Make ConformanceIsolationRequest cache per-ProtocolConformance

This request was looking through to the root conformance, which could
mess with the caching bits. Sink the "is nonisolated conformance" bit
down into ProtocolConformance, and have the request for a non-root
conformance be defined in terms of the request for the root
conformance.

Author: DougGregor

include/swift/AST/ProtocolConformance.h

@@ -131,6 +131,8 @@ class alignas(1 << DeclAlignInBits) ProtocolConformance
   /// conformance definition.
   Type ConformingType;
 
+  friend class ConformanceIsolationRequest;
+
 protected:
   // clang-format off
   //
@@ -139,9 +141,13 @@ class alignas(1 << DeclAlignInBits) ProtocolConformance
   union { uint64_t OpaqueBits;
 
     SWIFT_INLINE_BITFIELD_BASE(ProtocolConformance,
+                               1+
                                bitmax(NumProtocolConformanceKindBits, 8),
       /// The kind of protocol conformance.
-      Kind : bitmax(NumProtocolConformanceKindBits, 8)
+      Kind : bitmax(NumProtocolConformanceKindBits, 8),
+
+      /// Whether the computed actor isolation is nonisolated.
+      IsComputedNonisolated : 1
     );
 
     SWIFT_INLINE_BITFIELD_EMPTY(RootProtocolConformance, ProtocolConformance);
@@ -161,9 +167,6 @@ class alignas(1 << DeclAlignInBits) ProtocolConformance
       /// this conformance.
       IsPreconcurrencyEffectful : 1,
 
-      /// Whether the computed actor isolation is nonisolated.
-      IsComputedNonisolated : 1,
-
       /// Whether there is an explicit global actor specified for this
       /// conformance.
       HasExplicitGlobalActor : 1,
@@ -198,6 +201,15 @@ class alignas(1 << DeclAlignInBits) ProtocolConformance
   ProtocolConformance(ProtocolConformanceKind kind, Type conformingType)
     : ConformingType(conformingType) {
     Bits.ProtocolConformance.Kind = unsigned(kind);
+    Bits.ProtocolConformance.IsComputedNonisolated = false;
+  }
+
+  bool isComputedNonisolated() const {
+    return Bits.ProtocolConformance.IsComputedNonisolated;
+  }
+
+  void setComputedNonnisolated(bool value = true) {
+    Bits.ProtocolConformance.IsComputedNonisolated = value;
   }
 
 public:
@@ -591,14 +603,6 @@ class NormalProtocolConformance : public RootProtocolConformance,
   // Record the explicitly-specified global actor isolation.
   void setExplicitGlobalActorIsolation(TypeExpr *typeExpr);
 
-  bool isComputedNonisolated() const {
-    return Bits.NormalProtocolConformance.IsComputedNonisolated;
-  }
-
-  void setComputedNonnisolated(bool value = true) {
-    Bits.NormalProtocolConformance.IsComputedNonisolated = value;
-  }
-
 public:
   NormalProtocolConformance(Type conformingType, ProtocolDecl *protocol,
                             SourceLoc loc, DeclContext *dc,
@@ -622,7 +626,6 @@ class NormalProtocolConformance : public RootProtocolConformance,
     Bits.NormalProtocolConformance.HasComputedAssociatedConformances = false;
     Bits.NormalProtocolConformance.SourceKind =
         unsigned(ConformanceEntryKind::Explicit);
-    Bits.NormalProtocolConformance.IsComputedNonisolated = false;
     Bits.NormalProtocolConformance.HasExplicitGlobalActor = false;
     setExplicitGlobalActorIsolation(options.getGlobalActorIsolationType());
   }

lib/AST/TypeCheckRequests.cpp

@@ -1378,31 +1378,25 @@ ConformanceIsolationRequest::getCachedResult() const {
   // everything else, which is nearly every conformance, this request quickly
   // returns "nonisolated" so there is no point in caching it.
   auto conformance = std::get<0>(getStorage());
-  auto rootNormal =
-      dyn_cast<NormalProtocolConformance>(conformance->getRootConformance());
-  if (!rootNormal)
-    return ActorIsolation::forNonisolated(false);
 
   // Was actor isolation non-isolated?
-  if (rootNormal->isComputedNonisolated())
+  if (conformance->isComputedNonisolated())
     return ActorIsolation::forNonisolated(false);
 
-  ASTContext &ctx = rootNormal->getDeclContext()->getASTContext();
+  ASTContext &ctx = conformance->getDeclContext()->getASTContext();
   return ctx.evaluator.getCachedNonEmptyOutput(*this);
 }
 
 void ConformanceIsolationRequest::cacheResult(ActorIsolation result) const {
   auto conformance = std::get<0>(getStorage());
-  auto rootNormal =
-      cast<NormalProtocolConformance>(conformance->getRootConformance());
 
   // Common case: conformance is nonisolated.
   if (result.isNonisolated()) {
-    rootNormal->setComputedNonnisolated();
+    conformance->setComputedNonnisolated();
     return;
   }
 
-  ASTContext &ctx = rootNormal->getDeclContext()->getASTContext();
+  ASTContext &ctx = conformance->getDeclContext()->getASTContext();
   ctx.evaluator.cacheNonEmptyOutput(*this, std::move(result));
 }
 

lib/Sema/TypeCheckConcurrency.cpp

@@ -7954,6 +7954,9 @@ ConformanceIsolationRequest::evaluate(Evaluator &evaluator, ProtocolConformance
   if (!rootNormal)
     return ActorIsolation::forNonisolated(false);
 
+  if (conformance != rootNormal)
+    return rootNormal->getIsolation();
+
   // If the conformance is explicitly non-isolated, report that.
   if (rootNormal->getOptions().contains(ProtocolConformanceFlags::Nonisolated))
     return ActorIsolation::forNonisolated(false);