1 files changed, 195 insertions, 94 deletions

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 5391299c1e78..c3f36d415bdf 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -112,106 +112,199 @@ int skip_atoi(const char **s)
 /* Decimal conversion is by far the most typical, and is used
  * for /proc and /sys data. This directly impacts e.g. top performance
  * with many processes running. We optimize it for speed
- * using code from
- * http://www.cs.uiowa.edu/~jones/bcd/decimal.html
- * (with permission from the author, Douglas W. Jones). */
+ * using ideas described at <http://www.cs.uiowa.edu/~jones/bcd/divide.html>
+ * (with permission from the author, Douglas W. Jones).
+ */
 
-/* Formats correctly any integer in [0,99999].
- * Outputs from one to five digits depending on input.
- * On i386 gcc 4.1.2 -O2: ~250 bytes of code. */
+#if BITS_PER_LONG != 32 || BITS_PER_LONG_LONG != 64
+/* Formats correctly any integer in [0, 999999999] */
 static noinline_for_stack
-char *put_dec_trunc(char *buf, unsigned q)
+char *put_dec_full9(char *buf, unsigned q)
 {
-        unsigned d3, d2, d1, d0;
-        d1 = (q>>4) & 0xf;
-        d2 = (q>>8) & 0xf;
-        d3 = (q>>12);
-
-        d0 = 6*(d3 + d2 + d1) + (q & 0xf);
-        q = (d0 * 0xcd) >> 11;
-        d0 = d0 - 10*q;
-        *buf++ = d0 + '0'; /* least significant digit */
-        d1 = q + 9*d3 + 5*d2 + d1;
-        if (d1 != 0) {
-                q = (d1 * 0xcd) >> 11;
-                d1 = d1 - 10*q;
-                *buf++ = d1 + '0'; /* next digit */
-
-                d2 = q + 2*d2;
-                if ((d2 != 0) || (d3 != 0)) {
-                        q = (d2 * 0xd) >> 7;
-                        d2 = d2 - 10*q;
-                        *buf++ = d2 + '0'; /* next digit */
-
-                        d3 = q + 4*d3;
-                        if (d3 != 0) {
-                                q = (d3 * 0xcd) >> 11;
-                                d3 = d3 - 10*q;
-                                *buf++ = d3 + '0';  /* next digit */
-                                if (q != 0)
-                                        *buf++ = q + '0'; /* most sign. digit */
-                        }
-                }
-        }
+        unsigned r;
 
+        /*
+         * Possible ways to approx. divide by 10
+         * (x * 0x1999999a) >> 32 x < 1073741829 (multiply must be 64-bit)
+         * (x * 0xcccd) >> 19     x <      81920 (x < 262149 when 64-bit mul)
+         * (x * 0x6667) >> 18     x <      43699
+         * (x * 0x3334) >> 17     x <      16389
+         * (x * 0x199a) >> 16     x <      16389
+         * (x * 0x0ccd) >> 15     x <      16389
+         * (x * 0x0667) >> 14     x <       2739
+         * (x * 0x0334) >> 13     x <       1029
+         * (x * 0x019a) >> 12     x <       1029
+         * (x * 0x00cd) >> 11     x <       1029 shorter code than * 0x67 (on i386)
+         * (x * 0x0067) >> 10     x <        179
+         * (x * 0x0034) >>  9     x <         69 same
+         * (x * 0x001a) >>  8     x <         69 same
+         * (x * 0x000d) >>  7     x <         69 same, shortest code (on i386)
+         * (x * 0x0007) >>  6     x <         19
+         * See <http://www.cs.uiowa.edu/~jones/bcd/divide.html>
+         */
+        r      = (q * (uint64_t)0x1999999a) >> 32;
+        *buf++ = (q - 10 * r) + '0'; /* 1 */
+        q      = (r * (uint64_t)0x1999999a) >> 32;
+        *buf++ = (r - 10 * q) + '0'; /* 2 */
+        r      = (q * (uint64_t)0x1999999a) >> 32;
+        *buf++ = (q - 10 * r) + '0'; /* 3 */
+        q      = (r * (uint64_t)0x1999999a) >> 32;
+        *buf++ = (r - 10 * q) + '0'; /* 4 */
+        r      = (q * (uint64_t)0x1999999a) >> 32;
+        *buf++ = (q - 10 * r) + '0'; /* 5 */
+        /* Now value is under 10000, can avoid 64-bit multiply */
+        q      = (r * 0x199a) >> 16;
+        *buf++ = (r - 10 * q)  + '0'; /* 6 */
+        r      = (q * 0xcd) >> 11;
+        *buf++ = (q - 10 * r)  + '0'; /* 7 */
+        q      = (r * 0xcd) >> 11;
+        *buf++ = (r - 10 * q) + '0'; /* 8 */
+        *buf++ = q + '0'; /* 9 */
         return buf;
 }
-/* Same with if's removed. Always emits five digits */
+#endif
+
+/* Similar to above but do not pad with zeros.
+ * Code can be easily arranged to print 9 digits too, but our callers
+ * always call put_dec_full9() instead when the number has 9 decimal digits.
+ */
 static noinline_for_stack
-char *put_dec_full(char *buf, unsigned q)
+char *put_dec_trunc8(char *buf, unsigned r)
 {
-        /* BTW, if q is in [0,9999], 8-bit ints will be enough, */
-        /* but anyway, gcc produces better code with full-sized ints */
-        unsigned d3, d2, d1, d0;
-        d1 = (q>>4) & 0xf;
-        d2 = (q>>8) & 0xf;
-        d3 = (q>>12);
+        unsigned q;
+
+        /* Copy of previous function's body with added early returns */
+        q      = (r * (uint64_t)0x1999999a) >> 32;
+        *buf++ = (r - 10 * q) + '0'; /* 2 */
+        if (q == 0)
+                return buf;
+        r      = (q * (uint64_t)0x1999999a) >> 32;
+        *buf++ = (q - 10 * r) + '0'; /* 3 */
+        if (r == 0)
+                return buf;
+        q      = (r * (uint64_t)0x1999999a) >> 32;
+        *buf++ = (r - 10 * q) + '0'; /* 4 */
+        if (q == 0)
+                return buf;
+        r      = (q * (uint64_t)0x1999999a) >> 32;
+        *buf++ = (q - 10 * r) + '0'; /* 5 */
+        if (r == 0)
+                return buf;
+        q      = (r * 0x199a) >> 16;
+        *buf++ = (r - 10 * q)  + '0'; /* 6 */
+        if (q == 0)
+                return buf;
+        r      = (q * 0xcd) >> 11;
+        *buf++ = (q - 10 * r)  + '0'; /* 7 */
+        if (r == 0)
+                return buf;
+        q      = (r * 0xcd) >> 11;
+        *buf++ = (r - 10 * q) + '0'; /* 8 */
+        if (q == 0)
+                return buf;
+        *buf++ = q + '0'; /* 9 */
+        return buf;
+}
 
-        /*
-         * Possible ways to approx. divide by 10
-         * gcc -O2 replaces multiply with shifts and adds
-         * (x * 0xcd) >> 11: 11001101 - shorter code than * 0x67 (on i386)
-         * (x * 0x67) >> 10:  1100111
-         * (x * 0x34) >> 9:    110100 - same
-         * (x * 0x1a) >> 8:     11010 - same
-         * (x * 0x0d) >> 7:      1101 - same, shortest code (on i386)
-         */
-        d0 = 6*(d3 + d2 + d1) + (q & 0xf);
-        q = (d0 * 0xcd) >> 11;
-        d0 = d0 - 10*q;
-        *buf++ = d0 + '0';
-        d1 = q + 9*d3 + 5*d2 + d1;
-                q = (d1 * 0xcd) >> 11;
-                d1 = d1 - 10*q;
-                *buf++ = d1 + '0';
-
-                d2 = q + 2*d2;
-                        q = (d2 * 0xd) >> 7;
-                        d2 = d2 - 10*q;
-                        *buf++ = d2 + '0';
-
-                        d3 = q + 4*d3;
-                                q = (d3 * 0xcd) >> 11; /* - shorter code */
-                                /* q = (d3 * 0x67) >> 10; - would also work */
-                                d3 = d3 - 10*q;
-                                *buf++ = d3 + '0';
-                                        *buf++ = q + '0';
+/* There are two algorithms to print larger numbers.
+ * One is generic: divide by 1000000000 and repeatedly print
+ * groups of (up to) 9 digits. It's conceptually simple,
+ * but requires a (unsigned long long) / 1000000000 division.
+ *
+ * Second algorithm splits 64-bit unsigned long long into 16-bit chunks,
+ * manipulates them cleverly and generates groups of 4 decimal digits.
+ * It so happens that it does NOT require long long division.
+ *
+ * If long is > 32 bits, division of 64-bit values is relatively easy,
+ * and we will use the first algorithm.
+ * If long long is > 64 bits (strange architecture with VERY large long long),
+ * second algorithm can't be used, and we again use the first one.
+ *
+ * Else (if long is 32 bits and long long is 64 bits) we use second one.
+ */
 
-        return buf;
+#if BITS_PER_LONG != 32 || BITS_PER_LONG_LONG != 64
+
+/* First algorithm: generic */
+
+static
+char *put_dec(char *buf, unsigned long long n)
+{
+        if (n >= 100*1000*1000) {
+                while (n >= 1000*1000*1000)
+                        buf = put_dec_full9(buf, do_div(n, 1000*1000*1000));
+                if (n >= 100*1000*1000)
+                        return put_dec_full9(buf, n);
+        }
+        return put_dec_trunc8(buf, n);
 }
-/* No inlining helps gcc to use registers better */
+
+#else
+
+/* Second algorithm: valid only for 64-bit long longs */
+
 static noinline_for_stack
-char *put_dec(char *buf, unsigned long long num)
+char *put_dec_full4(char *buf, unsigned q)
 {
-        while (1) {
-                unsigned rem;
-                if (num < 100000)
-                        return put_dec_trunc(buf, num);
-                rem = do_div(num, 100000);
-                buf = put_dec_full(buf, rem);
-        }
+        unsigned r;
+        r      = (q * 0xcccd) >> 19;
+        *buf++ = (q - 10 * r) + '0';
+        q      = (r * 0x199a) >> 16;
+        *buf++ = (r - 10 * q)  + '0';
+        r      = (q * 0xcd) >> 11;
+        *buf++ = (q - 10 * r)  + '0';
+        *buf++ = r + '0';
+        return buf;
 }
 
+/* Based on code by Douglas W. Jones found at
+ * <http://www.cs.uiowa.edu/~jones/bcd/decimal.html#sixtyfour>
+ * (with permission from the author).
+ * Performs no 64-bit division and hence should be fast on 32-bit machines.
+ */
+static
+char *put_dec(char *buf, unsigned long long n)
+{
+        uint32_t d3, d2, d1, q, h;
+
+        if (n < 100*1000*1000)
+                return put_dec_trunc8(buf, n);
+
+        d1  = ((uint32_t)n >> 16); /* implicit "& 0xffff" */
+        h   = (n >> 32);
+        d2  = (h      ) & 0xffff;
+        d3  = (h >> 16); /* implicit "& 0xffff" */
+
+        q   = 656 * d3 + 7296 * d2 + 5536 * d1 + ((uint32_t)n & 0xffff);
+
+        buf = put_dec_full4(buf, q % 10000);
+        q   = q / 10000;
+
+        d1  = q + 7671 * d3 + 9496 * d2 + 6 * d1;
+        buf = put_dec_full4(buf, d1 % 10000);
+        q   = d1 / 10000;
+
+        d2  = q + 4749 * d3 + 42 * d2;
+        buf = put_dec_full4(buf, d2 % 10000);
+        q   = d2 / 10000;
+
+        d3  = q + 281 * d3;
+        if (!d3)
+                goto done;
+        buf = put_dec_full4(buf, d3 % 10000);
+        q   = d3 / 10000;
+        if (!q)
+                goto done;
+        buf = put_dec_full4(buf, q);
+ done:
+        while (buf[-1] == '0')
+                --buf;
+
+        return buf;
+}
+
+#endif
+
 /*
  * Convert passed number to decimal string.
  * Returns the length of string.  On buffer overflow, returns 0.
@@ -220,16 +313,22 @@ char *put_dec(char *buf, unsigned long long num)
  */
 int num_to_str(char *buf, int size, unsigned long long num)
 {
-        char tmp[21];           /* Enough for 2^64 in decimal */
+        char tmp[sizeof(num) * 3];
         int idx, len;
 
-        len = put_dec(tmp, num) - tmp;
+        /* put_dec() may work incorrectly for num = 0 (generate "", not "0") */
+        if (num <= 9) {
+                tmp[0] = '0' + num;
+                len = 1;
+        } else {
+                len = put_dec(tmp, num) - tmp;
+        }
 
         if (len > size)
                 return 0;
         for (idx = 0; idx < len; ++idx)
                 buf[idx] = tmp[len - idx - 1];
-        return  len;
+        return len;
 }
 
 #define ZEROPAD 1               /* pad with zero */
@@ -314,8 +413,8 @@ char *number(char *buf, char *end, unsigned long long num,
 
         /* generate full string in tmp[], in reverse order */
         i = 0;
-        if (num == 0)
-                tmp[i++] = '0';
+        if (num < spec.base)
+                tmp[i++] = digits[num] | locase;
         /* Generic code, for any base:
         else do {
                 tmp[i++] = (digits[do_div(num,base)] | locase);
@@ -611,7 +710,7 @@ char *ip4_string(char *p, const u8 *addr, const char *fmt)
         }
         for (i = 0; i < 4; i++) {
                 char temp[3];   /* hold each IP quad in reverse order */
-                int digits = put_dec_trunc(temp, addr[index]) - temp;
+                int digits = put_dec_trunc8(temp, addr[index]) - temp;
                 if (leading_zeros) {
                         if (digits < 3)
                                 *p++ = '0';
@@ -870,13 +969,15 @@ static noinline_for_stack
 char *pointer(const char *fmt, char *buf, char *end, void *ptr,
               struct printf_spec spec)
 {
+        int default_width = 2 * sizeof(void *) + (spec.flags & SPECIAL ? 2 : 0);
+
         if (!ptr && *fmt != 'K') {
                 /*
                  * Print (null) with the same width as a pointer so it makes
                  * tabular output look nice.
                  */
                 if (spec.field_width == -1)
-                        spec.field_width = 2 * sizeof(void *);
+                        spec.field_width = default_width;
                 return string(buf, end, "(null)", spec);
         }
 
@@ -931,7 +1032,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
                  */
                 if (in_irq() || in_serving_softirq() || in_nmi()) {
                         if (spec.field_width == -1)
-                                spec.field_width = 2 * sizeof(void *);
+                                spec.field_width = default_width;
                         return string(buf, end, "pK-error", spec);
                 }
                 if (!((kptr_restrict == 0) ||
@@ -948,7 +1049,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
         }
         spec.flags |= SMALL;
         if (spec.field_width == -1) {
-                spec.field_width = 2 * sizeof(void *);
+                spec.field_width = default_width;
                 spec.flags |= ZEROPAD;
         }
         spec.base = 16;