From: Andrew Trick <atrick@apple.com>
Date: Mon, 17 Jun 2013 21:45:18 +0000 (+0000)
Subject: MI-Sched: handle ReadAdvance latencies as used by Swift.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=71b9d94d6ba2933df0f7936c44cdb344336d46ef;p=oota-llvm.git

MI-Sched: handle ReadAdvance latencies as used by Swift.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184135 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/TargetSchedule.cpp b/lib/CodeGen/TargetSchedule.cpp
index 53cd11c5daa..64ee9d1c464 100644
--- a/lib/CodeGen/TargetSchedule.cpp
+++ b/lib/CodeGen/TargetSchedule.cpp
@@ -201,7 +201,10 @@ unsigned TargetSchedModel::computeOperandLatency(
     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).