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Commit 9b706aee authored by Denys Vlasenko's avatar Denys Vlasenko Committed by Thomas Gleixner
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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: default avatarDenys Vlasenko <vda.linux@googlemail.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent b6fbb669

arch/x86/boot/printf.c

+14 −10
Original line number Diff line number Diff line
@@ -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;

lib/vsprintf.c

+27 −22
Original line number Diff line number Diff line
@@ -26,6 +26,9 @@ 
#include <asm/page.h>		/* for PAGE_SIZE */

#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

 * @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') {

			base = 8;

			cp++;

			if ((toupper(*cp) == 'X') && isxdigit(cp[1])) {

			if ((TOLOWER(*cp) == 'x') && isxdigit(cp[1])) {

				cp++;

				base = 16;

			}

		}

	} else if (base == 16) {

		if (cp[0] == '0' && toupper(cp[1]) == 'X')

		if (cp[0] == '0' && TOLOWER(cp[1]) == 'x')

			cp += 2;

	}

	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;

		cp++;

	}
@@ -92,17 +95,17 @@ unsigned long long simple_strtoull(const char *cp,char **endp,unsigned int base) 
		if (*cp == '0') {

			base = 8;

			cp++;

			if ((toupper(*cp) == 'X') && isxdigit(cp[1])) {

			if ((TOLOWER(*cp) == 'x') && isxdigit(cp[1])) {

				cp++;

				base = 16;

			}

		}

	} else if (base == 16) {

		if (cp[0] == '0' && toupper(cp[1]) == 'X')

		if (cp[0] == '0' && TOLOWER(cp[1]) == 'x')

			cp += 2;

	}

	while (isxdigit(*cp) && (value = isdigit(*cp) ? *cp-'0' : (islower(*cp)

	    ? toupper(*cp) : *cp)-'A'+10) < base) {

	while (isxdigit(*cp)

	 && (value = isdigit(*cp) ? *cp-'0' : TOLOWER(*cp)-'a'+10) < base) {

		result = result*base + value;

		cp++;

	}
@@ -360,24 +363,25 @@ static noinline char* put_dec(char *buf, unsigned long long num) 
#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 */



static char *number(char *buf, char *end, unsigned long long num, int base, int size, int precision, int type)

{

	char sign,tmp[66];

	const char *digits;

	/* we are called with base 8, 10 or 16, only, thus don't need "g..."  */

	static const char small_digits[] = "0123456789abcdefx"; /* "ghijklmnopqrstuvwxyz"; */

	static const char large_digits[] = "0123456789ABCDEFX"; /* "GHIJKLMNOPQRSTUVWXYZ"; */

	/* 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 sign;

	char locase;

	int need_pfx = ((type & SPECIAL) && base != 10);

	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)

		type &= ~ZEROPAD;

	if (base < 2 || base > 36)

		return NULL;

	sign = 0;

	if (type & SIGN) {

		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';

	/* Generic code, for any base:

	else do {

		tmp[i++] = digits[do_div(num,base)];

		tmp[i++] = (digits[do_div(num,base)] | locase);

	} while (num != 0);

	*/

	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;

		if (base == 16) shift = 4;

		do {

			tmp[i++] = digits[((unsigned char)num) & mask];

			tmp[i++] = (digits[((unsigned char)num) & mask] | locase);

			num >>= shift;

		} while (num);

	} else { /* base 10 */
@@ -444,7 +448,7 @@ static char *number(char *buf, char *end, unsigned long long num, int base, int 
		++buf;

		if (base == 16) {

			if (buf < end)

				*buf = digits[16]; /* for arbitrary base: digits[33]; */

				*buf = ('X' | locase);

			++buf;

		}

	}
@@ -644,6 +648,7 @@ int vsnprintf(char *buf, size_t size, const char *fmt, va_list args) 
				continue;



			case 'p':

				flags |= SMALL;

				if (field_width == -1) {

					field_width = 2*sizeof(void *);

					flags |= ZEROPAD;
@@ -680,9 +685,9 @@ int vsnprintf(char *buf, size_t size, const char *fmt, va_list args) 
				base = 8;

				break;



			case 'X':

				flags |= LARGE;

			case 'x':

				flags |= SMALL;

			case 'X':

				base = 16;

				break;