Exposed a declarative way to specify that an attribute can be duplicated when merging attributes on a declaration. This replaces some hard-coded functionality from Sema.

llvm-svn: 199677

5 files changed, 31 insertions, 29 deletions

diff --git a/clang/docs/InternalsManual.rst b/clang/docs/InternalsManual.rst
index 40a1a09d9d7..eb19614e55d 100644
--- a/clang/docs/InternalsManual.rst
+++ b/clang/docs/InternalsManual.rst
@@ -1713,6 +1713,11 @@ For instance, ``AttributeList::AT_Interrupt`` is the shared parsed attribute
 kind, but ARMInterruptAttr and MSP430InterruptAttr are the semantic attributes 
 generated.
 
+By default, when declarations are merging attributes, an attribute will not be 
+duplicated. However, if an attribute can be duplicated during this merging 
+stage, set ``DuplicatesAllowedWhileMerging`` to ``1``, and the attribute will 
+be merged.
+
 If additional functionality is desired for the semantic form of the attribute, 
 the ``AdditionalMembers`` field specifies code to be copied verbatim into the 
 semantic attribute class object.
diff --git a/clang/include/clang/AST/Attr.h b/clang/include/clang/AST/Attr.h
index 01c32c0269b..822686a071d 100644
--- a/clang/include/clang/AST/Attr.h
+++ b/clang/include/clang/AST/Attr.h
@@ -108,6 +108,11 @@ public:
   // Pretty print this attribute.
   virtual void printPretty(raw_ostream &OS,
                            const PrintingPolicy &Policy) const = 0;
+
+  /// \brief By default, attributes cannot be duplicated when being merged;
+  /// however, an attribute can override this. Returns true if the attribute
+  /// can be duplicated when merging.
+  virtual bool duplicatesAllowed() const { return false; }
 };
 
 class InheritableAttr : public Attr {
diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
index 28b8ade7a26..82b991ac85f 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -210,6 +210,9 @@ class Attr {
   // Set to true if all of the attribute's arguments should be parsed in an
   // unevaluated context.
   bit ParseArgumentsAsUnevaluated = 0;
+  // Set to true if this attribute can be duplicated on a subject when merging
+  // attributes. By default, attributes are not merged.
+  bit DuplicatesAllowedWhileMerging = 0;
   // Lists language options, one of which is required to be true for the
   // attribute to be applicable. If empty, no language options are required.
   list<LangOpt> LangOpts = [];
@@ -340,6 +343,7 @@ def Availability : InheritableAttr {
              .Default(llvm::StringRef());
 } }];
   let HasCustomParsing = 1;
+  let DuplicatesAllowedWhileMerging = 1;
 //  let Subjects = SubjectList<[Named]>;
 }
 
@@ -1112,6 +1116,7 @@ def GuardedBy : InheritableAttr {
   let LateParsed = 1;
   let TemplateDependent = 1;
   let ParseArgumentsAsUnevaluated = 1;
+  let DuplicatesAllowedWhileMerging = 1;
   let Subjects = SubjectList<[Field, SharedVar], WarnDiag,
                              "ExpectedFieldOrGlobalVar">;
 }
@@ -1122,6 +1127,7 @@ def PtGuardedBy : InheritableAttr {
   let LateParsed = 1;
   let TemplateDependent = 1;
   let ParseArgumentsAsUnevaluated = 1;
+  let DuplicatesAllowedWhileMerging = 1;
   let Subjects = SubjectList<[Field, SharedVar], WarnDiag,
                              "ExpectedFieldOrGlobalVar">;
 }
@@ -1132,6 +1138,7 @@ def AcquiredAfter : InheritableAttr {
   let LateParsed = 1;
   let TemplateDependent = 1;
   let ParseArgumentsAsUnevaluated = 1;
+  let DuplicatesAllowedWhileMerging = 1;
   let Subjects = SubjectList<[Field, SharedVar], WarnDiag,
                              "ExpectedFieldOrGlobalVar">;
 }
@@ -1142,6 +1149,7 @@ def AcquiredBefore : InheritableAttr {
   let LateParsed = 1;
   let TemplateDependent = 1;
   let ParseArgumentsAsUnevaluated = 1;
+  let DuplicatesAllowedWhileMerging = 1;
   let Subjects = SubjectList<[Field, SharedVar], WarnDiag,
                              "ExpectedFieldOrGlobalVar">;
 }
@@ -1152,6 +1160,7 @@ def ExclusiveLockFunction : InheritableAttr {
   let LateParsed = 1;
   let TemplateDependent = 1;
   let ParseArgumentsAsUnevaluated = 1;
+  let DuplicatesAllowedWhileMerging = 1;
   let Subjects = SubjectList<[FunctionDefinition, FunctionTemplate]>;
 }
 
@@ -1161,6 +1170,7 @@ def SharedLockFunction : InheritableAttr {
   let LateParsed = 1;
   let TemplateDependent = 1;
   let ParseArgumentsAsUnevaluated = 1;
+  let DuplicatesAllowedWhileMerging = 1;
   let Subjects = SubjectList<[FunctionDefinition, FunctionTemplate]>;
 }
 
@@ -1190,6 +1200,7 @@ def ExclusiveTrylockFunction : InheritableAttr {
   let LateParsed = 1;
   let TemplateDependent = 1;
   let ParseArgumentsAsUnevaluated = 1;
+  let DuplicatesAllowedWhileMerging = 1;
   let Subjects = SubjectList<[FunctionDefinition, FunctionTemplate]>;
 }
 
@@ -1201,6 +1212,7 @@ def SharedTrylockFunction : InheritableAttr {
   let LateParsed = 1;
   let TemplateDependent = 1;
   let ParseArgumentsAsUnevaluated = 1;
+  let DuplicatesAllowedWhileMerging = 1;
   let Subjects = SubjectList<[FunctionDefinition, FunctionTemplate]>;
 }
 
@@ -1210,6 +1222,7 @@ def UnlockFunction : InheritableAttr {
   let LateParsed = 1;
   let TemplateDependent = 1;
   let ParseArgumentsAsUnevaluated = 1;
+  let DuplicatesAllowedWhileMerging = 1;
   let Subjects = SubjectList<[FunctionDefinition, FunctionTemplate]>;
 }
 
@@ -1228,6 +1241,7 @@ def LocksExcluded : InheritableAttr {
   let LateParsed = 1;
   let TemplateDependent = 1;
   let ParseArgumentsAsUnevaluated = 1;
+  let DuplicatesAllowedWhileMerging = 1;
   let Subjects = SubjectList<[FunctionDefinition, FunctionTemplate]>;
 }
 
@@ -1237,6 +1251,7 @@ def ExclusiveLocksRequired : InheritableAttr {
   let LateParsed = 1;
   let TemplateDependent = 1;
   let ParseArgumentsAsUnevaluated = 1;
+  let DuplicatesAllowedWhileMerging = 1;
   let Subjects = SubjectList<[FunctionDefinition, FunctionTemplate]>;
 }
 
@@ -1246,6 +1261,7 @@ def SharedLocksRequired : InheritableAttr {
   let LateParsed = 1;
   let TemplateDependent = 1;
   let ParseArgumentsAsUnevaluated = 1;
+  let DuplicatesAllowedWhileMerging = 1;
   let Subjects = SubjectList<[FunctionDefinition, FunctionTemplate]>;
 }
 
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index f71540c2040..6d46903c58b 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1795,34 +1795,7 @@ void Sema::MergeTypedefNameDecl(TypedefNameDecl *New, LookupResult &OldDecls) {
 
 /// DeclhasAttr - returns true if decl Declaration already has the target
 /// attribute.
-static bool
-DeclHasAttr(const Decl *D, const Attr *A) {
-  // There can be multiple AvailabilityAttr in a Decl. Make sure we copy
-  // all of them. It is mergeAvailabilityAttr in SemaDeclAttr.cpp that is
-  // responsible for making sure they are consistent.
-  const AvailabilityAttr *AA = dyn_cast<AvailabilityAttr>(A);
-  if (AA)
-    return false;
-
-  // The following thread safety attributes can also be duplicated.
-  switch (A->getKind()) {
-    case attr::ExclusiveLocksRequired:
-    case attr::SharedLocksRequired:
-    case attr::LocksExcluded:
-    case attr::ExclusiveLockFunction:
-    case attr::SharedLockFunction:
-    case attr::UnlockFunction:
-    case attr::ExclusiveTrylockFunction:
-    case attr::SharedTrylockFunction:
-    case attr::GuardedBy:
-    case attr::PtGuardedBy:
-    case attr::AcquiredBefore:
-    case attr::AcquiredAfter:
-      return false;
-    default:
-      ;
-  }
-
+static bool DeclHasAttr(const Decl *D, const Attr *A) {
   const OwnershipAttr *OA = dyn_cast<OwnershipAttr>(A);
   const AnnotateAttr *Ann = dyn_cast<AnnotateAttr>(A);
   for (Decl::attr_iterator i = D->attr_begin(), e = D->attr_end(); i != e; ++i)
@@ -1997,7 +1970,7 @@ static bool mergeDeclAttribute(Sema &S, NamedDecl *D, InheritableAttr *Attr,
     // AlignedAttrs are handled separately, because we need to handle all
     // such attributes on a declaration at the same time.
     NewAttr = 0;
-  else if (!DeclHasAttr(D, Attr))
+  else if (Attr->duplicatesAllowed() || !DeclHasAttr(D, Attr))
     NewAttr = cast<InheritableAttr>(Attr->clone(S.Context));
 
   if (NewAttr) {
diff --git a/clang/utils/TableGen/ClangAttrEmitter.cpp b/clang/utils/TableGen/ClangAttrEmitter.cpp
index c1916cba0ce..7caba492b3b 100644
--- a/clang/utils/TableGen/ClangAttrEmitter.cpp
+++ b/clang/utils/TableGen/ClangAttrEmitter.cpp
@@ -1353,6 +1353,9 @@ void EmitClangAttrClass(RecordKeeper &Records, raw_ostream &OS) {
     OS << "  virtual bool isLateParsed() const { return "
        << LateParsed << "; }\n";
 
+    if (R.getValueAsBit("DuplicatesAllowedWhileMerging"))
+      OS << "  virtual bool duplicatesAllowed() const { return true; }\n\n";
+
     OS << "};\n\n";
   }