4 files changed, 11 insertions, 10 deletions
diff --git a/lib/CodeGen/MachineScheduler.cpp b/lib/CodeGen/MachineScheduler.cpp
index 117b2bd..a32df78 100644
--- a/lib/CodeGen/MachineScheduler.cpp
+++ b/lib/CodeGen/MachineScheduler.cpp
@@ -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');
diff --git a/lib/Target/ARM/ARMScheduleA9.td b/lib/Target/ARM/ARMScheduleA9.td
index 404634f..4191931 100644
--- a/lib/Target/ARM/ARMScheduleA9.td
+++ b/lib/Target/ARM/ARMScheduleA9.td
@@ -1887,6 +1887,9 @@ def CortexA9Model : SchedMachineModel {
   let LoadLatency = 2; // Optimistic load latency assuming bypass.
                        // This is overriden by OperandCycles if the
                        // Itineraries are queried instead.
+  let ILPWindow = 10; // Don't reschedule small blocks to hide
+                      // latency. Minimum latency requirements are already
+                      // modeled strictly by reserving resources.
   let MispredictPenalty = 8; // Based on estimate of pipeline depth.
 
   let Itineraries = CortexA9Itineraries;
diff --git a/lib/Target/X86/X86Schedule.td b/lib/Target/X86/X86Schedule.td
index c14407f..d99d085 100644
--- a/lib/Target/X86/X86Schedule.td
+++ b/lib/Target/X86/X86Schedule.td
@@ -470,12 +470,17 @@ def IIC_NOP : InstrItinClass;
 // latencies. Since these latencies are not used for pipeline hazards,
 // they do not need to be exact.
 //
+// ILPWindow=10 is an arbitrary threshold that approximates cycles of
+// latency hidden by instruction buffers. The actual value is not very
+// important but should be zero for inorder and nonzero for OOO processors.
+//
 // The GenericModel contains no instruciton itineraries.
 def GenericModel : SchedMachineModel {
   let IssueWidth = 4;
   let MinLatency = 0;
   let LoadLatency = 4;
   let HighLatency = 10;
+  let ILPWindow = 10;
 }
 
 include "X86ScheduleAtom.td"
diff --git a/lib/Target/X86/X86ScheduleAtom.td b/lib/Target/X86/X86ScheduleAtom.td
index 8710261..1e5f2d6 100644
--- a/lib/Target/X86/X86ScheduleAtom.td
+++ b/lib/Target/X86/X86ScheduleAtom.td
@@ -525,6 +525,7 @@ def AtomModel : SchedMachineModel {
                        // OperandCycles may be used for expected latency.
   let LoadLatency = 3; // Expected cycles, may be overriden by OperandCycles.
   let HighLatency = 30;// Expected, may be overriden by OperandCycles.
+  let ILPWindow = 0; // Always try to hide expected latency.
 
   let Itineraries = AtomItineraries;
 }