On 06/07/2018 09:57 AM, Martin Sebor wrote:
> The attached patch enhances the strlen pass to more consistently
> deal with MEM_REF assignments (PR 86042) and to track string
> lengths across calls to memcpy that overwrite parts of a string
> with sequences of non-nul characters (PR 86043).
>
> Fixes for both bugs rely on changes to the same code so I chose
> to include them in the same patch.
>
> To fix PR 86042 the patch extends handle_char_store() to deal with
> more forms of multi-character assignments from MEM_REF (originally
> introduced in r256180). To handle assignments from strings of
> multiple nuls the patch also extends the initializer_zerop()
> function to understand MEM_REFs of the form:
>
> MEM[(char * {ref-all})&a] = MEM[(char * {ref-all})"..."];
>
> The solution for PR 86043 consists of two parts: the extension
> above which lets handle_char_store() recognize assignments of
> sequences of non-null characters that overwrite some portion of
> the leading non-zero characters in the destination and avoid
> discarding the destination information, and a similar extension
> to handle_builtin_memcpy().
>
> Martin
>
> gcc-86042.diff
>
>
> PR tree-optimization/86042 - missing strlen optimization after second strcpy
>
> gcc/ChangeLog:
>
> PR tree-optimization/86042
> * tree-ssa-strlen.c (handle_builtin_memcpy): Handle strict overlaps.
> (get_string_cst_length): Rename...
> (get_min_string_length): ...to this. Add argument.
> (handle_char_store): Extend to handle multi-character stores by
> MEM_REF.
> * tree.c (initializer_zerop): Use new argument. Handle MEM_REF.
> * tree.h (initializer_zerop): Add argument.
>
> gcc/testsuite/ChangeLog:
>
> PR tree-optimization/86042
> * gcc.dg/strlenopt-44.c: New test.
OK.
Thanks,
jeff
