@@ -16,6 +16,12 @@
<http://www.gnu.org/licenses/>. */
#include <string.h>
+#include <stdint.h>
+#include <limits.h>
+#include <string-fzb.h>
+#include <string-fzi.h>
+#include <string-extbyte.h>
+#include <memcopy.h>
#undef strcmp
@@ -29,19 +35,94 @@
int
STRCMP (const char *p1, const char *p2)
{
- const unsigned char *s1 = (const unsigned char *) p1;
- const unsigned char *s2 = (const unsigned char *) p2;
+ const op_t *x1, *x2;
+ op_t w1, w2;
unsigned char c1, c2;
+ uintptr_t i, n, ofs;
+ int diff;
- do
+ /* Handle the unaligned bytes of p1 first. */
+ n = -(uintptr_t)p1 % sizeof(op_t);
+ for (i = 0; i < n; ++i)
{
- c1 = (unsigned char) *s1++;
- c2 = (unsigned char) *s2++;
- if (c1 == '\0')
- return c1 - c2;
+ c1 = *p1++;
+ c2 = *p2++;
+ diff = c1 - c2;
+ if (c1 == '\0' || diff)
+ return diff;
}
- while (c1 == c2);
+ /* P1 is now aligned to unsigned long. P2 may or may not be. */
+ x1 = (const op_t *)p1;
+ w1 = *x1++;
+ ofs = (uintptr_t)p2 % sizeof(op_t);
+ if (ofs == 0)
+ {
+ x2 = (const op_t *)p2;
+ w2 = *x2++;
+ /* Aligned loop. If a difference is found, exit to compare the
+ bytes. Else if a zero is found we have equal strings. */
+ while (w1 == w2)
+ {
+ if (has_zero (w1))
+ return 0;
+ w1 = *x1++;
+ w2 = *x2++;
+ }
+ }
+ else
+ {
+ op_t w2a, w2b;
+ uintptr_t sh_1, sh_2;
+
+ x2 = (const op_t *)(p2 - ofs);
+ w2a = *x2++;
+ sh_1 = ofs * CHAR_BIT;
+ sh_2 = sizeof(op_t) * CHAR_BIT - sh_1;
+
+ /* Align the first partial of P2, with 0xff for the rest of the
+ bytes so that we can also apply the has_zero test to see if we
+ have already reached EOS. If we have, then we can simply fall
+ through to the final comparison. */
+ w2 = MERGE (w2a, sh_1, (op_t)-1, sh_2);
+ if (!has_zero (w2))
+ {
+ /* Unaligned loop. The invariant is that W2B, which is "ahead"
+ of W1, does not contain end-of-string. Therefore it is safe
+ (and necessary) to read another word from each while we do
+ not have a difference. */
+ while (1)
+ {
+ w2b = *x2++;
+ w2 = MERGE (w2a, sh_1, w2b, sh_2);
+ if (w1 != w2)
+ goto final_cmp;
+ if (has_zero (w2b))
+ break;
+ w1 = *x1++;
+ w2a = w2b;
+ }
+
+ /* Zero found in the second partial of P2. If we had EOS
+ in the aligned word, we have equality. */
+ if (has_zero (w1))
+ return 0;
+
+ /* Load the final word of P1 and align the final partial of P2. */
+ w1 = *x1++;
+ w2 = MERGE (w2b, sh_1, 0, sh_2);
+ }
+ }
+
+ final_cmp:
+ for (i = 0; i < sizeof (op_t); i++)
+ {
+ c1 = extractbyte (w1, i);
+ c2 = extractbyte (w2, i);
+ if (c1 == '\0' || c1 != c2)
+ return c1 - c2;
+ }
return c1 - c2;
}
+
libc_hidden_builtin_def (strcmp)
From: Richard Henderson <rth@twiddle.net> New generic implementation tries to use word operations along with the new string-fz{b,i} functions even for inputs with different alignments (with still uses aligned access plus merge operation to get a correct word by word comparison). Checked on x86_64-linux-gnu, i686-linux-gnu, sparc64-linux-gnu, and sparcv9-linux-gnu by removing the arch-specific assembly implementation and disabling multi-arch (it covers both LE and BE for 64 and 32 bits). Richard Henderson <rth@twiddle.net> Adhemerval Zanella <adhemerval.zanella@linaro.org> * string/strcmp.c: Rewrite using memcopy.h, string-fzb.h, string-fzi.h. --- string/strcmp.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 89 insertions(+), 8 deletions(-) -- 2.7.4