Reapply: [clang][diagnostics] Adding -Wpacked-non-pod to -Wall

Users will be informed when non-POD is not packed using -Wall. This
is also consistent with GCC.

Fixes PR#60832.

Differential Revision: https://reviews.llvm.org/D151162

clang/include/clang/Basic/DiagnosticGroups.td

@@ -1060,7 +1060,7 @@ def Consumed       : DiagGroup<"consumed">;
 // warning should be active _only_ when -Wall is passed in, mark it as
 // DefaultIgnore in addition to putting it here.
 def All : DiagGroup<"all", [Most, Parentheses, Switch, SwitchBool,
-                            MisleadingIndentation]>;
+                            MisleadingIndentation, PackedNonPod]>;
 
 // Warnings that should be in clang-cl /w4.
 def : DiagGroup<"CL4", [All, Extra]>;

clang/test/CodeGenCXX/warn-padded-packed.cpp → clang/test/CodeGenCXX/warn-all-padded-packed-packed-non-pod.cpp

@@ -1,5 +1,10 @@
 // RUN: %clang_cc1 -triple=x86_64-none-none -Wpadded -Wpacked -verify=expected,top %s -emit-llvm-only
 // RUN: %clang_cc1 -triple=x86_64-none-none -Wpadded -Wpacked -verify=expected,abi15 -fclang-abi-compat=15 %s -emit-llvm-only
+// -Wpacked-non-pod itself should not emit the "packed attribute is unnecessary" warnings.
+// RUN: %clang_cc1 -triple=x86_64-none-none -Wpacked-non-pod -verify=top %s -emit-llvm-only
+// -Wall should not emit the "packed attribute is unnecessary" warnings without -Wpacked.
+// RUN: %clang_cc1 -triple=x86_64-none-none -Wall -verify=top %s -emit-llvm-only
+
 
 struct S1 {
   char c;

clang/test/Misc/warning-wall.c

@@ -99,6 +99,7 @@ CHECK-NEXT:    -Wdangling-else
 CHECK-NEXT:  -Wswitch
 CHECK-NEXT:  -Wswitch-bool
 CHECK-NEXT:  -Wmisleading-indentation
+CHECK-NEXT:  -Wpacked-non-pod
 
 
 CHECK-NOT:-W