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MI Sched: Register pressure heuristics.

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Consider which set is being increased or decreased before comparing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187110 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick 2013-07-25 07:26:35 +00:00
parent 4b43ed53b6
commit 13372886a6
2 changed files with 36 additions and 8 deletions
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4
include/llvm/CodeGen/RegisterPressure.h
View File

@ -99,6 +99,10 @@ struct PressureElement {
PressureElement(unsigned id, int inc): PSetID(id), UnitIncrease(inc) {}
bool isValid() const { return PSetID != ~0U; }
// If signed PSetID is negative, it is invalid; convert it to INT_MAX to give
// it lowest priority.
int PSetRank() const { return PSetID & INT_MAX; }
};
/// Store the effects of a change in pressure on things that MI scheduler cares

40
lib/CodeGen/MachineScheduler.cpp
View File

@ -2024,6 +2024,30 @@ static bool tryGreater(int TryVal, int CandVal,
return false;
}
static bool tryPressure(const PressureElement &TryP,
const PressureElement &CandP,
ConvergingScheduler::SchedCandidate &TryCand,
ConvergingScheduler::SchedCandidate &Cand,
ConvergingScheduler::CandReason Reason) {
// If both candidates affect the same set, go with the smallest increase.
if (TryP.PSetID == CandP.PSetID) {
return tryLess(TryP.UnitIncrease, CandP.UnitIncrease, TryCand, Cand,
Reason);
}
// If one candidate decreases and the other increases, go with it.
if (tryLess(TryP.UnitIncrease < 0, CandP.UnitIncrease < 0, TryCand, Cand,
Reason)) {
return true;
}
// If TryP has lower Rank, it has a higher priority.
int TryRank = TryP.PSetRank();
int CandRank = CandP.PSetRank();
// If the candidates are decreasing pressure, reverse priority.
if (TryP.UnitIncrease < 0)
std::swap(TryRank, CandRank);
return tryGreater(TryRank, CandRank, TryCand, Cand, Reason);
}
static unsigned getWeakLeft(const SUnit *SU, bool isTop) {
return (isTop) ? SU->WeakPredsLeft : SU->WeakSuccsLeft;
}
@ -2089,15 +2113,15 @@ void ConvergingScheduler::tryCandidate(SchedCandidate &Cand,
TryCand, Cand, PhysRegCopy))
return;
// Avoid exceeding the target's limit.
if (tryLess(TryCand.RPDelta.Excess.UnitIncrease,
Cand.RPDelta.Excess.UnitIncrease, TryCand, Cand, RegExcess))
// Avoid exceeding the target's limit. If signed PSetID is negative, it is
// invalid; convert it to INT_MAX to give it lowest priority.
if (tryPressure(TryCand.RPDelta.Excess, Cand.RPDelta.Excess, TryCand, Cand,
RegExcess))
return;
// Avoid increasing the max critical pressure in the scheduled region.
if (tryLess(TryCand.RPDelta.CriticalMax.UnitIncrease,
Cand.RPDelta.CriticalMax.UnitIncrease,
TryCand, Cand, RegCritical))
if (tryPressure(TryCand.RPDelta.CriticalMax, Cand.RPDelta.CriticalMax,
TryCand, Cand, RegCritical))
return;
// Keep clustered nodes together to encourage downstream peephole
@ -2119,8 +2143,8 @@ void ConvergingScheduler::tryCandidate(SchedCandidate &Cand,
return;
}
// Avoid increasing the max pressure of the entire region.
if (tryLess(TryCand.RPDelta.CurrentMax.UnitIncrease,
Cand.RPDelta.CurrentMax.UnitIncrease, TryCand, Cand, RegMax))
if (tryPressure(TryCand.RPDelta.CurrentMax, Cand.RPDelta.CurrentMax,
TryCand, Cand, RegMax))
return;
// Avoid critical resource consumption and balance the schedule.