[PATCH v3 1/6] qemu/bswap: Replace bswapXX() by compiler __builtin_bswap()

[Philippe Mathieu-Daudé]

From: Philippe Mathieu-Daudé <philmd@redhat.com>

Use the compiler built-in function to byte swap values,
as the compiler is clever and will fold constants.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 include/qemu/bswap.h | 31 ++++++-------------------------
 1 file changed, 6 insertions(+), 25 deletions(-)

diff --git a/include/qemu/bswap.h b/include/qemu/bswap.h
index 346d05f2aa..ca2b4c3f15 100644
--- a/include/qemu/bswap.h
+++ b/include/qemu/bswap.h
@@ -37,31 +37,12 @@ static inline uint64_t bswap64(uint64_t x)
 #endif
 
 #ifdef BSWAP_FROM_FALLBACKS
-static inline uint16_t bswap16(uint16_t x)
-{
-    return (((x & 0x00ff) << 8) |
-            ((x & 0xff00) >> 8));
-}
-
-static inline uint32_t bswap32(uint32_t x)
-{
-    return (((x & 0x000000ffU) << 24) |
-            ((x & 0x0000ff00U) <<  8) |
-            ((x & 0x00ff0000U) >>  8) |
-            ((x & 0xff000000U) >> 24));
-}
-
-static inline uint64_t bswap64(uint64_t x)
-{
-    return (((x & 0x00000000000000ffULL) << 56) |
-            ((x & 0x000000000000ff00ULL) << 40) |
-            ((x & 0x0000000000ff0000ULL) << 24) |
-            ((x & 0x00000000ff000000ULL) <<  8) |
-            ((x & 0x000000ff00000000ULL) >>  8) |
-            ((x & 0x0000ff0000000000ULL) >> 24) |
-            ((x & 0x00ff000000000000ULL) >> 40) |
-            ((x & 0xff00000000000000ULL) >> 56));
-}
+#undef  bswap16
+#define bswap16(_x) __builtin_bswap16(_x)
+#undef  bswap32
+#define bswap32(_x) __builtin_bswap32(_x)
+#undef  bswap64
+#define bswap64(_x) __builtin_bswap64(_x)
 #endif
 
 #undef BSWAP_FROM_BYTESWAP
-- 
2.38.1