Commit f206fdd9 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc: Reduce csum_add() complexity for PPC64 



PPC64 does everything in C, gcc is able to skip calculation
when one of the operands in zero.

Move the constant folding in PPC32 part.

This helps GCC and reduces ppc64_defconfig by 170 bytes.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a4ca63dd4c4b09e1906d08fb814af5a41d0f3fcb.1644651363.git.christophe.leroy@csgroup.eu
parent a553476c

arch/powerpc/include/asm/checksum.h

+4 −5
Original line number Diff line number Diff line
@@ -95,16 +95,15 @@ static __always_inline __wsum csum_add(__wsum csum, __wsum addend) 
{

#ifdef __powerpc64__

	u64 res = (__force u64)csum;

#endif



	res += (__force u64)addend;

	return (__force __wsum)((u32)res + (res >> 32));

#else

	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

	asm("addc %0,%0,%1;"

	    "addze %0,%0;"

	    : "+r" (csum) : "r" (addend) : "xer");