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crypto: crc32: Optimize dynamic CRC table generation 

In barebox we have an option for dynamic formation of the CRC32
table (DYNAMIC_CRC_TABLE), but the source code declares a static
array which is simply filled with data, the resulting code becomes
even more than without DYNAMIC_CRC_TABLE option, due to the BSS usage.
CONFIG_DYNAMIC_CRC_TABLE=n
   text    data     bss     dec     hex filename
   1884       0       0    1884     75c crc32.o
CONFIG_DYNAMIC_CRC_TABLE=y
   text    data     bss     dec     hex filename
   1066       4    1024    2094     82e crc32.o

This patch provides dynamic buffer allocation for the CRC table,
which saves about 1 Kbyte, as it should be.
CONFIG_DYNAMIC_CRC_TABLE=y
   text    data     bss     dec     hex filename
   1062       0       4    1066     42a crc32.o

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
This commit is contained in:
Alexander Shiyan 2016-06-19 21:52:52 +03:00 committed by Sascha Hauer
parent c672fda23a
commit 2049dbb6fe
1 changed files with 7 additions and 8 deletions
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15
crypto/crc32.c
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@ -24,9 +24,7 @@
#ifdef CONFIG_DYNAMIC_CRC_TABLE
static int crc_table_empty = 1;
static ulong crc_table[256];
static void make_crc_table(void);
static ulong *crc_table;
/*
Generate a table for a byte-wise 32-bit CRC calculation on the polynomial:
@ -65,6 +63,8 @@ static void make_crc_table(void)
for (n = 0; n < sizeof(p)/sizeof(char); n++)
poly |= 1L << (31 - p[n]);
crc_table = xmalloc(sizeof(ulong) * 256);
for (n = 0; n < 256; n++)
{
c = (ulong)n;
@ -72,7 +72,6 @@ static void make_crc_table(void)
c = c & 1 ? poly ^ (c >> 1) : c >> 1;
crc_table[n] = c;
}
crc_table_empty = 0;
}
#else
/* ========================================================================
@ -147,8 +146,8 @@ STATIC uint32_t crc32(uint32_t crc, const void *_buf, unsigned int len)
const unsigned char *buf = _buf;
#ifdef CONFIG_DYNAMIC_CRC_TABLE
if (crc_table_empty)
make_crc_table();
if (!crc_table)
make_crc_table();
#endif
crc = crc ^ 0xffffffffL;
while (len >= 8)
@ -173,8 +172,8 @@ STATIC uint32_t crc32_no_comp(uint32_t crc, const void *_buf, unsigned int len)
const unsigned char *buf = _buf;
#ifdef CONFIG_DYNAMIC_CRC_TABLE
if (crc_table_empty)
make_crc_table();
if (!crc_table)
make_crc_table();
#endif
while (len >= 8)
{