1 //===-------- EdgeBundles.cpp - Bundles of CFG edges ----------------------===//
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 provides the implementation of the EdgeBundles analysis.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/CodeGen/EdgeBundles.h"
15 #include "llvm/CodeGen/MachineBasicBlock.h"
16 #include "llvm/CodeGen/MachineFunction.h"
17 #include "llvm/CodeGen/Passes.h"
18 #include "llvm/Support/CommandLine.h"
19 #include "llvm/Support/GraphWriter.h"
20 #include "llvm/Support/raw_ostream.h"
21 
22 using namespace llvm;
23 
24 static cl::opt<bool>
25 ViewEdgeBundles("view-edge-bundles", cl::Hidden,
26                 cl::desc("Pop up a window to show edge bundle graphs"));
27 
28 char EdgeBundles::ID = 0;
29 
30 INITIALIZE_PASS(EdgeBundles, "edge-bundles", "Bundle Machine CFG Edges",
31                 /* cfg = */true, /* analysis = */ true)
32 
33 char &llvm::EdgeBundlesID = EdgeBundles::ID;
34 
35 void EdgeBundles::getAnalysisUsage(AnalysisUsage &AU) const {
36   AU.setPreservesAll();
37   MachineFunctionPass::getAnalysisUsage(AU);
38 }
39 
40 bool EdgeBundles::runOnMachineFunction(MachineFunction &mf) {
41   MF = &mf;
42   EC.clear();
43   EC.grow(2 * MF->getNumBlockIDs());
44 
45   for (const auto &MBB : *MF) {
46     unsigned OutE = 2 * MBB.getNumber() + 1;
47     // Join the outgoing bundle with the ingoing bundles of all successors.
48     for (MachineBasicBlock::const_succ_iterator SI = MBB.succ_begin(),
49            SE = MBB.succ_end(); SI != SE; ++SI)
50       EC.join(OutE, 2 * (*SI)->getNumber());
51   }
52   EC.compress();
53   if (ViewEdgeBundles)
54     view();
55 
56   // Compute the reverse mapping.
57   Blocks.clear();
58   Blocks.resize(getNumBundles());
59 
60   for (unsigned i = 0, e = MF->getNumBlockIDs(); i != e; ++i) {
61     unsigned b0 = getBundle(i, false);
62     unsigned b1 = getBundle(i, true);
63     Blocks[b0].push_back(i);
64     if (b1 != b0)
65       Blocks[b1].push_back(i);
66   }
67 
68   return false;
69 }
70 
71 /// Specialize WriteGraph, the standard implementation won't work.
72 namespace llvm {
73 
74 template<>
75 raw_ostream &WriteGraph<>(raw_ostream &O, const EdgeBundles &G,
76                           bool ShortNames,
77                           const Twine &Title) {
78   const MachineFunction *MF = G.getMachineFunction();
79 
80   O << "digraph {\n";
81   for (const auto &MBB : *MF) {
82     unsigned BB = MBB.getNumber();
83     O << "\t\"BB#" << BB << "\" [ shape=box ]\n"
84       << '\t' << G.getBundle(BB, false) << " -> \"BB#" << BB << "\"\n"
85       << "\t\"BB#" << BB << "\" -> " << G.getBundle(BB, true) << '\n';
86     for (MachineBasicBlock::const_succ_iterator SI = MBB.succ_begin(),
87            SE = MBB.succ_end(); SI != SE; ++SI)
88       O << "\t\"BB#" << BB << "\" -> \"BB#" << (*SI)->getNumber()
89         << "\" [ color=lightgray ]\n";
90   }
91   O << "}\n";
92   return O;
93 }
94 
95 } // end namespace llvm
96 
97 /// view - Visualize the annotated bipartite CFG with Graphviz.
98 void EdgeBundles::view() const {
99   ViewGraph(*this, "EdgeBundles");
100 }
101