[PATCH] tcg/optimize: Add fallthrough annotations

[Thomas Huth <thuth@redhat.com>]

To be able to compile this file with -Werror=implicit-fallthrough,
we need to add some fallthrough annotations to the case statements
that might fall through. Unfortunately, the typical "/* fallthrough */"
comments do not work here as expected since some case labels are
wrapped in macros and the compiler fails to match the comments in
this case. But using __attribute__((fallthrough)) seems to work fine,
so let's use that instead.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 tcg/optimize.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tcg/optimize.c b/tcg/optimize.c
index 220f4601d5..c2768c9770 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -26,6 +26,12 @@
 #include "qemu/osdep.h"
 #include "tcg/tcg-op.h"
 
+#if __has_attribute(fallthrough)
+# define fallthrough() __attribute__((fallthrough))
+#else
+# define fallthrough() do {} while (0)
+#endif
+
 #define CASE_OP_32_64(x)                        \
         glue(glue(case INDEX_op_, x), _i32):    \
         glue(glue(case INDEX_op_, x), _i64)
@@ -855,6 +861,7 @@ void tcg_optimize(TCGContext *s)
             if ((arg_info(op->args[1])->mask & 0x80) != 0) {
                 break;
             }
+            fallthrough();
         CASE_OP_32_64(ext8u):
             mask = 0xff;
             goto and_const;
@@ -862,6 +869,7 @@ void tcg_optimize(TCGContext *s)
             if ((arg_info(op->args[1])->mask & 0x8000) != 0) {
                 break;
             }
+            fallthrough();
         CASE_OP_32_64(ext16u):
             mask = 0xffff;
             goto and_const;
@@ -869,6 +877,7 @@ void tcg_optimize(TCGContext *s)
             if ((arg_info(op->args[1])->mask & 0x80000000) != 0) {
                 break;
             }
+            fallthrough();
         case INDEX_op_ext32u_i64:
             mask = 0xffffffffU;
             goto and_const;
@@ -886,6 +895,7 @@ void tcg_optimize(TCGContext *s)
             if ((arg_info(op->args[1])->mask & 0x80000000) != 0) {
                 break;
             }
+            fallthrough();
         case INDEX_op_extu_i32_i64:
             /* We do not compute affected as it is a size changing op.  */
             mask = (uint32_t)arg_info(op->args[1])->mask;
-- 
2.18.2