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| author | Qing Zhao <qing.zhao@oracle.com> | 2018-05-31 20:01:42 +0000 |
|---|---|---|
| committer | Qing Zhao <qinzhao@gcc.gnu.org> | 2018-05-31 20:01:42 +0000 |
| commit | 8b0b334af3439179947522206b2478a28b908e61 (patch) | |
| tree | 1788b6670d6db9169fdfad6b15c80815fe4af24d /gcc/builtins.def | |
| parent | 28c84b6247e1ff5f3c7aa4c4912c361012fa3904 (diff) | |
| download | gcc-8b0b334af3439179947522206b2478a28b908e61.tar.gz | |
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
From-SVN: r261039
Diffstat (limited to 'gcc/builtins.def')
| -rw-r--r-- | gcc/builtins.def | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/gcc/builtins.def b/gcc/builtins.def index 449d08d682f..58b469844a7 100644 --- a/gcc/builtins.def +++ b/gcc/builtins.def @@ -971,6 +971,11 @@ DEF_BUILTIN_STUB (BUILT_IN_ALLOCA_WITH_ALIGN_AND_MAX, "__builtin_alloca_with_ali equality with zero. */ DEF_BUILTIN_STUB (BUILT_IN_MEMCMP_EQ, "__builtin_memcmp_eq") +/* An internal version of strcmp/strncmp, used when the result is only + tested for equality with zero. */ +DEF_BUILTIN_STUB (BUILT_IN_STRCMP_EQ, "__builtin_strcmp_eq") +DEF_BUILTIN_STUB (BUILT_IN_STRNCMP_EQ, "__builtin_strncmp_eq") + /* Object size checking builtins. */ DEF_GCC_BUILTIN (BUILT_IN_OBJECT_SIZE, "object_size", BT_FN_SIZE_CONST_PTR_INT, ATTR_PURE_NOTHROW_LEAF_LIST) DEF_EXT_LIB_BUILTIN_CHKP (BUILT_IN_MEMCPY_CHK, "__memcpy_chk", BT_FN_PTR_PTR_CONST_PTR_SIZE_SIZE, ATTR_RET1_NOTHROW_NONNULL_LEAF) |