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>

diff --git a/arch/x86/boot/printf.c b/arch/x86/boot/printf.c
index 1a09f93..7e7e890 100644 (file)
--- 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;
 

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 419993f..fd987b1 100644 (file)
--- 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;