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
17 #include "llvm/Analysis/CallGraphSCCPass.h"
25 class TargetTransformInfo;
27 namespace InlineConstants {
28 // Various magic constants used to adjust heuristics.
29 const int InstrCost = 5;
30 const int IndirectCallThreshold = 100;
31 const int CallPenalty = 25;
32 const int LastCallToStaticBonus = -15000;
33 const int ColdccPenalty = 2000;
34 const int NoreturnPenalty = 10000;
35 /// Do not inline functions which allocate this many bytes on the stack
36 /// when the caller is recursive.
37 const unsigned TotalAllocaSizeRecursiveCaller = 1024;
40 /// \brief Represents the cost of inlining a function.
42 /// This supports special values for functions which should "always" or
43 /// "never" be inlined. Otherwise, the cost represents a unitless amount;
44 /// smaller values increase the likelihood of the function being inlined.
46 /// Objects of this type also provide the adjusted threshold for inlining
47 /// based on the information available for a particular callsite. They can be
48 /// directly tested to determine if inlining should occur given the cost and
49 /// threshold for this cost metric.
52 AlwaysInlineCost = INT_MIN,
53 NeverInlineCost = INT_MAX
56 /// \brief The estimated cost of inlining this callsite.
59 /// \brief The adjusted threshold against which this cost was computed.
62 // Trivial constructor, interesting logic in the factory functions below.
63 InlineCost(int Cost, int Threshold) : Cost(Cost), Threshold(Threshold) {}
66 static InlineCost get(int Cost, int Threshold) {
67 assert(Cost > AlwaysInlineCost && "Cost crosses sentinel value");
68 assert(Cost < NeverInlineCost && "Cost crosses sentinel value");
69 return InlineCost(Cost, Threshold);
71 static InlineCost getAlways() {
72 return InlineCost(AlwaysInlineCost, 0);
74 static InlineCost getNever() {
75 return InlineCost(NeverInlineCost, 0);
78 /// \brief Test whether the inline cost is low enough for inlining.
79 LLVM_EXPLICIT operator bool() const {
80 return Cost < Threshold;
83 bool isAlways() const { return Cost == AlwaysInlineCost; }
84 bool isNever() const { return Cost == NeverInlineCost; }
85 bool isVariable() const { return !isAlways() && !isNever(); }
87 /// \brief Get the inline cost estimate.
88 /// It is an error to call this on an "always" or "never" InlineCost.
90 assert(isVariable() && "Invalid access of InlineCost");
94 /// \brief Get the cost delta from the threshold for inlining.
95 /// Only valid if the cost is of the variable kind. Returns a negative
96 /// value if the cost is too high to inline.
97 int getCostDelta() const { return Threshold - getCost(); }
100 /// \brief Cost analyzer used by inliner.
101 class InlineCostAnalysis : public CallGraphSCCPass {
102 const DataLayout *TD;
103 const TargetTransformInfo *TTI;
108 InlineCostAnalysis();
109 ~InlineCostAnalysis();
111 // Pass interface implementation.
112 void getAnalysisUsage(AnalysisUsage &AU) const;
113 bool runOnSCC(CallGraphSCC &SCC);
115 /// \brief Get an InlineCost object representing the cost of inlining this
118 /// Note that threshold is passed into this function. Only costs below the
119 /// threshold are computed with any accuracy. The threshold can be used to
120 /// bound the computation necessary to determine whether the cost is
121 /// sufficiently low to warrant inlining.
123 /// Also note that calling this function *dynamically* computes the cost of
124 /// inlining the callsite. It is an expensive, heavyweight call.
125 InlineCost getInlineCost(CallSite CS, int Threshold);
127 /// \brief Get an InlineCost with the callee explicitly specified.
128 /// This allows you to calculate the cost of inlining a function via a
129 /// pointer. This behaves exactly as the version with no explicit callee
130 /// parameter in all other respects.
132 // Note: This is used by out-of-tree passes, please do not remove without
133 // adding a replacement API.
134 InlineCost getInlineCost(CallSite CS, Function *Callee, int Threshold);
136 /// \brief Minimal filter to detect invalid constructs for inlining.
137 bool isInlineViable(Function &Callee);