intn: make digit_bit_size a constant

Use INTN_DIGIT_BITS instead of `sizeof(intn_digit_t) * 8`.

Signed-off-by: Davide Bettio <davide@uninstall.it>

Author: bettio

src/libAtomVM/intn.c

@@ -787,23 +787,21 @@ size_t intn_bnot(const intn_digit_t m[], size_t m_len, intn_integer_sign_t m_sig
 
 size_t intn_bsl(const intn_digit_t num[], size_t len, size_t n, intn_digit_t *out)
 {
-    size_t digit_bit_size = sizeof(uint32_t) * 8;
-
     size_t digit_left_bit_shift = n % 32;
     size_t right_shift_n = (32 - digit_left_bit_shift);
 
     size_t counted_digits = intn_count_digits(num, len);
     size_t ms_digit_bits = 32 - uint32_nlz(num[counted_digits - 1]);
-    size_t effective_bits_len = (counted_digits - 1) * digit_bit_size + ms_digit_bits;
-    size_t new_bits_len = size_align_up_pow2(effective_bits_len + n, digit_bit_size);
+    size_t effective_bits_len = (counted_digits - 1) * INTN_DIGIT_BITS + ms_digit_bits;
+    size_t new_bits_len = size_align_up_pow2(effective_bits_len + n, INTN_DIGIT_BITS);
 
-    size_t new_digits_count = new_bits_len / digit_bit_size;
+    size_t new_digits_count = new_bits_len / INTN_DIGIT_BITS;
 
     if (new_digits_count > INTN_BSL_MAX_RES_LEN) {
         return new_digits_count;
     }
 
-    size_t initial_zeros = MIN(n / digit_bit_size, INTN_BSL_MAX_RES_LEN);
+    size_t initial_zeros = MIN(n / INTN_DIGIT_BITS, INTN_BSL_MAX_RES_LEN);
     memset(out, 0, initial_zeros * sizeof(uint32_t));
 
     if (right_shift_n == 32) {
@@ -833,15 +831,14 @@ size_t intn_bsl(const intn_digit_t num[], size_t len, size_t n, intn_digit_t *ou
 void bsru(
     const uint32_t num[], size_t effective_bits_len, size_t n, uint32_t last_digit, uint32_t *out)
 {
-    size_t digit_bit_size = sizeof(uint32_t) * 8; // 32
-
-    size_t digit_right_bit_shift = n % digit_bit_size;
-    size_t left_shift_n = (digit_bit_size - digit_right_bit_shift);
+    size_t digit_right_bit_shift = n % INTN_DIGIT_BITS;
+    size_t left_shift_n = (INTN_DIGIT_BITS - digit_right_bit_shift);
 
-    size_t len_in_digits = size_align_up_pow2(effective_bits_len, digit_bit_size) / digit_bit_size;
+    size_t len_in_digits
+        = size_align_up_pow2(effective_bits_len, INTN_DIGIT_BITS) / INTN_DIGIT_BITS;
 
     // caller makes sure that discarded < len_in_digits
-    size_t discarded = n / digit_bit_size;
+    size_t discarded = n / INTN_DIGIT_BITS;
 
     if (left_shift_n == 32) {
         memcpy(out, num + discarded, (len_in_digits - discarded) * sizeof(uint32_t));
@@ -864,18 +861,17 @@ void bsru(
 size_t intn_bsr(
     const intn_digit_t num[], size_t len, intn_integer_sign_t num_sign, size_t n, intn_digit_t *out)
 {
-    size_t digit_bit_size = sizeof(uint32_t) * 8;
     size_t counted_digits = intn_count_digits(num, len);
     size_t ms_digit_bits = 32 - uint32_nlz(num[counted_digits - 1]);
-    size_t effective_bits_len = (counted_digits - 1) * digit_bit_size + ms_digit_bits;
+    size_t effective_bits_len = (counted_digits - 1) * INTN_DIGIT_BITS + ms_digit_bits;
 
     if (n >= effective_bits_len) {
         out[0] = (num_sign == IntNPositiveInteger) ? 0 : 1;
         return 1;
     }
 
     size_t shifted_len
-        = size_align_up_pow2(effective_bits_len - n, digit_bit_size) / digit_bit_size;
+        = size_align_up_pow2(effective_bits_len - n, INTN_DIGIT_BITS) / INTN_DIGIT_BITS;
 
     if (num_sign == IntNPositiveInteger) {
         bsru(num, effective_bits_len, n, 0, out);

src/libAtomVM/intn.h

@@ -52,6 +52,7 @@
 #define INTN_DIV_OUT_LEN(m, n) ((m) - (n) + 1 + 1)
 #define INTN_ABS_OUT_LEN(m) ((m) + 1)
 
+#define INTN_DIGIT_BITS 32
 #define INTN_MAX_UNSIGNED_BYTES_SIZE 32
 #define INTN_MAX_UNSIGNED_BITS_SIZE 256