[PATCH v2 3/5] MIPS: LLVMLinux: Fix an 'inline asm input/output type mismatch' error.

From: Daniel Sanders
Date: Mon Feb 09 2015 - 06:34:18 EST

Replace incorrect matching constraint that caused the error with an alternative
that still has the required constraints on the inline assembly.

This is the error message reported by clang:
arch/mips/include/asm/checksum.h:285:27: error: unsupported inline asm: input with type '__be32' (aka 'unsigned int') matching output with type 'unsigned short'
"0" (htonl(len)), "1" (htonl(proto)), "r" (sum));

The changed code can be compiled successfully by both gcc and clang.

Signed-off-by: Daniel Sanders <daniel.sanders@xxxxxxxxxx>
Signed-off-by: Toma Tabacu <toma.tabacu@xxxxxxxxxx>
Suggested-by: Maciej W. Rozycki <macro@xxxxxxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Markos Chandras <markos.chandras@xxxxxxxxxx>
Cc: Leonid Yegoshin <Leonid.Yegoshin@xxxxxxxxxx>
Cc: Maciej W. Rozycki <macro@xxxxxxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx


Rewrote the patch following Maciej's suggestion where he observed that
the assembly was somewhat strange and suggested correcting the
constraints and using a local of matching type.

arch/mips/include/asm/checksum.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/mips/include/asm/checksum.h b/arch/mips/include/asm/checksum.h
index 3418c51..48bfcaf 100644
--- a/arch/mips/include/asm/checksum.h
+++ b/arch/mips/include/asm/checksum.h
@@ -228,6 +228,8 @@ static __inline__ __sum16 csum_ipv6_magic(const struct in6_addr *saddr,
__u32 len, unsigned short proto,
__wsum sum)
+ __wsum tmp;
" .set push # csum_ipv6_magic\n"
" .set noreorder \n"
@@ -280,9 +282,9 @@ static __inline__ __sum16 csum_ipv6_magic(const struct in6_addr *saddr,

" addu %0, $1 # Add final carry\n"
" .set pop"
- : "=r" (sum), "=r" (proto)
+ : "=&r" (sum), "=&r" (tmp)
: "r" (saddr), "r" (daddr),
- "0" (htonl(len)), "1" (htonl(proto)), "r" (sum));
+ "0" (htonl(len)), "r" (htonl(proto)), "r" (sum));

return csum_fold(sum);

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