[SILOptimizer] Added MandatoryCombiner to passes.

The mandatory combiner is added both to the Onone pass and also to the
performance pass.

Author: nate-chandler

lib/SILOptimizer/PassManager/PassPipeline.cpp

@@ -597,6 +597,7 @@ SILPassPipelinePlan::getSILOptPreparePassPipeline(const SILOptions &Options) {
   }
 
   P.startPipeline("SILOpt Prepare Passes");
+  P.addMandatoryCombine();
   P.addAccessMarkerElimination();
 
   return P;
@@ -654,6 +655,9 @@ SILPassPipelinePlan
 SILPassPipelinePlan::getOnonePassPipeline(const SILOptions &Options) {
   SILPassPipelinePlan P(Options);
 
+  P.startPipeline("Mandatory Combines");
+  P.addMandatoryCombine();
+
   // First serialize the SIL if we are asked to.
   P.startPipeline("Serialization");
   P.addSerializeSILPass();