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/BlockFrequencyImpl.h"
16 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
17 #include "llvm/CodeGen/Passes.h"
18 #include "llvm/InitializePasses.h"
19 #include "llvm/Support/CommandLine.h"
20 #include "llvm/Support/Debug.h"
21 #include "llvm/Support/GraphWriter.h"
22 
23 using namespace llvm;
24 
25 #ifndef NDEBUG
26 enum GVDAGType {
27   GVDT_None,
28   GVDT_Fraction,
29   GVDT_Integer
30 };
31 
32 static cl::opt<GVDAGType>
33 ViewMachineBlockFreqPropagationDAG("view-machine-block-freq-propagation-dags",
34                                    cl::Hidden,
35           cl::desc("Pop up a window to show a dag displaying how machine block "
36                    "frequencies propagate through the CFG."),
37           cl::values(
38             clEnumValN(GVDT_None, "none",
39                        "do not display graphs."),
40             clEnumValN(GVDT_Fraction, "fraction", "display a graph using the "
41                        "fractional block frequency representation."),
42             clEnumValN(GVDT_Integer, "integer", "display a graph using the raw "
43                        "integer fractional block frequency representation."),
44             clEnumValEnd));
45 
46 namespace llvm {
47 
48 template <>
49 struct GraphTraits<MachineBlockFrequencyInfo *> {
50   typedef const MachineBasicBlock NodeType;
51   typedef MachineBasicBlock::const_succ_iterator ChildIteratorType;
52   typedef MachineFunction::const_iterator nodes_iterator;
53 
54   static inline
55   const NodeType *getEntryNode(const MachineBlockFrequencyInfo *G) {
56     return G->getFunction()->begin();
57   }
58 
59   static ChildIteratorType child_begin(const NodeType *N) {
60     return N->succ_begin();
61   }
62 
63   static ChildIteratorType child_end(const NodeType *N) {
64     return N->succ_end();
65   }
66 
67   static nodes_iterator nodes_begin(const MachineBlockFrequencyInfo *G) {
68     return G->getFunction()->begin();
69   }
70 
71   static nodes_iterator nodes_end(const MachineBlockFrequencyInfo *G) {
72     return G->getFunction()->end();
73   }
74 };
75 
76 template<>
77 struct DOTGraphTraits<MachineBlockFrequencyInfo*> :
78     public DefaultDOTGraphTraits {
79   explicit DOTGraphTraits(bool isSimple=false) :
80     DefaultDOTGraphTraits(isSimple) {}
81 
82   static std::string getGraphName(const MachineBlockFrequencyInfo *G) {
83     return G->getFunction()->getName();
84   }
85 
86   std::string getNodeLabel(const MachineBasicBlock *Node,
87                            const MachineBlockFrequencyInfo *Graph) {
88     std::string Result;
89     raw_string_ostream OS(Result);
90 
91     OS << Node->getName().str() << ":";
92     switch (ViewMachineBlockFreqPropagationDAG) {
93     case GVDT_Fraction:
94       Graph->printBlockFreq(OS, Node);
95       break;
96     case GVDT_Integer:
97       OS << Graph->getBlockFreq(Node).getFrequency();
98       break;
99     case GVDT_None:
100       llvm_unreachable("If we are not supposed to render a graph we should "
101                        "never reach this point.");
102     }
103 
104     return Result;
105   }
106 };
107 
108 
109 } // end namespace llvm
110 #endif
111 
112 INITIALIZE_PASS_BEGIN(MachineBlockFrequencyInfo, "machine-block-freq",
113                       "Machine Block Frequency Analysis", true, true)
114 INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
115 INITIALIZE_PASS_END(MachineBlockFrequencyInfo, "machine-block-freq",
116                     "Machine Block Frequency Analysis", true, true)
117 
118 char MachineBlockFrequencyInfo::ID = 0;
119 
120 
121 MachineBlockFrequencyInfo::
122 MachineBlockFrequencyInfo() :MachineFunctionPass(ID) {
123   initializeMachineBlockFrequencyInfoPass(*PassRegistry::getPassRegistry());
124   MBFI = new BlockFrequencyImpl<MachineBasicBlock, MachineFunction,
125                                 MachineBranchProbabilityInfo>();
126 }
127 
128 MachineBlockFrequencyInfo::~MachineBlockFrequencyInfo() {
129   delete MBFI;
130 }
131 
132 void MachineBlockFrequencyInfo::getAnalysisUsage(AnalysisUsage &AU) const {
133   AU.addRequired<MachineBranchProbabilityInfo>();
134   AU.setPreservesAll();
135   MachineFunctionPass::getAnalysisUsage(AU);
136 }
137 
138 bool MachineBlockFrequencyInfo::runOnMachineFunction(MachineFunction &F) {
139   MachineBranchProbabilityInfo &MBPI =
140     getAnalysis<MachineBranchProbabilityInfo>();
141   MBFI->doFunction(&F, &MBPI);
142 #ifndef NDEBUG
143   if (ViewMachineBlockFreqPropagationDAG != GVDT_None) {
144     view();
145   }
146 #endif
147   return false;
148 }
149 
150 /// Pop up a ghostview window with the current block frequency propagation
151 /// rendered using dot.
152 void MachineBlockFrequencyInfo::view() const {
153 // This code is only for debugging.
154 #ifndef NDEBUG
155   ViewGraph(const_cast<MachineBlockFrequencyInfo *>(this),
156             "MachineBlockFrequencyDAGs");
157 #else
158   errs() << "MachineBlockFrequencyInfo::view is only available in debug builds "
159     "on systems with Graphviz or gv!\n";
160 #endif // NDEBUG
161 }
162 
163 BlockFrequency MachineBlockFrequencyInfo::
164 getBlockFreq(const MachineBasicBlock *MBB) const {
165   return MBFI->getBlockFreq(MBB);
166 }
167 
168 MachineFunction *MachineBlockFrequencyInfo::getFunction() const {
169   return MBFI->Fn;
170 }
171 
172 raw_ostream &
173 MachineBlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
174                                           const BlockFrequency Freq) const {
175   return MBFI->printBlockFreq(OS, Freq);
176 }
177 
178 raw_ostream &
179 MachineBlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
180                                           const MachineBasicBlock *MBB) const {
181   return MBFI->printBlockFreq(OS, MBB);
182 }
183 
184 uint64_t MachineBlockFrequencyInfo::getEntryFreq() const {
185   return MBFI->getEntryFreq();
186 }
187