[PATCH] New option for automatically generating IT blocks

[Daniel Gutson]

Hi,
	I'm writing again to say that I'm still working on this, and will provide a new patch soon.

The patch I provided was OK, but the new one replaces the -mauto-it option with one more generic (-mimplicit-it=[mode]), where validations are extended to ARM mode.

I'm sorry to ask for review and then undo so many times, I'm just working actively on this on a backlog of issues; reviewing and eventually committing the patch will be a good time point once the command line interface of this feature is stabilized (i.e. next patch).

  Daniel.

Daniel Gutson wrote:
> Hi Richard,
>     in this new version of the patch, the IT FSM data is stored in the 
> section, so changing sections in the middle of IT blocks generates the 
> right code.
> 
> You might want to look at the test cases (arm-it-auto-*).
> 
> Please commit this for me if it's OK, since I don't have write access, 
> or let me know any other concern.
> 
> Thanks,
>     Daniel.
> 
>     gas/
>     * config/tc-arm.c (do_automatic_it): New variable.
>     (it_instruction_type): New enum.
>     (arm_it): New field.
>     (it_state): New enum.
>     (now_it): New macro.
>     (now_it_compatible): New function.
>     (conditional_insn): New function.
>     (set_it_insn_type): New macro.
>     (set_it_insn_type_last): New macro.
>     (do_t_add_sub): Call automatic IT machinery functions.
>     (do_t_arit3): Likewise.
>     (do_t_arit3c): Likewise.
>     (do_t_blx): Likewise.
>     (do_t_branch): Likewise.
>     (do_t_bkpt): Likewise.
>     (do_t_branch23): Likewise.
>     (do_t_bx): Likewise.
>     (do_t_bxj): Likewise.
>     (do_t_cps): Likewise.
>     (do_t_cpsi): Likewise.
>     (do_t_cbz): Likewise.
>     (do_t_it): Likewise.
>     (encode_thumb2_ldmstm): Likewise.
>     (do_t_ldst): Likewise.
>     (do_t_mov_cmp): Likewise.
>     (do_t_mvn_tst): Likewise.
>     (do_t_mul): Likewise.
>     (do_t_neg): Likewise.
>     (do_t_setend): Likewise.
>     (do_t_shift): Likewise.
>     (do_t_tb): Likewise.
>     (output_it_inst): New function.
>     (new_automatic_it_block): New function.
>     (close_automatic_it_block): New function.
>     (now_it_add_mask): New function.
>     (it_fsm_pre_encode): New function.
>     (handle_it_state): New function.
>     (it_fsm_post_encode): New function.
>     (force_automatic_it_block_close): New function.
>     (in_it_block): New function.
>     (md_assemble): Call automatic IT block machinery functions.
>     (arm_frob_label): Likewise.
>     (arm_opts): New element.
>     * config/tc-arm.h (it_state): New enum.
>     (current_it): New struct.
>     (arm_segment_info_type): New member added.
>     * doc/c-arm.texi: New option -mauto-it.
> 
>     gas/testsuite/
>     * gas/arm/arm-it-auto.d: New test.
>     * gas/arm/arm-it-auto.s: New file.
>     * gas/arm/arm-it-auto-2.d: New test case.
>     * gas/arm/arm-it-auto-2.s: New file.
>     * gas/arm/arm-it-auto-3.d: New test case.
>     * gas/arm/arm-it-auto-3.s: New file.
>     * gas/arm/thumb2_it_auto.d: New test.
>     * gas/arm/thumb2_it_bad.l: Error message updated.
>     * gas/arm/thumb2_it_bad_auto.d: New test.
>     * gas/arm/thumb2_it.d: Comment added.
>     * gas/arm/thumb2_it_bad.d: Comment added.
> 
> 
> Richard Earnshaw wrote:
>> On Fri, 2009-05-08 at 16:29 -0300, Daniel Gutson wrote:
>>> Hi,
>>>   apologies again, this is the current version of the patch.
>>>
>>> As I mentioned in the original post, with this patch the assembler 
>>> allows use of conditional Thumb-2 instructions without requiring 
>>> explicit IT instructions.
>>>
>>> The patch adds the -mauto-it command-line option to enable this 
>>> automatic generation of IT instructions. When not specified, the 
>>> original behavior takes place.
>>>
>>> I tested this by running the gas testsuite, plus the test cases I added.
>>> Please commit it for me if accepted, since I don't have write access.
>>>
>>
>> Looks generally ok, but I've a couple of questions about dark corners
>> that I can't spot immediate answers to when reading the code.
>>
>> What happens if the user writes
>>
>>     .text
>>     cmp    r0, #0
>>     addeq    r1, #2
>>     .data
>>     .word    33
>>     .text
>>     addne    r1, #3
>>
>> Do we get one or two IT instructions?  If the user puts an explicit ITE
>> instruction in the sequence does this get verified against both parts.
>>
>> What happens if we replace the .data section with a different code
>> section?  What if that also includes an IT block?
>>
>> R.
>>
>>
>>
>