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Backtracking only when it won't create a cycle.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@42384 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2007-09-27 00:25:29 +00:00
parent 693717fbe6
commit 6e4c46cea5
1 changed files with 35 additions and 23 deletions
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58
lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
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@ -326,6 +326,40 @@ void ScheduleDAGRRList::UnscheduleNodeBottomUp(SUnit *SU) {
AvailableQueue->push(SU);
}
// FIXME: This is probably too slow!
static void isReachable(SUnit *SU, SUnit *TargetSU,
SmallPtrSet<SUnit*, 32> &Visited, bool &Reached) {
if (Reached) return;
if (SU == TargetSU) {
Reached = true;
return;
}
if (!Visited.insert(SU)) return;
for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end(); I != E;
++I)
isReachable(I->Dep, TargetSU, Visited, Reached);
}
static bool isReachable(SUnit *SU, SUnit *TargetSU) {
SmallPtrSet<SUnit*, 32> Visited;
bool Reached = false;
isReachable(SU, TargetSU, Visited, Reached);
return Reached;
}
/// willCreateCycle - Returns true if adding an edge from SU to TargetSU will
/// create a cycle.
static bool willCreateCycle(SUnit *SU, SUnit *TargetSU) {
if (isReachable(TargetSU, SU))
return true;
for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
I != E; ++I)
if (I->Cost < 0 && isReachable(TargetSU, I->Dep))
return true;
return false;
}
/// BacktrackBottomUp - Backtrack scheduling to a previous cycle specified in
/// BTCycle in order to schedule a specific node. Returns the last unscheduled
/// SUnit. Also returns if a successor is unscheduled in the process.
@ -469,28 +503,6 @@ static MVT::ValueType getPhysicalRegisterVT(SDNode *N, unsigned Reg,
return N->getValueType(NumRes);
}
// FIXME: This is probably too slow!
static void isReachable(SUnit *SU, SUnit *TargetSU,
SmallPtrSet<SUnit*, 32> &Visited, bool &Reached) {
if (Reached) return;
if (SU == TargetSU) {
Reached = true;
return;
}
if (!Visited.insert(SU)) return;
for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end(); I != E;
++I)
isReachable(I->Dep, TargetSU, Visited, Reached);
}
static bool isReachable(SUnit *SU, SUnit *TargetSU) {
SmallPtrSet<SUnit*, 32> Visited;
bool Reached = false;
isReachable(SU, TargetSU, Visited, Reached);
return Reached;
}
/// DelayForLiveRegsBottomUp - Returns true if it is necessary to delay
/// scheduling of the given node to satisfy live physical register dependencies.
/// If the specific node is the last one that's available to schedule, do
@ -547,7 +559,7 @@ bool ScheduleDAGRRList::DelayForLiveRegsBottomUp(SUnit *SU, unsigned &CurCycle){
}
SUnit *OldSU = Sequence[LiveCycle];
if (!isReachable(Sequence[LiveCycle], SU)) {
if (!willCreateCycle(SU, OldSU)) {
// If CycleBound is greater than backtrack cycle, then some of SU
// successors are going to be unscheduled.
bool SuccUnsched = SU->CycleBound > LiveCycle;