DebugInfo: Correctly describe the lexical decl context of static member variable definitions.

The previous IR representation used the non-lexical decl context, which
placed the definitions in the same scope as the declarations (ie: within
the class) - this was hidden by the fact that LLVM currently doesn't
respect the context of global variable definitions at all, and always
puts them at the top level (as direct children of the compile_unit).
Having the correct lexical scope improves source fidelity and simplify
backend global variable emission (with changes coming shortly).

Doing something similar for non-member global variables would help
simplify/cleanup things further (see FIXME in the commit) and provide
similar source fidelity benefits to the final debug info.

llvm-svn: 220488

2 files changed, 22 insertions, 5 deletions

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 0d662372a11..a5ad633233e 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -3186,8 +3186,15 @@ void CGDebugInfo::EmitGlobalVariable(llvm::GlobalVariable *Var,
   if (LinkageName == DeclName)
     LinkageName = StringRef();
 
-  llvm::DIDescriptor DContext =
-    getContextDescriptor(dyn_cast<Decl>(D->getDeclContext()));
+  // Since we emit declarations (DW_AT_members) for static members, place the
+  // definition of those static members in the namespace they were declared in
+  // in the source code (the lexical decl context).
+  // FIXME: Generalize this for even non-member global variables where the
+  // declaration and definition may have different lexical decl contexts, once
+  // we have support for emitting declarations of (non-member) global variables.
+  llvm::DIDescriptor DContext = getContextDescriptor(
+      dyn_cast<Decl>(D->isStaticDataMember() ? D->getLexicalDeclContext()
+                                             : D->getDeclContext()));
 
   // Attempt to store one global variable for the declaration - even if we
   // emit a lot of fields.
diff --git a/clang/test/CodeGenCXX/debug-info-static-member.cpp b/clang/test/CodeGenCXX/debug-info-static-member.cpp
index cbe4acd4dd7..c65ccd64dd7 100644
--- a/clang/test/CodeGenCXX/debug-info-static-member.cpp
+++ b/clang/test/CodeGenCXX/debug-info-static-member.cpp
@@ -42,9 +42,10 @@ int main()
 // CHECK: ![[DECL_C:[0-9]+]] = metadata !{metadata !"0xd\00c\00{{.*}}", {{.*}} [ DW_TAG_member ] [c] [line {{.*}}, size 0, align 0, offset 0] [public] [static]
 // CHECK: metadata !"0xd\00const_c\00{{.*}}", {{.*}} [ DW_TAG_member ] [const_c] [line {{.*}}, size 0, align 0, offset 0] [public] [static]
 // CHECK: metadata !"0xd\00x_a\00{{.*}}", {{.*}} [ DW_TAG_member ] [x_a] {{.*}} [public] [static]
-// CHECK: metadata !{metadata !"0x34\00a\00{{.*}}", {{.*}} @_ZN1C1aE, metadata ![[DECL_A]]} ; [ DW_TAG_variable ] [a] {{.*}} [def]
-// CHECK: metadata !{metadata !"0x34\00b\00{{.*}}", {{.*}} @_ZN1C1bE, metadata ![[DECL_B]]} ; [ DW_TAG_variable ] [b] {{.*}} [def]
-// CHECK: metadata !{metadata !"0x34\00c\00{{.*}}", {{.*}} @_ZN1C1cE, metadata ![[DECL_C]]} ; [ DW_TAG_variable ] [c] {{.*}} [def]
+// CHECK: [[NS_X:![0-9]+]] = {{.*}} ; [ DW_TAG_namespace ] [x]
+// CHECK: metadata !{metadata !"0x34\00a\00{{.*}}", null, {{.*}} @_ZN1C1aE, metadata ![[DECL_A]]} ; [ DW_TAG_variable ] [a] {{.*}} [def]
+// CHECK: metadata !{metadata !"0x34\00b\00{{.*}}", null, {{.*}} @_ZN1C1bE, metadata ![[DECL_B]]} ; [ DW_TAG_variable ] [b] {{.*}} [def]
+// CHECK: metadata !{metadata !"0x34\00c\00{{.*}}", null, {{.*}} @_ZN1C1cE, metadata ![[DECL_C]]} ; [ DW_TAG_variable ] [c] {{.*}} [def]
 
 // Verify that even when a static member declaration is created lazily when
 // creating the definition, the declaration line is that of the canonical
@@ -57,3 +58,12 @@ struct V {
 };
 // CHECK: i32 42} ; [ DW_TAG_member ] [const_va] [line [[@LINE-2]],
 const int V::const_va;
+
+namespace x {
+struct y {
+  static int z;
+};
+int y::z;
+}
+
+// CHECK: metadata !{metadata !"0x34\00z\00{{.*}}", metadata [[NS_X]], {{.*}} ; [ DW_TAG_variable ] [z] {{.*}} [def]