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>

1 files changed, 27 insertions, 22 deletions

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 419993f58c6b..fd987b17bda7 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -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;