Martin Sebor <mse...@gmail.com> writes:
> Recent improvements to the strlen pass introduced the assumption
> that when the length of a string has been recorded by the pass
> the length is necessarily constant. Bug 83896 shows that this
> assumption is not always true, and that GCC fails with an ICE
> when it doesn't hold. To avoid the ICE the attached patch
> removes the assumption.
>
> x86_64-linux bootstrap successful, regression test in progress.
>
> Martin
>
> PR tree-optimization/83896 - ice in get_string_len on a call to strlen with
> non-constant length
>
> gcc/ChangeLog:
>
> PR tree-optimization/83896
> * tree-ssa-strlen.c (get_string_len): Avoid assuming length is constant.
>
> gcc/testsuite/ChangeLog:
>
> PR tree-optimization/83896
> * gcc.dg/strlenopt-43.c: New test.
>
> Index: gcc/tree-ssa-strlen.c
> ===================================================================
> --- gcc/tree-ssa-strlen.c (revision 256752)
> +++ gcc/tree-ssa-strlen.c (working copy)
> @@ -2772,7 +2772,9 @@ handle_pointer_plus (gimple_stmt_iterator *gsi)
> }
> }
>
> -/* Check if RHS is string_cst possibly wrapped by mem_ref. */
> +/* If RHS, either directly or indirectly, refers to a string of constant
> + length, return it. Otherwise return a negative value. */
> +
> static int
> get_string_len (tree rhs)
> {
I think this should be returning HOST_WIDE_INT given the unconstrained
tree_to_shwi return. Same type change for rhslen in the caller.
(Not my call, but it might be better to have a more specific function name,
given that the file already had "get_string_length" before this function
was added.)
> @@ -2789,7 +2791,8 @@ get_string_len (tree rhs)
> if (idx > 0)
> {
> strinfo *si = get_strinfo (idx);
> - if (si && si->full_string_p)
> + if (si && si->full_string_p
> + && TREE_CODE (si->nonzero_chars) == INTEGER_CST)
> return tree_to_shwi (si->nonzero_chars);
tree_fits_shwi_p?
Thanks,
Richard
> }
> }
> Index: gcc/testsuite/gcc.dg/strlenopt-43.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/strlenopt-43.c (nonexistent)
> +++ gcc/testsuite/gcc.dg/strlenopt-43.c (working copy)
> @@ -0,0 +1,13 @@
> +/* PR tree-optimization/83896 - ice in get_string_len on a call to strlen
> + with non-constant length
> + { dg-do compile }
> + { dg-options "-O2 -Wall" } */
> +
> +extern char a[5];
> +extern char b[];
> +
> +void f (void)
> +{
> + if (__builtin_strlen (b) != 4)
> + __builtin_memcpy (a, b, sizeof a);
> +}
