Don't attempt MTM heuristics without a scheduling model present.

This should fix the PPC buildbots.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178558 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/EarlyIfConversion.cpp

@@ -677,6 +677,10 @@ bool EarlyIfConverter::shouldConvertIf() {
   if (Stress)
     return true;
 
+  // Without a scheduling model, we can't make decisions.
+  if (!SchedModel->hasInstrSchedModel())
+    return false;
+
   if (!MinInstr)
     MinInstr = Traces->getEnsemble(MachineTraceMetrics::TS_MinInstrCount);