CodeMetrics.h revision a5157e68d183e1bdf010e94a15dc0c44b65f889b 
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 {
22class BasicBlock;
23class Function;
24class Instruction;
25class DataLayout;
26class TargetTransformInfo;
27class Value;
28
29/// \brief Check whether a call will lower to something small.
30///
31/// This tests checks whether this callsite will lower to something
32/// significantly cheaper than a traditional call, often a single
33/// instruction. Note that if isInstructionFree(CS.getInstruction()) would
34/// return true, so will this function.
35bool callIsSmall(ImmutableCallSite CS);
36
37/// \brief Utility to calculate the size and a few similar metrics for a set
38/// of basic blocks.
39struct CodeMetrics {
40  /// \brief True if this function contains a call to setjmp or other functions
41  /// with attribute "returns twice" without having the attribute itself.
42  bool exposesReturnsTwice;
43
44  /// \brief True if this function calls itself.
45  bool isRecursive;
46
47  /// \brief True if this function cannot be duplicated.
48  ///
49  /// True if this function contains one or more indirect branches, or it contains
50  /// one or more 'noduplicate' instructions.
51  bool notDuplicatable;
52
53  /// \brief True if this function calls alloca (in the C sense).
54  bool usesDynamicAlloca;
55
56  /// \brief Number of instructions in the analyzed blocks.
57  unsigned NumInsts;
58
59  /// \brief Number of analyzed blocks.
60  unsigned NumBlocks;
61
62  /// \brief Keeps track of basic block code size estimates.
63  DenseMap<const BasicBlock *, unsigned> NumBBInsts;
64
65  /// \brief Keep track of the number of calls to 'big' functions.
66  unsigned NumCalls;
67
68  /// \brief The number of calls to internal functions with a single caller.
69  ///
70  /// These are likely targets for future inlining, likely exposed by
71  /// interleaved devirtualization.
72  unsigned NumInlineCandidates;
73
74  /// \brief How many instructions produce vector values.
75  ///
76  /// The inliner is more aggressive with inlining vector kernels.
77  unsigned NumVectorInsts;
78
79  /// \brief How many 'ret' instructions the blocks contain.
80  unsigned NumRets;
81
82  CodeMetrics()
83      : exposesReturnsTwice(false), isRecursive(false), notDuplicatable(false),
84        usesDynamicAlloca(false), NumInsts(0), NumBlocks(0), NumCalls(0),
85        NumInlineCandidates(0), NumVectorInsts(0), NumRets(0) {}
86
87  /// \brief Add information about a block to the current state.
88  void analyzeBasicBlock(const BasicBlock *BB, const TargetTransformInfo &TTI);
89};
90
91}
92
93#endif
94