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