Optimize wl_fixed_t to/from double conversion functions

tests/fixed-benchmark.c

@@ -0,0 +1,88 @@
+/*
+ * Copyright © 2012 Intel Corporation
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of the copyright holders not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission.  The copyright holders make no representations
+ * about the suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+ * OF THIS SOFTWARE.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+#include <assert.h>
+#include "../src/wayland-private.h"
+
+volatile double global_d;
+
+static void
+magic_conversion(void)
+{
+	wl_fixed_t f;
+
+	for (f = 0; f < INT32_MAX; f++)
+		global_d = wl_fixed_to_double(f);
+}
+
+static void
+mul_conversion(void)
+{
+	wl_fixed_t f;
+
+	/* This will get optimized into multiplication by 1/256 */
+	for (f = 0; f < INT32_MAX; f++)
+		global_d = f / 256.0;
+}
+
+double factor = 256.0;
+
+static void
+div_conversion(void)
+{
+	wl_fixed_t f;
+
+	for (f = 0; f < INT32_MAX; f++)
+		global_d = f / factor;
+}
+
+static void
+benchmark(const char *s, void (*f)(void))
+{
+	struct timespec start, stop, elapsed;
+
+	clock_gettime(CLOCK_MONOTONIC, &start);
+	f();
+	clock_gettime(CLOCK_MONOTONIC, &stop);
+
+	elapsed.tv_sec = stop.tv_sec - start.tv_sec;
+	elapsed.tv_nsec = stop.tv_nsec - start.tv_nsec;
+	if (elapsed.tv_nsec < 0) {
+		elapsed.tv_nsec += 1000000000;
+		elapsed.tv_sec--;
+	}
+	printf("benchmarked %s:\t%ld.%09lds\n",
+	       s, elapsed.tv_sec, elapsed.tv_nsec);
+}
+
+int main(int argc, char *argv[])
+{
+	benchmark("magic", magic_conversion);
+	benchmark("div", div_conversion);
+	benchmark("mul", mul_conversion);
+
+	return 0;
+}