Implement function attribute artificial

Added support in clang for GCC function attribute 'artificial'. This attribute 
is used to control stepping behavior of debugger with respect to inline 
functions.

Patch By: Elizabeth Andrews (eandrews)

Differential Revision: https://reviews.llvm.org/D43259

llvm-svn: 325081

clang/include/clang/Basic/Attr.td

@@ -111,6 +111,9 @@ def SharedVar : SubsetSubject<Var,
 def GlobalVar : SubsetSubject<Var,
                              [{S->hasGlobalStorage()}], "global variables">;
 
+def InlineFunction : SubsetSubject<Function,
+                             [{S->isInlineSpecified()}], "inline functions">;
+
 // FIXME: this hack is needed because DeclNodes.td defines the base Decl node
 // type to be a class, not a definition. This makes it impossible to create an
 // attribute subject which accepts a Decl. Normally, this is not a problem,
@@ -588,6 +591,12 @@ def AlwaysInline : InheritableAttr {
   let Documentation = [Undocumented];
 }
 
+def Artificial : InheritableAttr {
+  let Spellings = [GCC<"artificial">];
+  let Subjects = SubjectList<[InlineFunction], WarnDiag>;
+  let Documentation = [ArtificialDocs];
+}
+
 def XRayInstrument : InheritableAttr {
   let Spellings = [Clang<"xray_always_instrument">,
                    Clang<"xray_never_instrument">];

clang/include/clang/Basic/AttrDocs.td

@@ -3273,3 +3273,13 @@ For more information see
 or `msvc documentation <https://docs.microsoft.com/pl-pl/cpp/cpp/selectany>`_.
 }];
 }
+
+def ArtificialDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+The ``artificial`` attribute is used with inline functions to treat the inline 
+function as a unit while debugging. For more information see GCC_ documentation.
+
+.. _GCC: https://gcc.gnu.org/onlinedocs/gcc-4.6.4/gcc/Function-Attributes.html
+  }];
+}

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -3235,7 +3235,7 @@ void CGDebugInfo::EmitFunctionStart(GlobalDecl GD, SourceLocation Loc,
   if (Name.startswith("\01"))
     Name = Name.substr(1);
 
-  if (!HasDecl || D->isImplicit()) {
+  if (!HasDecl || D->isImplicit() || D->hasAttr<ArtificialAttr>()) {
     Flags |= llvm::DINode::FlagArtificial;
     // Artificial functions should not silently reuse CurLoc.
     CurLoc = SourceLocation();

clang/lib/Sema/SemaDeclAttr.cpp

@@ -6057,6 +6057,9 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case AttributeList::AT_AlwaysInline:
     handleAlwaysInlineAttr(S, D, Attr);
     break;
+  case AttributeList::AT_Artificial:
+    handleSimpleAttribute<ArtificialAttr>(S, D, Attr);
+    break;
   case AttributeList::AT_AnalyzerNoReturn:
     handleAnalyzerNoReturnAttr(S, D, Attr);
     break;

clang/test/CodeGen/artificial.c

@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -triple=x86_64-unknown-linux-gnu -emit-llvm -debug-info-kind=limited %s -o - | FileCheck %s
+
+extern void foo();
+// CHECK: !DISubprogram(name: "foo"
+// CHECK-SAME: flags: DIFlagArtificial
+inline void __attribute__((artificial)) foo() {}
+
+void baz() {
+  foo();
+}

clang/test/Sema/artificial.c

@@ -0,0 +1,4 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+inline void __attribute__((artificial)) foo() {}
+void __attribute__((artificial)) bar() {} // expected-warning {{'artificial' attribute only applies to inline functions}}