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authorJosh Poimboeuf <jpoimboe@redhat.com>2016-05-06 09:22:25 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2016-05-09 11:54:29 -0700
commit8634de6d254462e6953b7dac772a1df4f44c8030 (patch)
tree3e6ad1be69b1c138f94c0795640685b9f6c33f65
parent44549e8f5eea4e0a41b487b63e616cb089922b99 (diff)
downloadlinux-8634de6d254462e6953b7dac772a1df4f44c8030.tar.gz
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>
-rw-r--r--include/linux/compiler-gcc.h2
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 */