PassPipeline: add a few utility passes in the low-level pipeline

To be able to remove lazy initialization of global read-only arrays

Author: eeckstein

lib/SILOptimizer/PassManager/PassPipeline.cpp

@@ -810,6 +810,9 @@ static void addLowLevelPassPipeline(SILPassPipelinePlan &P) {
   P.addDeadObjectElimination();
   P.addObjectOutliner();
   P.addDeadStoreElimination();
+  P.addDCE();
+  P.addSimplification();
+  P.addInitializeStaticGlobals();
 
   // dead-store-elimination can expose opportunities for dead object elimination.
   P.addDeadObjectElimination();

test/SILOptimizer/devirt_covariant_return.swift

@@ -235,7 +235,7 @@ public class D2: D1 {
 // that D2.foo() is inlined thanks to this.
 // CHECK-LABEL: sil hidden [noinline] @$s23devirt_covariant_return7driver2ys5Int32VAA2D2CF
 // CHECK-NOT: class_method
-// CHECK: checked_cast_br [exact] D1 in %{{.*}} : $D1 to D2
+// CHECK: checked_cast_br [exact] D1 in
 // CHECK: bb2
 // CHECK: global_addr
 // CHECK: load