From 4d8871a898b30f11c905b27954c18d826c0953c9 Mon Sep 17 00:00:00 2001
From: Bruno De Fraine <brunodf@synopsys.com>
Date: Tue, 29 Jun 2021 09:46:27 +0200
Subject: [PATCH] PR50767: clear non-distinct debuginfo for function with
 nodebug definition after undecorated declaration

Fix suggested by Yuanfang Chen:

Non-distinct debuginfo is attached to the function due to the undecorated declaration. Later, when seeing the function definition and `nodebug` attribute, the non-distinct debuginfo should be cleared.

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D104777
---
 clang/lib/CodeGen/CodeGenFunction.cpp | 10 ++++++++--
 clang/test/CodeGen/attr-nodebug2.c    | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/CodeGen/attr-nodebug2.c

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 0ca9465..578b8a8 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -1304,8 +1304,14 @@ void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn,
   QualType ResTy = BuildFunctionArgList(GD, Args);
 
   // Check if we should generate debug info for this function.
-  if (FD->hasAttr<NoDebugAttr>())
-    DebugInfo = nullptr; // disable debug info indefinitely for this function
+  if (FD->hasAttr<NoDebugAttr>()) {
+    // Clear non-distinct debug info that was possibly attached to the function
+    // due to an earlier declaration without the nodebug attribute
+    if (Fn)
+      Fn->setSubprogram(nullptr);
+    // Disable debug info indefinitely for this function
+    DebugInfo = nullptr;
+  }
 
   // The function might not have a body if we're generating thunks for a
   // function declaration.
diff --git a/clang/test/CodeGen/attr-nodebug2.c b/clang/test/CodeGen/attr-nodebug2.c
new file mode 100644
index 0000000..fd6eca1
--- /dev/null
+++ b/clang/test/CodeGen/attr-nodebug2.c
@@ -0,0 +1,34 @@
+// RUN: %clang_cc1 -x c -debug-info-kind=limited -debugger-tuning=gdb -dwarf-version=4 -O -disable-llvm-passes -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -x c++ -debug-info-kind=limited -debugger-tuning=gdb -dwarf-version=4 -O -disable-llvm-passes -emit-llvm -o - %s | FileCheck %s
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void t1();
+
+void use() { t1(); }
+
+__attribute__((nodebug)) void t1() {
+  int a = 10;
+  a++;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+// CHECK-LABEL: define{{.*}} void @use()
+// CHECK-SAME:  !dbg
+// CHECK-SAME:  {
+// CHECK:       !dbg
+// CHECK:       }
+
+// PR50767 Function __attribute__((nodebug)) inconsistency causes crash
+// illegal (non-distinct) !dbg metadata was being added to _Z2t1v definition
+
+// CHECK-LABEL: define{{.*}} void @t1()
+// CHECK-NOT:   !dbg
+// CHECK-SAME:  {
+// CHECK-NOT:   !dbg
+// CHECK:       }
-- 
2.7.4