2020-11-27 10:01:28

by Uros Bizjak

Subject: [PATCH] crypto: x86/sha512-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/sha512-avx-asm.S | 2 +-
arch/x86/crypto/sha512-ssse3-asm.S | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/crypto/sha512-avx-asm.S b/arch/x86/crypto/sha512-avx-asm.S
index 63470fd6ae32..684d58c8bc4f 100644
--- a/arch/x86/crypto/sha512-avx-asm.S
+++ b/arch/x86/crypto/sha512-avx-asm.S
@@ -278,7 +278,7 @@ frame_size = frame_GPRSAVE + GPRSAVE_SIZE
# "blocks" is the message length in SHA512 blocks
########################################################################
SYM_FUNC_START(sha512_transform_avx)
- cmp $0, msglen
+ test msglen, msglen
je nowork

# Allocate Stack Space
diff --git a/arch/x86/crypto/sha512-ssse3-asm.S b/arch/x86/crypto/sha512-ssse3-asm.S
index 7946a1bee85b..50812af0b083 100644
--- a/arch/x86/crypto/sha512-ssse3-asm.S
+++ b/arch/x86/crypto/sha512-ssse3-asm.S
@@ -280,7 +280,7 @@ frame_size = frame_GPRSAVE + GPRSAVE_SIZE
########################################################################
SYM_FUNC_START(sha512_transform_ssse3)

- cmp $0, msglen
+ test msglen, msglen
je nowork

# Allocate Stack Space
--
2.26.2

2020-12-04 07:17:42

by Herbert Xu

Subject: Re: [PATCH] crypto: x86/sha512-intel: Use TEST %reg,%reg instead of CMP $0,%reg

On Fri, Nov 27, 2020 at 10:59:43AM +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/sha512-avx-asm.S | 2 +-
> arch/x86/crypto/sha512-ssse3-asm.S | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)

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