On Tue, Feb 20, 2018 at 12:03:26PM -0700, Martin Sebor wrote:
> PR tree-optimization/84478 - [8 Regression] pdftex miscompilation on i386
>
> gcc/ChangeLog:
>
> PR tree-optimization/84478
> * gimple-fold.c (get_range_strlen): Set *MINLEN to zero.
> (get_range_strlen): Reset range on failure.
>
> gcc/testsuite/ChangeLog:
>
> PR tree-optimization/84478
> * gcc.c-torture/execute/pr84478.c: New test.
>
> Index: gcc/gimple-fold.c
> ===================================================================
> --- gcc/gimple-fold.c (revision 257796)
> +++ gcc/gimple-fold.c (working copy)
> @@ -1369,7 +1369,10 @@ get_range_strlen (tree arg, tree length[2], bitmap
> tree eltype = TREE_TYPE (type);
> if (TREE_CODE (type) != ARRAY_TYPE
> || !INTEGRAL_TYPE_P (eltype))
> - return false;
> + {
> + *minlen = ssize_int (0);
> + return false;
> + }
This is just one of the 13 spots where we return false, so this doesn't look
safe or sufficient to me, even when you actually honor the return value in
2 argument get_range_strlen. You'd really need to do
{
if (fuzzy)
- *maxlen = build_all_ones_cst (size_type_node);
+ {
+ *minlen = size_int (0);
+ *maxlen = build_all_ones_cst (size_type_node);
+ }
else
return false;
}
or just drop that if (fuzzy) stuff from there, but that breaks the warning
tests. It would help if you explained why you think it is a good idea
ignoring the other phi arguments if you have one (or more) where you can
determine length.
One variation of my patch could be instead of adding type 3 change
fuzzy from bool to int, and use fuzzy == 1 for the strlen value ranges and
fuzzy == 2 for the warning code (i.e. 2 operand get_range_strlen).
Note, my patch passed regtest on both x86_64-linux and i686-linux.
Jakub
