Re: [PATCH 1/8] Add Aarch64 SVE target description

Alan Hayward
2018-05-31T13:40:47Z

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Thanks for the reviews.
Pushed this with changes as below.

> On 31 May 2018, at 12:09, Simon Marchi <simon.marchi@ericsson.com> wrote:
>
> On 2018-05-11 06:52 AM, Alan Hayward wrote:
>> This patch adds the SVE target description. However, no code will
>> yet use it - that comes in the later patches.
>>
>> The create_feature_aarch64_sve function is not generated from XML.
>> This is because we need to know the sve vector size (VQ) in order
>> to size the registers correctly.
>>
>> A VQ of 0 is used when the hardware does not support SVE.
>> (SVE hardware will always have a valid vector size). I considered
>> using a bool to indicate SVE in addition to the VQ. Whilst this
>> may be slightly more readable initially, I think it's a little
>> odd to have two variables, eg:
>> aarch64_create_target_description (bool sve_supported, long vq)
>>
>> Alan.
>
> Hi Alan,
>
> This patch LGTM, I just noted some nits.
>
>> /* Initialize the current architecture based on INFO. If possible,
>> @@ -2864,7 +2875,8 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
>>
>> /* Ensure we always have a target descriptor. */
>> if (!tdesc_has_registers (tdesc))
>> - tdesc = aarch64_read_description ();
>> + /* SVE is not yet supported. */
>> + tdesc = aarch64_read_description (0);
>
> When there there is a comment above the single statement branch, braces become required:
>
> if (!tdesc_has_registers (tdesc))
> {
> /* SVE is not yet supported. */
> tdesc = aarch64_read_description (0);
> }

ok.

>
>> diff --git a/gdb/arch/aarch64.c b/gdb/arch/aarch64.c
>> index b85e460b6b..d1ec5cedf8 100644
>> --- a/gdb/arch/aarch64.c
>> +++ b/gdb/arch/aarch64.c
>> @@ -21,11 +21,13 @@
>>
>> #include "../features/aarch64-core.c"
>> #include "../features/aarch64-fpu.c"
>> +#include "../features/aarch64-sve.c"
>>
>> -/* Create the aarch64 target description. */
>> +/* Create the aarch64 target description. A non zero VQ value indicates both
>> + the presence of SVE and the SVE vector quotient. */
>
> What does "SVE vector quotient" mean? Is there maybe a simpler way to say it?
>

It’s explained in a later patch, but I should have explained it here.
Updated to (and moved into header):

/* Create the aarch64 target description. A non zero VQ value indicates both
the presence of SVE and the Vector Quotient - the number of 128bit chunks in
an SVE Z register. */

> Could you move this comment to the .h and put
>
> /* See arch/aarch64.h. */
>
> here?

Ok.

>
>> diff --git a/gdb/features/aarch64-sve.c b/gdb/features/aarch64-sve.c
>> new file mode 100644
>> index 0000000000..6442640a73
>> --- /dev/null
>> +++ b/gdb/features/aarch64-sve.c
>> @@ -0,0 +1,158 @@
>> +/* Copyright (C) 2017 Free Software Foundation, Inc.
>
> 2018
>

Ok.

Alan.
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