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/CodeGen/MachineBasicBlock.h"
  15 #include "llvm/CodeGen/MachineFunction.h"
  16 #include "llvm/CodeGen/Passes.h"
  17 #include "llvm/Support/CommandLine.h"
  18 #include "llvm/Support/GraphWriter.h"
  19 #include "llvm/Support/raw_ostream.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, /* is_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 (const auto &MBB : *MF) {
  45     unsigned OutE = 2 * MBB.getNumber() + 1;
  46     // Join the outgoing bundle with the ingoing bundles of all successors.
  47     for (MachineBasicBlock::const_succ_iterator SI = MBB.succ_begin(),
  48            SE = MBB.succ_end(); SI != SE; ++SI)
  49       EC.join(OutE, 2 * (*SI)->getNumber());
  50   }
  51   EC.compress();
  52   if (ViewEdgeBundles)
  53     view();
  54
  55   // Compute the reverse mapping.
  56   Blocks.clear();
  57   Blocks.resize(getNumBundles());
  58
  59   for (unsigned i = 0, e = MF->getNumBlockIDs(); i != e; ++i) {
  60     unsigned b0 = getBundle(i, false);
  61     unsigned b1 = getBundle(i, true);
  62     Blocks[b0].push_back(i);
  63     if (b1 != b0)
  64       Blocks[b1].push_back(i);
  65   }
  66
  67   return false;
  68 }
  69
  70 /// Specialize WriteGraph, the standard implementation won't work.
  71 namespace llvm {
  72
  73 template<>
  74 raw_ostream &WriteGraph<>(raw_ostream &O, const EdgeBundles &G,
  75                           bool ShortNames,
  76                           const Twine &Title) {
  77   const MachineFunction *MF = G.getMachineFunction();
  78
  79   O << "digraph {\n";
  80   for (const auto &MBB : *MF) {
  81     unsigned BB = MBB.getNumber();
  82     O << "\t\"" << printMBBReference(MBB) << "\" [ shape=box ]\n"
  83       << '\t' << G.getBundle(BB, false) << " -> \"" << printMBBReference(MBB)
  84       << "\"\n"
  85       << "\t\"" << printMBBReference(MBB) << "\" -> " << G.getBundle(BB, true)
  86       << '\n';
  87     for (MachineBasicBlock::const_succ_iterator SI = MBB.succ_begin(),
  88            SE = MBB.succ_end(); SI != SE; ++SI)
  89       O << "\t\"" << printMBBReference(MBB) << "\" -> \""
  90         << printMBBReference(**SI) << "\" [ 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 }