Changes in directory llvm/lib/CodeGen/SelectionDAG:
ScheduleDAGList.cpp updated: 1.46 -> 1.47
---
Log message:
Chain operands aren't real uses: they don't require the full latency of the
predecessor to finish before they can start.
---
Diffs of the changes: (+10 -4)
ScheduleDAGList.cpp | 14 ++++++++++----
1 files changed, 10 insertions(+), 4 deletions(-)
Index: llvm/lib/CodeGen/SelectionDAG/ScheduleDAGList.cpp
diff -u llvm/lib/CodeGen/SelectionDAG/ScheduleDAGList.cpp:1.46
llvm/lib/CodeGen/SelectionDAG/ScheduleDAGList.cpp:1.47
--- llvm/lib/CodeGen/SelectionDAG/ScheduleDAGList.cpp:1.46 Sat Mar 11
18:38:57 2006
+++ llvm/lib/CodeGen/SelectionDAG/ScheduleDAGList.cpp Sat Mar 11 21:52:09 2006
@@ -387,8 +387,6 @@
}
/// Schedule - Schedule the DAG using list scheduling.
-/// FIXME: Right now it only supports the burr (bottom up register reducing)
-/// heuristic.
void ScheduleDAGList::Schedule() {
DEBUG(std::cerr << "********** List Scheduling **********\n");
@@ -552,8 +550,16 @@
unsigned AvailableCycle = 0;
for (std::set<std::pair<SUnit*, bool> >::iterator I =
SuccSU->Preds.begin(),
E = SuccSU->Preds.end(); I != E; ++I) {
- AvailableCycle = std::max(AvailableCycle,
- I->first->Cycle + I->first->Latency);
+ // If this is a token edge, we don't need to wait for the full latency of
+ // the preceeding instruction (e.g. a long-latency load) unless there is
+ // also some other data dependence.
+ unsigned PredDoneCycle = I->first->Cycle;
+ if (!I->second)
+ PredDoneCycle += I->first->Latency;
+ else
+ PredDoneCycle += 1;
+
+ AvailableCycle = std::max(AvailableCycle, PredDoneCycle);
}
PendingQueue.push_back(std::make_pair(AvailableCycle, SuccSU));
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