Messages in this thread Patch in this message | | | Date | Mon, 24 Oct 2005 14:05:50 -0400 (EDT) | From | Nicolas Pitre <> | Subject | [PATCH 4/5] crypto/sha1.c: avoid successively shifting a long long |
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Shifting a long long about 7 times to store the length bits is suboptimal on most 32-bit architectures. Use a 32 bit scratch instead.
This provides an appreciable code reduction considering the _whole_ of the sha1_final() function:
arch old size new size reduction --------------------------------------------------------- i386 0xe0 0xc4 12.5% arm 0x15c 0xe8 33.3%
Smaller code in this case is of course faster code.
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 @@ -75,8 +75,8 @@ static void sha1_final(void* ctx, u8 *out) { struct sha1_ctx *sctx = ctx; - u32 i, j, index, padlen; - u64 t, count = sctx->count; + u64 count = sctx->count; + u32 i, j, index, padlen, t; u8 bits[8]; static const u8 padding[64] = { 0x80, }; @@ -90,7 +90,8 @@ bits[7] = 0xff & t; t>>=8; bits[6] = 0xff & t; t>>=8; bits[5] = 0xff & t; t>>=8; - bits[4] = 0xff & t; t>>=8; + bits[4] = 0xff & t; + t = count >> (32 - 3); bits[3] = 0xff & t; t>>=8; bits[2] = 0xff & t; t>>=8; bits[1] = 0xff & t; t>>=8; - 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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