Comment and revise the cyclic critical path code.

This should be much more clear now. It's still disabled pending testing.

llvm-svn: 189597

1 files changed, 0 insertions, 59 deletions

diff --git a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
index f6496e61877..17d31f48b1d 100644
--- a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -987,65 +987,6 @@ void ScheduleDAGInstrs::buildSchedGraph(AliasAnalysis *AA,
   PendingLoads.clear();
 }
 
-/// Compute the max cyclic critical path through the DAG. For loops that span
-/// basic blocks, MachineTraceMetrics should be used for this instead.
-unsigned ScheduleDAGInstrs::computeCyclicCriticalPath() {
-  // This only applies to single block loop.
-  if (!BB->isSuccessor(BB))
-    return 0;
-
-  unsigned MaxCyclicLatency = 0;
-  // Visit each live out vreg def to find def/use pairs that cross iterations.
-  for (SUnit::const_pred_iterator
-         PI = ExitSU.Preds.begin(), PE = ExitSU.Preds.end(); PI != PE; ++PI) {
-    MachineInstr *MI = PI->getSUnit()->getInstr();
-    for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
-      const MachineOperand &MO = MI->getOperand(i);
-      if (!MO.isReg() || !MO.isDef())
-        break;
-      unsigned Reg = MO.getReg();
-      if (!Reg || TRI->isPhysicalRegister(Reg))
-        continue;
-
-      const LiveInterval &LI = LIS->getInterval(Reg);
-      unsigned LiveOutHeight = PI->getSUnit()->getHeight();
-      unsigned LiveOutDepth = PI->getSUnit()->getDepth() + PI->getLatency();
-      // Visit all local users of the vreg def.
-      for (VReg2UseMap::iterator
-             UI = VRegUses.find(Reg); UI != VRegUses.end(); ++UI) {
-        if (UI->SU == &ExitSU)
-          continue;
-
-        // Only consider uses of the phi.
-        LiveRangeQuery LRQ(LI, LIS->getInstructionIndex(UI->SU->getInstr()));
-        if (!LRQ.valueIn()->isPHIDef())
-          continue;
-
-        // Cheat a bit and assume that a path spanning two iterations is a
-        // cycle, which could overestimate in strange cases. This allows cyclic
-        // latency to be estimated as the minimum height or depth slack.
-        unsigned CyclicLatency = 0;
-        if (LiveOutDepth > UI->SU->getDepth())
-          CyclicLatency = LiveOutDepth - UI->SU->getDepth();
-        unsigned LiveInHeight = UI->SU->getHeight() + PI->getLatency();
-        if (LiveInHeight > LiveOutHeight) {
-          if (LiveInHeight - LiveOutHeight < CyclicLatency)
-            CyclicLatency = LiveInHeight - LiveOutHeight;
-        }
-        else
-          CyclicLatency = 0;
-        DEBUG(dbgs() << "Cyclic Path: SU(" << PI->getSUnit()->NodeNum
-              << ") -> SU(" << UI->SU->NodeNum << ") = "
-              << CyclicLatency << "\n");
-        if (CyclicLatency > MaxCyclicLatency)
-          MaxCyclicLatency = CyclicLatency;
-      }
-    }
-  }
-  DEBUG(dbgs() << "Cyclic Critical Path: " << MaxCyclicLatency << "\n");
-  return MaxCyclicLatency;
-}
-
 void ScheduleDAGInstrs::dumpNode(const SUnit *SU) const {
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
   SU->getInstr()->dump();