Simon Anders added the comment:
Martin: I've boiled down the test case a bit more and removed all
Python-specific types and macros, so that it can now be compiled
stand-alone. (Updated test case 'findtest.c' attached.) I didn't feel
like diving into the code much deeper, and so I have sent it to Intel
Premier Support as Issue #448807. Let's see if they bother to
investigate it further.
__________________________________
Tracker <[EMAIL PROTECTED]>
<http://bugs.python.org/issue1084>
__________________________________
/*
Testcase for problem with 'icc -O3':
The function 'fastsearch' is taken from the source code of Python 2.5
and looks for the substring 'p' (of length 'm') within the string 's'
(of length 'n'). If 'mode' is 'FAST_COUNT' the number of occurences of
p in s is returned, and for 'FAST_SEARCH', the position of the first
occurence.
For the specific values used in main() below, the function returns
correctly '4', if compiled with at most optimization '-O2', but '-1'
for optimization level '-O3'.
I have just changed the Python-specific types to standard ones, otherwise
fastsearc() is as defined in file Objects/stringlib/fastsearch.h of
the Python 2.5.1 source code. It has been written by Fredrik Lundh and
is described in his blog here: http://effbot.org/zone/stringlib.htm
Simon Anders, [EMAIL PROTECTED], 2007-09-02
*/
#include <string.h>
#include <stdio.h>
#define FAST_COUNT 0
#define FAST_SEARCH 1
inline int
fastsearch(const char* s, int n,
const char* p, int m,
int mode)
{
long mask;
int skip, count = 0;
int i, j, mlast, w;
w = n - m;
if (w < 0)
return -1;
/* look for special cases */
if (m <= 1) {
if (m <= 0)
return -1;
/* use special case for 1-character strings */
if (mode == FAST_COUNT) {
for (i = 0; i < n; i++)
if (s[i] == p[0])
count++;
return count;
} else {
for (i = 0; i < n; i++)
if (s[i] == p[0])
return i;
}
return -1;
}
mlast = m - 1;
/* create compressed boyer-moore delta 1 table */
skip = mlast - 1;
/* process pattern[:-1] */
for (mask = i = 0; i < mlast; i++) {
mask |= (1 << (p[i] & 0x1F));
if (p[i] == p[mlast])
skip = mlast - i - 1;
}
/* process pattern[-1] outside the loop */
mask |= (1 << (p[mlast] & 0x1F));
for (i = 0; i <= w; i++) {
/* note: using mlast in the skip path slows things down on x86 */
if (s[i+m-1] == p[m-1]) {
/* candidate match */
for (j = 0; j < mlast; j++)
if (s[i+j] != p[j])
break;
if (j == mlast) {
/* got a match! */
if (mode != FAST_COUNT)
return i;
count++;
i = i + mlast;
continue;
}
/* miss: check if next character is part of pattern */
if (!(mask & (1 << (s[i+m] & 0x1F))))
i = i + m;
else
i = i + skip;
} else {
/* skip: check if next character is part of pattern */
if (!(mask & (1 << (s[i+m] & 0x1F))))
i = i + m;
}
}
if (mode != FAST_COUNT)
return -1;
return count;
}
int main ()
{
char* str = "foo2/**bar**/";
int str_len = strlen (str);
char* sub = "/**bar**/";
int sub_len = strlen (sub);
int offset = 0;
int res;
res = fastsearch (str, str_len, sub, sub_len, FAST_SEARCH);
printf ("%d\n", res);
return 0;
}
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