[metadata prespecialization] Bump availability.

Previously, the availability was 5.3.  Since
compareProtocolConformanceDescriptors was added in 5.4 and was used by
metadata accessors with baked-in checks for arguments which matched
prespecializations, 5.3 was incorrect.  Moreover, now that the searching
for matches is done by getGenericMetadata, the metadata accessors no
longer contain the early exits, so running against a 5.3 runtime would
entail the metadata accessor failing to produce canonical prespecialized
records.

Here, the availability is bumped to 5.4 which includes the runtime
changes to support the metadata accessors not having early exits to
return prespecialized records.

Author: nate-chandler

include/swift/AST/ASTContext.h

@@ -669,6 +669,10 @@ class ASTContext final {
   /// compiler for the target platform.
   AvailabilityContext getSwift53Availability();
 
+  /// Get the runtime availability of features introduced in the Swift 5.4
+  /// compiler for the target platform.
+  AvailabilityContext getSwift54Availability();
+
   /// Get the runtime availability of features that have been introduced in the
   /// Swift compiler for future versions of the target platform.
   AvailabilityContext getSwiftFutureAvailability();

lib/AST/Availability.cpp

@@ -306,21 +306,21 @@ AvailabilityContext ASTContext::getTypesInAbstractMetadataStateAvailability() {
 }
 
 AvailabilityContext ASTContext::getPrespecializedGenericMetadataAvailability() {
-  return getSwift53Availability();
+  return getSwift54Availability();
 }
 
 AvailabilityContext ASTContext::getCompareTypeContextDescriptorsAvailability() {
-  return getSwiftFutureAvailability();
+  return getSwift54Availability();
 }
 
 AvailabilityContext
 ASTContext::getCompareProtocolConformanceDescriptorsAvailability() {
-  return getSwiftFutureAvailability();
+  return getSwift54Availability();
 }
 
 AvailabilityContext
 ASTContext::getIntermodulePrespecializedGenericMetadataAvailability() {
-  return getSwiftFutureAvailability();
+  return getSwift54Availability();
 }
 
 AvailabilityContext ASTContext::getSwift52Availability() {
@@ -384,6 +384,10 @@ AvailabilityContext ASTContext::getSwift53Availability() {
   }
 }
 
+AvailabilityContext ASTContext::getSwift54Availability() {
+  return getSwiftFutureAvailability();
+}
+
 AvailabilityContext ASTContext::getSwiftFutureAvailability() {
   auto target = LangOpts.Target;
 

test/IRGen/generic_metatypes_future.swift

@@ -1,5 +1,5 @@
 
-// RUN: %swift -prespecialize-generic-metadata -module-name generic_metatypes -target x86_64-apple-macosx50.99  -emit-ir -disable-legacy-type-info -parse-stdlib -primary-file %s | %FileCheck --check-prefix=CHECK --check-prefix=CHECK-64 -DINT=i64 %s
+// RUN: %swift -prespecialize-generic-metadata -module-name generic_metatypes -target x86_64-apple-macosx99.99  -emit-ir -disable-legacy-type-info -parse-stdlib -primary-file %s | %FileCheck --check-prefix=CHECK --check-prefix=CHECK-64 -DINT=i64 %s
 // RUN: %swift -prespecialize-generic-metadata -module-name generic_metatypes -target x86_64-apple-ios99.0      -emit-ir -disable-legacy-type-info -parse-stdlib -primary-file %s | %FileCheck --check-prefix=CHECK --check-prefix=CHECK-64 -DINT=i64  %s
 // RUN: %swift -prespecialize-generic-metadata -module-name generic_metatypes -target x86_64-apple-tvos99.0     -emit-ir -disable-legacy-type-info -parse-stdlib -primary-file %s | %FileCheck --check-prefix=CHECK --check-prefix=CHECK-64 -DINT=i64  %s
 // RUN: %swift -prespecialize-generic-metadata -module-name generic_metatypes -target i386-apple-watchos9.99    -emit-ir -disable-legacy-type-info -parse-stdlib -primary-file %s | %FileCheck --check-prefix=CHECK --check-prefix=CHECK-32 -DINT=i32  %s