Messages in this thread Patch in this message | | | Date | Mon, 24 Oct 2005 13:57:06 -0400 (EDT) | From | Nicolas Pitre <> | Subject | [PATCH 2/5] crypto/sha1.c: avoid shifting count left and right |
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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>
Index: linux-2.6/crypto/sha1.c =================================================================== --- linux-2.6.orig/crypto/sha1.c +++ linux-2.6/crypto/sha1.c @@ -51,8 +51,8 @@ unsigned int partial, done; u32 temp[SHA_WORKSPACE_WORDS]; - partial = (sctx->count >> 3) & 0x3f; - sctx->count += len << 3; + partial = sctx->count & 0x3f; + sctx->count += len; done = 0; if ((partial + len) > 63) { @@ -80,7 +80,7 @@ u8 bits[8] = { 0, }; static const u8 padding[64] = { 0x80, }; - t = sctx->count; + t = sctx->count << 3; bits[7] = 0xff & t; t>>=8; bits[6] = 0xff & t; t>>=8; bits[5] = 0xff & t; t>>=8; @@ -91,7 +91,7 @@ bits[0] = 0xff & t; /* 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); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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