mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-09-07 01:54:50 +00:00
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@59445 91177308-0d34-0410-b5e6-96231b3b80d8
166 lines
6.0 KiB
C++
166 lines
6.0 KiB
C++
//===---- LatencyPriorityQueue.cpp - A latency-oriented priority queue ----===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements the LatencyPriorityQueue class, which is a
|
|
// SchedulingPriorityQueue that schedules using latency information to
|
|
// reduce the length of the critical path through the basic block.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#define DEBUG_TYPE "scheduler"
|
|
#include "LatencyPriorityQueue.h"
|
|
#include "llvm/Support/Debug.h"
|
|
using namespace llvm;
|
|
|
|
bool latency_sort::operator()(const SUnit *LHS, const SUnit *RHS) const {
|
|
unsigned LHSNum = LHS->NodeNum;
|
|
unsigned RHSNum = RHS->NodeNum;
|
|
|
|
// The most important heuristic is scheduling the critical path.
|
|
unsigned LHSLatency = PQ->getLatency(LHSNum);
|
|
unsigned RHSLatency = PQ->getLatency(RHSNum);
|
|
if (LHSLatency < RHSLatency) return true;
|
|
if (LHSLatency > RHSLatency) return false;
|
|
|
|
// After that, if two nodes have identical latencies, look to see if one will
|
|
// unblock more other nodes than the other.
|
|
unsigned LHSBlocked = PQ->getNumSolelyBlockNodes(LHSNum);
|
|
unsigned RHSBlocked = PQ->getNumSolelyBlockNodes(RHSNum);
|
|
if (LHSBlocked < RHSBlocked) return true;
|
|
if (LHSBlocked > RHSBlocked) return false;
|
|
|
|
// Finally, just to provide a stable ordering, use the node number as a
|
|
// deciding factor.
|
|
return LHSNum < RHSNum;
|
|
}
|
|
|
|
|
|
/// CalcNodePriority - Calculate the maximal path from the node to the exit.
|
|
///
|
|
int LatencyPriorityQueue::CalcLatency(const SUnit &SU) {
|
|
int &Latency = Latencies[SU.NodeNum];
|
|
if (Latency != -1)
|
|
return Latency;
|
|
|
|
std::vector<const SUnit*> WorkList;
|
|
WorkList.push_back(&SU);
|
|
while (!WorkList.empty()) {
|
|
const SUnit *Cur = WorkList.back();
|
|
bool AllDone = true;
|
|
int MaxSuccLatency = 0;
|
|
for (SUnit::const_succ_iterator I = Cur->Succs.begin(),E = Cur->Succs.end();
|
|
I != E; ++I) {
|
|
int SuccLatency = Latencies[I->Dep->NodeNum];
|
|
if (SuccLatency == -1) {
|
|
AllDone = false;
|
|
WorkList.push_back(I->Dep);
|
|
} else {
|
|
MaxSuccLatency = std::max(MaxSuccLatency, SuccLatency);
|
|
}
|
|
}
|
|
if (AllDone) {
|
|
Latencies[Cur->NodeNum] = MaxSuccLatency + Cur->Latency;
|
|
WorkList.pop_back();
|
|
}
|
|
}
|
|
|
|
return Latency;
|
|
}
|
|
|
|
/// CalculatePriorities - Calculate priorities of all scheduling units.
|
|
void LatencyPriorityQueue::CalculatePriorities() {
|
|
Latencies.assign(SUnits->size(), -1);
|
|
NumNodesSolelyBlocking.assign(SUnits->size(), 0);
|
|
|
|
// For each node, calculate the maximal path from the node to the exit.
|
|
std::vector<std::pair<const SUnit*, unsigned> > WorkList;
|
|
for (unsigned i = 0, e = SUnits->size(); i != e; ++i) {
|
|
const SUnit *SU = &(*SUnits)[i];
|
|
if (SU->Succs.empty())
|
|
WorkList.push_back(std::make_pair(SU, 0U));
|
|
}
|
|
|
|
while (!WorkList.empty()) {
|
|
const SUnit *SU = WorkList.back().first;
|
|
unsigned SuccLat = WorkList.back().second;
|
|
WorkList.pop_back();
|
|
int &Latency = Latencies[SU->NodeNum];
|
|
if (Latency == -1 || (SU->Latency + SuccLat) > (unsigned)Latency) {
|
|
Latency = SU->Latency + SuccLat;
|
|
for (SUnit::const_pred_iterator I = SU->Preds.begin(),E = SU->Preds.end();
|
|
I != E; ++I)
|
|
WorkList.push_back(std::make_pair(I->Dep, Latency));
|
|
}
|
|
}
|
|
}
|
|
|
|
/// getSingleUnscheduledPred - If there is exactly one unscheduled predecessor
|
|
/// of SU, return it, otherwise return null.
|
|
SUnit *LatencyPriorityQueue::getSingleUnscheduledPred(SUnit *SU) {
|
|
SUnit *OnlyAvailablePred = 0;
|
|
for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
|
|
I != E; ++I) {
|
|
SUnit &Pred = *I->Dep;
|
|
if (!Pred.isScheduled) {
|
|
// We found an available, but not scheduled, predecessor. If it's the
|
|
// only one we have found, keep track of it... otherwise give up.
|
|
if (OnlyAvailablePred && OnlyAvailablePred != &Pred)
|
|
return 0;
|
|
OnlyAvailablePred = &Pred;
|
|
}
|
|
}
|
|
|
|
return OnlyAvailablePred;
|
|
}
|
|
|
|
void LatencyPriorityQueue::push_impl(SUnit *SU) {
|
|
// Look at all of the successors of this node. Count the number of nodes that
|
|
// this node is the sole unscheduled node for.
|
|
unsigned NumNodesBlocking = 0;
|
|
for (SUnit::const_succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
|
|
I != E; ++I)
|
|
if (getSingleUnscheduledPred(I->Dep) == SU)
|
|
++NumNodesBlocking;
|
|
NumNodesSolelyBlocking[SU->NodeNum] = NumNodesBlocking;
|
|
|
|
Queue.push(SU);
|
|
}
|
|
|
|
|
|
// ScheduledNode - As nodes are scheduled, we look to see if there are any
|
|
// successor nodes that have a single unscheduled predecessor. If so, that
|
|
// single predecessor has a higher priority, since scheduling it will make
|
|
// the node available.
|
|
void LatencyPriorityQueue::ScheduledNode(SUnit *SU) {
|
|
for (SUnit::const_succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
|
|
I != E; ++I)
|
|
AdjustPriorityOfUnscheduledPreds(I->Dep);
|
|
}
|
|
|
|
/// AdjustPriorityOfUnscheduledPreds - One of the predecessors of SU was just
|
|
/// scheduled. If SU is not itself available, then there is at least one
|
|
/// predecessor node that has not been scheduled yet. If SU has exactly ONE
|
|
/// unscheduled predecessor, we want to increase its priority: it getting
|
|
/// scheduled will make this node available, so it is better than some other
|
|
/// node of the same priority that will not make a node available.
|
|
void LatencyPriorityQueue::AdjustPriorityOfUnscheduledPreds(SUnit *SU) {
|
|
if (SU->isAvailable) return; // All preds scheduled.
|
|
|
|
SUnit *OnlyAvailablePred = getSingleUnscheduledPred(SU);
|
|
if (OnlyAvailablePred == 0 || !OnlyAvailablePred->isAvailable) return;
|
|
|
|
// Okay, we found a single predecessor that is available, but not scheduled.
|
|
// Since it is available, it must be in the priority queue. First remove it.
|
|
remove(OnlyAvailablePred);
|
|
|
|
// Reinsert the node into the priority queue, which recomputes its
|
|
// NumNodesSolelyBlocking value.
|
|
push(OnlyAvailablePred);
|
|
}
|