Introducing a new method of tracking register pressure. We can't

precisely track pressure on a selection DAG, but we can at least keep
it balanced. This design accounts for various interesting aspects of
selection DAGS: register and subregister copies, glued nodes, dead
nodes, unused registers, etc.

Added SUnit::NumRegDefsLeft and ScheduleDAGSDNodes::RegDefIter.

Note: I disabled PrescheduleNodesWithMultipleUses when register
pressure is enabled, based on no evidence other than I don't think it
makes sense to have both enabled.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124853 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 2 deletions

diff --git a/lib/CodeGen/ScheduleDAG.cpp b/lib/CodeGen/ScheduleDAG.cpp
index 83f2dd07f1..3388889c9e 100644
--- a/lib/CodeGen/ScheduleDAG.cpp
+++ b/lib/CodeGen/ScheduleDAG.cpp
@@ -75,12 +75,12 @@ void ScheduleDAG::Run(MachineBasicBlock *bb,
 /// addPred - This adds the specified edge as a pred of the current node if
 /// not already.  It also adds the current node as a successor of the
 /// specified node.
-void SUnit::addPred(const SDep &D) {
+bool SUnit::addPred(const SDep &D) {
   // If this node already has this depenence, don't add a redundant one.
   for (SmallVector<SDep, 4>::const_iterator I = Preds.begin(), E = Preds.end();
        I != E; ++I)
     if (*I == D)
-      return;
+      return false;
   // Now add a corresponding succ to N.
   SDep P = D;
   P.setSUnit(this);
@@ -106,6 +106,7 @@ void SUnit::addPred(const SDep &D) {
     this->setDepthDirty();
     N->setHeightDirty();
   }
+  return true;
 }
 
 /// removePred - This removes the specified edge as a pred of the current
@@ -285,6 +286,7 @@ void SUnit::dumpAll(const ScheduleDAG *G) const {
 
   dbgs() << "  # preds left       : " << NumPredsLeft << "\n";
   dbgs() << "  # succs left       : " << NumSuccsLeft << "\n";
+  dbgs() << "  # rdefs left       : " << NumRegDefsLeft << "\n";
   dbgs() << "  Latency            : " << Latency << "\n";
   dbgs() << "  Depth              : " << Depth << "\n";
   dbgs() << "  Height             : " << Height << "\n";