[clang][Sema] Add -Wswitch-default warning option (llvm#73077)

Adds a warning, issued by the clang semantic analysis. The patch warns
on switch which don't have the default branch.

This is a counterpart of gcc's Wswitch-default.

Change-Id: Iba221a303560b88fd7e408a517cfba2d728b0931

Author: dongjianqiang2

clang/docs/ReleaseNotes.rst

@@ -436,6 +436,8 @@ Improvements to Clang's diagnostics
   of a base class is not called in the constructor of its derived class.
 - Clang no longer emits ``-Wmissing-variable-declarations`` for variables declared
   with the ``register`` storage class.
+- Clang's ``-Wswitch-default`` flag now diagnoses whenever a ``switch`` statement
+  does not have a ``default`` label.
 - Clang's ``-Wtautological-negation-compare`` flag now diagnoses logical
   tautologies like ``x && !x`` and ``!x || x`` in expressions. This also
   makes ``-Winfinite-recursion`` diagnose more cases.

clang/include/clang/Basic/DiagnosticGroups.td

@@ -634,7 +634,7 @@ def ShadowAll : DiagGroup<"shadow-all", [Shadow, ShadowFieldInConstructor,
 def Shorten64To32 : DiagGroup<"shorten-64-to-32">;
 def : DiagGroup<"sign-promo">;
 def SignCompare : DiagGroup<"sign-compare">;
-def : DiagGroup<"switch-default">;
+def SwitchDefault  : DiagGroup<"switch-default">;
 def : DiagGroup<"synth">;
 def SizeofArrayArgument : DiagGroup<"sizeof-array-argument">;
 def SizeofArrayDecay : DiagGroup<"sizeof-array-decay">;

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -10085,6 +10085,8 @@ def warn_missing_case : Warning<"%plural{"
   "3:enumeration values %1, %2, and %3 not handled in switch|"
   ":%0 enumeration values not handled in switch: %1, %2, %3...}0">,
   InGroup<Switch>;
+def warn_switch_default : Warning<"'switch' missing 'default' label">,
+  InGroup<SwitchDefault>, DefaultIgnore;
 
 def warn_unannotated_fallthrough : Warning<
   "unannotated fall-through between switch labels">,

clang/lib/Sema/SemaStmt.cpp

@@ -1344,10 +1344,7 @@ Sema::ActOnFinishSwitchStmt(SourceLocation SwitchLoc, Stmt *Switch,
       assert(!HasConstantCond ||
              (ConstantCondValue.getBitWidth() == CondWidth &&
               ConstantCondValue.isSigned() == CondIsSigned));
-#if NEEDS_PATCH_FOR_SWITCH
-//[clang][Sema] Add -Wswitch-default warning option (#73077)
       Diag(SwitchLoc, diag::warn_switch_default);
-#endif
     }
     bool ShouldCheckConstantCond = HasConstantCond;
 

clang/test/Sema/switch-default.cpp

@@ -1,7 +1,3 @@
-revert: breaks MIOpen composableKernel build 
-[clang][Sema] Add -Wswitch-default warning option (#73077)  
-   https://ontrack-internal.amd.com/browse/SWDEV-436625
-
 Reverts: breaks ompt tests
 [Libomptarget] Remove __tgt_image_info and use the ELF directly (#75720)