From f2d76ae4fdde180e120ea2d29d6ef881360b3cba Mon Sep 17 00:00:00 2001
From: Nick Thompson <nick.thompson@ge.com>
Date: Tue, 11 May 2010 11:29:52 +0100
Subject: [PATCH] Avoid use of divides in print_size
Modification of print_size to avoid use of divides and especially
long long divides. Keep the binary scale factor in terms of bit
shifts instead. This should be faster, since the previous code
gave the compiler no clues that the divides where always powers
of two, preventing optimisation.
Signed-off-by: Nick Thompson <nick.thompson@ge.com>
Acked-by: Timur Tabi <timur@freescale.com>
---
lib/display_options.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/lib/display_options.c b/lib/display_options.c
index 86df05d9e5..a711425b90 100644
--- a/lib/display_options.c
+++ b/lib/display_options.c
@@ -46,13 +46,14 @@ int display_options (void)
void print_size(unsigned long long size, const char *s)
{
unsigned long m = 0, n;
+ unsigned long long f;
static const char names[] = {'E', 'P', 'T', 'G', 'M', 'K'};
- unsigned long long d = 1ULL << (10 * ARRAY_SIZE(names));
+ unsigned long d = 10 * ARRAY_SIZE(names);
char c = 0;
unsigned int i;
- for (i = 0; i < ARRAY_SIZE(names); i++, d >>= 10) {
- if (size >= d) {
+ for (i = 0; i < ARRAY_SIZE(names); i++, d -= 10) {
+ if (size >> d) {
c = names[i];
break;
}
@@ -63,11 +64,12 @@ void print_size(unsigned long long size, const char *s)
return;
}
- n = size / d;
+ n = size >> d;
+ f = size & ((1ULL << d) - 1);
/* If there's a remainder, deal with it */
- if(size % d) {
- m = (10 * (size - (n * d)) + (d / 2) ) / d;
+ if (f) {
+ m = (10ULL * f + (1ULL << (d - 1))) >> d;
if (m >= 10) {
m -= 10;