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Further size optimisation

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman 2023-04-20 09:50:31 +01:00
parent d54cb83584
commit 880a6b34c2
1 changed files with 16 additions and 28 deletions
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44
library/bignum_core.c
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@ -33,35 +33,25 @@
#include "bn_mul.h" #include "bn_mul.h"
#include "constant_time_internal.h" #include "constant_time_internal.h"
size_t mbedtls_mpi_core_clz(mbedtls_mpi_uint a) inline size_t mbedtls_mpi_core_clz(mbedtls_mpi_uint a)
{ {
/* Note: the result is undefined for a == 0
* (because this is the behaviour of __builtin_clz).
*/
#if defined(__has_builtin) #if defined(__has_builtin)
#if __has_builtin(__builtin_clz) #if __has_builtin(__builtin_clz)
if (sizeof(mbedtls_mpi_uint) == sizeof(unsigned int)) { if (sizeof(mbedtls_mpi_uint) == sizeof(unsigned int)) {
// __builtin_clz is undefined if a == 0 return (size_t) __builtin_clz(a);
if (a == 0) {
return sizeof(mbedtls_mpi_uint) * 8;
} else {
return (size_t) __builtin_clz(a);
}
} }
#endif #endif
#if __has_builtin(__builtin_clzl) #if __has_builtin(__builtin_clzl)
if (sizeof(mbedtls_mpi_uint) == sizeof(unsigned long)) { if (sizeof(mbedtls_mpi_uint) == sizeof(unsigned long)) {
if (a == 0) { return (size_t) __builtin_clzl(a);
return sizeof(mbedtls_mpi_uint) * 8;
} else {
return (size_t) __builtin_clzl(a);
}
} }
#endif #endif
#if __has_builtin(__builtin_clzll) #if __has_builtin(__builtin_clzll)
if (sizeof(mbedtls_mpi_uint) == sizeof(unsigned long long)) { if (sizeof(mbedtls_mpi_uint) == sizeof(unsigned long long)) {
if (a == 0) { return (size_t) __builtin_clzll(a);
return sizeof(mbedtls_mpi_uint) * 8;
} else {
return (size_t) __builtin_clzll(a);
}
} }
#endif #endif
#endif #endif
@ -81,21 +71,19 @@ size_t mbedtls_mpi_core_clz(mbedtls_mpi_uint a)
size_t mbedtls_mpi_core_bitlen(const mbedtls_mpi_uint *A, size_t A_limbs) size_t mbedtls_mpi_core_bitlen(const mbedtls_mpi_uint *A, size_t A_limbs)
{ {
size_t i, j; int i;
size_t j;
if (A_limbs == 0) { if (A_limbs != 0) {
return 0; for (i = (int) A_limbs - 1; i >= 0; i--) {
} if (A[i] != 0) {
j = biL - mbedtls_mpi_core_clz(A[i]);
for (i = A_limbs - 1; i > 0; i--) { return (i * biL) + j;
if (A[i] != 0) { }
break;
} }
} }
j = biL - mbedtls_mpi_core_clz(A[i]); return 0;
return (i * biL) + j;
} }
/* Convert a big-endian byte array aligned to the size of mbedtls_mpi_uint /* Convert a big-endian byte array aligned to the size of mbedtls_mpi_uint