Re: [PATCH][ARM][gas] Make gas accept vcmp[e].f{32,64} <reg>, #0.0

[Will Newton <will dot newton at linaro dot org>]

On 7 August 2014 09:45, Kyrill Tkachov <kyrylo.tkachov@arm.com> wrote:
>
> On 05/08/14 15:14, Will Newton wrote:
>>
>> On 5 August 2014 14:11, Kyrill Tkachov <kyrylo.tkachov@arm.com> wrote:
>>>
>>> On 04/08/14 11:08, Will Newton wrote:
>>>>
>>>> On 4 August 2014 10:34, Kyrill Tkachov <kyrylo.tkachov@arm.com> wrote:
>>>>
>>>> Hi Kyrill,
>>>>
>>>>> The ARM ARM says that the VFP compare with zero instructions (vcmp,
>>>>> vcmpe)
>>>>> accept the zero in the form of a #0.0 immediate. However, gas currently
>>>>> only
>>>>> accepts #0. This patch fixes that and some simple tests are added.
>>>>>
>>>>> The new parse_ifimm_zerofunction is rather simple and is modelled on
>>>>> the
>>>>> parse_qfloat_immediate below it and didn't blow up in my testing.
>>>>>
>>>>>
>>>>> make check on gas passes and a gcc testsuite run doesn't show any
>>>>> problems.
>>>>>
>>>>> Ok for trunk?
>>>>>
>>>>> Thanks,
>>>>> Kyrill
>>>>>
>>>>> [gas/]
>>>>> 2014-06-24  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>>>>>
>>>>>       * config/tc-arm.c (parse_ifimm_zero): New function.
>>>>>       (enum operand_parse_code): Add OP_RSVD_FI0 value.
>>>>>       (parse_operands): Handle OP_RSVD_FI0.
>>>>>       (asm_opcode_insns): Use RSVD_FI0 for second operand of vcmp,
>>>>> vcmpe.
>>>>>
>>>>> [gas/testsuite/]
>>>>> 2014-06-24  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>>>>>
>>>>>       * gas/arm/ual-vcmp.s: New file.
>>>>>       * gas/arm/ual-vcmp.d: Likewise.
>>>>
>>>> Would it be possible to use my_get_expression or a similar parser for
>>>> this?
>>>
>>> Hi Will,
>>>
>>> Thanks for the suggestion, but I'm struggling to figure out what
>>> my_get_expression is supposed to be doing. Is it supposed to be taking a
>>> string and parsing it into an expressionS?
>>> I'm not very well versed in gas internal data types...
>>
>> Yes, that's pretty much it. I think an integer will be type O_constant
>> with the value in X_add_number and a floating point value O_big with a
>> value in generic_floating_point_number. The expr.c code is not pretty
>> but it should be possible to make it do something approaching what's
>> reguired...
>
>
> Hi Will,
>
> After a bit of investigation, it seems that atof_generic is what I need. It
> can handle any form of floating point zero, as well as plain old "0".
>
> From what I understand from looking around gas the global variable
> generic_floating_point_number is supposed to be used to store the various
> parts of a floating point representation and the way it's checked for 0.0 in
> config/atof-ieee.c is by comparing the .low and .leader components.
>
>  I've also added a *-bad.s testcase to make sure we reject non-zero
> immediates.
>
> make check on gas passes.
>
> How does this look?

Looks good to me (although I am not a maintainer).

> Thanks,
> Kyrill
>
> [gas/]
> 2014-08-07  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>
>
>         * config/tc-arm.c (parse_ifimm_zero): New function.
>         (enum operand_parse_code): Add OP_RSVD_FI0 value.
>         (parse_operands): Handle OP_RSVD_FI0.
>         (asm_opcode_insns): Use RSVD_FI0 for second operand of vcmp, vcmpe.
>
> [gas/testsuite/]
> 2014-08-07  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>
>
>         * gas/arm/ual-vcmp.s: New file.
>         * gas/arm/ual-vcmp.d: Likewise.
>         * gas/arm/vcmp-zero-bad.s: Likewise.
>         * gas/arm/vcmp-zero-bad.d: Likewise.
>         * gas/arm/vcmp-zero-bad.l: Likewise.



-- 
Will Newton
Toolchain Working Group, Linaro