The patch titled
Subject: byteswap: try to avoid __builtin_constant_p gcc bug
has been added to the -mm tree. Its filename is
byteswap-try-to-avoid-__builtin_constant_p-gcc-bug.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/byteswap-try-to-avoid-__builtin_constant_p-gcc-bug.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/byteswap-try-to-avoid-__builtin_constant_p-gcc-bug.patch
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------------------------------------------------------
From: Arnd Bergmann <arnd@xxxxxxxx>
Subject: byteswap: try to avoid __builtin_constant_p gcc bug
This is another attempt to avoid a regression in wwn_to_u64() after that
started using get_unaligned_be64(), which in turn ran into a bug on
gcc-4.9 through 6.1.
As part of the problem is how __builtin_constant_p gets evaluated on an
argument passed by reference into an inline function, this avoids the use
of __builtin_constant_p() for all architectures that set
CONFIG_ARCH_USE_BUILTIN_BSWAP. Most architectures do not set
ARCH_SUPPORTS_OPTIMIZED_INLINING, which means they probably do not suffer
from the problem in the qla2xxx driver, but they might still run into it
elsewhere.
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Reviewed-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Tested-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Tested-by: Quinn Tran <quinn.tran@xxxxxxxxxx>
Cc: Martin Jambor <mjambor@xxxxxxx>
Cc: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>
Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Thomas Graf <tgraf@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Himanshu Madhani <himanshu.madhani@xxxxxxxxxx>
Cc: Jan Hubicka <hubicka@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/uapi/linux/swab.h | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)
diff -puN include/uapi/linux/swab.h~byteswap-try-to-avoid-__builtin_constant_p-gcc-bug include/uapi/linux/swab.h
--- a/include/uapi/linux/swab.h~byteswap-try-to-avoid-__builtin_constant_p-gcc-bug
+++ a/include/uapi/linux/swab.h
@@ -45,9 +45,7 @@
static inline __attribute_const__ __u16 __fswab16(__u16 val)
{
-#ifdef __HAVE_BUILTIN_BSWAP16__
- return __builtin_bswap16(val);
-#elif defined (__arch_swab16)
+#if defined (__arch_swab16)
return __arch_swab16(val);
#else
return ___constant_swab16(val);
@@ -56,9 +54,7 @@ static inline __attribute_const__ __u16
static inline __attribute_const__ __u32 __fswab32(__u32 val)
{
-#ifdef __HAVE_BUILTIN_BSWAP32__
- return __builtin_bswap32(val);
-#elif defined(__arch_swab32)
+#if defined(__arch_swab32)
return __arch_swab32(val);
#else
return ___constant_swab32(val);
@@ -67,9 +63,7 @@ static inline __attribute_const__ __u32
static inline __attribute_const__ __u64 __fswab64(__u64 val)
{
-#ifdef __HAVE_BUILTIN_BSWAP64__
- return __builtin_bswap64(val);
-#elif defined (__arch_swab64)
+#if defined (__arch_swab64)
return __arch_swab64(val);
#elif defined(__SWAB_64_THRU_32__)
__u32 h = val >> 32;
@@ -102,28 +96,40 @@ static inline __attribute_const__ __u32
* __swab16 - return a byteswapped 16-bit value
* @x: value to byteswap
*/
+#ifdef __HAVE_BUILTIN_BSWAP16__
+#define __swab16(x) __builtin_bswap16((__u16)(x))
+#else
#define __swab16(x) \
(__builtin_constant_p((__u16)(x)) ? \
___constant_swab16(x) : \
__fswab16(x))
+#endif
/**
* __swab32 - return a byteswapped 32-bit value
* @x: value to byteswap
*/
+#ifdef __HAVE_BUILTIN_BSWAP32__
+#define __swab32(x) __builtin_bswap32((__u32)(x))
+#else
#define __swab32(x) \
(__builtin_constant_p((__u32)(x)) ? \
___constant_swab32(x) : \
__fswab32(x))
+#endif
/**
* __swab64 - return a byteswapped 64-bit value
* @x: value to byteswap
*/
+#ifdef __HAVE_BUILTIN_BSWAP64__
+#define __swab64(x) __builtin_bswap64((__u64)(x))
+#else
#define __swab64(x) \
(__builtin_constant_p((__u64)(x)) ? \
___constant_swab64(x) : \
__fswab64(x))
+#endif
/**
* __swahw32 - return a word-swapped 32-bit value
_
Patches currently in -mm which might be from arnd@xxxxxxxx are
byteswap-try-to-avoid-__builtin_constant_p-gcc-bug.patch
kernel-padata-hide-unused-functions.patch
drm-amdgpu-make-amdgpu_mn_get-wait-for-mmap_sem-killable-fix.patch
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