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[MiSched] Fix a logic error in tryPressure()

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Fixes a logic error in the MachineScheduler found by Steve Montgomery (and
confirmed by Andy). This has gone unfixed for months because the fix has been
found to introduce some small performance regressions. However, Andy has
recommended that, at this point, we fix this to avoid further dependence on the
incorrect behavior (and then follow-up separately on any regressions), and I
agree.

Fixes PR18883.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219512 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hal Finkel
2014-10-10 17:06:20 +00:00
parent f6e11eacdd
commit d3aa46a1bc
3 changed files with 7 additions and 5 deletions
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4
lib/CodeGen/MachineScheduler.cpp
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@@ -2495,8 +2495,8 @@ static bool tryPressure(const PressureChange &TryP,
}
// If one candidate decreases and the other increases, go with it.
// Invalid candidates have UnitInc==0.
if (tryLess(TryP.getUnitInc() < 0, CandP.getUnitInc() < 0, TryCand, Cand,
Reason)) {
if (tryGreater(TryP.getUnitInc() < 0, CandP.getUnitInc() < 0, TryCand, Cand,
Reason)) {
return true;
}
// If the candidates are decreasing pressure, reverse priority.