Metaphone performance improvement (php#10501)

* Don't do toupper() redundantly in encoding the data for metaphone

All inputs for ENCODE() are already uppercase, so there's no need to
spend time uppercasing them again.

* Don't compute uppercase letter redundantly in checks

If it's a zero-terminator check, or an isalpha() check, there's no need
to convert it to uppercase first.

* Clean-up LookAhead helper

* Add some letter caching to metaphone to increase performance

We don't have to re-read letters, and re-uppercase them if we already
did it once. By caching these results, we gain performance.
Furthermore, we can avoid fetching and uppercasing in some conditions by
first checking what we already had: e.g. if a condition depends on both
Prev_Letter and After_Next_Letter, but we already have Prev_Letter
cached, we can place that first to avoid a fetch+toupper of the
"after next letter".

Author: nielsdos

ext/standard/metaphone.c

@@ -78,7 +78,8 @@ static const char _codes[26] =
 };
 
 
-#define ENCODE(c) (isalpha(c) ? _codes[((toupper(c)) - 'A')] : 0)
+/* Note: these macros require an uppercase letter input! */
+#define ENCODE(c) (isalpha(c) ? _codes[((c) - 'A')] : 0)
 
 #define isvowel(c)  (ENCODE(c) & 1)		/* AEIOU */
 
@@ -101,16 +102,19 @@ static const char _codes[26] =
 /* I suppose I could have been using a character pointer instead of
  * accesssing the array directly... */
 
+#define Convert_Raw(c) toupper(c)
 /* Look at the next letter in the word */
-#define Next_Letter (toupper(word[w_idx+1]))
+#define Read_Raw_Next_Letter (word[w_idx+1])
+#define Read_Next_Letter (Convert_Raw(Read_Raw_Next_Letter))
 /* Look at the current letter in the word */
-#define Curr_Letter (toupper(word[w_idx]))
+#define Read_Raw_Curr_Letter (word[w_idx])
+#define Read_Curr_Letter (Convert_Raw(Read_Raw_Curr_Letter))
 /* Go N letters back. */
-#define Look_Back_Letter(n)	(w_idx >= n ? toupper(word[w_idx-n]) : '\0')
+#define Look_Back_Letter(n)	(w_idx >= n ? Convert_Raw(word[w_idx-n]) : '\0')
 /* Previous letter.  I dunno, should this return null on failure? */
-#define Prev_Letter (Look_Back_Letter(1))
+#define Read_Prev_Letter (Look_Back_Letter(1))
 /* Look two letters down.  It makes sure you don't walk off the string. */
-#define After_Next_Letter	(Next_Letter != '\0' ? toupper(word[w_idx+2]) \
+#define Read_After_Next_Letter	(Read_Raw_Next_Letter != '\0' ? Convert_Raw(word[w_idx+2]) \
 											     : '\0')
 #define Look_Ahead_Letter(n) (toupper(Lookahead((char *) word+w_idx, n)))
 
@@ -119,15 +123,13 @@ static const char _codes[26] =
 /* I probably could have just used strlen... */
 static char Lookahead(char *word, int how_far)
 {
-	char letter_ahead = '\0';	/* null by default */
 	int idx;
 	for (idx = 0; word[idx] != '\0' && idx < how_far; idx++);
 	/* Edge forward in the string... */
 
-	letter_ahead = word[idx];	/* idx will be either == to how_far or
-								 * at the end of the string
+	return  word[idx];			/* idx will be either == to how_far or
+								 * at the end of the string where it will be null
 								 */
-	return letter_ahead;
 }
 
 
@@ -164,6 +166,7 @@ static void metaphone(unsigned char *word, size_t word_len, zend_long max_phonem
 	int w_idx = 0;				/* point in the phonization we're at. */
 	size_t p_idx = 0;				/* end of the phoned phrase */
 	size_t max_buffer_len = 0;		/* maximum length of the destination buffer */
+	char curr_letter;
 	ZEND_ASSERT(word != NULL);
 	ZEND_ASSERT(max_phonemes >= 0);
 
@@ -179,18 +182,20 @@ static void metaphone(unsigned char *word, size_t word_len, zend_long max_phonem
 
 /*-- The first phoneme has to be processed specially. --*/
 	/* Find our first letter */
-	for (; !isalpha(Curr_Letter); w_idx++) {
+	for (; !isalpha(curr_letter = Read_Raw_Curr_Letter); w_idx++) {
 		/* On the off chance we were given nothing but crap... */
-		if (Curr_Letter == '\0') {
+		if (curr_letter == '\0') {
 			End_Phoned_Word();
 			return;
 		}
 	}
 
-	switch (Curr_Letter) {
+	curr_letter = Convert_Raw(curr_letter);
+
+	switch (curr_letter) {
 		/* AE becomes E */
 	case 'A':
-		if (Next_Letter == 'E') {
+		if (Read_Next_Letter == 'E') {
 			Phonize('E');
 			w_idx += 2;
 		}
@@ -204,24 +209,26 @@ static void metaphone(unsigned char *word, size_t word_len, zend_long max_phonem
 	case 'G':
 	case 'K':
 	case 'P':
-		if (Next_Letter == 'N') {
+		if (Read_Next_Letter == 'N') {
 			Phonize('N');
 			w_idx += 2;
 		}
 		break;
 		/* WH becomes W,
 		   WR becomes R
 		   W if followed by a vowel */
-	case 'W':
-		if (Next_Letter == 'R') {
-			Phonize(Next_Letter);
+	case 'W': {
+		char next_letter = Read_Next_Letter;
+		if (next_letter == 'R') {
+			Phonize('R');
 			w_idx += 2;
-		} else if (Next_Letter == 'H' || isvowel(Next_Letter)) {
+		} else if (next_letter == 'H' || isvowel(next_letter)) {
 			Phonize('W');
 			w_idx += 2;
 		}
 		/* else ignore */
 		break;
+	}
 		/* X becomes S */
 	case 'X':
 		Phonize('S');
@@ -236,7 +243,7 @@ static void metaphone(unsigned char *word, size_t word_len, zend_long max_phonem
 	case 'I':
 	case 'O':
 	case 'U':
-		Phonize(Curr_Letter);
+		Phonize(curr_letter);
 		w_idx++;
 		break;
 	default:
@@ -247,7 +254,7 @@ static void metaphone(unsigned char *word, size_t word_len, zend_long max_phonem
 
 
 	/* On to the metaphoning */
-	for (; Curr_Letter != '\0' &&
+	for (; (curr_letter = Read_Raw_Curr_Letter) != '\0' &&
 		 (max_phonemes == 0 || Phone_Len < (size_t)max_phonemes);
 		 w_idx++) {
 		/* How many letters to skip because an eariler encoding handled
@@ -263,18 +270,23 @@ static void metaphone(unsigned char *word, size_t word_len, zend_long max_phonem
 		 */
 
 		/* Ignore non-alphas */
-		if (!isalpha(Curr_Letter))
+		if (!isalpha(curr_letter))
 			continue;
 
+		curr_letter = Convert_Raw(curr_letter);
+		/* Note: we can't cache curr_letter from the previous loop
+		 * because of the skip_letter variable. */
+		char prev_letter = Read_Prev_Letter;
+
 		/* Drop duplicates, except CC */
-		if (Curr_Letter == Prev_Letter &&
-			Curr_Letter != 'C')
+		if (curr_letter == prev_letter &&
+			curr_letter != 'C')
 			continue;
 
-		switch (Curr_Letter) {
+		switch (curr_letter) {
 			/* B -> B unless in MB */
 		case 'B':
-			if (Prev_Letter != 'M')
+			if (prev_letter != 'M')
 				Phonize('B');
 			break;
 			/* 'sh' if -CIA- or -CH, but not SCH, except SCHW.
@@ -283,20 +295,20 @@ static void metaphone(unsigned char *word, size_t word_len, zend_long max_phonem
 			 *  dropped if -SCI-, SCE-, -SCY- (handed in S)
 			 *  else K
 			 */
-		case 'C':
-			if (MAKESOFT(Next_Letter)) {	/* C[IEY] */
-				if (After_Next_Letter == 'A' &&
-					Next_Letter == 'I') {	/* CIA */
+		case 'C': {
+			char next_letter = Read_Next_Letter;
+			if (MAKESOFT(next_letter)) {	/* C[IEY] */
+				if (next_letter == 'I' && Read_After_Next_Letter == 'A') {	/* CIA */
 					Phonize(SH);
 				}
 				/* SC[IEY] */
-				else if (Prev_Letter == 'S') {
+				else if (prev_letter == 'S') {
 					/* Dropped */
 				} else {
 					Phonize('S');
 				}
-			} else if (Next_Letter == 'H') {
-				if ((!traditional) && (After_Next_Letter == 'R' || Prev_Letter == 'S')) {	/* Christ, School */
+			} else if (next_letter == 'H') {
+				if ((!traditional) && (prev_letter == 'S' || Read_After_Next_Letter == 'R')) {	/* Christ, School */
 					Phonize('K');
 				} else {
 					Phonize(SH);
@@ -306,12 +318,13 @@ static void metaphone(unsigned char *word, size_t word_len, zend_long max_phonem
 				Phonize('K');
 			}
 			break;
+		}
 			/* J if in -DGE-, -DGI- or -DGY-
 			 * else T
 			 */
 		case 'D':
-			if (Next_Letter == 'G' &&
-				MAKESOFT(After_Next_Letter)) {
+			if (Read_Next_Letter == 'G' &&
+				MAKESOFT(Read_After_Next_Letter)) {
 				Phonize('J');
 				skip_letter++;
 			} else
@@ -323,47 +336,50 @@ static void metaphone(unsigned char *word, size_t word_len, zend_long max_phonem
 			 * else J if in -GE-, -GI, -GY and not GG
 			 * else K
 			 */
-		case 'G':
-			if (Next_Letter == 'H') {
+		case 'G': {
+			char next_letter = Read_Next_Letter;
+			if (next_letter == 'H') {
 				if (!(NOGHTOF(Look_Back_Letter(3)) ||
 					  Look_Back_Letter(4) == 'H')) {
 					Phonize('F');
 					skip_letter++;
 				} else {
 					/* silent */
 				}
-			} else if (Next_Letter == 'N') {
-				if (Isbreak(After_Next_Letter) ||
-					(After_Next_Letter == 'E' &&
+			} else if (next_letter == 'N') {
+				char after_next_letter = Read_After_Next_Letter;
+				if (Isbreak(after_next_letter) ||
+					(after_next_letter == 'E' &&
 					 Look_Ahead_Letter(3) == 'D')) {
 					/* dropped */
 				} else
 					Phonize('K');
-			} else if (MAKESOFT(Next_Letter) &&
-					   Prev_Letter != 'G') {
+			} else if (MAKESOFT(next_letter) &&
+					   prev_letter != 'G') {
 				Phonize('J');
 			} else {
 				Phonize('K');
 			}
 			break;
+		}
 			/* H if before a vowel and not after C,G,P,S,T */
 		case 'H':
-			if (isvowel(Next_Letter) &&
-				!AFFECTH(Prev_Letter))
+			if (isvowel(Read_Next_Letter) &&
+				!AFFECTH(prev_letter))
 				Phonize('H');
 			break;
 			/* dropped if after C
 			 * else K
 			 */
 		case 'K':
-			if (Prev_Letter != 'C')
+			if (prev_letter != 'C')
 				Phonize('K');
 			break;
 			/* F if before H
 			 * else P
 			 */
 		case 'P':
-			if (Next_Letter == 'H') {
+			if (Read_Next_Letter == 'H') {
 				Phonize('F');
 			} else {
 				Phonize('P');
@@ -377,44 +393,50 @@ static void metaphone(unsigned char *word, size_t word_len, zend_long max_phonem
 			/* 'sh' in -SH-, -SIO- or -SIA- or -SCHW-
 			 * else S
 			 */
-		case 'S':
-			if (Next_Letter == 'I' &&
-				(After_Next_Letter == 'O' ||
-				 After_Next_Letter == 'A')) {
+		case 'S': {
+			char next_letter = Read_Next_Letter;
+			char after_next_letter;
+			if (next_letter == 'I' &&
+				((after_next_letter = Read_After_Next_Letter) == 'O' ||
+				 after_next_letter == 'A')) {
 				Phonize(SH);
-			} else if (Next_Letter == 'H') {
+			} else if (next_letter == 'H') {
 				Phonize(SH);
 				skip_letter++;
-			} else if ((!traditional) && (Next_Letter == 'C' && Look_Ahead_Letter(2) == 'H' && Look_Ahead_Letter(3) == 'W')) {
+			} else if ((!traditional) && (next_letter == 'C' && Look_Ahead_Letter(2) == 'H' && Look_Ahead_Letter(3) == 'W')) {
 				Phonize(SH);
 				skip_letter += 2;
 			} else {
 				Phonize('S');
 			}
 			break;
+		}
 			/* 'sh' in -TIA- or -TIO-
 			 * else 'th' before H
 			 * else T
 			 */
-		case 'T':
-			if (Next_Letter == 'I' &&
-				(After_Next_Letter == 'O' ||
-				 After_Next_Letter == 'A')) {
+		case 'T': {
+			char next_letter = Read_Next_Letter;
+			char after_next_letter;
+			if (next_letter == 'I' &&
+				((after_next_letter = Read_After_Next_Letter) == 'O' ||
+				 after_next_letter == 'A')) {
 				Phonize(SH);
-			} else if (Next_Letter == 'H') {
+			} else if (next_letter == 'H') {
 				Phonize(TH);
 				skip_letter++;
-			} else if (!(Next_Letter == 'C' && After_Next_Letter == 'H')) {
+			} else if (!(next_letter == 'C' && Read_After_Next_Letter == 'H')) {
 				Phonize('T');
 			}
 			break;
+		}
 			/* F */
 		case 'V':
 			Phonize('F');
 			break;
 			/* W before a vowel, else dropped */
 		case 'W':
-			if (isvowel(Next_Letter))
+			if (isvowel(Read_Next_Letter))
 				Phonize('W');
 			break;
 			/* KS */
@@ -424,7 +446,7 @@ static void metaphone(unsigned char *word, size_t word_len, zend_long max_phonem
 			break;
 			/* Y if followed by a vowel */
 		case 'Y':
-			if (isvowel(Next_Letter))
+			if (isvowel(Read_Next_Letter))
 				Phonize('Y');
 			break;
 			/* S */
@@ -438,7 +460,7 @@ static void metaphone(unsigned char *word, size_t word_len, zend_long max_phonem
 		case 'M':
 		case 'N':
 		case 'R':
-			Phonize(Curr_Letter);
+			Phonize(curr_letter);
 			break;
 		default:
 			/* nothing */