PR21823: 'nodebug' attribute on global/static variables.

Make 'nodebug' on a global/static variable suppress all debug info
for the variable. Previously it would only suppress info for the
associated initializer function, if any.

Differential Revision: http://reviews.llvm.org/D19567

llvm-svn: 267746

clang/include/clang/Basic/Attr.td

@@ -973,7 +973,7 @@ def NoCommon : InheritableAttr {
 
 def NoDebug : InheritableAttr {
   let Spellings = [GCC<"nodebug">];
-  let Documentation = [Undocumented];
+  let Documentation = [NoDebugDocs];
 }
 
 def NoDuplicate : InheritableAttr {

clang/include/clang/Basic/AttrDocs.td

@@ -494,6 +494,15 @@ Query for this feature with ``__has_attribute(objc_method_family)``.
   }];
 }
 
+def NoDebugDocs : Documentation {
+  let Category = DocCatVariable;
+  let Content = [{
+The ``nodebug`` attribute allows you to suppress debugging information for a
+function, or for a variable declared with static storage duration, such as
+globals, class static data members, and static locals.
+  }];
+}
+
 def NoDuplicateDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -1014,6 +1014,8 @@ void CGDebugInfo::CollectRecordFields(
     // the corresponding declarations in the source program.
     for (const auto *I : record->decls())
       if (const auto *V = dyn_cast<VarDecl>(I)) {
+        if (V->hasAttr<NoDebugAttr>())
+          continue;
         // Reuse the existing static member declaration if one exists
         auto MI = StaticDataMemberCache.find(V->getCanonicalDecl());
         if (MI != StaticDataMemberCache.end()) {
@@ -3390,6 +3392,8 @@ llvm::DIGlobalVariable *CGDebugInfo::CollectAnonRecordDecls(
 void CGDebugInfo::EmitGlobalVariable(llvm::GlobalVariable *Var,
                                      const VarDecl *D) {
   assert(DebugKind >= codegenoptions::LimitedDebugInfo);
+  if (D->hasAttr<NoDebugAttr>())
+    return;
   // Create global variable debug descriptor.
   llvm::DIFile *Unit = nullptr;
   llvm::DIScope *DContext = nullptr;
@@ -3422,6 +3426,8 @@ void CGDebugInfo::EmitGlobalVariable(llvm::GlobalVariable *Var,
 void CGDebugInfo::EmitGlobalVariable(const ValueDecl *VD,
                                      llvm::Constant *Init) {
   assert(DebugKind >= codegenoptions::LimitedDebugInfo);
+  if (VD->hasAttr<NoDebugAttr>())
+    return;
   // Create the descriptor for the variable.
   llvm::DIFile *Unit = getOrCreateFile(VD->getLocation());
   StringRef Name = VD->getName();

clang/test/CodeGenCXX/debug-info-nodebug.cpp

@@ -0,0 +1,55 @@
+// RUN: %clang_cc1 -DSETNODEBUG=0 -emit-llvm -debug-info-kind=limited %s -o - | FileCheck %s --check-prefix=YESINFO
+// RUN: %clang_cc1 -DSETNODEBUG=1 -emit-llvm -debug-info-kind=limited %s -o - | FileCheck %s --check-prefix=NOINFO
+
+#if SETNODEBUG
+#define NODEBUG __attribute__((nodebug))
+#else
+#define NODEBUG
+#endif
+
+// Simple global variable declaration and definition.
+// Use the declaration so it gets emitted.
+NODEBUG int global_int_decl;
+NODEBUG int global_int_def = global_int_decl;
+// YESINFO-DAG: !DIGlobalVariable(name: "global_int_decl"
+// NOINFO-NOT:  !DIGlobalVariable(name: "global_int_decl"
+// YESINFO-DAG: !DIGlobalVariable(name: "global_int_def"
+// NOINFO-NOT:  !DIGlobalVariable(name: "global_int_def"
+
+// Const global variable. Use it so it gets emitted.
+NODEBUG static const int const_global_int_def = 1;
+void func1(int);
+void func2() { func1(const_global_int_def); }
+// YESINFO-DAG: !DIGlobalVariable(name: "const_global_int_def"
+// NOINFO-NOT:  !DIGlobalVariable(name: "const_global_int_def"
+
+// Global variable with a more involved type.
+// If the variable has no debug info, the type should not appear either.
+struct S1 {
+  int a;
+  int b;
+};
+NODEBUG S1 global_struct = { 2, 3 };
+// YESINFO-DAG: !DICompositeType({{.*}} name: "S1"
+// NOINFO-NOT:  !DICompositeType({{.*}} name: "S1"
+// YESINFO-DAG: !DIGlobalVariable(name: "global_struct"
+// NOINFO-NOT:  !DIGlobalVariable(name: "global_struct"
+
+// Static data members. Const member needs a use.
+struct S2 {
+  NODEBUG static int static_member;
+  NODEBUG static const int static_const_member = 4;
+};
+int S2::static_member = 5;
+int junk = S2::static_const_member;
+// YESINFO-DAG: !DIGlobalVariable(name: "static_member"
+// NOINFO-NOT:  !DIGlobalVariable(name: "static_member"
+// YESINFO-DAG: !DIDerivedType({{.*}} name: "static_const_member"
+// NOINFO-NOT:  !DIDerivedType({{.*}} name: "static_const_member"
+
+// Function-local static variable.
+void func3() {
+  NODEBUG static int func_local = 6;
+}
+// YESINFO-DAG: !DIGlobalVariable(name: "func_local"
+// NOINFO-NOT:  !DIGlobalVariable(name: "func_local"