1 //===- MachineBlockFrequencyInfo.cpp - MBB Frequency Analysis -------------===//
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 // Loops should be simplified before this analysis.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
15 #include "llvm/Analysis/BlockFrequencyInfoImpl.h"
16 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
17 #include "llvm/CodeGen/MachineFunction.h"
18 #include "llvm/CodeGen/MachineLoopInfo.h"
19 #include "llvm/CodeGen/Passes.h"
20 #include "llvm/InitializePasses.h"
21 #include "llvm/Support/CommandLine.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Support/GraphWriter.h"
24 
25 using namespace llvm;
26 
27 #define DEBUG_TYPE "block-freq"
28 
29 #ifndef NDEBUG
30 enum GVDAGType { GVDT_None, GVDT_Fraction, GVDT_Integer };
31 
32 static cl::opt<GVDAGType> ViewMachineBlockFreqPropagationDAG(
33     "view-machine-block-freq-propagation-dags", cl::Hidden,
34     cl::desc("Pop up a window to show a dag displaying how machine block "
35              "frequencies propagate through the CFG."),
36     cl::values(clEnumValN(GVDT_None, "none", "do not display graphs."),
37                clEnumValN(GVDT_Fraction, "fraction",
38                           "display a graph using the "
39                           "fractional block frequency representation."),
40                clEnumValN(GVDT_Integer, "integer",
41                           "display a graph using the raw "
42                           "integer fractional block frequency representation."),
43                clEnumValEnd));
44 
45 namespace llvm {
46 
47 template <> struct GraphTraits<MachineBlockFrequencyInfo *> {
48   typedef const MachineBasicBlock NodeType;
49   typedef MachineBasicBlock::const_succ_iterator ChildIteratorType;
50   typedef MachineFunction::const_iterator nodes_iterator;
51 
52   static inline const NodeType *
53   getEntryNode(const MachineBlockFrequencyInfo *G) {
54     return &G->getFunction()->front();
55   }
56 
57   static ChildIteratorType child_begin(const NodeType *N) {
58     return N->succ_begin();
59   }
60 
61   static ChildIteratorType child_end(const NodeType *N) {
62     return N->succ_end();
63   }
64 
65   static nodes_iterator nodes_begin(const MachineBlockFrequencyInfo *G) {
66     return G->getFunction()->begin();
67   }
68 
69   static nodes_iterator nodes_end(const MachineBlockFrequencyInfo *G) {
70     return G->getFunction()->end();
71   }
72 };
73 
74 template <>
75 struct DOTGraphTraits<MachineBlockFrequencyInfo *>
76     : public DefaultDOTGraphTraits {
77   explicit DOTGraphTraits(bool isSimple = false)
78       : DefaultDOTGraphTraits(isSimple) {}
79 
80   static std::string getGraphName(const MachineBlockFrequencyInfo *G) {
81     return G->getFunction()->getName();
82   }
83 
84   std::string getNodeLabel(const MachineBasicBlock *Node,
85                            const MachineBlockFrequencyInfo *Graph) {
86     std::string Result;
87     raw_string_ostream OS(Result);
88 
89     OS << Node->getName().str() << ":";
90     switch (ViewMachineBlockFreqPropagationDAG) {
91     case GVDT_Fraction:
92       Graph->printBlockFreq(OS, Node);
93       break;
94     case GVDT_Integer:
95       OS << Graph->getBlockFreq(Node).getFrequency();
96       break;
97     case GVDT_None:
98       llvm_unreachable("If we are not supposed to render a graph we should "
99                        "never reach this point.");
100     }
101 
102     return Result;
103   }
104 };
105 
106 } // end namespace llvm
107 #endif
108 
109 INITIALIZE_PASS_BEGIN(MachineBlockFrequencyInfo, "machine-block-freq",
110                       "Machine Block Frequency Analysis", true, true)
111 INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
112 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
113 INITIALIZE_PASS_END(MachineBlockFrequencyInfo, "machine-block-freq",
114                     "Machine Block Frequency Analysis", true, true)
115 
116 char MachineBlockFrequencyInfo::ID = 0;
117 
118 MachineBlockFrequencyInfo::MachineBlockFrequencyInfo()
119     : MachineFunctionPass(ID) {
120   initializeMachineBlockFrequencyInfoPass(*PassRegistry::getPassRegistry());
121 }
122 
123 MachineBlockFrequencyInfo::~MachineBlockFrequencyInfo() {}
124 
125 void MachineBlockFrequencyInfo::getAnalysisUsage(AnalysisUsage &AU) const {
126   AU.addRequired<MachineBranchProbabilityInfo>();
127   AU.addRequired<MachineLoopInfo>();
128   AU.setPreservesAll();
129   MachineFunctionPass::getAnalysisUsage(AU);
130 }
131 
132 bool MachineBlockFrequencyInfo::runOnMachineFunction(MachineFunction &F) {
133   MachineBranchProbabilityInfo &MBPI =
134       getAnalysis<MachineBranchProbabilityInfo>();
135   MachineLoopInfo &MLI = getAnalysis<MachineLoopInfo>();
136   if (!MBFI)
137     MBFI.reset(new ImplType);
138   MBFI->calculate(F, MBPI, MLI);
139 #ifndef NDEBUG
140   if (ViewMachineBlockFreqPropagationDAG != GVDT_None) {
141     view();
142   }
143 #endif
144   return false;
145 }
146 
147 void MachineBlockFrequencyInfo::releaseMemory() { MBFI.reset(); }
148 
149 /// Pop up a ghostview window with the current block frequency propagation
150 /// rendered using dot.
151 void MachineBlockFrequencyInfo::view() const {
152 // This code is only for debugging.
153 #ifndef NDEBUG
154   ViewGraph(const_cast<MachineBlockFrequencyInfo *>(this),
155             "MachineBlockFrequencyDAGs");
156 #else
157   errs() << "MachineBlockFrequencyInfo::view is only available in debug builds "
158             "on systems with Graphviz or gv!\n";
159 #endif // NDEBUG
160 }
161 
162 BlockFrequency
163 MachineBlockFrequencyInfo::getBlockFreq(const MachineBasicBlock *MBB) const {
164   return MBFI ? MBFI->getBlockFreq(MBB) : 0;
165 }
166 
167 const MachineFunction *MachineBlockFrequencyInfo::getFunction() const {
168   return MBFI ? MBFI->getFunction() : nullptr;
169 }
170 
171 raw_ostream &
172 MachineBlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
173                                           const BlockFrequency Freq) const {
174   return MBFI ? MBFI->printBlockFreq(OS, Freq) : OS;
175 }
176 
177 raw_ostream &
178 MachineBlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
179                                           const MachineBasicBlock *MBB) const {
180   return MBFI ? MBFI->printBlockFreq(OS, MBB) : OS;
181 }
182 
183 uint64_t MachineBlockFrequencyInfo::getEntryFreq() const {
184   return MBFI ? MBFI->getEntryFreq() : 0;
185 }
186