1 //===- InlineCost.h - Cost analysis for inliner -----------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements heuristics for inlining decisions.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_ANALYSIS_INLINECOST_H
15 #define LLVM_ANALYSIS_INLINECOST_H
20 #include "llvm/ADT/DenseMap.h"
21 #include "llvm/ADT/ValueMap.h"
22 #include "llvm/Analysis/CodeMetrics.h"
30 template<class PtrType, unsigned SmallSize>
34 namespace InlineConstants {
35 // Various magic constants used to adjust heuristics.
36 const int InstrCost = 5;
37 const int IndirectCallBonus = -100;
38 const int CallPenalty = 25;
39 const int LastCallToStaticBonus = -15000;
40 const int ColdccPenalty = 2000;
41 const int NoreturnPenalty = 10000;
44 /// InlineCost - Represent the cost of inlining a function. This
45 /// supports special values for functions which should "always" or
46 /// "never" be inlined. Otherwise, the cost represents a unitless
47 /// amount; smaller values increase the likelihood of the function
56 // This is a do-it-yourself implementation of
59 // We used to use bitfields, but they were sometimes miscompiled (PR3822).
60 enum { TYPE_BITS = 2 };
61 enum { COST_BITS = unsigned(sizeof(unsigned)) * CHAR_BIT - TYPE_BITS };
62 unsigned TypedCost; // int Cost : COST_BITS; unsigned Type : TYPE_BITS;
64 Kind getType() const {
65 return Kind(TypedCost >> COST_BITS);
69 // Sign-extend the bottom COST_BITS bits.
70 return (int(TypedCost << TYPE_BITS)) >> TYPE_BITS;
73 InlineCost(int C, int T) {
74 TypedCost = (unsigned(C << TYPE_BITS) >> TYPE_BITS) | (T << COST_BITS);
75 assert(getCost() == C && "Cost exceeds InlineCost precision");
78 static InlineCost get(int Cost) { return InlineCost(Cost, Value); }
79 static InlineCost getAlways() { return InlineCost(0, Always); }
80 static InlineCost getNever() { return InlineCost(0, Never); }
82 bool isVariable() const { return getType() == Value; }
83 bool isAlways() const { return getType() == Always; }
84 bool isNever() const { return getType() == Never; }
86 /// getValue() - Return a "variable" inline cost's amount. It is
87 /// an error to call this on an "always" or "never" InlineCost.
88 int getValue() const {
89 assert(getType() == Value && "Invalid access of InlineCost");
94 /// InlineCostAnalyzer - Cost analyzer used by inliner.
95 class InlineCostAnalyzer {
98 unsigned ConstantWeight;
99 unsigned AllocaWeight;
101 ArgInfo(unsigned CWeight, unsigned AWeight)
102 : ConstantWeight(CWeight), AllocaWeight(AWeight)
106 struct FunctionInfo {
109 /// ArgumentWeights - Each formal argument of the function is inspected to
110 /// see if it is used in any contexts where making it a constant or alloca
111 /// would reduce the code size. If so, we add some value to the argument
113 std::vector<ArgInfo> ArgumentWeights;
115 /// analyzeFunction - Add information about the specified function
116 /// to the current structure.
117 void analyzeFunction(Function *F, const TargetData *TD);
119 /// NeverInline - Returns true if the function should never be
120 /// inlined into any caller.
124 // The Function* for a function can be changed (by ArgumentPromotion);
125 // the ValueMap will update itself when this happens.
126 ValueMap<const Function *, FunctionInfo> CachedFunctionInfo;
128 // TargetData if available, or null.
129 const TargetData *TD;
131 int CountBonusForConstant(Value *V, Constant *C = NULL);
132 int ConstantFunctionBonus(CallSite CS, Constant *C);
133 int getInlineSize(CallSite CS, Function *Callee);
134 int getInlineBonuses(CallSite CS, Function *Callee);
136 InlineCostAnalyzer(): TD(0) {}
138 void setTargetData(const TargetData *TData) { TD = TData; }
140 /// getInlineCost - The heuristic used to determine if we should inline the
141 /// function call or not.
143 InlineCost getInlineCost(CallSite CS,
144 SmallPtrSet<const Function *, 16> &NeverInline);
145 /// getCalledFunction - The heuristic used to determine if we should inline
146 /// the function call or not. The callee is explicitly specified, to allow
147 /// you to calculate the cost of inlining a function via a pointer. The
148 /// result assumes that the inlined version will always be used. You should
149 /// weight it yourself in cases where this callee will not always be called.
150 InlineCost getInlineCost(CallSite CS,
152 SmallPtrSet<const Function *, 16> &NeverInline);
154 /// getSpecializationBonus - The heuristic used to determine the per-call
155 /// performance boost for using a specialization of Callee with argument
156 /// SpecializedArgNos replaced by a constant.
157 int getSpecializationBonus(Function *Callee,
158 SmallVectorImpl<unsigned> &SpecializedArgNo);
160 /// getSpecializationCost - The heuristic used to determine the code-size
161 /// impact of creating a specialized version of Callee with argument
162 /// SpecializedArgNo replaced by a constant.
163 InlineCost getSpecializationCost(Function *Callee,
164 SmallVectorImpl<unsigned> &SpecializedArgNo);
166 /// getInlineFudgeFactor - Return a > 1.0 factor if the inliner should use a
167 /// higher threshold to determine if the function call should be inlined.
168 float getInlineFudgeFactor(CallSite CS);
170 /// resetCachedFunctionInfo - erase any cached cost info for this function.
171 void resetCachedCostInfo(Function* Caller) {
172 CachedFunctionInfo[Caller] = FunctionInfo();
175 /// growCachedCostInfo - update the cached cost info for Caller after Callee
176 /// has been inlined. If Callee is NULL it means a dead call has been
178 void growCachedCostInfo(Function* Caller, Function* Callee);
180 /// clear - empty the cache of inline costs
184 /// callIsSmall - If a call is likely to lower to a single target instruction,
185 /// or is otherwise deemed small return true.
186 bool callIsSmall(const Function *Callee);