Re: [PATCH][Tree-optimization/PR89772]fold memchr builtins for character not in constant nul-padded string

[JunMa]

在 2019/3/21 下午1:06, Bin.Cheng 写道:

On Thu, Mar 21, 2019 at 12:57 PM JunMa <ju...@linux.alibaba.com> wrote:

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?

I suppose that it's for GCC10?

Thanks,
bin

Since it's a P3 normal bug, so the patch is for GCC10.
Sorry for the misleading, and thanks for pointing it out.

Regards Jun

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.