Simplify conversion in BCMath (#14157)

This simplifies the code, and also might indirectly improve performance
due to a decrease in instruction cache pressure. Although the latter is
probably negligible.

This works because 0x30 has no overlapping bits with [0, 9].

Author: nielsdos

ext/bcmath/libbcmath/src/convert.c

@@ -21,20 +21,16 @@
 # include <emmintrin.h>
 #endif
 
-static char *bc_copy_and_shift_numbers(char *restrict dest, const char *source, const char *source_end, unsigned char shift, bool add)
+char *bc_copy_and_toggle_bcd(char *restrict dest, const char *source, const char *source_end)
 {
-	size_t bulk_shift = SWAR_REPEAT(shift);
-	if (!add) {
-		bulk_shift = -bulk_shift;
-		shift = -shift;
-	}
+	const size_t bulk_shift = SWAR_REPEAT('0');
 
 #ifdef __SSE2__
 	/* SIMD SSE2 bulk shift + copy */
-	__m128i shift_vector = _mm_set1_epi8(shift);
+	__m128i shift_vector = _mm_set1_epi8('0');
 	while (source + sizeof(__m128i) <= source_end) {
 		__m128i bytes = _mm_loadu_si128((const __m128i *) source);
-		bytes = _mm_add_epi8(bytes, shift_vector);
+		bytes = _mm_xor_si128(bytes, shift_vector);
 		_mm_storeu_si128((__m128i *) dest, bytes);
 
 		source += sizeof(__m128i);
@@ -50,28 +46,18 @@ static char *bc_copy_and_shift_numbers(char *restrict dest, const char *source,
 		size_t bytes;
 		memcpy(&bytes, source, sizeof(bytes));
 
-		bytes += bulk_shift;
+		bytes ^= bulk_shift;
 		memcpy(dest, &bytes, sizeof(bytes));
 
 		source += sizeof(size_t);
 		dest += sizeof(size_t);
 	}
 
 	while (source < source_end) {
-		*dest = *source + shift;
+		*dest = *source ^ '0';
 		dest++;
 		source++;
 	}
 
 	return dest;
 }
-
-char *bc_copy_ch_val(char *restrict dest, const char *source, const char *source_end)
-{
-	return bc_copy_and_shift_numbers(dest, source, source_end, '0', false);
-}
-
-char *bc_copy_bcd_val(char *restrict dest, const char *source, const char *source_end)
-{
-	return bc_copy_and_shift_numbers(dest, source, source_end, '0', true);
-}

ext/bcmath/libbcmath/src/convert.h

@@ -17,7 +17,6 @@
 #ifndef BCMATH_CONVERT_H
 #define BCMATH_CONVERT_H
 
-char *bc_copy_ch_val(char *restrict dest, const char *source, const char *source_end);
-char *bc_copy_bcd_val(char *restrict dest, const char *source, const char *source_end);
+char *bc_copy_and_toggle_bcd(char *restrict dest, const char *source, const char *source_end);
 
 #endif

ext/bcmath/libbcmath/src/num2str.c

@@ -57,13 +57,13 @@ zend_string *bc_num2str_ex(bc_num num, size_t scale)
 
 	/* Load the whole number. */
 	const char *nptr = num->n_value;
-	sptr = bc_copy_bcd_val(sptr, nptr, nptr + num->n_len);
+	sptr = bc_copy_and_toggle_bcd(sptr, nptr, nptr + num->n_len);
 	nptr += num->n_len;
 
 	/* Now the fraction. */
 	if (scale > 0) {
 		*sptr++ = '.';
-		sptr = bc_copy_bcd_val(sptr, nptr, nptr + min_scale);
+		sptr = bc_copy_and_toggle_bcd(sptr, nptr, nptr + min_scale);
 		for (index = num->n_scale; index < scale; index++) {
 			*sptr++ = BCD_CHAR(0);
 		}

ext/bcmath/libbcmath/src/str2num.c

@@ -165,12 +165,12 @@ bool bc_str2num(bc_num *num, const char *str, const char *end, size_t scale, boo
 		 * 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.
 		 */
-		nptr = bc_copy_ch_val(nptr, fractional_ptr, fractional_end);
+		nptr = bc_copy_and_toggle_bcd(nptr, fractional_ptr, fractional_end);
 	} else {
 		const char *integer_end = integer_ptr + digits;
-		nptr = bc_copy_ch_val(nptr, integer_ptr, integer_end);
+		nptr = bc_copy_and_toggle_bcd(nptr, integer_ptr, integer_end);
 		if (str_scale > 0) {
-			nptr = bc_copy_ch_val(nptr, fractional_ptr, fractional_end);
+			nptr = bc_copy_and_toggle_bcd(nptr, fractional_ptr, fractional_end);
 		}
 	}