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Date: Sun, 20 Mar 2016 13:31:27 +0100 From: Nicolai Stange <nicstange@...il.com> To: Herbert Xu <herbert@...dor.apana.org.au> Cc: Tadeusz Struk <tadeusz.struk@...el.com>, Michal Marek <mmarek@...e.com>, Andrzej Zaborowski <andrew.zaborowski@...el.com>, Stephan Mueller <smueller@...onox.de>, Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org, Nicolai Stange <nicstange@...il.com> Subject: [PATCH v2 06/14] lib/mpi: mpi_read_buffer(): optimize skipping of leading zero limbs Currently, if the number of leading zeros is greater than fits into a complete limb, mpi_read_buffer() skips them by iterating over them limb-wise. Instead of skipping the high order zero limbs within the loop as shown above, adjust the copying loop's bounds. Signed-off-by: Nicolai Stange <nicstange@...il.com> --- lib/mpi/mpicoder.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c index 623439e..2fd8d41 100644 --- a/lib/mpi/mpicoder.c +++ b/lib/mpi/mpicoder.c @@ -184,7 +184,9 @@ int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes, p = buf; *nbytes = n - lzeros; - for (i = a->nlimbs - 1; i >= 0; i--) { + for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB, + lzeros %= BYTES_PER_MPI_LIMB; + i >= 0; i--) { alimb = a->d[i]; #if BYTES_PER_MPI_LIMB == 4 *p++ = alimb >> 24; @@ -205,15 +207,11 @@ int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes, #endif if (lzeros > 0) { - if (lzeros >= sizeof(alimb)) { - p -= sizeof(alimb); - } else { - mpi_limb_t *limb1 = (void *)p - sizeof(alimb); - mpi_limb_t *limb2 = (void *)p - sizeof(alimb) - + lzeros; - *limb1 = *limb2; - p -= lzeros; - } + mpi_limb_t *limb1 = (void *)p - sizeof(alimb); + mpi_limb_t *limb2 = (void *)p - sizeof(alimb) + + lzeros; + *limb1 = *limb2; + p -= lzeros; lzeros -= sizeof(alimb); } } -- 2.7.3
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