在 2019/3/21 下午12:51, JunMa 写道:
Hi
For now, gcc can not fold code like:
const char a[5] = "123"
__builtin_memchr (a, '7', sizeof a)
It tries to avoid folding out of string length although length of a is 5.
This is a bit conservative, it's safe to folding memchr/bcmp/memcmp
builtins when constant string stores in array with some trailing nuls.
This patch folds these cases by exposing additional length of
trailing nuls in c_getstr().
Bootstrapped/regtested on x86_64-linux, ok for trunk?
Regards
JunMa
gcc/ChangeLog
2019-03-21 Jun Ma <ju...@linux.alibaba.com>
PR Tree-optimization/89772
* fold-const.c (c_getstr): Add new parameter to get length of
additional
trailing nuls after constant string.
* gimple-fold.c (gimple_fold_builtin_memchr): consider trailing
nuls in
out-of-bound accesses checking.
* fold-const-call.c (fold_const_call): Likewise.
gcc/testsuite/ChangeLog
2019-03-21 Jun Ma <ju...@linux.alibaba.com>
PR Tree-optimization/89772
* gcc.dg/builtin-memchr-4.c: New test.
Ping.
Regards
JunMa
