8b0b334af3
Patch for PR83026 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 Inline strcmp with small constant strings https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83026 missing strlen optimization for strcmp of unequal strings The design doc for PR78809 is at: https://www.mail-archive.com/gcc@gcc.gnu.org/msg83822.html this patch is for the second part of change of PR78809 and PR83026: B. for strncmp (s1, s2, n) (!)= 0 or strcmp (s1, s2) (!)= 0 B.1. (PR83026) When the lengths of both arguments are constant and it's a strcmp: * if the lengths are NOT equal, we can safely fold the call to a non-zero value. * otherwise, do nothing now. B.2. (PR78809) When the length of one argument is constant, try to replace the call with a __builtin_str(n)cmp_eq call where possible, i.e: strncmp (s, STR, C) (!)= 0 in which, s is a pointer to a string, STR is a string with constant length, C is a constant. if (C <= strlen(STR) && sizeof_array(s) > C) { replace this call with __builtin_strncmp_eq (s, STR, C) (!)= 0 } if (C > strlen(STR) { it can be safely treated as a call to strcmp (s, STR) (!)= 0 can handled by the following strcmp. } strcmp (s, STR) (!)= 0 in which, s is a pointer to a string, STR is a string with constant length. if (sizeof_array(s) > strlen(STR)) { replace this call with __builtin_strcmp_eq (s, STR, strlen(STR)+1) (!)= 0 } later when expanding the new __builtin_str(n)cmp_eq calls, first expand them as __builtin_memcmp_eq, if the expansion does not succeed, change them back to call to __builtin_str(n)cmp. adding test case strcmpopt_2.c and strcmpopt_4.c into gcc.dg for part B of PR78809 adding test case strcmpopt_3.c into gcc.dg for PR83026 From-SVN: r261039 |
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