[U-Boot] [PATCH v2] Avoid use of divides in print_size

[U-Boot] [PATCH v2] Avoid use of divides in print_size

[Nick Thompson]

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>
---
Since v1:
Removed misplaced brackets that resulted in round-up value of
5 rather than the intended 0.5. Now passes Timur Tabi's test.

 lib/display_options.c |   14 ++++++++------
 1 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/lib/display_options.c b/lib/display_options.c
index 86df05d..14a2da5 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 + (1 << (d - 1))) >> d;
 
 		if (m >= 10) {
 			m -= 10;
-- 
1.7.0.4