[PATCH 2/2] powerpc32: add support for csum_add()

The C version of csum_add() as defined in include/net/checksum.h gives the
following assembly:
       0:       7c 04 1a 14     add     r0,r4,r3
       4:       7c 64 00 10     subfc   r3,r4,r0
       8:       7c 63 19 10     subfe   r3,r3,r3
       c:       7c 63 00 50     subf    r3,r3,r0

include/net/checksum.h also offers the possibility to define an arch specific
function.
This patch provides a ppc32 specific csum_add() inline function.

Signed-off-by: Christophe Leroy <redacted>

---
 arch/powerpc/include/asm/checksum.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/powerpc/include/asm/checksum.h b/arch/powerpc/include/asm/checksum.h
index cfe806a..a13aa1f 100644
--- a/arch/powerpc/include/asm/checksum.h
+++ b/arch/powerpc/include/asm/checksum.h

@@ -141,6 +141,19 @@ static inline __sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
 {
 	return csum_fold(csum_tcpudp_nofold(saddr, daddr, len, proto, sum));
 }
+
+#define HAVE_ARCH_CSUM_ADD
+static inline __wsum csum_add(__wsum csum, __wsum addend)
+{
+    __asm__("\n\
+	addc %0,%0,%1 \n\
+	addze %0,%0 \n\
+	"
+	: "=r" (csum)
+	: "r" (addend), "0"(csum));
+	return csum;
+}
+
 #endif
 #endif
 #endif /* __KERNEL__ */

-- 
2.1.0

Christophe Leroy [off-list ref] wrote on 2014/09/19 15:57:56:

Subject: [PATCH 2/2] powerpc32: add support for csum_add()

The C version of csum_add() as defined in include/net/checksum.h gives 

the

following assembly:
       0:       7c 04 1a 14     add     r0,r4,r3
       4:       7c 64 00 10     subfc   r3,r4,r0
       8:       7c 63 19 10     subfe   r3,r3,r3
       c:       7c 63 00 50     subf    r3,r3,r0

include/net/checksum.h also offers the possibility to define an arch 

specific

function.
This patch provides a ppc32 specific csum_add() inline function.

Signed-off-by: Christophe Leroy <redacted>

---

Ouch, this is still so. Back in 2010 I reported this to gcc:
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43892

Anyway, 
        Acked-by: Joakim Tjernlund [off-list ref]

Christophe Leroy [off-list ref] wrote on 2014/09/19 15:57:56:

+#define HAVE_ARCH_CSUM_ADD
+static inline __wsum csum_add(__wsum csum, __wsum addend)
+{
+    __asm__("\n\
+   addc %0,%0,%1 \n\
+   addze %0,%0 \n\
+   "
+   : "=r" (csum)
+   : "r" (addend), "0"(csum));

hmm, I wonder if not this is better written as:
: "+r" (csum): "r" (addend))

  Jocke