From: Nicolas Pitre <nico@cam.org>
Date: Sun, 13 Nov 2005 00:17:33 +0000 (+1100)
Subject: [CRYPTO] sha1: Avoid shifting count left and right
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=fa9b98fdab5b57ecb4dd3d6c2489e262af458c44;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git

[CRYPTO] sha1: Avoid shifting count left and right

This patch avoids shifting the count left and right needlessly for each
call to sha1_update().  It instead can be done only once at the end in
sha1_final().

Keeping the previous test example (sha1_update() successively called with
len=64), a 1.3% performance increase can be observed on i386, or 0.2% on
ARM.  The generated code is also smaller on ARM.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

diff --git a/crypto/sha1.c b/crypto/sha1.c
index 7b1abca29365..8048e2dd3c14 100644
--- a/crypto/sha1.c
+++ b/crypto/sha1.c
@@ -52,8 +52,8 @@ static void sha1_update(void *ctx, const u8 *data, unsigned int len)
 	unsigned int partial, done;
 	const u8 *src;
 
-	partial = (sctx->count >> 3) & 0x3f;
-	sctx->count += len << 3;
+	partial = sctx->count & 0x3f;
+	sctx->count += len;
 	done = 0;
 	src = data;
 
@@ -88,10 +88,10 @@ static void sha1_final(void* ctx, u8 *out)
 	__be64 bits;
 	static const u8 padding[64] = { 0x80, };
 
-	bits = cpu_to_be64(sctx->count);
+	bits = cpu_to_be64(sctx->count << 3);
 
 	/* Pad out to 56 mod 64 */
-	index = (sctx->count >> 3) & 0x3f;
+	index = sctx->count & 0x3f;
 	padlen = (index < 56) ? (56 - index) : ((64+56) - index);
 	sha1_update(sctx, padding, padlen);