Avoid needless memsets by creating a variant of bc_new_num that doesn't memset (#14133)

Also avoid some memsets where we do call bc_new_num.

After:
```
1.2066178321838
1.5389559268951
1.6050860881805
```

Before:
```
1.3858470916748
1.6806011199951
1.9091980457306
```

Author: nielsdos

ext/bcmath/libbcmath/src/add.c

@@ -58,7 +58,6 @@ bc_num bc_add(bc_num n1, bc_num n2, size_t scale_min)
 			case 0:
 				/* They are equal! return zero with the correct scale! */
 				sum = bc_new_num (1, MAX(scale_min, MAX(n1->n_scale, n2->n_scale)));
-				memset(sum->n_value, 0, sum->n_scale + 1);
 				break;
 			case 1:
 				/* n2 is less than n1, subtract n2 from n1. */

ext/bcmath/libbcmath/src/bcmath.h

@@ -86,6 +86,8 @@ void bc_init_numbers(void);
 
 bc_num _bc_new_num_ex(size_t length, size_t scale, bool persistent);
 
+bc_num _bc_new_num_nonzeroed_ex(size_t length, size_t scale, bool persistent);
+
 void _bc_free_num_ex(bc_num *num, bool persistent);
 
 /* Make a copy of a number! Just increments the reference count! */
@@ -167,8 +169,9 @@ void bc_raise_bc_exponent(bc_num base, bc_num exponent, bc_num *resul, size_t sc
 bool bc_sqrt(bc_num *num, size_t scale);
 
 /* Prototypes needed for external utility routines. */
-#define bc_new_num(length, scale)	_bc_new_num_ex((length), (scale), 0)
-#define bc_free_num(num)			_bc_free_num_ex((num), 0)
-#define bc_num2str(num)				bc_num2str_ex((num), (num->n_scale))
+#define bc_new_num(length, scale)			_bc_new_num_ex((length), (scale), 0)
+#define bc_new_num_nonzeroed(length, scale)	_bc_new_num_nonzeroed_ex((length), (scale), 0)
+#define bc_free_num(num)					_bc_free_num_ex((num), 0)
+#define bc_num2str(num)						bc_num2str_ex((num), (num->n_scale))
 
 #endif

ext/bcmath/libbcmath/src/div.c

@@ -97,7 +97,6 @@ bool bc_divide(bc_num n1, bc_num n2, bc_num *quot, int scale)
 	if (n2->n_scale == 0 && n2->n_len == 1 && *n2->n_value == 1) {
 		qval = bc_new_num (n1->n_len, scale);
 		qval->n_sign = (n1->n_sign == n2->n_sign ? PLUS : MINUS);
-		memset(&qval->n_value[n1->n_len], 0, scale);
 		memcpy(qval->n_value, n1->n_value, n1->n_len + MIN(n1->n_scale, scale));
 		bc_free_num (quot);
 		*quot = qval;
@@ -146,7 +145,6 @@ bool bc_divide(bc_num n1, bc_num n2, bc_num *quot, int scale)
 
 	/* Allocate and zero the storage for the quotient. */
 	qval = bc_new_num (qdigits - scale, scale);
-	memset(qval->n_value, 0, qdigits);
 
 	/* Allocate storage for the temporary storage mval. */
 	mval = (unsigned char *) safe_emalloc(1, len2, 1);

ext/bcmath/libbcmath/src/init.c

@@ -35,8 +35,7 @@
 #include <string.h>
 #include "zend_alloc.h"
 
-/* new_num allocates a number and sets fields to known values. */
-bc_num _bc_new_num_ex(size_t length, size_t scale, bool persistent)
+static zend_always_inline bc_num _bc_new_num_nonzeroed_ex_internal(size_t length, size_t scale, bool persistent)
 {
 	/* PHP Change: malloc() -> pemalloc(), removed free_list code, merged n_ptr and n_value */
 	bc_num temp = safe_pemalloc(1, sizeof(bc_struct) + length, scale, persistent);
@@ -45,10 +44,21 @@ bc_num _bc_new_num_ex(size_t length, size_t scale, bool persistent)
 	temp->n_scale = scale;
 	temp->n_refs = 1;
 	temp->n_value = (char *) temp + sizeof(bc_struct);
+	return temp;
+}
+
+/* new_num allocates a number and sets fields to known values. */
+bc_num _bc_new_num_ex(size_t length, size_t scale, bool persistent)
+{
+	bc_num temp = _bc_new_num_nonzeroed_ex_internal(length, scale, persistent);
 	memset(temp->n_value, 0, length + scale);
 	return temp;
 }
 
+bc_num _bc_new_num_nonzeroed_ex(size_t length, size_t scale, bool persistent)
+{
+	return _bc_new_num_nonzeroed_ex_internal(length, scale, persistent);
+}
 
 /* "Frees" a bc_num NUM.  Actually decreases reference count and only
    frees the storage if reference count is zero. */

ext/bcmath/libbcmath/src/recmul.c

@@ -68,7 +68,7 @@ static void _bc_simp_mul(bc_num n1, size_t n1len, bc_num n2, int n2len, bc_num *
 
 	int prodlen = n1len + n2len + 1;
 
-	*prod = bc_new_num (prodlen, 0);
+	*prod = bc_new_num_nonzeroed(prodlen, 0);
 
 	n1end = (char *) (n1->n_value + n1len - 1);
 	n2end = (char *) (n2->n_value + n2len - 1);

ext/bcmath/libbcmath/src/str2num.c

@@ -154,12 +154,12 @@ bool bc_str2num(bc_num *num, const char *str, const char *end, size_t scale, boo
 		zero_int = true;
 		digits = 1;
 	}
-	*num = bc_new_num (digits, str_scale);
+	*num = bc_new_num_nonzeroed(digits, str_scale);
 	(*num)->n_sign = *str == '-' ? MINUS : PLUS;
 	char *nptr = (*num)->n_value;
 
 	if (zero_int) {
-		nptr++;
+		*nptr++ = 0;
 		/*
 		 * If zero_int is true and the str_scale is 0, there is an early return,
 		 * so here str_scale is always greater than 0.

ext/bcmath/libbcmath/src/sub.c

@@ -59,7 +59,6 @@ bc_num bc_sub(bc_num n1, bc_num n2, size_t scale_min)
 				/* They are equal! return zero! */
 				size_t res_scale = MAX (scale_min, MAX(n1->n_scale, n2->n_scale));
 				diff = bc_new_num (1, res_scale);
-				memset(diff->n_value, 0, res_scale + 1);
 				break;
 			}
 			case 1: