[llvm] [AMDGPU] AMDGPUIGroupLP: Avoid repeating reachability checks in greedy algorithm (PR #182463)

[Matt Arsenault via llvm-commits]

================
@@ -729,21 +728,36 @@ void PipelineSolver::greedyFind(
       LLVM_DEBUG(dbgs() << "SGID # " << CandSGID << " has conflicting rule\n");
       continue;
     }
-    TempCost = addEdges(SyncPipeline, CurrSU.first, CandSGID, AddedEdges);
+
+    std::list<std::pair<SUnit *, SUnit *>> TempEdges;
+    TempCost = addEdges(SyncPipeline, CurrSU.first, CandSGID, TempEdges);
     LLVM_DEBUG(dbgs() << "Cost of Group " << TempCost << "\n");
+
     if (TempCost < BestNodeCost || BestNodeCost == -1) {
+      BestEdges = TempEdges;
       BestGroup = Match;
       BestNodeCost = TempCost;
       BestGroupID = CandSGID;
+
+      if (BestNodeCost == 0)
+        break;
     }
-    removeEdges(AddedEdges);
-    if (BestNodeCost == 0)
-      break;
+
+    removeEdges(TempEdges);
   }
 
   if (BestGroupID != -1) {
     BestGroup->add(*CurrSU.first);
-    addEdges(SyncPipeline, CurrSU.first, BestGroupID, AddedEdges);
+    if (AddedEdges.empty())
+      AddedEdges = BestEdges;
+    else
+      AddedEdges.splice(std::prev(AddedEdges.cend()), BestEdges);
+    std::for_each(BestEdges.begin(), BestEdges.end(),
----------------
arsenm wrote:

Avoid std::for_each for normal code 

https://github.com/llvm/llvm-project/pull/182463