[MCA][Scheduler] Track resources that were found busy when issuing an instruction.

This is a follow up of r353706. When the scheduler fails to issue a ready
instruction to the underlying pipelines, it now updates a mask of 'busy resource
units'. That information will be used in future to obtain the set of
"problematic" resources in the case of bottlenecks caused by resource pressure.
No functional change intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@353728 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/MCA/HardwareUnits/Scheduler.h b/include/llvm/MCA/HardwareUnits/Scheduler.h
index 53e416b16433117905267c716ea62a499d7fe2e3..6e1d68020feaef3716b000822b4d6f74c6aa8dad 100644 (file)
--- a/include/llvm/MCA/HardwareUnits/Scheduler.h
+++ b/include/llvm/MCA/HardwareUnits/Scheduler.h
@@ -96,6 +96,13 @@ class Scheduler : public HardwareUnit {
   std::vector<InstRef> ReadySet;
   std::vector<InstRef> IssuedSet;
 
+  // A mask of busy resource units. It defaults to the empty set (i.e. a zero
+  // mask), and it is cleared at the beginning of every cycle.
+  // It is updated every time the scheduler fails to issue an instruction from
+  // the ready set due to unavailable pipeline resources.
+  // Each bit of the mask represents an unavailable resource.
+  uint64_t BusyResourceUnits;
+
   /// Verify the given selection strategy and set the Strategy member
   /// accordingly.  If no strategy is provided, the DefaultSchedulerStrategy is
   /// used.
@@ -126,7 +133,7 @@ public:
 
   Scheduler(std::unique_ptr<ResourceManager> RM, LSUnit &Lsu,
             std::unique_ptr<SchedulerStrategy> SelectStrategy)
-      : LSU(Lsu), Resources(std::move(RM)) {
+      : LSU(Lsu), Resources(std::move(RM)), BusyResourceUnits(0) {
     initializeStrategy(std::move(SelectStrategy));
   }
 
@@ -194,6 +201,10 @@ public:
   /// resources are not available.
   InstRef select();
 
+  /// Returns a mask of busy resources. Each bit of the mask identifies a unique
+  /// processor resource unit. In the absence of bottlenecks caused by resource
+  /// pressure, the mask value returned by this method is always zero.
+  uint64_t getBusyResourceUnits() const { return BusyResourceUnits; }
   bool arePipelinesFullyUsed() const {
     return !Resources->getAvailableProcResUnits();
   }

diff --git a/lib/MCA/HardwareUnits/Scheduler.cpp b/lib/MCA/HardwareUnits/Scheduler.cpp
index fb1080dc02c398309d09b6147b528fa4020690aa..b8cd62f8bd4c40d3281e5eded77908b39891d47c 100644 (file)
--- a/lib/MCA/HardwareUnits/Scheduler.cpp
+++ b/lib/MCA/HardwareUnits/Scheduler.cpp
@@ -140,6 +140,7 @@ InstRef Scheduler::select() {
         Strategy->compare(IR, ReadySet[QueueIndex])) {
       const InstrDesc &D = IR.getInstruction()->getDesc();
       uint64_t BusyResourceMask = Resources->checkAvailability(D);
+      BusyResourceUnits |= BusyResourceMask;
       if (!BusyResourceMask)
         QueueIndex = I;
     }
@@ -196,6 +197,8 @@ void Scheduler::cycleEvent(SmallVectorImpl<ResourceRef> &Freed,
     IR.getInstruction()->cycleEvent();
 
   promoteToReadySet(Ready);
+
+  BusyResourceUnits = 0;
 }
 
 bool Scheduler::mustIssueImmediately(const InstRef &IR) const {