From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: z constraint in powerpc inline assembly ?
Date: Thu, 16 Jan 2020 07:11:36 +0100 [thread overview]
Message-ID: <d72263a1-fe17-3192-6930-35ec8394c699@c-s.fr> (raw)
Hi Segher,
I'm trying to see if we could enhance TCP checksum calculations by
splitting inline assembly blocks to give GCC the opportunity to mix it
with other stuff, but I'm getting difficulties with the carry.
As far as I can read in the documentation, the z constraint represents
'‘XER[CA]’ carry bit (part of the XER register)'
I've tried the following, but I get errors. Can you help ?
unsigned long cksum(unsigned long a, unsigned long b, unsigned long c)
{
unsigned long sum;
unsigned long carry;
asm("addc %0, %2, %3" : "=r"(sum), "=z"(carry) : "r"(a), "r"(b));
asm("adde %0, %0, %2" : "+r"(sum), "+z"(carry) : "r"(c));
asm("addze %0, %0" : "+r"(sum) : "z"(carry));
return sum;
}
csum.c: In function 'cksum':
csum.c:6:2: error: inconsistent operand constraints in an 'asm'
asm("addc %0, %2, %3" : "=r"(sum), "=z"(carry) : "r"(a), "r"(b));
^
csum.c:7:2: error: inconsistent operand constraints in an 'asm'
asm("adde %0, %0, %2" : "+r"(sum), "+z"(carry) : "r"(c));
^
csum.c:8:2: error: inconsistent operand constraints in an 'asm'
asm("addze %0, %0" : "+r"(sum) : "z"(carry));
^
Thanks
Christophe
next reply other threads:[~2020-01-16 6:14 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 6:11 Christophe Leroy [this message]
2020-01-16 8:06 ` z constraint in powerpc inline assembly ? Gabriel Paubert
2020-01-16 13:57 ` Segher Boessenkool
2020-01-16 17:42 ` [PosibleSpam] " Gabriel Paubert
2020-01-16 14:01 ` Segher Boessenkool
2020-01-16 15:54 ` David Laight
2020-01-16 16:21 ` Segher Boessenkool
2020-01-16 16:52 ` David Laight
2020-01-16 17:10 ` Christophe Leroy
2020-01-16 17:20 ` David Laight
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