[PATCH] Fix tree forwprop a second time (PR middle-end/38200)

[Richard Guenther]

On Fri, Nov 21, 2008 at 3:40 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> My earlier patch to forward_propagate_addr_expr_1 contained a thinko,
> as for x = &a; *x = b; replacement with a = b; we know a's address
> has been taken, so a = (a's type) b; is invalid GIMPLE (a = b;
> generated previously was also invalid GIMPLE if the type conversion
> wasn't useless).  The following patch thus never adds a cast,
> just checks if the conversion is useless.  For
> x = &a;
> x->j = b;
> transforming it to
> a.j = b;
> doesn't change LHS nor RHS side, so this checking isn't needed.
>
> Ok if bootstrap+regtest succeeds on x86_64-linux?

Ok.

Thanks,
Richard.

> 2008-11-21  Jakub Jelinek  <jakub@redhat.com>
>
>        PR middle-end/38200
>        * tree-ssa-forwprop.c (forward_propagate_addr_expr_1): Only
>        propagate x = &a into *x = b if conversion from b to a's type is
>        useless.
>
>        * gcc.dg/pr38200.c: New test.
>
> --- gcc/tree-ssa-forwprop.c.jj  2008-11-18 19:24:09.000000000 +0100
> +++ gcc/tree-ssa-forwprop.c     2008-11-21 15:19:55.000000000 +0100
> @@ -719,30 +719,18 @@ forward_propagate_addr_expr_1 (tree name
>      propagate the ADDR_EXPR into the use of NAME and fold the result.  */
>   if (TREE_CODE (lhs) == INDIRECT_REF
>       && TREE_OPERAND (lhs, 0) == name
> -      && may_propagate_address_into_dereference (def_rhs, lhs))
> +      && may_propagate_address_into_dereference (def_rhs, lhs)
> +      && (lhsp != gimple_assign_lhs_ptr (use_stmt)
> +         || useless_type_conversion_p (TREE_TYPE (TREE_OPERAND (def_rhs, 0)),
> +                                       TREE_TYPE (rhs))))
> -      bool valid = true;
> -      if (lhsp == gimple_assign_lhs_ptr (use_stmt)
> -         && !useless_type_conversion_p (TREE_TYPE (TREE_OPERAND (def_rhs, 0)),
> -                                        TREE_TYPE (rhs))
> -         && !CONVERT_EXPR_CODE_P (rhs_code))
> -       {
> -         if (rhs_code == SSA_NAME)
> -           gimple_assign_set_rhs_code (use_stmt, NOP_EXPR);
> -         else
> -           valid = false;
> -       }
> -      if (valid)
> -       {
> -         *lhsp = unshare_expr (TREE_OPERAND (def_rhs, 0));
> -         fold_stmt_inplace (use_stmt);
> -         tidy_after_forward_propagate_addr (use_stmt);
> +      *lhsp = unshare_expr (TREE_OPERAND (def_rhs, 0));
> +      fold_stmt_inplace (use_stmt);
> +      tidy_after_forward_propagate_addr (use_stmt);
>
> -         /* Continue propagating into the RHS if this was not the only
> -            use.  */
> -         if (single_use_p)
> -           return true;
> -       }
> +      /* Continue propagating into the RHS if this was not the only use.  */
> +      if (single_use_p)
> +       return true;
>     }
>
>   /* Strip away any outer COMPONENT_REF, ARRAY_REF or ADDR_EXPR
> --- gcc/testsuite/gcc.dg/pr38200.c.jj   2008-11-21 15:21:52.000000000 +0100
> +++ gcc/testsuite/gcc.dg/pr38200.c      2008-11-21 15:07:25.000000000 +0100
> @@ -0,0 +1,16 @@
> +/* PR middle-end/38200 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fno-strict-aliasing" } */
> +
> +typedef int (*callptr) (void);
> +int foo (void **x);
> +void foo2 (callptr *);
> +int (*foo_ptr) (void **x) = foo;
> +
> +void
> +bar (void)
> +{
> +  void *ptr;
> +  foo2 ((callptr *) &ptr);
> +  *(void **) &foo_ptr = ptr;
> +}
>
>        Jakub
>