[Parser][NFC] Move the core parsing of an attribute into a separate method (#107300)

Refactor attribute parsing so that the main code parsing an attribute
can be called by a separate code path that doesn't start with the
'__attribute' keyword.

Author: bwendling

clang/include/clang/Parse/Parser.h

@@ -2943,6 +2943,9 @@ class Parser : public CodeCompletionHandler {
     return false;
   }
 
+  bool ParseSingleGNUAttribute(ParsedAttributes &Attrs, SourceLocation &EndLoc,
+                               LateParsedAttrList *LateAttrs = nullptr,
+                               Declarator *D = nullptr);
   void ParseGNUAttributes(ParsedAttributes &Attrs,
                           LateParsedAttrList *LateAttrs = nullptr,
                           Declarator *D = nullptr);

clang/lib/Parse/ParseDecl.cpp

@@ -146,6 +146,86 @@ void Parser::ParseAttributes(unsigned WhichAttrKinds, ParsedAttributes &Attrs,
   } while (MoreToParse);
 }
 
+/// ParseSingleGNUAttribute - Parse a single GNU attribute.
+///
+/// [GNU]  attrib:
+///          empty
+///          attrib-name
+///          attrib-name '(' identifier ')'
+///          attrib-name '(' identifier ',' nonempty-expr-list ')'
+///          attrib-name '(' argument-expression-list [C99 6.5.2] ')'
+///
+/// [GNU]  attrib-name:
+///          identifier
+///          typespec
+///          typequal
+///          storageclass
+bool Parser::ParseSingleGNUAttribute(ParsedAttributes &Attrs,
+                                     SourceLocation &EndLoc,
+                                     LateParsedAttrList *LateAttrs,
+                                     Declarator *D) {
+  IdentifierInfo *AttrName = Tok.getIdentifierInfo();
+  if (!AttrName)
+    return true;
+
+  SourceLocation AttrNameLoc = ConsumeToken();
+
+  if (Tok.isNot(tok::l_paren)) {
+    Attrs.addNew(AttrName, AttrNameLoc, nullptr, AttrNameLoc, nullptr, 0,
+                 ParsedAttr::Form::GNU());
+    return false;
+  }
+
+  bool LateParse = false;
+  if (!LateAttrs)
+    LateParse = false;
+  else if (LateAttrs->lateAttrParseExperimentalExtOnly()) {
+    // The caller requested that this attribute **only** be late
+    // parsed for `LateAttrParseExperimentalExt` attributes. This will
+    // only be late parsed if the experimental language option is enabled.
+    LateParse = getLangOpts().ExperimentalLateParseAttributes &&
+                IsAttributeLateParsedExperimentalExt(*AttrName);
+  } else {
+    // The caller did not restrict late parsing to only
+    // `LateAttrParseExperimentalExt` attributes so late parse
+    // both `LateAttrParseStandard` and `LateAttrParseExperimentalExt`
+    // attributes.
+    LateParse = IsAttributeLateParsedExperimentalExt(*AttrName) ||
+                IsAttributeLateParsedStandard(*AttrName);
+  }
+
+  // Handle "parameterized" attributes
+  if (!LateParse) {
+    ParseGNUAttributeArgs(AttrName, AttrNameLoc, Attrs, &EndLoc, nullptr,
+                          SourceLocation(), ParsedAttr::Form::GNU(), D);
+    return false;
+  }
+
+  // Handle attributes with arguments that require late parsing.
+  LateParsedAttribute *LA =
+      new LateParsedAttribute(this, *AttrName, AttrNameLoc);
+  LateAttrs->push_back(LA);
+
+  // Attributes in a class are parsed at the end of the class, along
+  // with other late-parsed declarations.
+  if (!ClassStack.empty() && !LateAttrs->parseSoon())
+    getCurrentClass().LateParsedDeclarations.push_back(LA);
+
+  // Be sure ConsumeAndStoreUntil doesn't see the start l_paren, since it
+  // recursively consumes balanced parens.
+  LA->Toks.push_back(Tok);
+  ConsumeParen();
+  // Consume everything up to and including the matching right parens.
+  ConsumeAndStoreUntil(tok::r_paren, LA->Toks, /*StopAtSemi=*/true);
+
+  Token Eof;
+  Eof.startToken();
+  Eof.setLocation(Tok.getLocation());
+  LA->Toks.push_back(Eof);
+
+  return false;
+}
+
 /// ParseGNUAttributes - Parse a non-empty attributes list.
 ///
 /// [GNU] attributes:
@@ -223,64 +303,9 @@ void Parser::ParseGNUAttributes(ParsedAttributes &Attrs,
             AttributeCommonInfo::Syntax::AS_GNU);
         break;
       }
-      IdentifierInfo *AttrName = Tok.getIdentifierInfo();
-      if (!AttrName)
-        break;
 
-      SourceLocation AttrNameLoc = ConsumeToken();
-
-      if (Tok.isNot(tok::l_paren)) {
-        Attrs.addNew(AttrName, AttrNameLoc, nullptr, AttrNameLoc, nullptr, 0,
-                     ParsedAttr::Form::GNU());
-        continue;
-      }
-
-      bool LateParse = false;
-      if (!LateAttrs)
-        LateParse = false;
-      else if (LateAttrs->lateAttrParseExperimentalExtOnly()) {
-        // The caller requested that this attribute **only** be late
-        // parsed for `LateAttrParseExperimentalExt` attributes. This will
-        // only be late parsed if the experimental language option is enabled.
-        LateParse = getLangOpts().ExperimentalLateParseAttributes &&
-                    IsAttributeLateParsedExperimentalExt(*AttrName);
-      } else {
-        // The caller did not restrict late parsing to only
-        // `LateAttrParseExperimentalExt` attributes so late parse
-        // both `LateAttrParseStandard` and `LateAttrParseExperimentalExt`
-        // attributes.
-        LateParse = IsAttributeLateParsedExperimentalExt(*AttrName) ||
-                    IsAttributeLateParsedStandard(*AttrName);
-      }
-
-      // Handle "parameterized" attributes
-      if (!LateParse) {
-        ParseGNUAttributeArgs(AttrName, AttrNameLoc, Attrs, &EndLoc, nullptr,
-                              SourceLocation(), ParsedAttr::Form::GNU(), D);
-        continue;
-      }
-
-      // Handle attributes with arguments that require late parsing.
-      LateParsedAttribute *LA =
-          new LateParsedAttribute(this, *AttrName, AttrNameLoc);
-      LateAttrs->push_back(LA);
-
-      // Attributes in a class are parsed at the end of the class, along
-      // with other late-parsed declarations.
-      if (!ClassStack.empty() && !LateAttrs->parseSoon())
-        getCurrentClass().LateParsedDeclarations.push_back(LA);
-
-      // Be sure ConsumeAndStoreUntil doesn't see the start l_paren, since it
-      // recursively consumes balanced parens.
-      LA->Toks.push_back(Tok);
-      ConsumeParen();
-      // Consume everything up to and including the matching right parens.
-      ConsumeAndStoreUntil(tok::r_paren, LA->Toks, /*StopAtSemi=*/true);
-
-      Token Eof;
-      Eof.startToken();
-      Eof.setLocation(Tok.getLocation());
-      LA->Toks.push_back(Eof);
+      if (ParseSingleGNUAttribute(Attrs, EndLoc, LateAttrs, D))
+        break;
     } while (Tok.is(tok::comma));
 
     if (ExpectAndConsume(tok::r_paren))