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qdev: Use clz in print_size 

We can compute a floor log2 value with clz rather than a division loop.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Message-id: 1375208443-17288-3-git-send-email-rth@twiddle.net
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Richard Henderson 2013-07-30 08:20:43 -10:00 committed by Anthony Liguori
parent e76c756fd3
commit 1197cbb9ed
1 changed files with 13 additions and 7 deletions
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20
hw/core/qdev-properties.c
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@ -1172,15 +1172,21 @@ static int parse_size(DeviceState *dev, Property *prop, const char *str)
static int print_size(DeviceState *dev, Property *prop, char *dest, size_t len)
{
uint64_t *ptr = qdev_get_prop_ptr(dev, prop);
char suffixes[] = {'T', 'G', 'M', 'K', 'B'};
int i = 0;
uint64_t div;
static const char suffixes[] = { 'B', 'K', 'M', 'G', 'T' };
uint64_t div, val = *(uint64_t *)qdev_get_prop_ptr(dev, prop);
int i;
for (div = 1ULL << 40; !(*ptr / div) ; div >>= 10) {
i++;
/* Compute floor(log2(val)). */
i = 64 - clz64(val);
/* Find the power of 1024 that we'll display as the units. */
i /= 10;
if (i >= ARRAY_SIZE(suffixes)) {
i = ARRAY_SIZE(suffixes) - 1;
}
return snprintf(dest, len, "%0.03f%c", (double)*ptr/div, suffixes[i]);
div = 1ULL << (i * 10);
return snprintf(dest, len, "%0.03f%c", (double)val/div, suffixes[i]);
}
PropertyInfo qdev_prop_size = {