CodeMetrics.h revision 9b081d9691f4509af58919db5760235ca319c9da 
1//===- CodeMetrics.h - Code cost measurements -------------------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements various weight measurements for code, helping
11// the Inliner and other passes decide whether to duplicate its contents.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_ANALYSIS_CODEMETRICS_H
16#define LLVM_ANALYSIS_CODEMETRICS_H
17
18#include "llvm/ADT/DenseMap.h"
19
20namespace llvm {
21  class BasicBlock;
22  class Function;
23  class TargetData;
24  class Value;
25
26  /// \brief Check whether a call will lower to something small.
27  ///
28  /// This tests checks whether calls to this function will lower to something
29  /// significantly cheaper than a traditional call, often a single
30  /// instruction.
31  bool callIsSmall(const Function *F);
32
33  /// \brief Utility to calculate the size and a few similar metrics for a set
34  /// of basic blocks.
35  struct CodeMetrics {
36    /// \brief True if this function contains a call to setjmp or other functions
37    /// with attribute "returns twice" without having the attribute itself.
38    bool exposesReturnsTwice;
39
40    /// \brief True if this function calls itself.
41    bool isRecursive;
42
43    /// \brief True if this function contains one or more indirect branches.
44    bool containsIndirectBr;
45
46    /// \brief True if this function calls alloca (in the C sense).
47    bool usesDynamicAlloca;
48
49    /// \brief Number of instructions in the analyzed blocks.
50    unsigned NumInsts;
51
52    /// \brief Number of analyzed blocks.
53    unsigned NumBlocks;
54
55    /// \brief Keeps track of basic block code size estimates.
56    DenseMap<const BasicBlock *, unsigned> NumBBInsts;
57
58    /// \brief Keep track of the number of calls to 'big' functions.
59    unsigned NumCalls;
60
61    /// \brief The number of calls to internal functions with a single caller.
62    ///
63    /// These are likely targets for future inlining, likely exposed by
64    /// interleaved devirtualization.
65    unsigned NumInlineCandidates;
66
67    /// \brief How many instructions produce vector values.
68    ///
69    /// The inliner is more aggressive with inlining vector kernels.
70    unsigned NumVectorInsts;
71
72    /// \brief How many 'ret' instructions the blocks contain.
73    unsigned NumRets;
74
75    CodeMetrics() : exposesReturnsTwice(false), isRecursive(false),
76                    containsIndirectBr(false), usesDynamicAlloca(false),
77                    NumInsts(0), NumBlocks(0), NumCalls(0),
78                    NumInlineCandidates(0), NumVectorInsts(0),
79                    NumRets(0) {}
80
81    /// \brief Add information about a block to the current state.
82    void analyzeBasicBlock(const BasicBlock *BB, const TargetData *TD = 0);
83
84    /// \brief Add information about a function to the current state.
85    void analyzeFunction(Function *F, const TargetData *TD = 0);
86  };
87}
88
89#endif
90