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[PATCH 8/9] powerpc: simplify csum_add(a, b) in case a or b is constant 0

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Simplify csum_add(a, b) in case a or b is constant 0

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/include/asm/checksum.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/powerpc/include/asm/checksum.h b/arch/powerpc/include/asm/checksum.h
index 56deea8..f8a9704 100644
--- a/arch/powerpc/include/asm/checksum.h
+++ b/arch/powerpc/include/asm/checksum.h
@@ -119,7 +119,13 @@ static inline __wsum csum_add(__wsum csum, __wsum addend)
 {
 #ifdef __powerpc64__
 	u64 res = (__force u64)csum;
+#endif
+	if (__builtin_constant_p(csum) && csum == 0)
+		return addend;
+	if (__builtin_constant_p(addend) && addend == 0)
+		return csum;
 
+#ifdef __powerpc64__
 	res += (__force u64)addend;
 	return (__force __wsum)((u32)res + (res >> 32));
 #else
-- 
2.1.0

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[PATCH 0/9] powerpc32: set of optimisation of network checksum functions Christophe Leroy <christophe.leroy@c-s.fr> - 2015-09-22 16:40 +0200
  [PATCH 7/9] powerpc32: optimise csum_partial() loop Christophe Leroy <christophe.leroy@c-s.fr> - 2015-09-22 16:40 +0200
  [PATCH 1/9] powerpc: unexport csum_tcpudp_magic Christophe Leroy <christophe.leroy@c-s.fr> - 2015-09-22 16:40 +0200
  [PATCH 6/9] powerpc32: optimise a few instructions in csum_partial() Christophe Leroy <christophe.leroy@c-s.fr> - 2015-09-22 16:40 +0200
  [PATCH 9/9] powerpc: optimise csum_partial() call when len is  constant Christophe Leroy <christophe.leroy@c-s.fr> - 2015-09-22 16:40 +0200
  [PATCH 3/9] powerpc32: checksum_wrappers_64 becomes checksum_wrappers Christophe Leroy <christophe.leroy@c-s.fr> - 2015-09-22 16:40 +0200
  [PATCH 5/9] powerpc32: rewrite csum_partial_copy_generic() based on  copy_tofrom_user() Christophe Leroy <christophe.leroy@c-s.fr> - 2015-09-22 16:40 +0200
  [PATCH 8/9] powerpc: simplify csum_add(a, b) in case a or b is  constant 0 Christophe Leroy <christophe.leroy@c-s.fr> - 2015-09-22 16:40 +0200
  Re: [PATCH 0/9] powerpc32: set of optimisation of network checksum  functions David Miller <davem@davemloft.net> - 2015-09-24 00:40 +0200

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