SILOptimizer: add a LICM pass at mid-level in the pass pipeline.

It's needed to hoist global_init calls.

Author: eeckstein

lib/SILOptimizer/PassManager/PassPipeline.cpp

@@ -453,6 +453,9 @@ static bool addMidLevelPassPipeline(SILPassPipelinePlan &P) {
   // for CapturePropagation.
   P.addDeadArgSignatureOpt();
 
+  // A LICM pass at mid-level is mainly needed to hoist addressors of globals.
+  // It needs to be before global_init functions are inlined.
+  P.addLICM();
   // Run loop unrolling after inlining and constant propagation, because loop
   // trip counts may have became constant.
   P.addLoopUnroll();