Further size optimisation
Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/bignum_core.c b/library/bignum_core.c
index 9b6c414..1f3a57c 100644
--- a/library/bignum_core.c
+++ b/library/bignum_core.c
@@ -33,35 +33,25 @@
#include "bn_mul.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 __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);
- }
+ 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);
- }
+ 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);
- }
+ return (size_t) __builtin_clzll(a);
}
#endif
#endif
@@ -81,21 +71,19 @@
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) {
- return 0;
- }
-
- for (i = A_limbs - 1; i > 0; i--) {
- if (A[i] != 0) {
- break;
+ if (A_limbs != 0) {
+ for (i = (int) A_limbs - 1; i >= 0; i--) {
+ if (A[i] != 0) {
+ j = biL - mbedtls_mpi_core_clz(A[i]);
+ return (i * biL) + j;
+ }
}
}
- j = biL - mbedtls_mpi_core_clz(A[i]);
-
- return (i * biL) + j;
+ return 0;
}
/* Convert a big-endian byte array aligned to the size of mbedtls_mpi_uint