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>
33 namespace InlineConstants {
34 // Various magic constants used to adjust heuristics.
35 const int InstrCost = 5;
36 const int IndirectCallBonus = 500;
37 const int CallPenalty = 25;
38 const int LastCallToStaticBonus = -15000;
39 const int ColdccPenalty = 2000;
40 const int NoreturnPenalty = 10000;
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 likelyhood of the function
55 // This is a do-it-yourself implementation of
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;
63 Kind getType() const {
64 return Kind(TypedCost >> COST_BITS);
68 // Sign-extend the bottom COST_BITS bits.
69 return (int(TypedCost << TYPE_BITS)) >> TYPE_BITS;
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");
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); }
81 bool isVariable() const { return getType() == Value; }
82 bool isAlways() const { return getType() == Always; }
83 bool isNever() const { return getType() == Never; }
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");
93 /// InlineCostAnalyzer - Cost analyzer used by inliner.
94 class InlineCostAnalyzer {
97 unsigned ConstantWeight;
98 unsigned AllocaWeight;
99 unsigned ConstantBonus;
101 ArgInfo(unsigned CWeight, unsigned AWeight, unsigned CBonus)
102 : ConstantWeight(CWeight), AllocaWeight(AWeight), ConstantBonus(CBonus)
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;
117 /// analyzeFunction - Add information about the specified function
118 /// to the current structure.
119 void analyzeFunction(Function *F);
121 /// NeverInline - Returns true if the function should never be
122 /// inlined into any caller.
126 // The Function* for a function can be changed (by ArgumentPromotion);
127 // the ValueMap will update itself when this happens.
128 ValueMap<const Function *, FunctionInfo> CachedFunctionInfo;
132 /// getInlineCost - The heuristic used to determine if we should inline the
133 /// function call or not.
135 InlineCost getInlineCost(CallSite CS,
136 SmallPtrSet<const Function *, 16> &NeverInline);
137 /// getCalledFunction - The heuristic used to determine if we should inline
138 /// the function call or not. The callee is explicitly specified, to allow
139 /// you to calculate the cost of inlining a function via a pointer. The
140 /// result assumes that the inlined version will always be used. You should
141 /// weight it yourself in cases where this callee will not always be called.
142 InlineCost getInlineCost(CallSite CS,
144 SmallPtrSet<const Function *, 16> &NeverInline);
146 /// getSpecializationBonus - The heuristic used to determine the per-call
147 /// performance boost for using a specialization of Callee with argument
148 /// SpecializedArgNos replaced by a constant.
149 int getSpecializationBonus(Function *Callee,
150 SmallVectorImpl<unsigned> &SpecializedArgNo);
152 /// getSpecializationCost - The heuristic used to determine the code-size
153 /// impact of creating a specialized version of Callee with argument
154 /// SpecializedArgNo replaced by a constant.
155 InlineCost getSpecializationCost(Function *Callee,
156 SmallVectorImpl<unsigned> &SpecializedArgNo);
158 /// getInlineFudgeFactor - Return a > 1.0 factor if the inliner should use a
159 /// higher threshold to determine if the function call should be inlined.
160 float getInlineFudgeFactor(CallSite CS);
162 /// resetCachedFunctionInfo - erase any cached cost info for this function.
163 void resetCachedCostInfo(Function* Caller) {
164 CachedFunctionInfo[Caller] = FunctionInfo();
167 /// growCachedCostInfo - update the cached cost info for Caller after Callee
168 /// has been inlined. If Callee is NULL it means a dead call has been
170 void growCachedCostInfo(Function* Caller, Function* Callee);
172 /// clear - empty the cache of inline costs
176 /// callIsSmall - If a call is likely to lower to a single target instruction,
177 /// or is otherwise deemed small return true.
178 bool callIsSmall(const Function *Callee);