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      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 (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, 0);
     61     unsigned b1 = getBundle(i, 1);
     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 template<>
     73 raw_ostream &WriteGraph<>(raw_ostream &O, const EdgeBundles &G,
     74                           bool ShortNames,
     75                           const Twine &Title) {
     76   const MachineFunction *MF = G.getMachineFunction();
     77 
     78   O << "digraph {\n";
     79   for (const auto &MBB : *MF) {
     80     unsigned BB = MBB.getNumber();
     81     O << "\t\"BB#" << BB << "\" [ shape=box ]\n"
     82       << '\t' << G.getBundle(BB, false) << " -> \"BB#" << BB << "\"\n"
     83       << "\t\"BB#" << BB << "\" -> " << G.getBundle(BB, true) << '\n';
     84     for (MachineBasicBlock::const_succ_iterator SI = MBB.succ_begin(),
     85            SE = MBB.succ_end(); SI != SE; ++SI)
     86       O << "\t\"BB#" << BB << "\" -> \"BB#" << (*SI)->getNumber()
     87         << "\" [ color=lightgray ]\n";
     88   }
     89   O << "}\n";
     90   return O;
     91 }
     92 }
     93 
     94 /// view - Visualize the annotated bipartite CFG with Graphviz.
     95 void EdgeBundles::view() const {
     96   ViewGraph(*this, "EdgeBundles");
     97 }
     98