Ping for the following patch sent in 3 months ago in the end of GCC8: https://www.mail-archive.com/gcc-patches@gcc.gnu.org/msg184075.html
I have rebased the patch on the latest GCC9 thunk.
bootstraped and tested on both X86 and Aarch64. no regression.
the following are more details:
========
Hi, this is the 3rd version for this patch.
the main change compared with 2nd version are:
1. do not use “compute_objsize” to get the minimum object size per Jeff
and Richard’s
comment. Instead, add a new function “determine_min_objsize” for this purpose.
This new
function calls “compute_builtin_object_size” to get the minimum objsize,
however, due to
the fact that “compute_builtin_object_size” does nothing for SSA_NAME when
optimize > 0 (don’t
know the exactly reason for this), inside “determine_min_objsize”, I have to
add more code
to catch up some simple SSA_NAME cases.
2. in gimple-fold.c and tree-ssa-structalias.c, add the handling of the
new
BUILT_IN_STRCMP_EQ and BUILT_IN_STRNCMP_EQ in the same places where
BUILT_IN_STRCMP and BUILT_IN_STRNCMP is checked.
3. some format change and comments change per Jeff’s comment.
let me know if you have any comments.
thanks a lot.
Qing
*********************************
2nd Patch for PR78009
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
bootstraped and tested on both X86 and Aarch64. no regression.
************************************************
gcc/ChangeLog
+2018-05-21 <qing.z...@oracle.com>
+
+ PR middle-end/78809
+ PR middle-end/83026
+ * builtins.c (expand_builtin): Add the handling of BUILT_IN_STRCMP_EQ
+ and BUILT_IN_STRNCMP_EQ.
+ * builtins.def: Add new builtins BUILT_IN_STRCMP_EQ and
+ BUILT_IN_STRNCMP_EQ.
+ * gimple-fold.c (gimple_fold_builtin_string_compare): Add the
+ handling of BUILTIN_IN_STRCMP_EQ and BUILT_IN_STRNCMP_EQ.
+ (gimple_fold_builtin): Likewise.
+ * tree-ssa-strlen.c (compute_string_length): New function.
+ (determine_min_obsize): New function.
+ (handle_builtin_string_cmp): New function to handle calls to
+ string compare functions.
+ (strlen_optimize_stmt): Add handling to builtin string compare
+ calls.
+ * tree-ssa-structalias.c (find_func_aliases_for_builtin_call):
+ Add the handling of BUILT_IN_STRCMP_EQ and BUILT_IN_STRNCMP_EQ.
+ * tree.c (build_common_builtin_nodes): Add new defines of
+ BUILT_IN_STRNCMP_EQ and BUILT_IN_STRCMP_EQ.
+
gcc/testsuite/ChangeLog
+2018-05-21 <qing.z...@oracle.com>
+
+ PR middle-end/78809
+ * gcc.dg/strcmpopt_2.c: New testcase.
+ * gcc.dg/strcmpopt_3.c: New testcase.
+
+ PR middle-end/83026
+ * gcc.dg/strcmpopt_3.c: New testcase.
PR78809_B.patch
Description: Binary data
