EdgeBundles.cpp revision 360784 
1//===-------- EdgeBundles.cpp - Bundles of CFG edges ----------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file provides the implementation of the EdgeBundles analysis.
10//
11//===----------------------------------------------------------------------===//
12
13#include "llvm/CodeGen/EdgeBundles.h"
14#include "llvm/CodeGen/MachineBasicBlock.h"
15#include "llvm/CodeGen/MachineFunction.h"
16#include "llvm/CodeGen/Passes.h"
17#include "llvm/InitializePasses.h"
18#include "llvm/Support/CommandLine.h"
19#include "llvm/Support/GraphWriter.h"
20#include "llvm/Support/raw_ostream.h"
21
22using namespace llvm;
23
24static cl::opt<bool>
25ViewEdgeBundles("view-edge-bundles", cl::Hidden,
26                cl::desc("Pop up a window to show edge bundle graphs"));
27
28char EdgeBundles::ID = 0;
29
30INITIALIZE_PASS(EdgeBundles, "edge-bundles", "Bundle Machine CFG Edges",
31                /* cfg = */true, /* is_analysis = */ true)
32
33char &llvm::EdgeBundlesID = EdgeBundles::ID;
34
35void EdgeBundles::getAnalysisUsage(AnalysisUsage &AU) const {
36  AU.setPreservesAll();
37  MachineFunctionPass::getAnalysisUsage(AU);
38}
39
40bool 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.
72namespace llvm {
73
74template<>
75raw_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\"" << printMBBReference(MBB) << "\" [ shape=box ]\n"
84      << '\t' << G.getBundle(BB, false) << " -> \"" << printMBBReference(MBB)
85      << "\"\n"
86      << "\t\"" << printMBBReference(MBB) << "\" -> " << G.getBundle(BB, true)
87      << '\n';
88    for (MachineBasicBlock::const_succ_iterator SI = MBB.succ_begin(),
89           SE = MBB.succ_end(); SI != SE; ++SI)
90      O << "\t\"" << printMBBReference(MBB) << "\" -> \""
91        << printMBBReference(**SI) << "\" [ color=lightgray ]\n";
92  }
93  O << "}\n";
94  return O;
95}
96
97} // end namespace llvm
98
99/// view - Visualize the annotated bipartite CFG with Graphviz.
100void EdgeBundles::view() const {
101  ViewGraph(*this, "EdgeBundles");
102}
103