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Implement ffs() / fls() and use the latter to compute the MSB.

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This commit is contained in:
Dag-Erling Smørgrav 2017-04-05 20:58:46 +02:00
parent 36739778ce
commit 206c6ffc85
5 changed files with 150 additions and 37 deletions
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51
configure.ac
View file

@ -21,19 +21,6 @@ AC_C_CONST
AC_C_RESTRICT
AC_C_VOLATILE
AC_C_BIGENDIAN
AC_TYPE_INT16_T
AC_TYPE_INT32_T
AC_TYPE_INT8_T
AC_TYPE_INTMAX_T
AC_TYPE_INTPTR_T
AC_TYPE_OFF_T
AC_TYPE_SIZE_T
AC_TYPE_SSIZE_T
AC_TYPE_UINT16_T
AC_TYPE_UINT32_T
AC_TYPE_UINT8_T
AC_TYPE_UINTMAX_T
AC_TYPE_UINTPTR_T
# libtool
LT_PREREQ([2.2.6])
@ -46,15 +33,46 @@ PKG_INSTALLDIR
# other programs
AC_PROG_INSTALL
############################################################################
#
# Types
#
AC_TYPE_INT16_T
AC_TYPE_INT32_T
AC_TYPE_INT8_T
AC_TYPE_INTMAX_T
AC_TYPE_INTPTR_T
AC_TYPE_OFF_T
AC_TYPE_SIZE_T
AC_TYPE_SSIZE_T
AC_TYPE_UINT16_T
AC_TYPE_UINT32_T
AC_TYPE_UINT8_T
AC_TYPE_UINTMAX_T
AC_TYPE_UINTPTR_T
############################################################################
#
# Headers and functions
#
AC_CHECK_HEADERS([endian.h sys/endian.h])
AC_CHECK_HEADERS([endian.h sys/endian.h strings.h])
AX_GCC_BUILTIN([__builtin_bswap16])
AX_GCC_BUILTIN([__builtin_bswap32])
AX_GCC_BUILTIN([__builtin_bswap64])
AX_GCC_BUILTIN([__builtin_clz])
AX_GCC_BUILTIN([__builtin_clzl])
AX_GCC_BUILTIN([__builtin_clzll])
AX_GCC_BUILTIN([__builtin_ctz])
AX_GCC_BUILTIN([__builtin_ctzl])
AX_GCC_BUILTIN([__builtin_ctzll])
AX_GCC_BUILTIN([__builtin_ffs])
AX_GCC_BUILTIN([__builtin_ffsl])
AX_GCC_BUILTIN([__builtin_ffsll])
# No compiler we know of has these
#AX_GCC_BUILTIN([__builtin_fls])
#AX_GCC_BUILTIN([__builtin_flsl])
#AX_GCC_BUILTIN([__builtin_flsll])
AC_CHECK_DECLS([
bswap16, bswap32, bswap64,
bswap16v, bswap32v, bswap64v,
@ -76,6 +94,11 @@ AC_CHECK_DECLS([
#include <endian.h>
#endif
]])
AC_CHECK_FUNCS([ffs ffsl ffsll fls flsl flsll], [], [], [[
#if HAVE_STRINGS_H
#include <strings.h>
#endif
]])
AC_CHECK_FUNCS([strlcat strlcmp strlcpy])
AC_CHECK_FUNCS([wcslcat wcslcmp wcslcpy])

103
include/cryb/bitwise.h
View file

@ -54,6 +54,109 @@ CRYB_ROL_ROR(64);
#undef CRYB_ROL_ROR
#if !HAVE_FFS
#define ffs cryb_ffs
#endif
#if !HAVE_FFSL
#define ffsl cryb_ffsl
#endif
#if !HAVE_FFSLL
#define ffsll cryb_ffsll
#endif
#if !HAVE_FLS
#define fls cryb_fls
#endif
#if !HAVE_FLSL
#define flsl cryb_flsl
#endif
#if !HAVE_FLSLL
#define flsll cryb_flsll
#endif
static inline int cryb_ffs(int n) {
#if HAVE___BUILTIN_FFS
return (__builtin_ffs(n));
#elif HAVE___BUILTIN_CTZ
return (n ? __builtin_ctz(n) : 0);
#else
int i = 8 * sizeof n - 1;
for (i > 0)
if (n & (1 << --i))
break;
return (i);
#endif
}
static inline int cryb_ffsl(long int n) {
#if HAVE___BUILTIN_FFSL
return (__builtin_ffsl(n));
#elif HAVE___BUILTIN_CLZ
return (n ? __builtin_ctz(n) : 0);
#else
int i = 8 * sizeof n - 1;
for (i > 0)
if (n & (1 << --i))
break;
return (i);
#endif
}
static inline int cryb_ffsll(long long int n) {
#if HAVE___BUILTIN_FFSLL
return (__builtin_ffsll(n));
#elif HAVE___BUILTIN_CLZ
return (n ? __builtin_ctz(n) : 0);
#else
int i = 8 * sizeof n - 1;
for (i > 0)
if (n & (1 << --i))
break;
return (i);
#endif
}
static inline int cryb_fls(int n) {
#if HAVE___BUILTIN_FLS
return (__builtin_fls(n));
#elif HAVE___BUILTIN_CLZ
return (n ? (8 * sizeof n) - __builtin_clz(n) : 0);
#else
int i = 8 * sizeof n - 1;
for (i > 0)
if (n & (1 << --i))
break;
return (i);
#endif
}
static inline int cryb_flsl(long int n) {
#if HAVE___BUILTIN_FLSL
return (__builtin_flsl(n));
#elif HAVE___BUILTIN_CLZ
return (n ? (8 * sizeof n) - __builtin_clzl(n) : 0);
#else
int i = 8 * sizeof n - 1;
for (i > 0)
if (n & (1 << --i))
break;
return (i);
#endif
}
static inline int cryb_flsll(long long int n) {
#if HAVE___BUILTIN_FLSLL
return (__builtin_flsll(n));
#elif HAVE___BUILTIN_CLZ
return (n ? (8 * sizeof n) - __builtin_clzll(n) : 0);
#else
int i = 8 * sizeof n - 1;
for (i > 0)
if (n & (1 << --i))
break;
return (i);
#endif
}
CRYB_END
#endif

10
lib/mpi/cryb_mpi_add_abs.c
View file

@ -31,7 +31,9 @@
#include <stddef.h>
#include <stdint.h>
#include <strings.h>
#include <cryb/bitwise.h>
#include <cryb/mpi.h>
#include "cryb_mpi_impl.h"
@ -104,13 +106,7 @@ mpi_add_abs(cryb_mpi *X, const cryb_mpi *A, const cryb_mpi *B)
}
if (X->words[i] == 0)
--i;
/* compute msb of msw */
/* XXX should use flsl() */
for (X->msb = 31; X->msb > 0; --X->msb)
if (X->words[i] & (1 << X->msb))
break;
/* add msw offset */
X->msb += i * 32 + 1;
X->msb = i * 32 + flsl(X->words[i]);
X->neg = 0;
return (0);
}

11
lib/mpi/cryb_mpi_load.c
View file

@ -31,7 +31,9 @@
#include <stddef.h>
#include <stdint.h>
#include <strings.h>
#include <cryb/bitwise.h>
#include <cryb/endian.h>
#include <cryb/mpi.h>
@ -70,13 +72,6 @@ mpi_load(cryb_mpi *X, const uint8_t *a, size_t len)
--i;
CRYB_NO_DEFAULT_CASE;
}
/* i now points to the msw */
/* compute msb of msw */
/* XXX use flsl() */
for (X->msb = 31; X->msb > 0; --X->msb)
if (X->words[i] & (1 << X->msb))
break;
/* add msw offset */
X->msb += i * 32 + 1;
X->msb = i * 32 + flsl(X->words[i]);
return (0);
}

12
lib/mpi/cryb_mpi_sub_abs.c
View file

@ -31,7 +31,9 @@
#include <stddef.h>
#include <stdint.h>
#include <strings.h>
#include <cryb/bitwise.h>
#include <cryb/mpi.h>
#include "cryb_mpi_impl.h"
@ -92,15 +94,9 @@ mpi_sub_abs(cryb_mpi *X, const cryb_mpi *A, const cryb_mpi *B)
c = cn;
++i;
}
while (i > 0 && X->words[i] == 0)
while (X->words[i] == 0)
--i;
/* compute msb of msw */
/* XXX use flsl() */
for (X->msb = 31; X->msb > 0; --X->msb)
if (X->words[i] & (1 << X->msb))
break;
/* add msw offset */
X->msb += i * 32 + 1;
X->msb = i * 32 + flsl(X->words[i]);
X->neg = 0;
return (0);
}