Small code to test GCC's loop unrolling on SH4

sh4_gcc_test_unroll.c

#include <sys/time.h>
#include <stdio.h>
#include <stdint.h>
#include <kos.h>

static const unsigned int test = 8;

KOS_INIT_FLAGS(INIT_DEFAULT);

static uint16_t buffer_bgr555[0x80000];
static uint16_t buffer_rgb565[0x80000];

static uint64_t read_counter_us(void)
{
	struct timeval tv;

	gettimeofday(&tv, NULL);

	return tv.tv_sec * 1000000ull + (uint64_t)tv.tv_usec;
}

static uint16_t bgr555_to_rgb565(uint16_t bgr)
{
	return ((bgr & 0x001f) << 11)
		| ((bgr & 0x03e0) << 1)
		| ((bgr & 0x7c00) >> 10);
}

static uint32_t bgr32_to_rgb32(uint32_t bgr)
{
	return ((bgr & 0x001f001f) << 11)
		| ((bgr & 0x03e003e0) << 1)
		| ((bgr & 0x7c007c00) >> 10);
}

static uint64_t bgr64_to_rgb64(uint64_t bgr)
{
	return ((bgr & 0x001f001f001f001full) << 11)
		| ((bgr & 0x03e003e003e003e0ull) << 1)
		| ((bgr & 0x7c007c007c007c00ull) >> 10);
}

static void convert_buffer(uint16_t * restrict bgr555,
			   uint16_t * restrict rgb565,
			   unsigned int size)
{
	unsigned int i;
	uint32_t * restrict bgr32;
	uint32_t * restrict rgb32;
	uint64_t * restrict bgr64;
	uint64_t * restrict rgb64;

	switch (test) {
	case 0:
		for (i = 0; i < size; i++)
			rgb565[i] = bgr555_to_rgb565(bgr555[i]);
		break;
	case 1:
		for (i = 0; i < size; i += 2) {
			rgb565[i + 0] = bgr555_to_rgb565(bgr555[i + 0]);
			rgb565[i + 1] = bgr555_to_rgb565(bgr555[i + 1]);
		}
		break;
	case 2:
		for (i = 0; i < size; i += 4) {
			rgb565[i + 0] = bgr555_to_rgb565(bgr555[i + 0]);
			rgb565[i + 1] = bgr555_to_rgb565(bgr555[i + 1]);
			rgb565[i + 2] = bgr555_to_rgb565(bgr555[i + 2]);
			rgb565[i + 3] = bgr555_to_rgb565(bgr555[i + 3]);
		}
		break;
	case 3:
		for (i = 0; i < size; i += 8) {
			rgb565[i + 0] = bgr555_to_rgb565(bgr555[i + 0]);
			rgb565[i + 1] = bgr555_to_rgb565(bgr555[i + 1]);
			rgb565[i + 2] = bgr555_to_rgb565(bgr555[i + 2]);
			rgb565[i + 3] = bgr555_to_rgb565(bgr555[i + 3]);
			rgb565[i + 4] = bgr555_to_rgb565(bgr555[i + 4]);
			rgb565[i + 5] = bgr555_to_rgb565(bgr555[i + 5]);
			rgb565[i + 6] = bgr555_to_rgb565(bgr555[i + 6]);
			rgb565[i + 7] = bgr555_to_rgb565(bgr555[i + 7]);
		}
		break;
	case 4:
		bgr32 = (uint32_t *) bgr555;
		rgb32 = (uint32_t *) rgb565;

		for (i = 0; i < size / 2; i++)
			rgb32[i] = bgr32_to_rgb32(bgr32[i]);
		break;
	case 5:
		bgr32 = (uint32_t *) bgr555;
		rgb32 = (uint32_t *) rgb565;

		for (i = 0; i < size / 2; i += 2) {
			rgb32[i + 0] = bgr32_to_rgb32(bgr32[i + 0]);
			rgb32[i + 1] = bgr32_to_rgb32(bgr32[i + 1]);
		}
		break;
	case 6:
		bgr32 = (uint32_t *) bgr555;
		rgb32 = (uint32_t *) rgb565;

		for (i = 0; i < size / 2; i += 4) {
			rgb32[i + 0] = bgr32_to_rgb32(bgr32[i + 0]);
			rgb32[i + 1] = bgr32_to_rgb32(bgr32[i + 1]);
			rgb32[i + 2] = bgr32_to_rgb32(bgr32[i + 2]);
			rgb32[i + 3] = bgr32_to_rgb32(bgr32[i + 3]);
		}
		break;
	case 7:
		bgr32 = (uint32_t *) bgr555;
		rgb32 = (uint32_t *) rgb565;

		for (i = 0; i < size / 2; i += 8) {
			rgb32[i + 0] = bgr32_to_rgb32(bgr32[i + 0]);
			rgb32[i + 1] = bgr32_to_rgb32(bgr32[i + 1]);
			rgb32[i + 2] = bgr32_to_rgb32(bgr32[i + 2]);
			rgb32[i + 3] = bgr32_to_rgb32(bgr32[i + 3]);
			rgb32[i + 4] = bgr32_to_rgb32(bgr32[i + 4]);
			rgb32[i + 5] = bgr32_to_rgb32(bgr32[i + 5]);
			rgb32[i + 6] = bgr32_to_rgb32(bgr32[i + 6]);
			rgb32[i + 7] = bgr32_to_rgb32(bgr32[i + 7]);
		}
		break;
	case 8:
		bgr64 = (uint64_t *) bgr555;
		rgb64 = (uint64_t *) rgb565;

		for (i = 0; i < size / 4; i++)
			rgb64[i] = bgr64_to_rgb64(bgr64[i]);
		break;
	case 9:
		bgr64 = (uint64_t *) bgr555;
		rgb64 = (uint64_t *) rgb565;

		for (i = 0; i < size / 4; i += 2) {
			rgb64[i + 0] = bgr64_to_rgb64(bgr64[i + 0]);
			rgb64[i + 1] = bgr64_to_rgb64(bgr64[i + 1]);
		}
		break;
	case 10:
		bgr64 = (uint64_t *) bgr555;
		rgb64 = (uint64_t *) rgb565;

		for (i = 0; i < size / 4; i += 4) {
			rgb64[i + 0] = bgr64_to_rgb64(bgr64[i + 0]);
			rgb64[i + 1] = bgr64_to_rgb64(bgr64[i + 1]);
			rgb64[i + 2] = bgr64_to_rgb64(bgr64[i + 2]);
			rgb64[i + 3] = bgr64_to_rgb64(bgr64[i + 3]);
		}
		break;
	case 11:
		bgr64 = (uint64_t *) bgr555;
		rgb64 = (uint64_t *) rgb565;

		for (i = 0; i < size / 4; i += 8) {
			rgb64[i + 0] = bgr64_to_rgb64(bgr64[i + 0]);
			rgb64[i + 1] = bgr64_to_rgb64(bgr64[i + 1]);
			rgb64[i + 2] = bgr64_to_rgb64(bgr64[i + 2]);
			rgb64[i + 3] = bgr64_to_rgb64(bgr64[i + 3]);
			rgb64[i + 4] = bgr64_to_rgb64(bgr64[i + 4]);
			rgb64[i + 5] = bgr64_to_rgb64(bgr64[i + 5]);
			rgb64[i + 6] = bgr64_to_rgb64(bgr64[i + 6]);
			rgb64[i + 7] = bgr64_to_rgb64(bgr64[i + 7]);
		}
		break;
	}
}

int main(void)
{
	uint64_t before, after;

	before = read_counter_us();

	convert_buffer(buffer_bgr555, buffer_rgb565, 0x80000);

	after = read_counter_us();

	printf("Frames converted in %llu us\n", after - before);

	return 0;
}

/*
 * Compile with: kos-cc -O3 test.c -o test
 *
 * RESULTS:
 *
 * test 0: 157 ms
 * test 1: 90 ms
 * test 2: 124 ms
 * test 3: 140 ms
 *
 * test 4: 80 ms
 * test 5: 46 ms
 * test 6: 64 ms
 * test 7: 72 ms
 *
 * test 8: 53 ms
 * test 9: 36 ms
 * test 10: 47 ms
 * test 11: 48 ms
 *
 * Compiling with: kos-cc  -O3 -funroll-loops test.c -o test
 *
 * RESULTS:
 *
 * test 0: 140 ms
 * test 4: 72 ms
 * test 8: 54 ms
 */