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