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x86: trivial printk optimizations

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In arch/x86/boot/printf.c gets rid of unused tail of digits: const char
*digits = "0123456789abcdefghijklmnopqrstuvwxyz"; (we are using 0-9a-f
only)

Uses smaller/faster lowercasing (by ORing with 0x20)
if we know that we work on numbers/digits. Makes
strtoul smaller, and also we are getting rid of

  static const char small_digits[] = "0123456789abcdefx";
  static const char large_digits[] = "0123456789ABCDEFX";

since this works equally well:

  static const char digits[16] = "0123456789ABCDEF";

Size savings:

$ size vmlinux.org vmlinux
   text    data     bss     dec     hex filename
 877320  112252   90112 1079684  107984 vmlinux.org
 877048  112252   90112 1079412  107874 vmlinux

It may be also a tiny bit faster because code has less
branches now, but I doubt it is measurable.

[ hugh@veritas.com: uppercase pointers fix ]

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Denys Vlasenko
2008-02-09 23:24:09 +01:00
committed by Thomas Gleixner
parent b6fbb669c8
commit 9b706aee7d
2 changed files with 41 additions and 32 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
arch/x86/boot/printf.c
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@@ -33,8 +33,8 @@ static int skip_atoi(const char **s)
#define PLUS 4 /* show plus */
#define SPACE 8 /* space if plus */
#define LEFT 16 /* left justified */
#define SPECIAL 32 /* 0x */
#define LARGE 64 /* use 'ABCDEF' instead of 'abcdef' */
#define SMALL 32 /* Must be 32 == 0x20 */
#define SPECIAL 64 /* 0x */
#define do_div(n,base) ({ \
int __res; \
@@ -45,12 +45,16 @@ __res; })
static char *number(char *str, long num, int base, int size, int precision,
int type)
{
char c, sign, tmp[66];
const char *digits = "0123456789abcdefghijklmnopqrstuvwxyz";
/* we are called with base 8, 10 or 16, only, thus don't need "G..." */
static const char digits[16] = "0123456789ABCDEF"; /* "GHIJKLMNOPQRSTUVWXYZ"; */
char tmp[66];
char c, sign, locase;
int i;
if (type & LARGE)
digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
/* locase = 0 or 0x20. ORing digits or letters with 'locase'
* produces same digits or (maybe lowercased) letters */
locase = (type & SMALL);
if (type & LEFT)
type &= ~ZEROPAD;
if (base < 2 || base > 36)
@@ -81,7 +85,7 @@ static char *number(char *str, long num, int base, int size, int precision,
tmp[i++] = '0';
else
while (num != 0)
tmp[i++] = digits[do_div(num, base)];
tmp[i++] = (digits[do_div(num, base)] | locase);
if (i > precision)
precision = i;
size -= precision;
@@ -95,7 +99,7 @@ static char *number(char *str, long num, int base, int size, int precision,
*str++ = '0';
else if (base == 16) {
*str++ = '0';
*str++ = digits[33];
*str++ = ('X' | locase);
}
}
if (!(type & LEFT))
@@ -244,9 +248,9 @@ int vsprintf(char *buf, const char *fmt, va_list args)
base = 8;
break;
case 'X':
flags |= LARGE;
case 'x':
flags |= SMALL;
case 'X':
base = 16;
break;