[PATCH 4/4] qemu/bswap: Let cpu_to_endian() functions handle constant expressions

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

cpu_to_endian() and endian_to_cpu() can be extended to handle
constant expressions. That way the programmer doesn't need to
remember the const_X() API exists.

Suggested-by: Stefan Hajnoczi <stefanha@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 include/qemu/bswap.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/qemu/bswap.h b/include/qemu/bswap.h
index de256cea3ab..8827e4760b9 100644
--- a/include/qemu/bswap.h
+++ b/include/qemu/bswap.h
@@ -191,12 +191,16 @@ static inline void bswap64s(uint64_t *s)
 #define CPU_CONVERT(endian, size, type)\
 static inline type endian ## size ## _to_cpu(type v)\
 {\
-    return glue(endian, _bswap)(v, size);\
+    return __builtin_constant_p(v) ?\
+           const_ ## endian ## size(v) :\
+           glue(endian, _bswap)(v, size);\
 }\
 \
 static inline type cpu_to_ ## endian ## size(type v)\
 {\
-    return glue(endian, _bswap)(v, size);\
+    return __builtin_constant_p(v) ?\
+           const_ ## endian ## size(v) :\
+           glue(endian, _bswap)(v, size);\
 }\
 \
 static inline void endian ## size ## _to_cpus(type *p)\
-- 
2.26.2