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From 5a3112e24aa41c50703739ccf419bad6136eb797 Mon Sep 17 00:00:00 2001
From: Markus Armbruster <armbru@redhat.com>
Date: Wed, 22 Jan 2014 12:13:55 +0100
Subject: [PATCH 4/4] qdev: Use clz in print_size

RH-Author: Markus Armbruster <armbru@redhat.com>
Message-id: <1390392835-21809-3-git-send-email-armbru@redhat.com>
Patchwork-id: 56888
O-Subject: [PATCH 7.0 qemu-kvm 2/2] qdev: Use clz in print_size
Bugzilla: 1034876
RH-Acked-by: Marcel Apfelbaum <marcel.a@redhat.com>
RH-Acked-by: Orit Wasserman <owasserm@redhat.com>
RH-Acked-by: Dr. David Alan Gilbert (git) <dgilbert@redhat.com>
RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>

From: Richard Henderson <rth@twiddle.net>

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>
(cherry picked from commit 1197cbb9eda1dc82e2fa1815ca62bc3de158353e)
Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 hw/core/qdev-properties.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/core/qdev-properties.c |   20 +++++++++++++-------
 1 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
index d6d10c9..dc8ae69 100644
--- a/hw/core/qdev-properties.c
+++ b/hw/core/qdev-properties.c
@@ -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 = {
-- 
1.7.1