Re: [PATCH] Correct dir.c to compile on Solaris 9

On Sunday 15 April 2007, Johannes Schindelin wrote:

On Sun, 15 Apr 2007, Shawn O. Pearce wrote:

quoted

 static int simple_length(const char *match)
 {
-	const char special[256] = {
-		[0] = 1, ['?'] = 1,
-		['\\'] = 1, ['*'] = 1,
-		['['] = 1
-	};
 	int len = -1;
 
 	for (;;) {
 		unsigned char c = *match++;
 		len++;
-		if (special[c])
+		switch (c) {
+		case 0: case '?':
+		case '\\': case '*':
+		case '[':
 			return len;
+		}
 	}
 }

You are replacing a table-based check with a switch based, which might be 
substantially slower (depends on how often cmp_name() is called).

Or faster. When the table gives a cache miss and has to be
loaded from main memory, I am quite sure that 5 compares in a row are
faster than the cache miss.

Actually, with the switch, the compiler is free to implement it with a
table (and gcc usually does this, probably even using a substantially
smaller table). The table-based check in contrast looks
like some kind of micro-optimization which makes the code IMHO more
difficult to read, and which only would be justified with meassured
improvements.

Josef