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Size/perf optimisation for mbedtls_mpi_core_clz

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman 2023-04-19 17:40:28 +01:00
parent 3c3b94a31b
commit fe8a8cd100
3 changed files with 102 additions and 0 deletions
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30
library/bignum_core.c
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@ -35,6 +35,36 @@
size_t mbedtls_mpi_core_clz(mbedtls_mpi_uint a)
{
#if defined(__has_builtin)
#if __has_builtin(__builtin_clz)
if (sizeof(mbedtls_mpi_uint) == sizeof(unsigned int)) {
// __builtin_clz is undefined if a == 0
if (a == 0) {
return sizeof(mbedtls_mpi_uint) * 8;
} else {
return (size_t) __builtin_clz(a);
}
}
#endif
#if __has_builtin(__builtin_clzl)
if (sizeof(mbedtls_mpi_uint) == sizeof(unsigned long)) {
if (a == 0) {
return sizeof(mbedtls_mpi_uint) * 8;
} else {
return (size_t) __builtin_clzl(a);
}
}
#endif
#if __has_builtin(__builtin_clzll)
if (sizeof(mbedtls_mpi_uint) == sizeof(unsigned long long)) {
if (a == 0) {
return sizeof(mbedtls_mpi_uint) * 8;
} else {
return (size_t) __builtin_clzll(a);
}
}
#endif
#endif
size_t j;
mbedtls_mpi_uint mask = (mbedtls_mpi_uint) 1 << (biL - 1);