Add a simple target-independent heuristic to allow targets with no

instruction itinerary data to back-schedule loads.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61070 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/ScheduleDAGInstrs.cpp b/lib/CodeGen/ScheduleDAGInstrs.cpp
index 30e1846..fa42d39 100644 (file)
--- a/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -225,6 +225,12 @@ void ScheduleDAGInstrs::ComputeLatency(SUnit *SU) {
   // all nodes flagged together into this SUnit.
   SU->Latency =
     InstrItins.getLatency(SU->getInstr()->getDesc().getSchedClass());
+
+  // Simplistic target-independent heuristic: assume that loads take
+  // extra time.
+  if (InstrItins.isEmpty())
+    if (SU->getInstr()->getDesc().mayLoad())
+      SU->Latency += 2;
 }
 
 void ScheduleDAGInstrs::dumpNode(const SUnit *SU) const {