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;
100 ArgInfo(unsigned CWeight, unsigned AWeight)
101 : ConstantWeight(CWeight), AllocaWeight(AWeight) {}
104 struct FunctionInfo {
107 /// ArgumentWeights - Each formal argument of the function is inspected to
108 /// see if it is used in any contexts where making it a constant or alloca
109 /// would reduce the code size. If so, we add some value to the argument
111 std::vector<ArgInfo> ArgumentWeights;
113 /// CountCodeReductionForConstant - Figure out an approximation for how
114 /// many instructions will be constant folded if the specified value is
116 unsigned CountCodeReductionForConstant(Value *V);
118 /// CountCodeReductionForAlloca - Figure out an approximation of how much
119 /// smaller the function will be if it is inlined into a context where an
120 /// argument becomes an alloca.
122 unsigned CountCodeReductionForAlloca(Value *V);
124 /// analyzeFunction - Add information about the specified function
125 /// to the current structure.
126 void analyzeFunction(Function *F);
128 /// NeverInline - Returns true if the function should never be
129 /// inlined into any caller.
133 // The Function* for a function can be changed (by ArgumentPromotion);
134 // the ValueMap will update itself when this happens.
135 ValueMap<const Function *, FunctionInfo> CachedFunctionInfo;
139 /// getInlineCost - The heuristic used to determine if we should inline the
140 /// function call or not.
142 InlineCost getInlineCost(CallSite CS,
143 SmallPtrSet<const Function *, 16> &NeverInline);
144 /// getCalledFunction - The heuristic used to determine if we should inline
145 /// the function call or not. The callee is explicitly specified, to allow
146 /// you to calculate the cost of inlining a function via a pointer. The
147 /// result assumes that the inlined version will always be used. You should
148 /// weight it yourself in cases where this callee will not always be called.
149 InlineCost getInlineCost(CallSite CS,
151 SmallPtrSet<const Function *, 16> &NeverInline);
153 /// getInlineFudgeFactor - Return a > 1.0 factor if the inliner should use a
154 /// higher threshold to determine if the function call should be inlined.
155 float getInlineFudgeFactor(CallSite CS);
157 /// resetCachedFunctionInfo - erase any cached cost info for this function.
158 void resetCachedCostInfo(Function* Caller) {
159 CachedFunctionInfo[Caller] = FunctionInfo();
162 /// growCachedCostInfo - update the cached cost info for Caller after Callee
163 /// has been inlined. If Callee is NULL it means a dead call has been
165 void growCachedCostInfo(Function* Caller, Function* Callee);
167 /// clear - empty the cache of inline costs
171 /// callIsSmall - If a call is likely to lower to a single target instruction,
172 /// or is otherwise deemed small return true.
173 bool callIsSmall(const Function *Callee);