Re: [PATCH][GCC][ARM] Dot Product commandline options [Patch (1/8)]

["Richard Earnshaw (lists)" <Richard dot Earnshaw at arm dot com>]

On 06/10/17 13:44, Tamar Christina wrote:
> Hi All,
> 
> This is a respin of the patch with the feedback processed.
> 
> Regtested on arm-none-eabi, armeb-none-eabi,
> aarch64-none-elf and aarch64_be-none-elf with no issues found.
> 
> Ok for trunk?
> 
> gcc/
> 2017-10-06  Tamar Christina  <tamar.christina@arm.com>
> 
>         * config/arm/arm.h (TARGET_DOTPROD): New.
>         * config/arm/arm.c (arm_arch_dotprod): New.
>         (arm_option_reconfigure_globals): Add arm_arch_dotprod.
>         * config/arm/arm-c.c (__ARM_FEATURE_DOTPROD): New.
>         * config/arm/arm-cpus.in (cortex-a55, cortex-75): Enabled +dotprod.
>         (armv8.2-a, cortex-a75.cortex-a55): Likewise.
>         (feature dotprod, group dotprod, ALL_SIMD_INTERNAL): New.
>         (ALL_FPU_INTERNAL): Use ALL_SIMD_INTERNAL.
>         * config/arm/t-multilib (v8_2_a_simd_variants): Add dotprod.
>         * doc/invoke.texi (armv8.2-a): Document dotprod
> ________________________________________
> From: Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>
> Sent: Wednesday, September 13, 2017 11:01:55 AM
> To: Tamar Christina; gcc-patches@gcc.gnu.org
> Cc: nd; Ramana Radhakrishnan; Richard Earnshaw; nickc@redhat.com
> Subject: Re: [PATCH][GCC][ARM] Dot Product commandline options [Patch (1/8)]
> 
> Hi Tamar,
> 
> On 01/09/17 14:19, Tamar Christina wrote:
>> Hi All,
>>
>> This patch adds support for the +dotprod extension to ARM.
>> Dot Product requires Adv.SIMD to work and so enables this option
>> by default when enabled.
>>
>> It is available from ARMv8.2-a and onwards and is enabled by
>> default on Cortex-A55 and Cortex-A75.
>>
>> Regtested and bootstrapped on arm-none-eabi and no issues.
> 
> I'm assuming you mean arm-none-linux-gnueabihf :)
> 
>> Ok for trunk?
>>
>> gcc/
>> 2017-09-01  Tamar Christina  <tamar.christina@arm.com>
>>
>>       * config/arm/arm.h (TARGET_DOTPROD): New.
>>       * config/arm/arm.c (arm_arch_dotprod): New.
>>       (arm_option_reconfigure_globals): Add arm_arch_dotprod.
>>       * config/arm/arm-c.c (__ARM_FEATURE_DOTPROD): New.
>>       * config/arm/arm-cpus.in (cortex-a55, cortex-75): Enabled +dotprod.
>>       (armv8.2-a, cortex-a75.cortex-a55): Likewise.
>>       * config/arm/arm-isa.h (isa_bit_dotprod, ISA_DOTPROD): New.
> 
> arm-isa.h is now autogenerated after r251799 so you'll need to rebase on
> top of that.
> That being said, that patch was temporarily reverted [1] so you'll have
> to apply it manually in your
> tree to rebase, or wait until it is reapplied.
> 
> [1] https://gcc.gnu.org/ml/gcc-patches/2017-09/msg00579.html
> 
> The patch looks ok to me otherwise with a documentation nit below.
> 
>>       * config/arm/t-multilib (v8_2_a_simd_variants): Add dotprod.
>>       * doc/invoke.texi (armv8.2-a): Document dotprod
>>
> 
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -15492,6 +15492,10 @@ The ARMv8.1 Advanced SIMD and floating-point instructions.
>   The cryptographic instructions.  This also enables the Advanced SIMD and
>   floating-point instructions.
> 
> +@item +dotprod
> +Enable the Dot Product extension.  This also enables Advanced SIMD instructions
> +and allows auto vectorization of dot products to the Dot Product instructions.
> 
> This should be "auto-vectorization"
> 
> Thanks,
> Kyrill
> 
> 
> 


Hmm, can you arrange to add patches as text/plain attachments, so that
when I reply the patch is included for comments, please?

+# double-precision FP. Make sure bits that are not an FPU bit go
instructions
+# ALL_SIMD instead of ALL_SIMD_INTERNAL.

Two spaces after full stop.  The new sentence doesn't make sense.
Instead, I think you should probably put the following:

"ALL_FPU lists all the feature bits associated with the floating-point
unit; these will all be removed if the floating-point unit is disabled
(eg -mfloat-abi=soft).  ALL_FPU_INTERNAL must ONLY contain features that
form part of a named -mfpu option; it is used to map the capabilities
back to a named FPU for the benefit of the assembler.  ALL_SIMD_INTERNAL
and ALL_SIMD are similarly defined to help with the construction of
ALL_FPU and ALL_FPU_INTERNAL; they describe the SIMD extensions that are
either part of a named FPU or optional extensions respectively."

You might need to rejig the other sentence there as well to make it more
consistent.

@@ -239,6 +243,7 @@ define fgroup FP_D32	FP_DBL fp_d32
 define fgroup FP_ARMv8	FPv5 FP_D32
 define fgroup NEON	FP_D32 neon
 define fgroup CRYPTO	NEON crypto
+define fgroup DOTPROD   NEON dotprod

lines above have a hard tab between the group name and the features it
contains.  Your entry has spaces.  Please fix for consistency.

@@ -1473,9 +1479,10 @@ begin cpu cortex-a55
  cname cortexa55
  tune for cortex-a53
  tune flags LDSCHED
- architecture armv8.2-a+fp16
+ architecture armv8.2-a+fp16+dotprod
  fpu neon-fp-armv8
  option crypto add FP_ARMv8 CRYPTO
+ option dotprod add FP_ARMv8 DOTPROD

We don't have an option entry for +fp16 (all Cortex-a55 cores implement
it), so we should treat dotprod similarly here.  Crypto is a special
case because it isn't enabled by default.  Similarly for the other cores
later in the patch.