[llvm] r290162 - [PM] Rework a loop in the CGSCC update logic to be more conservative and

[Chandler Carruth via llvm-commits]

Author: chandlerc
Date: Mon Dec 19 21:32:17 2016
New Revision: 290162

URL: http://llvm.org/viewvc/llvm-project?rev=290162&view=rev
Log:
[PM] Rework a loop in the CGSCC update logic to be more conservative and
clear. The current RefSCC can occur in exactly one position so we should
just enforce that and leverage the property rather than checking for it
anywhere.

This addresses review comments made on another patch.

Modified:
    llvm/trunk/lib/Analysis/CGSCCPassManager.cpp

Modified: llvm/trunk/lib/Analysis/CGSCCPassManager.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/CGSCCPassManager.cpp?rev=290162&r1=290161&r2=290162&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/CGSCCPassManager.cpp (original)
+++ llvm/trunk/lib/Analysis/CGSCCPassManager.cpp Mon Dec 19 21:32:17 2016
@@ -329,13 +329,17 @@ LazyCallGraph::SCC &llvm::updateCGAndAna
       assert(G.lookupSCC(N) == C && "Changed the SCC when splitting RefSCCs!");
       RC = &C->getOuterRefSCC();
       assert(G.lookupRefSCC(N) == RC && "Failed to update current RefSCC!");
-      for (RefSCC *NewRC : reverse(NewRefSCCs))
-        if (NewRC != RC) {
-          UR.RCWorklist.insert(NewRC);
-          if (DebugLogging)
-            dbgs() << "Enqueuing a new RefSCC in the update worklist: "
-                   << *NewRC << "\n";
-        }
+      assert(NewRefSCCs.front() == RC &&
+             "New current RefSCC not first in the returned list!");
+      for (RefSCC *NewRC : reverse(
+               make_range(std::next(NewRefSCCs.begin()), NewRefSCCs.end()))) {
+        assert(NewRC != RC && "Should not encounter the current RefSCC further "
+                              "in the postorder list of new RefSCCs.");
+        UR.RCWorklist.insert(NewRC);
+        if (DebugLogging)
+          dbgs() << "Enqueuing a new RefSCC in the update worklist: " << *NewRC
+                 << "\n";
+      }
     }
   }