2020-11-27 10:19:05

by Uros Bizjak

Subject: [PATCH] crypto: x86/poly1305-intel: Use TEST %reg,%reg instead of CMP $0,%reg

CMP $0,%reg can't set overflow flag, so we can use shorter TEST %reg,%reg
instruction when only zero and sign flags are checked (E,L,LE,G,GE conditions).

Signed-off-by: Uros Bizjak <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
---
arch/x86/crypto/poly1305-x86_64-cryptogams.pl | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/crypto/poly1305-x86_64-cryptogams.pl b/arch/x86/crypto/poly1305-x86_64-cryptogams.pl
index 7d568012cc15..71fae5a09e56 100644
--- a/arch/x86/crypto/poly1305-x86_64-cryptogams.pl
+++ b/arch/x86/crypto/poly1305-x86_64-cryptogams.pl
@@ -251,7 +251,7 @@ $code.=<<___;
mov %rax,8($ctx)
mov %rax,16($ctx)

- cmp \$0,$inp
+ test $inp,$inp
je .Lno_key
___
$code.=<<___ if (!$kernel);
--
2.26.2

2020-12-04 07:18:21

by Herbert Xu

Subject: Re: [PATCH] crypto: x86/poly1305-intel: Use TEST %reg,%reg instead of CMP $0,%reg

On Fri, Nov 27, 2020 at 11:18:12AM +0100, Uros Bizjak wrote:
> CMP $0,%reg can't set overflow flag, so we can use shorter TEST %reg,%reg
> instruction when only zero and sign flags are checked (E,L,LE,G,GE conditions).
>
> Signed-off-by: Uros Bizjak <[email protected]>
> Cc: Herbert Xu <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> ---
> arch/x86/crypto/poly1305-x86_64-cryptogams.pl | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)

Patch applied. Thanks.
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt