[PATCH] D67159: [clang] New __attribute__((__clang_builtin)).

[Simon Tatham via Phabricator via cfe-commits]

simon_tatham created this revision.
simon_tatham added reviewers: dmgreen, miyuki, ostannard.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

This allows you to declare a function with a name of your choice (say
`foo`), but have clang treat it as if it were a builtin function (say
`__builtin_foo`), by writing

  static __inline__ __attribute__((__clang_builtin(__builtin_foo)))
  int foo(args);

I'm intending to use this for the ACLE intrinsics for MVE, which have
to be polymorphic on their argument types and also implemented by
builtins. This commit itself just introduces the new attribute, and
doesn't use it for anything.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D67159

Files:
  clang/include/clang/Basic/Attr.td
  clang/lib/AST/Decl.cpp
  clang/lib/Sema/SemaDeclAttr.cpp
  clang/test/Misc/pragma-attribute-supported-attributes-list.test


Index: clang/test/Misc/pragma-attribute-supported-attributes-list.test
===================================================================
--- clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -36,6 +36,7 @@
 // CHECK-NEXT: Callback (SubjectMatchRule_function)
 // CHECK-NEXT: Capability (SubjectMatchRule_record, SubjectMatchRule_type_alias)
 // CHECK-NEXT: CarriesDependency (SubjectMatchRule_variable_is_parameter, SubjectMatchRule_objc_method, SubjectMatchRule_function)
+// CHECK-NEXT: ClangBuiltinOverride (SubjectMatchRule_function)
 // CHECK-NEXT: Cold (SubjectMatchRule_function)
 // CHECK-NEXT: Common (SubjectMatchRule_variable)
 // CHECK-NEXT: Constructor (SubjectMatchRule_function)
Index: clang/lib/Sema/SemaDeclAttr.cpp
===================================================================
--- clang/lib/Sema/SemaDeclAttr.cpp
+++ clang/lib/Sema/SemaDeclAttr.cpp
@@ -5041,6 +5041,13 @@
       AL.getAttributeSpellingListIndex()));
 }
 
+static void handleClangBuiltinOverrideAttribute(Sema &S, Decl *D,
+                                                const ParsedAttr &AL) {
+  D->addAttr(::new (S.Context) ClangBuiltinOverrideAttr(
+      AL.getRange(), S.Context, AL.getArgAsIdent(0)->Ident,
+      AL.getAttributeSpellingListIndex()));
+}
+
 //===----------------------------------------------------------------------===//
 // Checker-specific attribute handlers.
 //===----------------------------------------------------------------------===//
@@ -7430,6 +7437,10 @@
   case ParsedAttr::AT_MSAllocator:
     handleMSAllocatorAttr(S, D, AL);
     break;
+
+  case ParsedAttr::AT_ClangBuiltinOverride:
+    handleClangBuiltinOverrideAttribute(S, D, AL);
+    break;
   }
 }
 
Index: clang/lib/AST/Decl.cpp
===================================================================
--- clang/lib/AST/Decl.cpp
+++ clang/lib/AST/Decl.cpp
@@ -3075,10 +3075,18 @@
 /// functions as their wrapped builtins. This shouldn't be done in general, but
 /// it's useful in Sema to diagnose calls to wrappers based on their semantics.
 unsigned FunctionDecl::getBuiltinID(bool ConsiderWrapperFunctions) const {
-  if (!getIdentifier())
-    return 0;
+  unsigned BuiltinID;
+
+  if (hasAttr<ClangBuiltinOverrideAttr>()) {
+    IdentifierInfo *II = getAttr<ClangBuiltinOverrideAttr>()->getBuiltinName();
+    BuiltinID = II->getBuiltinID();
+  } else {
+    if (!getIdentifier())
+      return 0;
+
+    BuiltinID = getIdentifier()->getBuiltinID();
+  }
 
-  unsigned BuiltinID = getIdentifier()->getBuiltinID();
   if (!BuiltinID)
     return 0;
 
@@ -3102,7 +3110,8 @@
 
   // If the function is marked "overloadable", it has a different mangled name
   // and is not the C library function.
-  if (!ConsiderWrapperFunctions && hasAttr<OverloadableAttr>())
+  if (!ConsiderWrapperFunctions && hasAttr<OverloadableAttr>() &&
+      !hasAttr<ClangBuiltinOverrideAttr>())
     return 0;
 
   if (!Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID))
Index: clang/include/clang/Basic/Attr.td
===================================================================
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -593,6 +593,12 @@
   let Subjects = SubjectList<[Function, GlobalVar], ErrorDiag>;
   let Documentation = [Undocumented];
 }
+def ClangBuiltinOverride : Attr {
+  let Spellings = [GCC<"__clang_builtin">];
+  let Args = [IdentifierArgument<"BuiltinName">];
+  let Subjects = SubjectList<[Function], ErrorDiag>;
+  let Documentation = [Undocumented];
+}
 
 def Aligned : InheritableAttr {
   let Spellings = [GCC<"aligned">, Declspec<"align">, Keyword<"alignas">,


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