"Bin.Cheng" <amker.ch...@gmail.com> wrote:
>I suspect codes in prepare_decl_rtl:
>
> case VAR_DECL:
> case PARM_DECL:
> case RESULT_DECL:
> *ws = 0;
> obj = *expr_p;
>
> if (DECL_RTL_SET_P (obj))
> break;
>
> if (DECL_MODE (obj) == BLKmode)
> x = produce_memory_decl_rtl (obj, regno);
> else
> x = gen_raw_REG (DECL_MODE (obj), (*regno)++);
>
>It generates RTX_REG(regno) for an var_decl which is an array has
>DECL_MODE == OImode.
>
>Any suggestions?
Addr_expr cost should be computed by
Looking at the cost for the address computation. Not by simply expanding the
address_expr. Look at get_inner_reference and handle the returned base
specially.
Richard.
>On Sun, Apr 28, 2013 at 3:15 PM, Bin.Cheng <amker.ch...@gmail.com>
>wrote:
>> Hi,
>> Currently tree-ssa-loop-ivopts.c doesn't calculate addr_expr's cost,
>> while uses target_spill_cost instead, as in function
>> force_expr_to_var_cost. When I experimented with ivopts by calling
>> computation_cost to calculate cost of ADDR_EXPR, I encountered assert
>> failure in expand_expr_addr_expr_1, because:
>> 0) The failure comes with (ADDR_EXPR (ARRAY_REF (local_var_decl)));
>> 1) computation_cost calls walk_tree/prepare_decl_rtl to prepare
>> RTX_REG for variables in ADDR_EXPR, which is the local_var_decl;
>> 2) computation_cost calls expand_expr to do the expanding work.
>> 3) function expand_expr_addr_expr_1 returns the RTX_REG as the result
>> of expanding, which violates the assertion "gcc_assert (MEM_P
>> (result))". The corresponding code in expand_expr_addr_expr_1 is like
>> :
>>
>> default:
>> /* If the object is a DECL, then expand it for its rtl. Don't
>bypass
>> expand_expr, as that can have various side effects; LABEL_DECLs
>for
>> example, may not have their DECL_RTL set yet. Expand the rtl of
>> CONSTRUCTORs too, which should yield a memory reference for the
>> constructor's contents. Assume language specific tree nodes can
>> be expanded in some interesting way. */
>> gcc_assert (TREE_CODE (exp) < LAST_AND_UNUSED_TREE_CODE);
>> if (DECL_P (exp)
>> || TREE_CODE (exp) == CONSTRUCTOR
>> || TREE_CODE (exp) == COMPOUND_LITERAL_EXPR)
>> {
>> result = expand_expr (exp, target, tmode,
>> modifier == EXPAND_INITIALIZER
>> ? EXPAND_INITIALIZER : EXPAND_CONST_ADDRESS);
>>
>> /* If the DECL isn't in memory, then the DECL wasn't properly
>> marked TREE_ADDRESSABLE, which will be either a front-end
>> or a tree optimizer bug. */
>>
>> if (TREE_ADDRESSABLE (exp)
>> && ! MEM_P (result)
>> && ! targetm.calls.allocate_stack_slots_for_args())
>> {
>> error ("local frame unavailable (naked function?)");
>> return result;
>> }
>> else
>> gcc_assert (MEM_P (result));
>> result = XEXP (result, 0);
>>
>> /* ??? Is this needed anymore? */
>> if (DECL_P (exp))
>> TREE_USED (exp) = 1;
>>
>> if (modifier != EXPAND_INITIALIZER
>> && modifier != EXPAND_CONST_ADDRESS
>> && modifier != EXPAND_SUM)
>> result = force_operand (result, target);
>> return result;
>> }
>>
>> So the question is
>> Is it as expected that cost of ADDR_EXPR cannot be calculated by
>> computation_cost? Or the assertion is because of immature
>> computation_cost/prepare_decl_rtl?
>>
>> I am not sure whether I described the problem clearly, please feel
>> free to ask for more information. Thanks for your patience.
>>
>> --
>> Best Regards.
