[AMDGPU][NFC] rename some constants for readability (#145870)

Author: ssahasra

llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp

@@ -151,14 +151,14 @@ enum RegisterMapping {
   SQ_MAX_PGM_VGPRS = 1024, // Maximum programmable VGPRs across all targets.
   AGPR_OFFSET = 512,       // Maximum programmable ArchVGPRs across all targets.
   SQ_MAX_PGM_SGPRS = 128,  // Maximum programmable SGPRs across all targets.
-  NUM_EXTRA_VGPRS = 9,     // Reserved slots for DS.
   // Artificial register slots to track LDS writes into specific LDS locations
   // if a location is known. When slots are exhausted or location is
   // unknown use the first slot. The first slot is also always updated in
   // addition to known location's slot to properly generate waits if dependent
   // instruction's location is unknown.
-  EXTRA_VGPR_LDS = 0,
-  NUM_ALL_VGPRS = SQ_MAX_PGM_VGPRS + NUM_EXTRA_VGPRS, // Where SGPR starts.
+  FIRST_LDS_VGPR = SQ_MAX_PGM_VGPRS, // Extra slots for LDS stores.
+  NUM_LDS_VGPRS = 9,                 // One more than the stores we track.
+  NUM_ALL_VGPRS = SQ_MAX_PGM_VGPRS + NUM_LDS_VGPRS, // Where SGPRs start.
 };
 
 // Enumerate different types of result-returning VMEM operations. Although
@@ -488,7 +488,7 @@ class WaitcntBrackets {
   unsigned char VgprVmemTypes[NUM_ALL_VGPRS] = {0};
   // Store representative LDS DMA operations. The only useful info here is
   // alias info. One store is kept per unique AAInfo.
-  SmallVector<const MachineInstr *, NUM_EXTRA_VGPRS - 1> LDSDMAStores;
+  SmallVector<const MachineInstr *, NUM_LDS_VGPRS - 1> LDSDMAStores;
 };
 
 // This abstracts the logic for generating and updating S_WAIT* instructions
@@ -1062,15 +1062,15 @@ void WaitcntBrackets::updateByEvent(const SIInstrInfo *TII,
             }
           }
         }
-        if (Slot || LDSDMAStores.size() == NUM_EXTRA_VGPRS - 1)
+        if (Slot || LDSDMAStores.size() == NUM_LDS_VGPRS - 1)
           break;
         LDSDMAStores.push_back(&Inst);
         Slot = LDSDMAStores.size();
         break;
       }
-      setRegScore(SQ_MAX_PGM_VGPRS + EXTRA_VGPR_LDS + Slot, T, CurrScore);
+      setRegScore(FIRST_LDS_VGPR + Slot, T, CurrScore);
       if (Slot)
-        setRegScore(SQ_MAX_PGM_VGPRS + EXTRA_VGPR_LDS, T, CurrScore);
+        setRegScore(FIRST_LDS_VGPR, T, CurrScore);
     }
   }
 }
@@ -1122,7 +1122,7 @@ void WaitcntBrackets::print(raw_ostream &OS) const {
         if (RegScore <= LB)
           continue;
         unsigned RelScore = RegScore - LB - 1;
-        if (J < SQ_MAX_PGM_VGPRS + EXTRA_VGPR_LDS) {
+        if (J < FIRST_LDS_VGPR) {
           OS << RelScore << ":v" << J << " ";
         } else {
           OS << RelScore << ":ds ";
@@ -1914,7 +1914,7 @@ bool SIInsertWaitcnts::generateWaitcntInstBefore(MachineInstr &MI,
           continue;
 
         // LOAD_CNT is only relevant to vgpr or LDS.
-        unsigned RegNo = SQ_MAX_PGM_VGPRS + EXTRA_VGPR_LDS;
+        unsigned RegNo = FIRST_LDS_VGPR;
         // Only objects with alias scope info were added to LDSDMAScopes array.
         // In the absense of the scope info we will not be able to disambiguate
         // aliasing here. There is no need to try searching for a corresponding