// argument becomes an alloca. 160 /// 161 unsigned CountCodeReductionForAlloca(Value *V); 162 163 /// analyzeFunction - Add information about the specified function 164 /// to the current structure. 165 void analyzeFunction(Function *F); 166 }; 167 168 std::map<const Function *, FunctionInfo> CachedFunctionInfo; 169 170 public: 171 172 /// getInlineCost - The heuristic used to determine if we should inline the 173 /// function call or not. 174 /// 175 InlineCost getInlineCost(CallSite CS, 176 SmallPtrSet<const Function *, 16> &NeverInline); 177 178 /// getInlineFudgeFactor - Return a > 1.0 factor if the inliner should use a 179 /// higher threshold to determine if the function call should be inlined. 180 float getInlineFudgeFactor(CallSite CS); 181 182 /// resetCachedFunctionInfo - erase any cached cost info for this function. 183 void resetCachedCostInfo(Function* Caller) { 184 CachedFunctionInfo[Caller] = FunctionInfo(); 185 } 186 187 /// growCachedCostInfo - update the cached cost info for Caller after Callee 188 /// has been inlined. If Callee is NULL it means a dead call has been 189 /// eliminated. 190 void growCachedCostInfo(Function* Caller, Function* Callee); 191 }; 192} 193 194#endif 195