Re: [patch] missing COND_EXPR case in walk_stmt_load_store_addr_ops

[Richard Guenther <richard dot guenther at gmail dot com>]

On Mon, Aug 16, 2010 at 1:57 PM, Zbigniew Chamski
<zbigniew.chamski@gmail.com> wrote:
> All,
>
> walk_stmt_load_store_ops does not handle the case of COND_EXPR on the
> RHS of a GIMPLE assign statement, i.e., in 'selection assignments' of
> the form
>
> ?v = [cond_expr] a RELOP b : x ? y;
>
> This may result in an ICE at SSA verification time if/when the
> ADDR_EXPRs inside the selection expression are not taken into account.
> ?There is a corner case in libiberty (plus-demangle-template() in
> cplus-dem.c) where the only occurrence of an ADDR_TAKEN on variable
> 'pattern' ends up in a selection expression. ?A call to
> 'execute_update_addresses_taken()' will miss it, resulting in an
> "address taken, but ADDRESSABLE bit not set" error at SSA verification
> time. ?This normally goes unnoticed because there are no calls to
> 'execute_update_addresses_taken()' after SRA and the COND_EXPRs appear
> on the RHS much later, during LIM. ?However, the bug will be triggered
> if/when execute_fold_all_builtins ?(or a custom pass) alters data
> addressing and sets TODO_update_address_taken. ?In my case it was
> uncovered by a custom pass.
>
> The root cause is in the logic of 'walk_stmt_load_store_ops' which
> lacks the COND_EXPR case for simple assigns. ?A proposed patch is
> below, bootstrapped and tested (C & C++) on x86_64-unknown-linux-gnu.
>
> Comments welcome!

The patch is ok for trunk and the 4.5 branch (do you have a testcase?).

Thanks,
Richard.

> ? ?Zbigniew
>
> Index: gcc/gimple.c
> ===================================================================
> --- gcc/gimple.c ? ? ? ?(revision 163224)
> +++ gcc/gimple.c ? ? ? ?(working copy)
> @@ -4746,6 +4746,45 @@
> ? return NULL_TREE;
> ?}
>
> +
> +/* For an assignment STMT which contains a selection expression on the RHS,
> + ? i.e.,
> +
> + ? ? lhs = [cond_expr] a RELOP b ? x : y;
> +
> + ? search the entire selection expression for occurrences of ADDR_EXPR, and
> + ? if found, apply VISIT_ADDR callback on STMT, the corresponding ADDR_EXPR
> + ? operand and DATA. ?Return TRUE if any of the callback invocations
> + ? returned TRUE. ?*/
> +
> +static inline bool
> +stmt_visit_select_addr_ops (gimple stmt, tree select_expr, void *data,
> + ? ? ? ? ? ? ? ? ? ? ? ? ? bool (*visit_addr)(gimple, tree, void *))
> +{
> + ?bool ret = false;
> + ?tree condop1, condop2;
> + ?tree trueval, falseval;
> +
> + ?condop1 = TREE_OPERAND (TREE_OPERAND (select_expr, 0), 0);
> + ?if (TREE_CODE (condop1) == ADDR_EXPR)
> + ? ?ret |= visit_addr (stmt, condop1, data);
> +
> + ?condop2 = TREE_OPERAND (TREE_OPERAND (select_expr, 1), 0);
> + ?if (TREE_CODE (condop2) == ADDR_EXPR)
> + ? ?ret |= visit_addr (stmt, condop2, data);
> +
> + ?trueval = TREE_OPERAND (select_expr, 1);
> + ?if (TREE_CODE (trueval) == ADDR_EXPR)
> + ? ?ret |= visit_addr (stmt, trueval, data);
> +
> + ?falseval = TREE_OPERAND (select_expr, 2);
> + ?if (TREE_CODE (falseval) == ADDR_EXPR)
> + ? ?ret |= visit_addr (stmt, falseval, data);
> +
> + ?return ret;
> +}
> +
> +
> ?/* For the statement STMT call the callbacks VISIT_LOAD, VISIT_STORE and
> ? ?VISIT_ADDR if non-NULL on loads, store and address-taken operands
> ? ?passing the STMT, the base of the operand and DATA to it. ?The base
> @@ -4761,6 +4800,7 @@
> ?{
> ? bool ret = false;
> ? unsigned i;
> +
> ? if (gimple_assign_single_p (stmt))
> ? ? {
> ? ? ? tree lhs, rhs;
> @@ -4785,6 +4825,9 @@
> ? ? ? ? ? ? ? ? ? && TREE_CODE (OBJ_TYPE_REF_OBJECT (rhs)) == ADDR_EXPR)
> ? ? ? ? ? ?ret |= visit_addr (stmt, TREE_OPERAND (OBJ_TYPE_REF_OBJECT (rhs),
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 0), data);
> + ? ? ? ? else if (TREE_CODE (rhs) == COND_EXPR)
> + ? ? ? ? ? ret |= stmt_visit_select_addr_ops (stmt, rhs, data, visit_addr);
> +
> ? ? ? ? ? lhs = gimple_assign_lhs (stmt);
> ? ? ? ? ?if (TREE_CODE (lhs) == TARGET_MEM_REF
> ? ? ? ? ? ? ? && TMR_BASE (lhs) != NULL_TREE
>