perf: avoid repeated case conversions

This eeks out an improvement of about 0.8% in CPU time and 1.3% in wall
time:

    Summary of cpu time and (wall time):

                        best    avg      sd     +/-      p     (best)    (avg)      (sd)     +/-      p
         pathological 0.20382 0.21317 0.06488 [-3.4%] 0.0005 (0.20383) (0.21318) (0.06485) [-3.4%] 0.0005
            command-t 0.15238 0.15889 0.05256 [-0.8%]  0.005 (0.15238) (0.15890) (0.05256) [-0.8%]  0.005
    chromium (subset) 1.17132 1.19209 0.03527 [-0.1%]  0.025 (0.26559) (0.27217) (0.01463) [-0.2%]
     chromium (whole) 0.91269 0.92064 0.06820 [-0.9%]  0.005 (0.10191) (0.10619) (0.02936) [-0.8%]   0.05
           big (400k) 1.38361 1.39376 0.03947 [-0.8%]  0.005 (0.15141) (0.15477) (0.01254) [-0.9%]   0.05
                total 3.84099 3.87856 0.18165 [-0.8%]  0.005 (0.88459) (0.90520) (0.13043) [-1.3%]  0.005

Author: wincent

lua/wincent/commandt/lib/score.c

@@ -45,6 +45,7 @@ static float recursive_match(
         for (size_t j = haystack_idx; j <= m->rightmost_match_p[i]; j++) {
             char c = needle_char;
             char d = haystack_contents[j];
+            char d_lower = d >= 'A' && d <= 'Z' ? d | 0x20 : d;
             if (d == '.') {
                 if (j == 0 ||
                     haystack_contents[j - 1] == '/') { // This is a dot-file.
@@ -58,11 +59,10 @@ static float recursive_match(
                         return 0.0f;
                     }
                 }
-            } else if (m->ignore_case && d >= 'A' && d <= 'Z') {
-                d |= 0x20; // Lowercase (same as adding 32).
             }
 
-            if (c == d) {
+            char match_char = m->ignore_case ? d_lower : d;
+            if (c == match_char) {
                 memoized = &m->memo[j * m->needle_length + i];
                 if (*memoized != UNSET_SCORE) {
                     return *memoized > seen_score ? *memoized : seen_score;
@@ -75,15 +75,13 @@ static float recursive_match(
                 if (distance > 1) {
                     float factor = 1.0f;
                     char last = haystack_contents[j - 1];
-                    char curr =
-                        haystack_contents[j]; // Case matters, so get again.
                     if (last == '/') {
                         factor = 0.9f;
                     } else if (last == '-' || last == '_' || last == ' ' ||
                                (last >= '0' && last <= '9')) {
                         factor = 0.8f;
-                    } else if (last >= 'a' && last <= 'z' && curr >= 'A' &&
-                               curr <= 'Z') {
+                    } else if (last >= 'a' && last <= 'z' && d >= 'A' &&
+                               d <= 'Z') {
                         factor = 0.8f;
                     } else if (last == '.') {
                         factor = 0.7f;