VirtRegIndependenceGraph.cc

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/*
    Copyright (c) 2002-2010 Tampere University.
 
    This file is part of TTA-Based Codesign Environment (TCE).
 
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/**
 * @file VirtRegIndependenceGraph.cc
 *
 * @author Pekka Jääskeläinen 2010
 * @note rating: red
 */
#include "hash_set.hh"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/Function.h"
#include "boost/graph/graphviz.hpp"
#include "VirtRegMap.h"
#include "VirtRegIndependenceGraph.hh"
#include "MachineInstrDDG.hh"
#include "MapTools.hh"
 
// #define DEBUG_FDPG
/**
 * Constructs the graph from an LLVM MachineFunction.
 */
VirtRegIndependenceGraph::VirtRegIndependenceGraph(
    llvm::MachineFunction& mf, llvm::VirtRegMap& vrm) :
    vrm_(vrm) {
 
    MachineInstrDDG tddg(*vrm.TII, *vrm.TRI, mf,  true); 
    MachineInstrDDG::RegisterSet regs = tddg.allRegisters();
#ifdef DEBUG_FDPG    
    Application::logStream() << "building FDPG" << std::endl;
#endif
    // add the virtual regs as nodes 
    for (MachineInstrDDG::RegisterSet::const_iterator i = regs.begin(); 
         i != regs.end(); ++i) {
        MachineInstrDDG::Register reg = *i;
 
        if (llvm::TargetRegisterInfo::isPhysicalRegister(reg)) 
            continue;
 
        addNode(reg);
    }
 
#ifdef DEBUG_FDPG
    Application::logStream() << "finding TDDG paths" << std::endl;
#endif
    // this should speed up hasPath() as all known paths are
    // computed only once
    tddg.findAllPaths();
#ifdef DEBUG_FDPG
    Application::logStream() << "finding TDDG paths done" << std::endl;
#endif
    MachineInstrDDG::RegisterSet unhandledRegs = regs;
    for (MachineInstrDDG::RegisterSet::const_iterator i = regs.begin(); 
         i != regs.end(); ++i) {
        MachineInstrDDG::Register reg = *i;
        MIDDGNode* instrA = tddg.vregDefiner(reg);
        for (MachineInstrDDG::RegisterSet::const_iterator u = 
                 unhandledRegs.begin(); 
             u != unhandledRegs.end(); ++u) {
            MachineInstrDDG::Register otherReg = *u;
            MIDDGNode* instrB = tddg.vregDefiner(otherReg);
            if (instrB == NULL) {
                Application::logStream() 
                    << "could not find definer for " << otherReg << std::endl;
                abortWithError("Cannot proceed.");
            }
            if (!tddg.hasPath(*instrA, *instrB) &&
                !tddg.hasPath(*instrB, *instrA)) {
                addEdge(reg, otherReg);
            }
        }
        unhandledRegs.erase(reg);
    }
#ifdef DEBUG_FDPG
    Application::logStream() << "building FDPG done" << std::endl;
#endif
#if 0
    // this is exremely slow as there are often huge number of edges in FDPG
    std::string s(mf.getFunction()->getNameStr() + "_fdpg.dot");
    std::ofstream o(s.c_str());
    boost::write_graphviz(
        o, fdpg_, make_label_writer(get(boost::vertex_name, fdpg_)));
#endif
}
 
/** 
 * Returns the number of new false deps introduced by assigning the given
 * physical register to the given live interval.
 */
int
VirtRegIndependenceGraph::newFalseDepsFromAssign(
    llvm::LiveInterval* interval, MachineInstrDDG::Register physReg) {
 
    if (llvm::TargetRegisterInfo::isPhysicalRegister(interval->reg)) {
        Application::logStream() 
            << "Should not see assigned intervals here. Got: " 
            << interval->reg
            << std::endl;
        return true;
    }
 
    // look at all connected live Intervals in the FDPG and see if they have
    // been assigned the same PhysReg we are trying to assign this one
 
    int foundFalseDeps = 0;
    std::set<MachineInstrDDG::Register> adjacent = adjacentNodes(interval->reg);
    for (std::set<MachineInstrDDG::Register>::const_iterator i = 
             adjacent.begin(); i != adjacent.end(); ++i) {
        MachineInstrDDG::Register virtReg = *i;
        bool isPhysRegAssigned = vrm_.hasPhys(virtReg);
        if (isPhysRegAssigned && vrm_.getPhys(virtReg) == physReg) {
            ++foundFalseDeps;
        }
    }
    return foundFalseDeps;
}
 
void 
VirtRegIndependenceGraph::addNode(MachineInstrDDG::Register virtReg) {    
    vertexMap_[virtReg] = boost::add_vertex(fdpg_);
    vregMap_[vertexMap_[virtReg]] = virtReg;
    boost::put(boost::vertex_name, fdpg_, vertexMap_[virtReg], virtReg);
}
 
void 
VirtRegIndependenceGraph::addEdge(
    MachineInstrDDG::Register nodeA, MachineInstrDDG::Register nodeB) {
    boost::add_edge(vertexMap_[nodeA], vertexMap_[nodeB], fdpg_);
}
 
std::set<MachineInstrDDG::Register>
VirtRegIndependenceGraph::adjacentNodes(MachineInstrDDG::Register node) {
    std::set<MachineInstrDDG::Register> nodes;
 
    boost::graph_traits<FDPG>::adjacency_iterator i, end;
    i = boost::adjacent_vertices(vertexMap_[node], fdpg_).first;
    end = boost::adjacent_vertices(vertexMap_[node], fdpg_).second;
    for (; i != end; ++i) {
        MachineInstrDDG::Register virtReg = vregMap_[*i];
        nodes.insert(virtReg);
    }
 
    return nodes;
}