Debug Info: Attempt to resolve forward declarations if we are not emitting

limited debug info.

This is another small addendum to r184252.

rdar://problem/14101097

llvm-svn: 184473

3 files changed, 49 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 8240c0846d5..f8c814cb94f 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -1886,6 +1886,22 @@ llvm::DIType CGDebugInfo::getTypeOrNull(QualType Ty) {
   return llvm::DIType();
 }
 
+/// ContainsFwdDecl - True if Ty is either a forward declaration or a
+/// derived type of a forward declaration.
+static bool ContainsFwdDecl(llvm::DIType Ty) {
+  // Composite types such as structs inherit from DIDerivedType, so
+  // check this first and do an early exit.
+  if (Ty.isForwardDecl())
+    return true;
+
+  if (Ty.isDerivedType()) {
+    llvm::DIDerivedType DTy(Ty);
+    return ContainsFwdDecl(DTy.getTypeDerivedFrom());
+  }
+
+  return false;
+}
+
 /// getCompletedTypeOrNull - Get the type from the cache or return null if it
 /// doesn't exist.
 llvm::DIType CGDebugInfo::getCompletedTypeOrNull(QualType Ty) {
@@ -1904,8 +1920,17 @@ llvm::DIType CGDebugInfo::getCompletedTypeOrNull(QualType Ty) {
   }
 
   // Verify that any cached debug info still exists.
-  if (V != 0)
-    return llvm::DIType(cast<llvm::MDNode>(V));
+  if (V != 0) {
+    llvm::DIType CachedType(cast<llvm::MDNode>(V));
+
+    // Unless we are limiting debug info, attempt to resolve any
+    // forward declarations.
+    if (DebugKind > CodeGenOptions::LimitedDebugInfo &&
+        ContainsFwdDecl(CachedType))
+      return llvm::DIType();
+
+    return CachedType;
+  }
 
   return llvm::DIType();
 }
diff --git a/clang/test/CodeGen/debug-info-record.c b/clang/test/CodeGen/debug-info-record.c
index 55927ca667a..546a8b9806e 100644
--- a/clang/test/CodeGen/debug-info-record.c
+++ b/clang/test/CodeGen/debug-info-record.c
@@ -1,5 +1,5 @@
 // RUN: %clang_cc1 -triple x86_64-unk-unk -fno-limit-debug-info -o - -emit-llvm -g %s | FileCheck %s
-// Check that we emit debug info for a struct even if it is typedef'd before using.
+// Check that we emit debug info for a struct even if it is typedef'd.
 // rdar://problem/14101097
 //
 // FIXME: This should work with -flimit-debug-info, too.
diff --git a/clang/test/CodeGen/debug-info-record2.c b/clang/test/CodeGen/debug-info-record2.c
new file mode 100644
index 00000000000..3f28296318c
--- /dev/null
+++ b/clang/test/CodeGen/debug-info-record2.c
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -triple x86_64-unk-unk -fno-limit-debug-info -o - -emit-llvm -g %s | FileCheck %s
+// Check that we emit debug info for a struct even if it is typedef'd before using.
+// rdar://problem/14101097
+//
+// FIXME: This should work with -flimit-debug-info, too.
+
+// Make sure this is not a forward declaration.
+// CHECK-NOT: [ DW_TAG_structure_type ] [elusive_s] {{.*}} [fwd]
+// CHECK: [ DW_TAG_member ] [foo]
+// CHECK: [ DW_TAG_member ] [bar]
+typedef struct elusive_s* elusive_t;
+elusive_t first_use = (void*)0;
+struct elusive_s {
+  int foo;
+  float bar;
+};
+
+int baz(void* x) {
+  elusive_t s = x;
+  return s->foo;
+}