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292 lines
8.7 KiB
C++
292 lines
8.7 KiB
C++
// $Id$ -*-C++-*-
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//***************************************************************************
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// File:
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// SchedPriorities.h
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//
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// Purpose:
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// Encapsulate heuristics for instruction scheduling.
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//
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// Strategy:
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// Priority ordering rules:
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// (1) Max delay, which is the order of the heap S.candsAsHeap.
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// (2) Instruction that frees up a register.
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// (3) Instruction that has the maximum number of dependent instructions.
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// Note that rules 2 and 3 are only used if issue conflicts prevent
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// choosing a higher priority instruction by rule 1.
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//
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// History:
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// 7/30/01 - Vikram Adve - Created
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//**************************************************************************/
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#include "SchedPriorities.h"
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#include "llvm/Analysis/LiveVar/FunctionLiveVarInfo.h"
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#include "llvm/Support/CFG.h"
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#include "Support/PostOrderIterator.h"
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using std::cerr;
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SchedPriorities::SchedPriorities(const Function *, const SchedGraph *G,
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FunctionLiveVarInfo &LVI)
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: curTime(0), graph(G), methodLiveVarInfo(LVI),
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nodeDelayVec(G->getNumNodes(), INVALID_LATENCY), // make errors obvious
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earliestForNode(G->getNumNodes(), 0),
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earliestReadyTime(0),
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nextToTry(candsAsHeap.begin()) {
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computeDelays(graph);
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}
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void
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SchedPriorities::initialize()
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{
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initializeReadyHeap(graph);
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}
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void
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SchedPriorities::computeDelays(const SchedGraph* graph)
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{
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po_iterator<const SchedGraph*> poIter = po_begin(graph), poEnd =po_end(graph);
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for ( ; poIter != poEnd; ++poIter)
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{
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const SchedGraphNode* node = *poIter;
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cycles_t nodeDelay;
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if (node->beginOutEdges() == node->endOutEdges())
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nodeDelay = node->getLatency();
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else
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{
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// Iterate over the out-edges of the node to compute delay
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nodeDelay = 0;
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for (SchedGraphNode::const_iterator E=node->beginOutEdges();
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E != node->endOutEdges(); ++E)
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{
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cycles_t sinkDelay = getNodeDelayRef((*E)->getSink());
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nodeDelay = std::max(nodeDelay, sinkDelay + (*E)->getMinDelay());
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}
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}
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getNodeDelayRef(node) = nodeDelay;
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}
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}
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void
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SchedPriorities::initializeReadyHeap(const SchedGraph* graph)
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{
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const SchedGraphNode* graphRoot = graph->getRoot();
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assert(graphRoot->getMachineInstr() == NULL && "Expect dummy root");
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// Insert immediate successors of dummy root, which are the actual roots
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sg_succ_const_iterator SEnd = succ_end(graphRoot);
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for (sg_succ_const_iterator S = succ_begin(graphRoot); S != SEnd; ++S)
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this->insertReady(*S);
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#undef TEST_HEAP_CONVERSION
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#ifdef TEST_HEAP_CONVERSION
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cerr << "Before heap conversion:\n";
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copy(candsAsHeap.begin(), candsAsHeap.end(),
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ostream_iterator<NodeDelayPair*>(cerr,"\n"));
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#endif
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candsAsHeap.makeHeap();
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nextToTry = candsAsHeap.begin();
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#ifdef TEST_HEAP_CONVERSION
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cerr << "After heap conversion:\n";
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copy(candsAsHeap.begin(), candsAsHeap.end(),
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ostream_iterator<NodeDelayPair*>(cerr,"\n"));
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#endif
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}
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void
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SchedPriorities::insertReady(const SchedGraphNode* node)
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{
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candsAsHeap.insert(node, nodeDelayVec[node->getNodeId()]);
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candsAsSet.insert(node);
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mcands.clear(); // ensure reset choices is called before any more choices
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earliestReadyTime = std::min(earliestReadyTime,
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earliestForNode[node->getNodeId()]);
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if (SchedDebugLevel >= Sched_PrintSchedTrace)
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{
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cerr << " Node " << node->getNodeId() << " will be ready in Cycle "
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<< earliestForNode[node->getNodeId()] << "; "
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<< " Delay = " <<(long)getNodeDelayRef(node) << "; Instruction: \n";
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cerr << " " << *node->getMachineInstr() << "\n";
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}
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}
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void
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SchedPriorities::issuedReadyNodeAt(cycles_t curTime,
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const SchedGraphNode* node)
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{
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candsAsHeap.removeNode(node);
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candsAsSet.erase(node);
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mcands.clear(); // ensure reset choices is called before any more choices
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if (earliestReadyTime == getEarliestForNodeRef(node))
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{// earliestReadyTime may have been due to this node, so recompute it
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earliestReadyTime = HUGE_LATENCY;
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for (NodeHeap::const_iterator I=candsAsHeap.begin();
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I != candsAsHeap.end(); ++I)
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if (candsAsHeap.getNode(I))
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earliestReadyTime = std::min(earliestReadyTime,
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getEarliestForNodeRef(candsAsHeap.getNode(I)));
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}
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// Now update ready times for successors
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for (SchedGraphNode::const_iterator E=node->beginOutEdges();
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E != node->endOutEdges(); ++E)
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{
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cycles_t& etime = getEarliestForNodeRef((*E)->getSink());
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etime = std::max(etime, curTime + (*E)->getMinDelay());
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}
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}
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//----------------------------------------------------------------------
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// Priority ordering rules:
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// (1) Max delay, which is the order of the heap S.candsAsHeap.
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// (2) Instruction that frees up a register.
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// (3) Instruction that has the maximum number of dependent instructions.
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// Note that rules 2 and 3 are only used if issue conflicts prevent
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// choosing a higher priority instruction by rule 1.
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//----------------------------------------------------------------------
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inline int
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SchedPriorities::chooseByRule1(std::vector<candIndex>& mcands)
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{
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return (mcands.size() == 1)? 0 // only one choice exists so take it
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: -1; // -1 indicates multiple choices
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}
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inline int
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SchedPriorities::chooseByRule2(std::vector<candIndex>& mcands)
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{
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assert(mcands.size() >= 1 && "Should have at least one candidate here.");
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for (unsigned i=0, N = mcands.size(); i < N; i++)
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if (instructionHasLastUse(methodLiveVarInfo,
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candsAsHeap.getNode(mcands[i])))
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return i;
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return -1;
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}
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inline int
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SchedPriorities::chooseByRule3(std::vector<candIndex>& mcands)
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{
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assert(mcands.size() >= 1 && "Should have at least one candidate here.");
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int maxUses = candsAsHeap.getNode(mcands[0])->getNumOutEdges();
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int indexWithMaxUses = 0;
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for (unsigned i=1, N = mcands.size(); i < N; i++)
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{
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int numUses = candsAsHeap.getNode(mcands[i])->getNumOutEdges();
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if (numUses > maxUses)
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{
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maxUses = numUses;
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indexWithMaxUses = i;
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}
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}
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return indexWithMaxUses;
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}
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const SchedGraphNode*
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SchedPriorities::getNextHighest(const SchedulingManager& S,
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cycles_t curTime)
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{
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int nextIdx = -1;
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const SchedGraphNode* nextChoice = NULL;
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if (mcands.size() == 0)
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findSetWithMaxDelay(mcands, S);
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while (nextIdx < 0 && mcands.size() > 0)
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{
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nextIdx = chooseByRule1(mcands); // rule 1
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if (nextIdx == -1)
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nextIdx = chooseByRule2(mcands); // rule 2
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if (nextIdx == -1)
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nextIdx = chooseByRule3(mcands); // rule 3
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if (nextIdx == -1)
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nextIdx = 0; // default to first choice by delays
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// We have found the next best candidate. Check if it ready in
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// the current cycle, and if it is feasible.
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// If not, remove it from mcands and continue. Refill mcands if
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// it becomes empty.
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nextChoice = candsAsHeap.getNode(mcands[nextIdx]);
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if (getEarliestForNodeRef(nextChoice) > curTime
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|| ! instrIsFeasible(S, nextChoice->getMachineInstr()->getOpCode()))
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{
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mcands.erase(mcands.begin() + nextIdx);
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nextIdx = -1;
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if (mcands.size() == 0)
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findSetWithMaxDelay(mcands, S);
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}
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}
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if (nextIdx >= 0)
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{
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mcands.erase(mcands.begin() + nextIdx);
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return nextChoice;
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}
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else
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return NULL;
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}
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void
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SchedPriorities::findSetWithMaxDelay(std::vector<candIndex>& mcands,
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const SchedulingManager& S)
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{
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if (mcands.size() == 0 && nextToTry != candsAsHeap.end())
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{ // out of choices at current maximum delay;
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// put nodes with next highest delay in mcands
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candIndex next = nextToTry;
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cycles_t maxDelay = candsAsHeap.getDelay(next);
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for (; next != candsAsHeap.end()
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&& candsAsHeap.getDelay(next) == maxDelay; ++next)
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mcands.push_back(next);
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nextToTry = next;
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if (SchedDebugLevel >= Sched_PrintSchedTrace)
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{
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cerr << " Cycle " << (long)getTime() << ": "
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<< "Next highest delay = " << (long)maxDelay << " : "
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<< mcands.size() << " Nodes with this delay: ";
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for (unsigned i=0; i < mcands.size(); i++)
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cerr << candsAsHeap.getNode(mcands[i])->getNodeId() << ", ";
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cerr << "\n";
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}
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}
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}
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bool
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SchedPriorities::instructionHasLastUse(FunctionLiveVarInfo &LVI,
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const SchedGraphNode* graphNode) {
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const MachineInstr *MI = graphNode->getMachineInstr();
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std::hash_map<const MachineInstr*, bool>::const_iterator
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ui = lastUseMap.find(MI);
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if (ui != lastUseMap.end())
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return ui->second;
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// else check if instruction is a last use and save it in the hash_map
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bool hasLastUse = false;
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const BasicBlock* bb = graphNode->getBB();
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const ValueSet &LVs = LVI.getLiveVarSetBeforeMInst(MI, bb);
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for (MachineInstr::const_val_op_iterator OI = MI->begin(), OE = MI->end();
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OI != OE; ++OI)
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if (!LVs.count(*OI)) {
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hasLastUse = true;
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break;
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}
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return lastUseMap[MI] = hasLastUse;
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}
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