[llvm] r187110 - MI Sched: Register pressure heuristics.
Andrew Trick
atrick at apple.com
Thu Jul 25 00:26:35 PDT 2013
Author: atrick
Date: Thu Jul 25 02:26:35 2013
New Revision: 187110
URL: http://llvm.org/viewvc/llvm-project?rev=187110&view=rev
Log:
MI Sched: Register pressure heuristics.
Consider which set is being increased or decreased before comparing.
Modified:
llvm/trunk/include/llvm/CodeGen/RegisterPressure.h
llvm/trunk/lib/CodeGen/MachineScheduler.cpp
Modified: llvm/trunk/include/llvm/CodeGen/RegisterPressure.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/RegisterPressure.h?rev=187110&r1=187109&r2=187110&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/RegisterPressure.h (original)
+++ llvm/trunk/include/llvm/CodeGen/RegisterPressure.h Thu Jul 25 02:26:35 2013
@@ -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
Modified: llvm/trunk/lib/CodeGen/MachineScheduler.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineScheduler.cpp?rev=187110&r1=187109&r2=187110&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineScheduler.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineScheduler.cpp Thu Jul 25 02:26:35 2013
@@ -2024,6 +2024,30 @@ static bool tryGreater(int TryVal, int C
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(S
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(S
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.
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