[llvm-commits] [llvm] r128164 - /llvm/trunk/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp

[Andrew Trick]

Author: atrick
Date: Wed Mar 23 15:42:39 2011
New Revision: 128164

URL: http://llvm.org/viewvc/llvm-project?rev=128164&view=rev
Log:
Ensure that def-side physreg copies are scheduled above any other uses
so the scheduler can't create new interferences on the copies
themselves. Prior to this fix the scheduler could get stuck in a loop
creating copies.
Fixes PR9509.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp?rev=128164&r1=128163&r2=128164&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp Wed Mar 23 15:42:39 2011
@@ -935,6 +935,15 @@
       AddPred(SuccSU, D);
       DelDeps.push_back(std::make_pair(SuccSU, *I));
     }
+    else {
+      // Avoid scheduling the def-side copy before other successors. Otherwise
+      // we could introduce another physreg interference on the copy and
+      // continue inserting copies indefinitely.
+      SDep D(CopyFromSU, SDep::Order, /*Latency=*/0,
+             /*Reg=*/0, /*isNormalMemory=*/false,
+             /*isMustAlias=*/false, /*isArtificial=*/true);
+      AddPred(SuccSU, D);
+    }
   }
   for (unsigned i = 0, e = DelDeps.size(); i != e; ++i)
     RemovePred(DelDeps[i].first, DelDeps[i].second);