Hi Jeff,
First, many thanks for the reviews!
Jeff Law <l...@redhat.com> writes:
> On 07/13/2017 02:39 AM, Richard Sandiford wrote:
>> The new iterators are:
>>
>> - FOR_EACH_MODE_IN_CLASS: iterate over all the modes in a mode class.
>>
>> - FOR_EACH_MODE_FROM: iterate over all the modes in a class,
>> starting at a given mode.
>>
>> - FOR_EACH_WIDER_MODE: iterate over all the modes in a class,
>> starting at the next widest mode after a given mode.
>>
>> - FOR_EACH_2XWIDER_MODE: same, but considering only modes that
>> are two times wider than the previous mode.
>>
>> - FOR_EACH_MODE_UNTIL: iterate over all the modes in a class until
>> a given mode is reached.
>>
>> - FOR_EACH_MODE: iterate over all the modes in a class between
>> two given modes, inclusive of the first but not the second.
>>
>> These help with the stronger type checking added by later patches,
>> since every new mode will be in the same class as the previous one.
>>
>> 2017-07-13 Richard Sandiford <richard.sandif...@linaro.org>
>> Alan Hayward <alan.hayw...@arm.com>
>> David Sherwood <david.sherw...@arm.com>
>>
>> gcc/
>> * machmode.h (mode_traits): New structure.
>> (get_narrowest_mode): New function.
>> (mode_iterator::start): Likewise.
>> (mode_iterator::iterate_p): Likewise.
>> (mode_iterator::get_wider): Likewise.
>> (mode_iterator::get_known_wider): Likewise.
>> (mode_iterator::get_2xwider): Likewise.
>> (FOR_EACH_MODE_IN_CLASS): New mode iterator.
>> (FOR_EACH_MODE): Likewise.
>> (FOR_EACH_MODE_FROM): Likewise.
>> (FOR_EACH_MODE_UNTIL): Likewise.
>> (FOR_EACH_WIDER_MODE): Likewise.
>> (FOR_EACH_2XWIDER_MODE): Likewise.
>> * builtins.c (expand_builtin_strlen): Use new mode iterators.
>> * combine.c (simplify_comparison): Likewise
>> * config/i386/i386.c (type_natural_mode): Likewise.
>> * cse.c (cse_insn): Likewise.
>> * dse.c (find_shift_sequence): Likewise.
>> * emit-rtl.c (init_derived_machine_modes): Likewise.
>> (init_emit_once): Likewise.
>> * explow.c (hard_function_value): Likewise.
>> * expmed.c (init_expmed_one_mode): Likewise.
>> (extract_fixed_bit_field_1): Likewise.
>> (extract_bit_field_1): Likewise.
>> (expand_divmod): Likewise.
>> (emit_store_flag_1): Likewise.
>> * expr.c (init_expr_target): Likewise.
>> (convert_move): Likewise.
>> (alignment_for_piecewise_move): Likewise.
>> (widest_int_mode_for_size): Likewise.
>> (emit_block_move_via_movmem): Likewise.
>> (copy_blkmode_to_reg): Likewise.
>> (set_storage_via_setmem): Likewise.
>> (compress_float_constant): Likewise.
>> * omp-low.c (omp_clause_aligned_alignment): Likewise.
>> * optabs-query.c (get_best_extraction_insn): Likewise.
>> * optabs.c (expand_binop): Likewise.
>> (expand_twoval_unop): Likewise.
>> (expand_twoval_binop): Likewise.
>> (widen_leading): Likewise.
>> (widen_bswap): Likewise.
>> (expand_parity): Likewise.
>> (expand_unop): Likewise.
>> (prepare_cmp_insn): Likewise.
>> (prepare_float_lib_cmp): Likewise.
>> (expand_float): Likewise.
>> (expand_fix): Likewise.
>> (expand_sfix_optab): Likewise.
>> * postreload.c (move2add_use_add2_insn): Likewise.
>> * reg-stack.c (reg_to_stack): Likewise.
>> * reginfo.c (choose_hard_reg_mode): Likewise.
>> * rtlanal.c (init_num_sign_bit_copies_in_rep): Likewise.
>> * stmt.c (emit_case_decision_tree): Likewise.
>> * stor-layout.c (mode_for_size): Likewise.
>> (smallest_mode_for_size): Likewise.
>> (mode_for_vector): Likewise.
>> (finish_bitfield_representative): Likewise.
>> * tree-ssa-math-opts.c (target_supports_divmod_p): Likewise.
>> * tree-vect-generic.c (type_for_widest_vector_mode): Likewise.
>> * tree-vect-stmts.c (vectorizable_conversion): Likewise.
>> * var-tracking.c (prepare_call_arguments): Likewise.
>>
>> gcc/ada/
>> * gcc-interface/misc.c (fp_prec_to_size): Use new mode iterators.
>> (fp_size_to_prec): Likewise.
>>
>> gcc/c-family/
>> * c-common.c (c_common_fixed_point_type_for_size): Use new mode
>> iterators.
>> * c-cppbuiltin.c (c_cpp_builtins): Likewise.
> So in some cases I see that we have loops like this:
>
> for (; mode != VOIDmode; mode = GET_WIDER_MODE (mode))
>
> Which iterates from the current mode through all the remaining modes,
> with each iteration using a wider mode than the previous iteration.
> GET_WIDER_MODE is always going to give us something in the same class or
> VOIDmode.
>
> This is getting translated into:
>
> FOR_EACH_MODE_FROM (mode, mode)
>
> The two loops have different steps. The original steps to a wider mode
> each iteration. The new one may step to a different mode of the same
> width IIUC.
>
> Am I missing something here?
The new iterators use GET_MODE_WIDER or GET_MODE_2XWIDER to step,
and the patch is only supposed to convert loops that have matching steps.
It wasn't supposed to convert loops that step through modes as numerical
values, but I see now that I fluffed it with:
Index: gcc/expmed.c
===================================================================
--- gcc/expmed.c 2017-07-13 09:17:39.972572368 +0100
+++ gcc/expmed.c 2017-07-13 09:18:21.531429258 +0100
@@ -204,8 +204,7 @@ init_expmed_one_mode (struct init_expmed
if (SCALAR_INT_MODE_P (mode))
{
- for (mode_from = MIN_MODE_INT; mode_from <= MAX_MODE_INT;
- mode_from = (machine_mode)(mode_from + 1))
+ FOR_EACH_MODE_IN_CLASS (mode_from, MODE_INT)
init_expmed_one_conv (all, mode, mode_from, speed);
}
if (GET_MODE_CLASS (mode) == MODE_INT)
Sorry about that! Will fix.
[Maybe in this case the change is safe, since I'm not sure we support
multiple full-integer modes with the same width. It's still too subtle
for a mechanical change like this though.]
Is that patch OK with that hunk removed?
Thanks,
Richard
> I realize you won't want to use FOR_EACH_WIDER_MODE since that's got a
> different starting point. But we might want to have an iterator that
> starts at the current mode, but steps to the net wider mode within the
> class. That would match the existing loops in several places and would
> avoid having to review each one of those use cases to ensure that the
> difference in steps isn't important.
>
> Thoughts? Am I missing something?
>
> jeff
