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ext/bcmath: Made the same changes to _bc_do_add as _bc_do_sub (#14196)
The code for _bc_do_add and _bc_do_sub were written slightly differently for similar processing (and add was slower than sub), so I changed the code to one similar to sub. Also, _bc_do_add has been changed to use SIMD to perform faster calculations when possible.
This commit is contained in:
Saki Takamachi
@@ -41,75 +41,123 @@
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bc_num _bc_do_add(bc_num n1, bc_num n2, size_t scale_min)
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{
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bc_num sum;
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size_t sum_scale, sum_digits;
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size_t sum_len = MAX(n1->n_len, n2->n_len) + 1;
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size_t sum_scale = MAX(n1->n_scale, n2->n_scale);
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size_t min_len = MIN (n1->n_len, n2->n_len);
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size_t min_scale = MIN(n1->n_scale, n2->n_scale);
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size_t min_bytes = min_len + min_scale;
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char *n1ptr, *n2ptr, *sumptr;
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size_t n1bytes, n2bytes;
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bool carry;
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bool carry = 0;
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size_t count;
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/* Prepare sum. */
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sum_scale = MAX (n1->n_scale, n2->n_scale);
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sum_digits = MAX (n1->n_len, n2->n_len) + 1;
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sum = bc_new_num (sum_digits, MAX(sum_scale, scale_min));
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sum = bc_new_num (sum_len, MAX(sum_scale, scale_min));
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/* Start with the fraction part. Initialize the pointers. */
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n1bytes = n1->n_scale;
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n2bytes = n2->n_scale;
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n1ptr = (char *) (n1->n_value + n1->n_len + n1bytes - 1);
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n2ptr = (char *) (n2->n_value + n2->n_len + n2bytes - 1);
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sumptr = (char *) (sum->n_value + sum_scale + sum_digits - 1);
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n1ptr = (char *) (n1->n_value + n1->n_len + n1->n_scale - 1);
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n2ptr = (char *) (n2->n_value + n2->n_len + n2->n_scale - 1);
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sumptr = (char *) (sum->n_value + sum_scale + sum_len - 1);
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/* Add the fraction part. First copy the longer fraction.*/
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if (n1bytes != n2bytes) {
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if (n1bytes > n2bytes) {
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while (n1bytes > n2bytes) {
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*sumptr-- = *n1ptr--;
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n1bytes--;
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}
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} else {
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while (n2bytes > n1bytes) {
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*sumptr-- = *n2ptr--;
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n2bytes--;
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}
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if (n1->n_scale != min_scale) {
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/* n1 has the longer scale */
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for (count = n1->n_scale - min_scale; count > 0; count--) {
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*sumptr-- = *n1ptr--;
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}
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} else {
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/* n2 has the longer scale */
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for (count = n2->n_scale - min_scale; count > 0; count--) {
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*sumptr-- = *n2ptr--;
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}
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}
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/* Now add the remaining fraction part and equal size integer parts. */
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n1bytes += n1->n_len;
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n2bytes += n2->n_len;
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carry = 0;
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while ((n1bytes > 0) && (n2bytes > 0)) {
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count = 0;
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/* Uses SIMD to perform calculations at high speed. */
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if (min_bytes >= sizeof(BC_UINT_T)) {
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sumptr++;
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n1ptr++;
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n2ptr++;
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while (count + sizeof(BC_UINT_T) <= min_bytes) {
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sumptr -= sizeof(BC_UINT_T);
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n1ptr -= sizeof(BC_UINT_T);
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n2ptr -= sizeof(BC_UINT_T);
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BC_UINT_T n1bytes;
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BC_UINT_T n2bytes;
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memcpy(&n1bytes, n1ptr, sizeof(n1bytes));
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memcpy(&n2bytes, n2ptr, sizeof(n2bytes));
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#if BC_LITTLE_ENDIAN
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/* Little endian requires changing the order of bytes. */
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n1bytes = BC_BSWAP(n1bytes);
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n2bytes = BC_BSWAP(n2bytes);
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#endif
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/*
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* In order to add 1 to the "next digit" when a carry occurs, adjust it so that it
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* overflows when add 10.
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* e.g.
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* 00001001(9) + 00000001(1) = 00001010(10) to
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* 11111111 + 00000001 = 00000000(0) and carry 1
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*/
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n1bytes += SWAR_REPEAT(0xF6) + n2bytes + carry;
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/* If the most significant bit is 0, a carry has occurred. */
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carry = !(n1bytes & ((BC_UINT_T) 1 << (8 * sizeof(BC_UINT_T) - 1)));
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/*
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* The calculation result is a mixture of bytes that have been carried and bytes that have not.
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* The most significant bit of each byte is 0 if it is carried forward, and 1 if it is not.
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* Using this, subtract the 0xF6 added for adjustment from the byte that has not been carried
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* over to return it to the correct value as a decimal number.
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*/
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BC_UINT_T sum_mask = ((n1bytes & SWAR_REPEAT(0x80)) >> 7) * 0xF6;
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n1bytes -= sum_mask;
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#if BC_LITTLE_ENDIAN
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/* Little endian requires changing the order of bytes back. */
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n1bytes = BC_BSWAP(n1bytes);
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#endif
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memcpy(sumptr, &n1bytes, sizeof(n1bytes));
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count += sizeof(BC_UINT_T);
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}
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sumptr--;
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n1ptr--;
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n2ptr--;
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}
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for (; count < min_bytes; count++) {
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*sumptr = *n1ptr-- + *n2ptr-- + carry;
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if (*sumptr > (BASE - 1)) {
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carry = 1;
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if (*sumptr >= BASE) {
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*sumptr -= BASE;
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carry = 1;
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} else {
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carry = 0;
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}
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sumptr--;
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n1bytes--;
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n2bytes--;
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}
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/* Now add carry the longer integer part. */
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if (n1bytes == 0) {
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n1bytes = n2bytes;
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n1ptr = n2ptr;
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}
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while (n1bytes-- > 0) {
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*sumptr = *n1ptr-- + carry;
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if (*sumptr > (BASE - 1)) {
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carry = true;
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*sumptr -= BASE;
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} else {
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carry = false;
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if (n1->n_len != n2->n_len) {
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if (n2->n_len > n1->n_len) {
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n1ptr = n2ptr;
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}
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for (count = sum_len - min_len; count > 1; count--) {
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*sumptr = *n1ptr-- + carry;
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if (*sumptr >= BASE) {
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*sumptr -= BASE;
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carry = 1;
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} else {
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carry = 0;
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}
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sumptr--;
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}
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sumptr--;
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}
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/* Set final carry. */
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if (carry) {
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*sumptr += 1;
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}
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*sumptr += carry;
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/* Adjust sum and return. */
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_bc_rm_leading_zeros(sum);
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