[llvm] r184135 - MI-Sched: handle ReadAdvance latencies as used by Swift.

[Andrew Trick]

Author: atrick
Date: Mon Jun 17 16:45:18 2013
New Revision: 184135

URL: http://llvm.org/viewvc/llvm-project?rev=184135&view=rev
Log:
MI-Sched: handle ReadAdvance latencies as used by Swift.

Modified:
    llvm/trunk/lib/CodeGen/TargetSchedule.cpp

Modified: llvm/trunk/lib/CodeGen/TargetSchedule.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/TargetSchedule.cpp?rev=184135&r1=184134&r2=184135&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/TargetSchedule.cpp (original)
+++ llvm/trunk/lib/CodeGen/TargetSchedule.cpp Mon Jun 17 16:45:18 2013
@@ -201,7 +201,10 @@ unsigned TargetSchedModel::computeOperan
     if (UseDesc->NumReadAdvanceEntries == 0)
       return Latency;
     unsigned UseIdx = findUseIdx(UseMI, UseOperIdx);
-    return Latency - STI->getReadAdvanceCycles(UseDesc, UseIdx, WriteID);
+    int Advance = STI->getReadAdvanceCycles(UseDesc, UseIdx, WriteID);
+    if (Advance > 0 && (unsigned)Advance > Latency) // unsigned wrap
+      return 0;
+    return Latency - Advance;
   }
   // If DefIdx does not exist in the model (e.g. implicit defs), then return
   // unit latency (defaultDefLatency may be too conservative).