[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.

llvm-svn: 353728

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/MCA/HardwareUnits/Scheduler.cpp b/llvm/lib/MCA/HardwareUnits/Scheduler.cpp
index fb1080dc02c..b8cd62f8bd4 100644
--- a/llvm/lib/MCA/HardwareUnits/Scheduler.cpp
+++ b/llvm/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 {