Make 'rawValue' and 'init(rawValue:)' inlinable for non-resilient enums (#15589)

Small potential perf win...or rather regain, since we apparently used
to do this. It's a bit trickier to say whether we should do the same
for resilient enums, since /in theory/ a later version of the library
might decide to use different raw values.

https://bugs.swift.org/browse/SR-7094

Author: jrose-apple

lib/Sema/DerivedConformanceRawRepresentable.cpp

@@ -145,6 +145,17 @@ static VarDecl *deriveRawRepresentable_raw(TypeChecker &tc,
     addGetterToReadOnlyDerivedProperty(tc, propDecl, rawType);
   getterDecl->setBodySynthesizer(&deriveBodyRawRepresentable_raw);
 
+  // If the containing module is not resilient, make sure clients can get at
+  // the raw value without function call overhead.
+  if (parentDC->getParentModule()->getResilienceStrategy() !=
+      ResilienceStrategy::Resilient) {
+    AccessScope access =
+        enumDecl->getFormalAccessScope(nullptr,
+                                       /*treatUsableFromInlineAsPublic*/true);
+    if (access.isPublic())
+      getterDecl->getAttrs().add(new (C) InlinableAttr(/*implicit*/false));
+  }
+
   auto dc = cast<IterableDeclContext>(parentDecl);
   dc->addMember(getterDecl);
   dc->addMember(propDecl);
@@ -343,6 +354,17 @@ static ConstructorDecl *deriveRawRepresentable_init(TypeChecker &tc,
   initDecl->copyFormalAccessFrom(enumDecl, /*sourceIsParentContext*/true);
   initDecl->setValidationStarted();
 
+  // If the containing module is not resilient, make sure clients can construct
+  // an instance without function call overhead.
+  if (parentDC->getParentModule()->getResilienceStrategy() !=
+      ResilienceStrategy::Resilient) {
+    AccessScope access =
+        enumDecl->getFormalAccessScope(nullptr,
+                                       /*treatUsableFromInlineAsPublic*/true);
+    if (access.isPublic())
+      initDecl->getAttrs().add(new (C) InlinableAttr(/*implicit*/false));
+  }
+
   tc.Context.addSynthesizedDecl(initDecl);
 
   cast<IterableDeclContext>(parentDecl)->addMember(initDecl);

lib/Sema/TypeCheckAttr.cpp

@@ -1984,7 +1984,10 @@ void AttributeChecker::visitUsableFromInlineAttr(UsableFromInlineAttr *attr) {
 
   // On internal declarations, @inlinable implies @usableFromInline.
   if (VD->getAttrs().hasAttribute<InlinableAttr>()) {
-    diagnoseAndRemoveAttr(attr, diag::inlinable_implies_usable_from_inline);
+    if (attr->isImplicit())
+      attr->setInvalid();
+    else
+      diagnoseAndRemoveAttr(attr, diag::inlinable_implies_usable_from_inline);
     return;
   }
 }

test/SILGen/enum_raw_representable.swift

@@ -0,0 +1,12 @@
+// RUN: %target-swift-frontend -emit-silgen -enable-sil-ownership %s | %FileCheck %s
+// RUN: %target-swift-frontend -emit-silgen -enable-sil-ownership -enable-resilience %s | %FileCheck -check-prefix=CHECK-RESILIENT %s
+
+public enum E: Int {
+  case a, b, c
+}
+
+// CHECK-DAG: sil [serialized] @$S22enum_raw_representable1EO0B5ValueACSgSi_tcfC
+// CHECK-DAG: sil [serialized] @$S22enum_raw_representable1EO0B5ValueSivg
+
+// CHECK-RESILIENT-DAG: sil @$S22enum_raw_representable1EO0B5ValueACSgSi_tcfC
+// CHECK-RESILIENT-DAG: sil @$S22enum_raw_representable1EO0B5ValueSivg