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MIsched: add an ILP window property to machine model.

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This was an experimental option, but needs to be defined
per-target. e.g. PPC A2 needs to aggressively hide latency.

I converted some in-order scheduling tests to A2. Hal is working on
more test cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171946 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick
2013-01-09 03:36:49 +00:00
parent 2af949dddd
commit 47579cf390
9 changed files with 51 additions and 27 deletions
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12
lib/CodeGen/MachineScheduler.cpp
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@ -48,15 +48,6 @@ static cl::opt<unsigned> MISchedCutoff("misched-cutoff", cl::Hidden,
static bool ViewMISchedDAGs = false;
#endif // NDEBUG
// Threshold to very roughly model an out-of-order processor's instruction
// buffers. If the actual value of this threshold matters much in practice, then
// it can be specified by the machine model. For now, it's an experimental
// tuning knob to determine when and if it matters.
static cl::opt<unsigned> ILPWindow("ilp-window", cl::Hidden,
cl::desc("Allow expected latency to exceed the critical path by N cycles "
"before attempting to balance ILP"),
cl::init(10U));
// Experimental heuristics
static cl::opt<bool> EnableLoadCluster("misched-cluster", cl::Hidden,
cl::desc("Enable load clustering."), cl::init(true));
@ -1297,7 +1288,8 @@ void ConvergingScheduler::SchedBoundary::setLatencyPolicy(CandPolicy &Policy) {
if (L > RemLatency)
RemLatency = L;
}
if (RemLatency + ExpectedLatency >= Rem->CriticalPath + ILPWindow
unsigned CriticalPathLimit = Rem->CriticalPath + SchedModel->getILPWindow();
if (RemLatency + ExpectedLatency >= CriticalPathLimit
&& RemLatency > Rem->getMaxRemainingCount(SchedModel)) {
Policy.ReduceLatency = true;
DEBUG(dbgs() << "Increase ILP: " << Available.getName() << '\n');