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| author |   Josh Poimboeuf <jpoimboe@redhat.com> | 2016-05-06 09:22:25 -0500 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2016-05-09 11:54:29 -0700 |
| commit | 8634de6d254462e6953b7dac772a1df4f44c8030 (patch) | |
| tree | 3e6ad1be69b1c138f94c0795640685b9f6c33f65 /include/linux/compiler-gcc.h | |
| parent | Linux 4.6-rc7 (diff) | |
| download | linux-dev-8634de6d254462e6953b7dac772a1df4f44c8030.tar.xz linux-dev-8634de6d254462e6953b7dac772a1df4f44c8030.zip | |
compiler-gcc: require gcc 4.8 for powerpc __builtin_bswap16()
gcc support for __builtin_bswap16() was supposedly added for powerpc in
gcc 4.6, and was then later added for other architectures in gcc 4.8.
However, Stephen Rothwell reported that attempting to use it on powerpc
in gcc 4.6 fails with:
lib/vsprintf.c:160:2: error: initializer element is not constant
lib/vsprintf.c:160:2: error: (near initialization for 'decpair[0]')
lib/vsprintf.c:160:2: error: initializer element is not constant
lib/vsprintf.c:160:2: error: (near initialization for 'decpair[1]')
...
I'm not entirely sure what those errors mean, but I don't see them on
gcc 4.8. So let's consider gcc 4.8 to be the official starting point
for __builtin_bswap16().
Arnd Bergmann adds:
"I found the commit in gcc-4.8 that replaced the powerpc-specific
implementation of __builtin_bswap16 with an architecture-independent
one. Apparently the powerpc version (gcc-4.6 and 4.7) just mapped to
the lhbrx/sthbrx instructions, so it ended up not being a constant,
though the intent of the patch was mainly to add support for the
builtin to x86:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52624
has the patch that went into gcc-4.8 and more information."
Fixes: 7322dd755e7d ("byteswap: try to avoid __builtin_constant_p gcc bug")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Tested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/compiler-gcc.h')
| -rw-r--r-- | include/linux/compiler-gcc.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index eeae401a2412..3d5202eda22f 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -246,7 +246,7 @@ #define __HAVE_BUILTIN_BSWAP32__ #define __HAVE_BUILTIN_BSWAP64__ #endif -#if GCC_VERSION >= 40800 || (defined(__powerpc__) && GCC_VERSION >= 40600) +#if GCC_VERSION >= 40800 #define __HAVE_BUILTIN_BSWAP16__ #endif #endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */ |