[OPTIM] halog: speed up fgets2-64 by about 10%

This version uses more 64-bit lookups and two 32-bit lookups
to converge faster. This saves about 10% performance.

diff --git a/contrib/halog/fgets2-64.c b/contrib/halog/fgets2-64.c
index 9209c087cd3bac45107c8122121819cdb6449c7e..236b970dd2dbb6e87bb7feb1ff0da885822018b5 100644 (file)
--- a/contrib/halog/fgets2-64.c
+++ b/contrib/halog/fgets2-64.c
@@ -62,7 +62,7 @@ static inline unsigned int has_zero64(unsigned long long x)
 #define FGETS2_BUFSIZE         (256*1024)
 const char *fgets2(FILE *stream)
 {
-       static char buffer[FGETS2_BUFSIZE + 5];
+       static char buffer[FGETS2_BUFSIZE + 9]; // +9 to have zeroes past the end
        static char *end = buffer;
        static char *line = buffer;
 
@@ -72,15 +72,35 @@ const char *fgets2(FILE *stream)
        next = line;
 
        while (1) {
-               /* this is a speed-up, we read 32 bits at once and check for an
+               /* this is a speed-up, we read 64 bits at once and check for an
                 * LF character there. We stop if found then continue one at a
                 * time.
                 */
-               while (next < end && (((unsigned long)next) & 7) && *next != '\n')
-                       next++;
 
-               /* now next is multiple of 4 or equal to end */
-               while (next <= (end-32)) {
+               if (next <= (end-12)) {
+                       /* max 3 bytes tested here */
+                       while ((((unsigned long)next) & 3) && *next != '\n')
+                               next++;
+
+                       /* maybe we have can skip 4 more bytes */
+                       if ((((unsigned long)next) & 4) && !has_zero(*(unsigned int *)next ^ 0x0A0A0A0AU))
+                               next += 4;
+               }
+
+               /* now next is multiple of 8 or equal to end */
+               while (next <= (end-68)) {
+                       if (has_zero64(*(unsigned long long *)next ^ 0x0A0A0A0A0A0A0A0AULL))
+                               break;
+                       next += 8;
+                       if (has_zero64(*(unsigned long long *)next ^ 0x0A0A0A0A0A0A0A0AULL))
+                               break;
+                       next += 8;
+                       if (has_zero64(*(unsigned long long *)next ^ 0x0A0A0A0A0A0A0A0AULL))
+                               break;
+                       next += 8;
+                       if (has_zero64(*(unsigned long long *)next ^ 0x0A0A0A0A0A0A0A0AULL))
+                               break;
+                       next += 8;
                        if (has_zero64(*(unsigned long long *)next ^ 0x0A0A0A0A0A0A0A0AULL))
                                break;
                        next += 8;
@@ -95,6 +115,10 @@ const char *fgets2(FILE *stream)
                        next += 8;
                }
 
+               /* maybe we can skip 4 more bytes */
+               if (!has_zero(*(unsigned int *)next ^ 0x0A0A0A0AU))
+                       next += 4;
+
                /* we finish if needed. Note that next might be slightly higher
                 * than end here because we might have gone past it above.
                 */