From: Andre Noll <maan@systemlinux.org>
Date: Tue, 2 Apr 2013 17:10:08 +0000 (+0000)
Subject: compress: Further optimize inner loop.
X-Git-Tag: v0.4.13~29^2
X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=commitdiff_plain;h=0a6c0e26b73d0cbf4b324b38e1be484d6a6c27e8;ds=sidebyside

compress: Further optimize inner loop.

This kills the local adjusted_sample variable of the inner loop of
compress_post_select().  Surprisingly enough, this saves another 5%
of execution time.
---

diff --git a/compress_filter.c b/compress_filter.c
index b01c01a4..499a9e76 100644
--- a/compress_filter.c
+++ b/compress_filter.c
@@ -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,