Revert "Add mandatory SIL pass implementing '@_alwaysEmitConformanceMetadata' protocol attribute"

Author: shahmishal

include/swift/SILOptimizer/PassManager/Passes.def

@@ -98,8 +98,6 @@ PASS(AccessEnforcementSelection, "access-enforcement-selection",
      "Access Enforcement Selection")
 PASS(AccessEnforcementWMO, "access-enforcement-wmo",
      "Access Enforcement Whole Module Optimization")
-PASS(AlwaysEmitConformanceMetadataPreservation, "preserve-always-emit-conformance-metadata",
-     "Mark conformances to @_alwaysEmitConformanceMetadata protocols as externally visible")
 PASS(CrossModuleOptimization, "cmo",
      "Perform cross-module optimization")
 PASS(AccessSummaryDumper, "access-summary-dump",

lib/IRGen/IRGenModule.cpp

@@ -1330,11 +1330,6 @@ bool IRGenerator::canEmitWitnessTableLazily(SILWitnessTable *wt) {
   if (wt->getLinkage() == SILLinkage::Shared)
     return true;
 
-  // Check if this type is set to be explicitly externally visible
-  NominalTypeDecl *ConformingTy = wt->getConformingNominal();
-  if (PrimaryIGM->getSILModule().isExternallyVisibleDecl(ConformingTy))
-    return false;
-
   switch (wt->getConformingNominal()->getEffectiveAccess()) {
     case AccessLevel::Private:
     case AccessLevel::FilePrivate:

lib/SILOptimizer/Mandatory/AlwaysEmitConformanceMetadataPreservation.cpp

@@ -1,7 +1,6 @@
 target_sources(swiftSILOptimizer PRIVATE
   AccessEnforcementSelection.cpp
   AccessMarkerElimination.cpp
-  AlwaysEmitConformanceMetadataPreservation.cpp
   AddressLowering.cpp
   CapturePromotion.cpp
   ClosureLifetimeFixup.cpp

lib/SILOptimizer/Mandatory/CMakeLists.txt

@@ -875,7 +875,6 @@ SILPassPipelinePlan::getLoweringPassPipeline(const SILOptions &Options) {
   P.startPipeline("Lowering");
   P.addLowerHopToActor(); // FIXME: earlier for more opportunities?
   P.addOwnershipModelEliminator();
-  P.addAlwaysEmitConformanceMetadataPreservation();
   P.addIRGenPrepare();
 
   return P;