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Chain operands aren't real uses: they don't require the full latency of the 

predecessor to finish before they can start.

llvm-svn: 26717
This commit is contained in:
Chris Lattner 2006-03-12 03:52:09 +00:00
parent 572003ca15
commit 86a9b60a25
1 changed files with 10 additions and 4 deletions
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14
llvm/lib/CodeGen/SelectionDAG/ScheduleDAGList.cpp
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@ -387,8 +387,6 @@ void ScheduleDAGList::dumpSchedule() const {
} }
/// Schedule - Schedule the DAG using list scheduling. /// Schedule - Schedule the DAG using list scheduling.
/// FIXME: Right now it only supports the burr (bottom up register reducing)
/// heuristic.
void ScheduleDAGList::Schedule() { void ScheduleDAGList::Schedule() {
DEBUG(std::cerr << "********** List Scheduling **********\n"); DEBUG(std::cerr << "********** List Scheduling **********\n");
@ -552,8 +550,16 @@ void ScheduleDAGList::ReleaseSucc(SUnit *SuccSU, bool isChain) {
unsigned AvailableCycle = 0; unsigned AvailableCycle = 0;
for (std::set<std::pair<SUnit*, bool> >::iterator I = SuccSU->Preds.begin(), for (std::set<std::pair<SUnit*, bool> >::iterator I = SuccSU->Preds.begin(),
E = SuccSU->Preds.end(); I != E; ++I) { E = SuccSU->Preds.end(); I != E; ++I) {
AvailableCycle = std::max(AvailableCycle, // If this is a token edge, we don't need to wait for the full latency of
I->first->Cycle + I->first->Latency); // the preceeding instruction (e.g. a long-latency load) unless there is
// also some other data dependence.
unsigned PredDoneCycle = I->first->Cycle;
if (!I->second)
PredDoneCycle += I->first->Latency;
else
PredDoneCycle += 1;
AvailableCycle = std::max(AvailableCycle, PredDoneCycle);
} }
PendingQueue.push_back(std::make_pair(AvailableCycle, SuccSU)); PendingQueue.push_back(std::make_pair(AvailableCycle, SuccSU));