llvm/lib/CodeGen/EdgeBundles.cpp

   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/ADT/Twine.h"
  15 #include "llvm/CodeGen/MachineBasicBlock.h"
  16 #include "llvm/CodeGen/MachineFunction.h"
  17 #include "llvm/CodeGen/Passes.h"
  18 #include "llvm/InitializePasses.h"
  19 #include "llvm/Support/CommandLine.h"
  20 #include "llvm/Support/GraphWriter.h"
  21 #include "llvm/Support/raw_ostream.h"
  22
  23 using namespace llvm;
  24
  25 static cl::opt<bool>
  26 ViewEdgeBundles("view-edge-bundles", cl::Hidden,
  27                 cl::desc("Pop up a window to show edge bundle graphs"));
  28
  29 char EdgeBundles::ID = 0;
  30
  31 INITIALIZE_PASS(EdgeBundles, "edge-bundles", "Bundle Machine CFG Edges",
  32                 /* cfg = */true, /* is_analysis = */ true)
  33
  34 char &llvm::EdgeBundlesID = EdgeBundles::ID;
  35
  36 void EdgeBundles::getAnalysisUsage(AnalysisUsage &AU) const {
  37   AU.setPreservesAll();
  38   MachineFunctionPass::getAnalysisUsage(AU);
  39 }
  40
  41 bool EdgeBundles::runOnMachineFunction(MachineFunction &mf) {
  42   MF = &mf;
  43   EC.clear();
  44   EC.grow(2 * MF->getNumBlockIDs());
  45
  46   for (const auto &MBB : *MF) {
  47     unsigned OutE = 2 * MBB.getNumber() + 1;
  48     // Join the outgoing bundle with the ingoing bundles of all successors.
  49     for (const MachineBasicBlock *Succ : MBB.successors())
  50       EC.join(OutE, 2 * Succ->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 namespace llvm {
  72
  73 /// Specialize WriteGraph, the standard implementation won't work.
  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\"" << 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 (const MachineBasicBlock *Succ : MBB.successors())
  89       O << "\t\"" << printMBBReference(MBB) << "\" -> \""
  90         << printMBBReference(*Succ) << "\" [ color=lightgray ]\n";
  91   }
  92   O << "}\n";
  93   return O;
  94 }
  95
  96 } // end namespace llvm
  97
  98 /// view - Visualize the annotated bipartite CFG with Graphviz.
  99 void EdgeBundles::view() const {
 100   ViewGraph(*this, "EdgeBundles");
 101 }