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.
