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x86: trivial printk optimizations 

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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
arch/x86/boot/printf.c
View File

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

49
lib/vsprintf.c
View File

@ -26,6 +26,9 @@
#include <asm/page.h> /* for PAGE_SIZE */ #include <asm/page.h> /* for PAGE_SIZE */
#include <asm/div64.h> #include <asm/div64.h>
/* Works only for digits and letters, but small and fast */
#define TOLOWER(x) ((x) | 0x20)
/** /**
* simple_strtoul - convert a string to an unsigned long * simple_strtoul - convert a string to an unsigned long
* @cp: The start of the string * @cp: The start of the string
@ -41,17 +44,17 @@ unsigned long simple_strtoul(const char *cp,char **endp,unsigned int base)
if (*cp == '0') { if (*cp == '0') {
base = 8; base = 8;
cp++; cp++;
if ((toupper(*cp) == 'X') && isxdigit(cp[1])) { if ((TOLOWER(*cp) == 'x') && isxdigit(cp[1])) {
cp++; cp++;
base = 16; base = 16;
} }
} }
} else if (base == 16) { } else if (base == 16) {
if (cp[0] == '0' && toupper(cp[1]) == 'X') if (cp[0] == '0' && TOLOWER(cp[1]) == 'x')
cp += 2; cp += 2;
} }
while (isxdigit(*cp) && while (isxdigit(*cp) &&
(value = isdigit(*cp) ? *cp-'0' : toupper(*cp)-'A'+10) < base) { (value = isdigit(*cp) ? *cp-'0' : TOLOWER(*cp)-'a'+10) < base) {
result = result*base + value; result = result*base + value;
cp++; cp++;
} }
@ -92,17 +95,17 @@ unsigned long long simple_strtoull(const char *cp,char **endp,unsigned int base)
if (*cp == '0') { if (*cp == '0') {
base = 8; base = 8;
cp++; cp++;
if ((toupper(*cp) == 'X') && isxdigit(cp[1])) { if ((TOLOWER(*cp) == 'x') && isxdigit(cp[1])) {
cp++; cp++;
base = 16; base = 16;
} }
} }
} else if (base == 16) { } else if (base == 16) {
if (cp[0] == '0' && toupper(cp[1]) == 'X') if (cp[0] == '0' && TOLOWER(cp[1]) == 'x')
cp += 2; cp += 2;
} }
while (isxdigit(*cp) && (value = isdigit(*cp) ? *cp-'0' : (islower(*cp) while (isxdigit(*cp)
? toupper(*cp) : *cp)-'A'+10) < base) { && (value = isdigit(*cp) ? *cp-'0' : TOLOWER(*cp)-'a'+10) < base) {
result = result*base + value; result = result*base + value;
cp++; cp++;
} }
@ -360,24 +363,25 @@ static noinline char* put_dec(char *buf, unsigned long long num)
#define PLUS 4 /* show plus */ #define PLUS 4 /* show plus */
#define SPACE 8 /* space if plus */ #define SPACE 8 /* space if plus */
#define LEFT 16 /* left justified */ #define LEFT 16 /* left justified */
#define SPECIAL 32 /* 0x */ #define SMALL 32 /* Must be 32 == 0x20 */
#define LARGE 64 /* use 'ABCDEF' instead of 'abcdef' */ #define SPECIAL 64 /* 0x */
static char *number(char *buf, char *end, unsigned long long num, int base, int size, int precision, int type) static char *number(char *buf, char *end, unsigned long long num, int base, int size, int precision, int type)
{ {
char sign,tmp[66]; /* we are called with base 8, 10 or 16, only, thus don't need "G..." */
const char *digits; static const char digits[16] = "0123456789ABCDEF"; /* "GHIJKLMNOPQRSTUVWXYZ"; */
/* we are called with base 8, 10 or 16, only, thus don't need "g..." */
static const char small_digits[] = "0123456789abcdefx"; /* "ghijklmnopqrstuvwxyz"; */ char tmp[66];
static const char large_digits[] = "0123456789ABCDEFX"; /* "GHIJKLMNOPQRSTUVWXYZ"; */ char sign;
char locase;
int need_pfx = ((type & SPECIAL) && base != 10); int need_pfx = ((type & SPECIAL) && base != 10);
int i; int i;
digits = (type & LARGE) ? large_digits : small_digits; /* locase = 0 or 0x20. ORing digits or letters with 'locase'
* produces same digits or (maybe lowercased) letters */
locase = (type & SMALL);
if (type & LEFT) if (type & LEFT)
type &= ~ZEROPAD; type &= ~ZEROPAD;
if (base < 2 || base > 36)
return NULL;
sign = 0; sign = 0;
if (type & SIGN) { if (type & SIGN) {
if ((signed long long) num < 0) { if ((signed long long) num < 0) {
@ -404,7 +408,7 @@ static char *number(char *buf, char *end, unsigned long long num, int base, int
tmp[i++] = '0'; tmp[i++] = '0';
/* Generic code, for any base: /* Generic code, for any base:
else do { else do {
tmp[i++] = digits[do_div(num,base)]; tmp[i++] = (digits[do_div(num,base)] | locase);
} while (num != 0); } while (num != 0);
*/ */
else if (base != 10) { /* 8 or 16 */ else if (base != 10) { /* 8 or 16 */
@ -412,7 +416,7 @@ static char *number(char *buf, char *end, unsigned long long num, int base, int
int shift = 3; int shift = 3;
if (base == 16) shift = 4; if (base == 16) shift = 4;
do { do {
tmp[i++] = digits[((unsigned char)num) & mask]; tmp[i++] = (digits[((unsigned char)num) & mask] | locase);
num >>= shift; num >>= shift;
} while (num); } while (num);
} else { /* base 10 */ } else { /* base 10 */
@ -444,7 +448,7 @@ static char *number(char *buf, char *end, unsigned long long num, int base, int
++buf; ++buf;
if (base == 16) { if (base == 16) {
if (buf < end) if (buf < end)
*buf = digits[16]; /* for arbitrary base: digits[33]; */ *buf = ('X' | locase);
++buf; ++buf;
} }
} }
@ -644,6 +648,7 @@ int vsnprintf(char *buf, size_t size, const char *fmt, va_list args)
continue; continue;
case 'p': case 'p':
flags |= SMALL;
if (field_width == -1) { if (field_width == -1) {
field_width = 2*sizeof(void *); field_width = 2*sizeof(void *);
flags |= ZEROPAD; flags |= ZEROPAD;
@ -680,9 +685,9 @@ int vsnprintf(char *buf, size_t size, const char *fmt, va_list args)
base = 8; base = 8;
break; break;
case 'X':
flags |= LARGE;
case 'x': case 'x':
flags |= SMALL;
case 'X':
base = 16; base = 16;
break; break;