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 53cd11c..64ee9d1 100644
--- a/lib/CodeGen/TargetSchedule.cpp
+++ b/lib/CodeGen/TargetSchedule.cpp
@@ -201,7 +201,10 @@
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).