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MachineScheduler: Remember top/bottom choice in bidirectional scheduling

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Remember the last choice for the top/bottom scheduling boundary in
bidirectional scheduling mode. The top choice should not change if we
schedule at the bottom and vice versa.

This allows us to improve compiletime: We only recalculate the best pick
for one border and re-use the cached top-pick from the other border.

Differential Revision: http://reviews.llvm.org/D19350

llvm-svn: 273766
This commit is contained in:
Matthias Braun
2016-06-25 02:03:36 +00:00
parent b164a9843b
commit cc676c47a3
2 changed files with 77 additions and 11 deletions
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59
llvm/lib/CodeGen/MachineScheduler.cpp
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@@ -2557,6 +2557,8 @@ void GenericScheduler::initialize(ScheduleDAGMI *dag) {
DAG->MF.getSubtarget().getInstrInfo()->CreateTargetMIHazardRecognizer(
Itin, DAG);
}
TopCand.SU = nullptr;
BotCand.SU = nullptr;
}
/// Initialize the per-region scheduling policy.
@@ -2954,17 +2956,56 @@ SUnit *GenericScheduler::pickNodeBidirectional(bool &IsTopNode) {
CandPolicy TopPolicy;
setPolicy(TopPolicy, /*IsPostRA=*/false, Top, &Bot);
// Prefer bottom scheduling when heuristics are silent.
CandPolicy NoPolicy;
SchedCandidate Cand(NoPolicy);
// See if BotCand is still valid (because we previously scheduled from Top).
DEBUG(dbgs() << "Picking from Bot:\n");
pickNodeFromQueue(Bot, BotPolicy, DAG->getBotRPTracker(), Cand);
assert(Cand.Reason != NoCand && "failed to find the first candidate");
if (!BotCand.isValid() || BotCand.SU->isScheduled ||
BotCand.Policy != BotPolicy) {
BotCand.reset(CandPolicy());
pickNodeFromQueue(Bot, BotPolicy, DAG->getBotRPTracker(), BotCand);
assert(BotCand.Reason != NoCand && "failed to find the first candidate");
} else {
DEBUG(traceCandidate(BotCand));
#ifndef NDEBUG
if (VerifyScheduling) {
SchedCandidate TCand;
TCand.reset(CandPolicy());
pickNodeFromQueue(Bot, BotPolicy, DAG->getBotRPTracker(), TCand);
assert(TCand.SU == BotCand.SU &&
"Last pick result should correspond to re-picking right now");
}
#endif
}
// Check if the top Q has a better candidate.
DEBUG(dbgs() << "Picking from Top:\n");
pickNodeFromQueue(Top, TopPolicy, DAG->getTopRPTracker(), Cand);
assert(Cand.Reason != NoCand && "failed to find the first candidate");
if (!TopCand.isValid() || TopCand.SU->isScheduled ||
TopCand.Policy != TopPolicy) {
TopCand.reset(CandPolicy());
pickNodeFromQueue(Top, TopPolicy, DAG->getTopRPTracker(), TopCand);
assert(TopCand.Reason != NoCand && "failed to find the first candidate");
} else {
DEBUG(traceCandidate(TopCand));
#ifndef NDEBUG
if (VerifyScheduling) {
SchedCandidate TCand;
TCand.reset(CandPolicy());
pickNodeFromQueue(Top, TopPolicy, DAG->getTopRPTracker(), TCand);
assert(TCand.SU == TopCand.SU &&
"Last pick result should correspond to re-picking right now");
}
#endif
}
// Pick best from BotCand and TopCand.
assert(BotCand.isValid());
assert(TopCand.isValid());
SchedCandidate Cand = BotCand;
TopCand.Reason = NoCand;
tryCandidate(Cand, TopCand, nullptr);
if (TopCand.Reason != NoCand) {
Cand.setBest(TopCand);
DEBUG(traceCandidate(Cand));
}
IsTopNode = Cand.AtTop;
tracePick(Cand);
@@ -2984,7 +3025,7 @@ SUnit *GenericScheduler::pickNode(bool &IsTopNode) {
SU = Top.pickOnlyChoice();
if (!SU) {
CandPolicy NoPolicy;
SchedCandidate TopCand(NoPolicy);
TopCand.reset(NoPolicy);
pickNodeFromQueue(Top, NoPolicy, DAG->getTopRPTracker(), TopCand);
assert(TopCand.Reason != NoCand && "failed to find a candidate");
tracePick(TopCand);
@@ -2995,7 +3036,7 @@ SUnit *GenericScheduler::pickNode(bool &IsTopNode) {
SU = Bot.pickOnlyChoice();
if (!SU) {
CandPolicy NoPolicy;
SchedCandidate BotCand(NoPolicy);
BotCand.reset(NoPolicy);
pickNodeFromQueue(Bot, NoPolicy, DAG->getBotRPTracker(), BotCand);
assert(BotCand.Reason != NoCand && "failed to find a candidate");
tracePick(BotCand);