CodeMetrics.h revision 3574eca1b02600bac4e625297f4ecf745f4c4f32 
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#include "llvm/Support/CallSite.h"
20
21namespace llvm {
22  class BasicBlock;
23  class Function;
24  class Instruction;
25  class DataLayout;
26  class Value;
27
28  /// \brief Check whether an instruction is likely to be "free" when lowered.
29  bool isInstructionFree(const Instruction *I, const DataLayout *TD = 0);
30
31  /// \brief Check whether a call will lower to something small.
32  ///
33  /// This tests checks whether this callsite will lower to something
34  /// significantly cheaper than a traditional call, often a single
35  /// instruction. Note that if isInstructionFree(CS.getInstruction()) would
36  /// return true, so will this function.
37  bool callIsSmall(ImmutableCallSite CS);
38
39  /// \brief Utility to calculate the size and a few similar metrics for a set
40  /// of basic blocks.
41  struct CodeMetrics {
42    /// \brief True if this function contains a call to setjmp or other functions
43    /// with attribute "returns twice" without having the attribute itself.
44    bool exposesReturnsTwice;
45
46    /// \brief True if this function calls itself.
47    bool isRecursive;
48
49    /// \brief True if this function contains one or more indirect branches.
50    bool containsIndirectBr;
51
52    /// \brief True if this function calls alloca (in the C sense).
53    bool usesDynamicAlloca;
54
55    /// \brief Number of instructions in the analyzed blocks.
56    unsigned NumInsts;
57
58    /// \brief Number of analyzed blocks.
59    unsigned NumBlocks;
60
61    /// \brief Keeps track of basic block code size estimates.
62    DenseMap<const BasicBlock *, unsigned> NumBBInsts;
63
64    /// \brief Keep track of the number of calls to 'big' functions.
65    unsigned NumCalls;
66
67    /// \brief The number of calls to internal functions with a single caller.
68    ///
69    /// These are likely targets for future inlining, likely exposed by
70    /// interleaved devirtualization.
71    unsigned NumInlineCandidates;
72
73    /// \brief How many instructions produce vector values.
74    ///
75    /// The inliner is more aggressive with inlining vector kernels.
76    unsigned NumVectorInsts;
77
78    /// \brief How many 'ret' instructions the blocks contain.
79    unsigned NumRets;
80
81    CodeMetrics() : exposesReturnsTwice(false), isRecursive(false),
82                    containsIndirectBr(false), usesDynamicAlloca(false),
83                    NumInsts(0), NumBlocks(0), NumCalls(0),
84                    NumInlineCandidates(0), NumVectorInsts(0),
85                    NumRets(0) {}
86
87    /// \brief Add information about a block to the current state.
88    void analyzeBasicBlock(const BasicBlock *BB, const DataLayout *TD = 0);
89
90    /// \brief Add information about a function to the current state.
91    void analyzeFunction(Function *F, const DataLayout *TD = 0);
92  };
93}
94
95#endif
96