[MachineSched] Add a first valid reason [nfc]

For debugging, distinguish the first valid candidate encountered and
a preference decision driven by node number.

Author: preames

llvm/include/llvm/CodeGen/MachineScheduler.h

@@ -1099,7 +1099,8 @@ class GenericSchedulerBase : public MachineSchedStrategy {
     BotPathReduce,
     TopDepthReduce,
     TopPathReduce,
-    NodeOrder
+    NodeOrder,
+    FirstValid
   };
 
 #ifndef NDEBUG

llvm/lib/CodeGen/MachineScheduler.cpp

@@ -3267,6 +3267,7 @@ const char *GenericSchedulerBase::getReasonStr(
   case BotHeightReduce:return "BOT-HEIGHT";
   case BotPathReduce:  return "BOT-PATH  ";
   case NodeOrder:      return "ORDER     ";
+  case FirstValid:     return "FIRST     ";
   };
   // clang-format on
   llvm_unreachable("Unknown reason!");
@@ -3688,7 +3689,7 @@ bool GenericScheduler::tryCandidate(SchedCandidate &Cand,
                                     SchedBoundary *Zone) const {
   // Initialize the candidate if needed.
   if (!Cand.isValid()) {
-    TryCand.Reason = NodeOrder;
+    TryCand.Reason = FirstValid;
     return true;
   }
 
@@ -4103,7 +4104,7 @@ bool PostGenericScheduler::tryCandidate(SchedCandidate &Cand,
                                         SchedCandidate &TryCand) {
   // Initialize the candidate if needed.
   if (!Cand.isValid()) {
-    TryCand.Reason = NodeOrder;
+    TryCand.Reason = FirstValid;
     return true;
   }
 

llvm/test/CodeGen/AArch64/misched-detail-resource-booking-01.mir

@@ -387,8 +387,8 @@ body:             |
 # CHECK-NEXT:     selecting CortexA55UnitALU[0] available @3c
 # CHECK-NEXT: Queue BotQ.P:
 # CHECK-NEXT: Queue BotQ.A: 12 11
-# CHECK-NEXT:   Cand SU(12) ORDER
-# CHECK-NEXT: Pick Bot ORDER
+# CHECK-NEXT:   Cand SU(12) FIRST
+# CHECK-NEXT: Pick Bot FIRST
 # CHECK-NEXT: Scheduling SU(12) $q1 = COPY %12:fpr128
 # CHECK-NEXT:   Ready @3c
 # CHECK-NEXT:   CortexA55UnitALU +1x1u
@@ -561,8 +561,8 @@ body:             |
 # CHECK-NEXT:     selecting CortexA55UnitFPALU[0] available @7c
 # CHECK-NEXT: Queue BotQ.P:
 # CHECK-NEXT: Queue BotQ.A: 10 8
-# CHECK-NEXT:   Cand SU(10) ORDER
-# CHECK-NEXT: Pick Bot ORDER
+# CHECK-NEXT:   Cand SU(10) FIRST
+# CHECK-NEXT: Pick Bot FIRST
 # CHECK-NEXT: Scheduling SU(10) %12:fpr128 = UMULLv4i16_v4i32 %3.dsub:fpr128, %11:fpr64
 # CHECK-NEXT:   Ready @7c
 # CHECK-NEXT:   CortexA55UnitFPALU +2x1u
@@ -830,8 +830,8 @@ body:             |
 # CHECK-NEXT:     selecting CortexA55UnitFPALU[1] available @10c
 # CHECK-NEXT: Queue BotQ.P: 3
 # CHECK-NEXT: Queue BotQ.A: 7 5
-# CHECK-NEXT:   Cand SU(7) ORDER
-# CHECK-NEXT: Pick Bot ORDER
+# CHECK-NEXT:   Cand SU(7) FIRST
+# CHECK-NEXT: Pick Bot FIRST
 # CHECK-NEXT: Scheduling SU(7) %9:fpr64 = XTNv4i16 %8:fpr128
 # CHECK-NEXT:   Ready @10c
 # CHECK-NEXT:   CortexA55UnitFPALU +1x1u
@@ -1040,7 +1040,7 @@ body:             |
 # CHECK-NEXT:     selecting CortexA55UnitFPALU[0] available @12c
 # CHECK-NEXT: Queue BotQ.P: 0
 # CHECK-NEXT: Queue BotQ.A: 3 6
-# CHECK-NEXT:   Cand SU(3) ORDER
+# CHECK-NEXT:   Cand SU(3) FIRST
 # CHECK-NEXT:   Cand SU(6) ORDER
 # CHECK-NEXT: Pick Bot ORDER
 # CHECK-NEXT: Scheduling SU(6) %8:fpr128 = ANDv16i8 %1:fpr128, %6:fpr128
@@ -1155,7 +1155,7 @@ body:             |
 # CHECK-NEXT:     selecting CortexA55UnitALU[0] available @13c
 # CHECK-NEXT: Queue BotQ.P: 1 4
 # CHECK-NEXT: Queue BotQ.A: 3 0
-# CHECK-NEXT:   Cand SU(3) ORDER
+# CHECK-NEXT:   Cand SU(3) FIRST
 # CHECK-NEXT: Pick Bot PHYS-REG
 # CHECK-NEXT: Scheduling SU(3) %3:fpr128 = EXTv16i8 %0:fpr128, %0:fpr128, 8
 # CHECK-NEXT:   Ready @13c
@@ -1405,7 +1405,7 @@ body:             |
 # CHECK-NEXT:     selecting CortexA55UnitFPALU[0] available @16c
 # CHECK-NEXT: Queue BotQ.P:
 # CHECK-NEXT: Queue BotQ.A: 2 4
-# CHECK-NEXT:   Cand SU(2) ORDER
+# CHECK-NEXT:   Cand SU(2) FIRST
 # CHECK-NEXT:   Cand SU(4) PHYS-REG
 # CHECK-NEXT: Pick Bot PHYS-REG
 # CHECK-NEXT: Scheduling SU(4) %6:fpr128 = MOVIv2d_ns 17

llvm/test/CodeGen/AArch64/misched-detail-resource-booking-02.mir

@@ -224,8 +224,8 @@ body:             |
 # CHECK-NEXT:     selecting CortexA55UnitALU[0] available @0c
 # CHECK-NEXT: Queue BotQ.P: 
 # CHECK-NEXT: Queue BotQ.A: 2 1 0 
-# CHECK-NEXT:   Cand SU(2) ORDER                              
-# CHECK-NEXT: Pick Bot ORDER     
+# CHECK-NEXT:   Cand SU(2) FIRST                              
+# CHECK-NEXT: Pick Bot FIRST     
 # CHECK-NEXT: Scheduling SU(2) $x5 = ADDXrr $x2, $x2
 # CHECK-NEXT:   Ready @0c
 # CHECK-NEXT:   CortexA55UnitALU +1x1u
@@ -318,7 +318,7 @@ body:             |
 # CHECK-NEXT:     selecting CortexA55UnitALU[1] available @0c
 # CHECK-NEXT: Queue BotQ.P: 
 # CHECK-NEXT: Queue BotQ.A: 0 1 
-# CHECK-NEXT:   Cand SU(0) ORDER                              
+# CHECK-NEXT:   Cand SU(0) FIRST                              
 # CHECK-NEXT:   Cand SU(1) ORDER                              
 # CHECK-NEXT: Pick Bot ORDER     
 # CHECK-NEXT: Scheduling SU(1) $x4 = ADDXrr $x1, $x1