tcg/optimize: Add fallthrough annotations

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 (by introducing a new QEMU_FALLTHROUGH
macro in our compiler.h header file).

Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20201211152426.350966-11-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
index 1b9e58e82be6385eaf88f28f01bcd7d6ff03db99..df9ec08f8a86a7e4ac026dff3771c8ebc1e3f765 100644 (file)
--- a/include/qemu/compiler.h
+++ b/include/qemu/compiler.h
@@ -222,4 +222,15 @@ extern void QEMU_NORETURN QEMU_ERROR("code path is reachable")
 #define qemu_build_not_reached()  g_assert_not_reached()
 #endif
 
+/**
+ * In most cases, normal "fallthrough" comments are good enough for
+ * switch-case statements, but sometimes the compiler has problems
+ * with those. In that case you can use QEMU_FALLTHROUGH instead.
+ */
+#if __has_attribute(fallthrough)
+# define QEMU_FALLTHROUGH __attribute__((fallthrough))
+#else
+# define QEMU_FALLTHROUGH do {} while (0) /* fallthrough */
+#endif
+
 #endif /* COMPILER_H */

diff --git a/tcg/optimize.c b/tcg/optimize.c
index 220f4601d5a3e50d9b7124fb460469f6e60f3157..7ca71de9567f5bef6a41b1e7f45688217f04b46f 100644 (file)
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -855,6 +855,7 @@ void tcg_optimize(TCGContext *s)
             if ((arg_info(op->args[1])->mask & 0x80) != 0) {
                 break;
             }
+            QEMU_FALLTHROUGH;
         CASE_OP_32_64(ext8u):
             mask = 0xff;
             goto and_const;
@@ -862,6 +863,7 @@ void tcg_optimize(TCGContext *s)
             if ((arg_info(op->args[1])->mask & 0x8000) != 0) {
                 break;
             }
+            QEMU_FALLTHROUGH;
         CASE_OP_32_64(ext16u):
             mask = 0xffff;
             goto and_const;
@@ -869,6 +871,7 @@ void tcg_optimize(TCGContext *s)
             if ((arg_info(op->args[1])->mask & 0x80000000) != 0) {
                 break;
             }
+            QEMU_FALLTHROUGH;
         case INDEX_op_ext32u_i64:
             mask = 0xffffffffU;
             goto and_const;
@@ -886,6 +889,7 @@ void tcg_optimize(TCGContext *s)
             if ((arg_info(op->args[1])->mask & 0x80000000) != 0) {
                 break;
             }
+            QEMU_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;