compress: Further optimize inner loop.
authorAndre Noll <maan@systemlinux.org>
Tue, 2 Apr 2013 17:10:08 +0000 (17:10 +0000)
committerAndre Noll <maan@systemlinux.org>
Sun, 21 Apr 2013 13:54:26 +0000 (15:54 +0200)
This kills the local adjusted_sample variable of the inner loop of
compress_post_select().  Surprisingly enough, this saves another 5%
of execution time.

compress_filter.c

index b01c01a..499a9e7 100644 (file)
@@ -75,19 +75,23 @@ next_buffer:
                op = para_malloc(length);
        for (i = 0; i < length / 2; i++) {
                /* be careful in that heat, my dear */
-               int sample = *ip++, adjusted_sample;
+               int sample = *ip++;
+               bool neg = false;
 
-               adjusted_sample = sample > 0? sample : -sample;
-               adjusted_sample *= pcd->current_gain;
-               adjusted_sample >>= gain_shift;
-               if (adjusted_sample > 32767) { /* clip */
-                       adjusted_sample = 32767;
+               if (sample < 0) {
+                       sample = -sample;
+                       neg = true;
+               }
+               sample *= pcd->current_gain;
+               sample >>= gain_shift;
+               if (sample > 32767) { /* clip */
+                       sample = 32767;
                        pcd->current_gain = (3 * pcd->current_gain +
                                (1 << pcd->conf->inertia_arg)) / 4;
                        pcd->peak = 0;
-               } else if (adjusted_sample > pcd->peak)
-                       pcd->peak = adjusted_sample;
-               op[i] = sample >= 0? adjusted_sample : -adjusted_sample;
+               } else if (sample > pcd->peak)
+                       pcd->peak = sample;
+               op[i] = neg? -sample : sample;
                if (++pcd->num_samples & mask)
                        continue;
 //             PARA_DEBUG_LOG("gain: %u, peak: %u\n", pcd->current_gain,