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, 14 insertions, 10 deletions

diff --git a/arch/x86/boot/printf.c b/arch/x86/boot/printf.c
index 1a09f9309d3c..7e7e890699be 100644
--- a/arch/x86/boot/printf.c
+++ b/arch/x86/boot/printf.c
@@ -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;