Clean up some mistreatment of enumerations.

llvm-svn: 313953

clang/include/clang/AST/Decl.h

@@ -349,7 +349,14 @@ public:
 
   /// Kinds of explicit visibility.
   enum ExplicitVisibilityKind {
+    /// Do an LV computation for, ultimately, a type.
+    /// Visibility may be restricted by type visibility settings and
+    /// the visibility of template arguments.
     VisibilityForType,
+
+    /// Do an LV computation for, ultimately, a non-type declaration.
+    /// Visibility may be restricted by value visibility settings and
+    /// the visibility of template arguments.
     VisibilityForValue
   };
 

clang/lib/AST/Decl.cpp

@@ -103,28 +103,22 @@ TranslationUnitDecl::TranslationUnitDecl(ASTContext &ctx)
 /// Does this computation kind permit us to consider additional
 /// visibility settings from attributes and the like?
 static bool hasExplicitVisibilityAlready(LVComputationKind computation) {
-  return ((unsigned(computation) & IgnoreExplicitVisibilityBit) != 0);
+  return computation.IgnoreExplicitVisibility;
 }
 
 /// Given an LVComputationKind, return one of the same type/value sort
 /// that records that it already has explicit visibility.
 static LVComputationKind
-withExplicitVisibilityAlready(LVComputationKind oldKind) {
-  LVComputationKind newKind =
-    static_cast<LVComputationKind>(unsigned(oldKind) |
-                                   IgnoreExplicitVisibilityBit);
-  assert(oldKind != LVForType          || newKind == LVForExplicitType);
-  assert(oldKind != LVForValue         || newKind == LVForExplicitValue);
-  assert(oldKind != LVForExplicitType  || newKind == LVForExplicitType);
-  assert(oldKind != LVForExplicitValue || newKind == LVForExplicitValue);
-  return newKind;
+withExplicitVisibilityAlready(LVComputationKind Kind) {
+  Kind.IgnoreExplicitVisibility = true;
+  return Kind;
 }
 
 static Optional<Visibility> getExplicitVisibility(const NamedDecl *D,
                                                   LVComputationKind kind) {
-  assert(!hasExplicitVisibilityAlready(kind) &&
+  assert(!kind.IgnoreExplicitVisibility &&
          "asking for explicit visibility when we shouldn't be");
-  return D->getExplicitVisibility((NamedDecl::ExplicitVisibilityKind) kind);
+  return D->getExplicitVisibility(kind.getExplicitVisibilityKind());
 }
 
 /// Is the given declaration a "type" or a "value" for the purposes of
@@ -190,7 +184,7 @@ static Optional<Visibility> getVisibilityOf(const NamedDecl *D,
 
 LinkageInfo LinkageComputer::getLVForType(const Type &T,
                                           LVComputationKind computation) {
-  if (computation == LVForLinkageOnly)
+  if (computation.IgnoreAllVisibility)
     return LinkageInfo(T.getLinkage(), DefaultVisibility, true);
   return getTypeLinkageAndVisibility(&T);
 }
@@ -359,21 +353,11 @@ void LinkageComputer::mergeTemplateLV(
 /// that would match the given rules?
 static bool hasDirectVisibilityAttribute(const NamedDecl *D,
                                          LVComputationKind computation) {
-  switch (computation) {
-  case LVForType:
-  case LVForExplicitType:
-    if (D->hasAttr<TypeVisibilityAttr>())
-      return true;
-    // fallthrough
-  case LVForValue:
-  case LVForExplicitValue:
-    if (D->hasAttr<VisibilityAttr>())
-      return true;
+  if (computation.IgnoreAllVisibility)
     return false;
-  case LVForLinkageOnly:
-    return false;
-  }
-  llvm_unreachable("bad visibility computation kind");
+
+  return (computation.isTypeVisibility() && D->hasAttr<TypeVisibilityAttr>()) ||
+         D->hasAttr<VisibilityAttr>();
 }
 
 /// Should we consider visibility associated with the template
@@ -675,13 +659,10 @@ LinkageComputer::getLVForNamespaceScopeDecl(const NamedDecl *D,
     // Add in global settings if the above didn't give us direct visibility.
     if (!LV.isVisibilityExplicit()) {
       // Use global type/value visibility as appropriate.
-      Visibility globalVisibility;
-      if (computation == LVForValue) {
-        globalVisibility = Context.getLangOpts().getValueVisibilityMode();
-      } else {
-        assert(computation == LVForType);
-        globalVisibility = Context.getLangOpts().getTypeVisibilityMode();
-      }
+      Visibility globalVisibility =
+          computation.isValueVisibility()
+              ? Context.getLangOpts().getValueVisibilityMode()
+              : Context.getLangOpts().getTypeVisibilityMode();
       LV.mergeVisibility(globalVisibility, /*explicit*/ false);
 
       // If we're paying attention to global visibility, apply
@@ -1011,8 +992,9 @@ bool NamedDecl::isLinkageValid() const {
   if (!hasCachedLinkage())
     return true;
 
-  Linkage L =
-      LinkageComputer{}.computeLVForDecl(this, LVForLinkageOnly).getLinkage();
+  Linkage L = LinkageComputer{}
+                  .computeLVForDecl(this, LVComputationKind::forLinkageOnly())
+                  .getLinkage();
   return L == getCachedLinkage();
 }
 
@@ -1032,7 +1014,9 @@ ObjCStringFormatFamily NamedDecl::getObjCFStringFormattingFamily() const {
 Linkage NamedDecl::getLinkageInternal() const {
   // We don't care about visibility here, so ask for the cheapest
   // possible visibility analysis.
-  return LinkageComputer{}.getLVForDecl(this, LVForLinkageOnly).getLinkage();
+  return LinkageComputer{}
+      .getLVForDecl(this, LVComputationKind::forLinkageOnly())
+      .getLinkage();
 }
 
 LinkageInfo NamedDecl::getLinkageAndVisibility() const {
@@ -1357,7 +1341,7 @@ LinkageInfo LinkageComputer::getLVForDecl(const NamedDecl *D,
   if (D->hasAttr<InternalLinkageAttr>())
     return getInternalLinkageFor(D);
 
-  if (computation == LVForLinkageOnly && D->hasCachedLinkage())
+  if (computation.IgnoreAllVisibility && D->hasCachedLinkage())
     return LinkageInfo(D->getCachedLinkage(), DefaultVisibility, false);
 
   if (llvm::Optional<LinkageInfo> LI = lookup(D, computation))
@@ -1398,7 +1382,10 @@ LinkageInfo LinkageComputer::getLVForDecl(const NamedDecl *D,
 }
 
 LinkageInfo LinkageComputer::getDeclLinkageAndVisibility(const NamedDecl *D) {
-  return getLVForDecl(D, usesTypeVisibility(D) ? LVForType : LVForValue);
+  return getLVForDecl(D,
+                      LVComputationKind(usesTypeVisibility(D)
+                                            ? NamedDecl::VisibilityForType
+                                            : NamedDecl::VisibilityForValue));
 }
 
 Module *NamedDecl::getOwningModuleForLinkage() const {

clang/lib/AST/Linkage.h

@@ -22,38 +22,50 @@
 #include "llvm/ADT/Optional.h"
 
 namespace clang {
-enum : unsigned {
-  IgnoreExplicitVisibilityBit = 2,
-  IgnoreAllVisibilityBit = 4
-};
-
 /// Kinds of LV computation.  The linkage side of the computation is
 /// always the same, but different things can change how visibility is
 /// computed.
-enum LVComputationKind {
-  /// Do an LV computation for, ultimately, a type.
-  /// Visibility may be restricted by type visibility settings and
-  /// the visibility of template arguments.
-  LVForType = NamedDecl::VisibilityForType,
+struct LVComputationKind {
+  /// The kind of entity whose visibility is ultimately being computed;
+  /// visibility computations for types and non-types follow different rules.
+  unsigned ExplicitKind : 1;
+  /// Whether explicit visibility attributes should be ignored. When set,
+  /// visibility may only be restricted by the visibility of template arguments.
+  unsigned IgnoreExplicitVisibility : 1;
+  /// Whether all visibility should be ignored. When set, we're only interested
+  /// in computing linkage.
+  unsigned IgnoreAllVisibility : 1;
 
-  /// Do an LV computation for, ultimately, a non-type declaration.
-  /// Visibility may be restricted by value visibility settings and
-  /// the visibility of template arguments.
-  LVForValue = NamedDecl::VisibilityForValue,
+  explicit LVComputationKind(NamedDecl::ExplicitVisibilityKind EK)
+      : ExplicitKind(EK), IgnoreExplicitVisibility(false),
+        IgnoreAllVisibility(false) {}
 
-  /// Do an LV computation for, ultimately, a type that already has
-  /// some sort of explicit visibility.  Visibility may only be
-  /// restricted by the visibility of template arguments.
-  LVForExplicitType = (LVForType | IgnoreExplicitVisibilityBit),
+  NamedDecl::ExplicitVisibilityKind getExplicitVisibilityKind() const {
+    return static_cast<NamedDecl::ExplicitVisibilityKind>(ExplicitKind);
+  }
 
-  /// Do an LV computation for, ultimately, a non-type declaration
-  /// that already has some sort of explicit visibility.  Visibility
-  /// may only be restricted by the visibility of template arguments.
-  LVForExplicitValue = (LVForValue | IgnoreExplicitVisibilityBit),
+  bool isTypeVisibility() const {
+    return getExplicitVisibilityKind() == NamedDecl::VisibilityForType;
+  }
+  bool isValueVisibility() const {
+    return getExplicitVisibilityKind() == NamedDecl::VisibilityForValue;
+  }
 
   /// Do an LV computation when we only care about the linkage.
-  LVForLinkageOnly =
-      LVForValue | IgnoreExplicitVisibilityBit | IgnoreAllVisibilityBit
+  static LVComputationKind forLinkageOnly() {
+    LVComputationKind Result(NamedDecl::VisibilityForValue);
+    Result.IgnoreExplicitVisibility = true;
+    Result.IgnoreAllVisibility = true;
+    return Result;
+  }
+
+  unsigned toBits() {
+    unsigned Bits = 0;
+    Bits = (Bits << 1) | ExplicitKind;
+    Bits = (Bits << 1) | IgnoreExplicitVisibility;
+    Bits = (Bits << 1) | IgnoreAllVisibility;
+    return Bits;
+  }
 };
 
 class LinkageComputer {
@@ -66,14 +78,12 @@ class LinkageComputer {
   // using C = Foo<B, B>;
   // using D = Foo<C, C>;
   //
-  // Note that the unsigned is actually a LVComputationKind; ubsan's enum
-  // sanitizer doesn't like tombstone/empty markers outside of
-  // LVComputationKind's range.
+  // The unsigned represents an LVComputationKind.
   using QueryType = std::pair<const NamedDecl *, unsigned>;
   llvm::SmallDenseMap<QueryType, LinkageInfo, 8> CachedLinkageInfo;
 
   static QueryType makeCacheKey(const NamedDecl *ND, LVComputationKind Kind) {
-    return std::make_pair(ND, static_cast<unsigned>(Kind));
+    return std::make_pair(ND, Kind.toBits());
   }
 
   llvm::Optional<LinkageInfo> lookup(const NamedDecl *ND,