[PATCH][ARM] PR target/71270 fix neon_valid_immediate for big-endian

[PATCH][ARM] PR target/71270 fix neon_valid_immediate for big-endian

[Kyrill Tkachov]

[-- Attachment #1: Type: text/plain, Size: 1630 bytes --]

Hi all,

In this wrong-code issue the RTL tries to load a const_vector:
(const_vector:V8QI [
         (const_int 1 [0x1])
         (const_int 0 [0])
         (const_int 1 [0x1])
         (const_int 0 [0])
         (const_int 1 [0x1])
         (const_int 0 [0])
         (const_int 1 [0x1])
         (const_int 0 [0])
     ])

into a NEON register. The logic for that is in neon_valid_immediate which does a number of tricks
to decide what value and of what size to do a VMOV on to load the correct vector immediate into the register.
It goes wrong on big-endian. On both big and little-endian this outputs:
vmov.i16    d18, #0x1

This is wrong on big-endian. The vector layout has to be such as if loaded from memory.
I've tried various approaches of fixing neon_valid_immediate to generate the correct immediate but have been unsuccessful,
resulting in regressions in various parts of the testsuite or making a big mess of the function.

Given that armeb is not a target of major concern I believe the safest route at this stage is to only allow vector constants
that will obviously work on big-endian, that is the ones that are just a single element duplicated in all lanes.

This patch fixes the execution failures:
FAIL: gfortran.dg/intrinsic_pack_1.f90
FAIL: gfortran.dg/c_f_pointer_logical.f03
FAIL: gcc.dg/torture/pr60183.c
FAIL: gcc.dg/vect/pr51581-4.c

on armeb-none-eabi.

Ok for trunk?

Thanks,
Kyrill

2017-01-06  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

     PR target/71270
     * config/arm/arm.c (neon_valid_immediate): Reject vector constants
     in big-endian mode when they are not a single duplicated value.

[-- Attachment #2: armeb-vec.patch --]
[-- Type: text/x-patch, Size: 710 bytes --]

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 45e0a3cd11fa650f456f7382ffbbcd1c932b95eb..2beee8ebe94eeadd6fb1d5b119e3b474e1ab902a 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -11542,6 +11542,12 @@ neon_valid_immediate (rtx op, machine_mode mode, int inverse,
 	return 18;
     }
 
+  /* The tricks done in the code below apply for little-endian vector layout.
+     For big-endian vectors only allow vectors of the form { a, a, a..., a }.
+     FIXME: Implement logic for big-endian vectors.  */
+  if (BYTES_BIG_ENDIAN && vector && !const_vec_duplicate_p (op))
+    return -1;
+
   /* Splat vector constant out into a byte vector.  */
   for (i = 0; i < n_elts; i++)
     {

Re: [PATCH][ARM] PR target/71270 fix neon_valid_immediate for big-endian

[Kyrill Tkachov]

Ping.
https://gcc.gnu.org/ml/gcc-patches/2017-01/msg00381.html

Thanks,
Kyrill

On 06/01/17 11:54, Kyrill Tkachov wrote:
> Hi all,
>
> In this wrong-code issue the RTL tries to load a const_vector:
> (const_vector:V8QI [
>         (const_int 1 [0x1])
>         (const_int 0 [0])
>         (const_int 1 [0x1])
>         (const_int 0 [0])
>         (const_int 1 [0x1])
>         (const_int 0 [0])
>         (const_int 1 [0x1])
>         (const_int 0 [0])
>     ])
>
> into a NEON register. The logic for that is in neon_valid_immediate which does a number of tricks
> to decide what value and of what size to do a VMOV on to load the correct vector immediate into the register.
> It goes wrong on big-endian. On both big and little-endian this outputs:
> vmov.i16    d18, #0x1
>
> This is wrong on big-endian. The vector layout has to be such as if loaded from memory.
> I've tried various approaches of fixing neon_valid_immediate to generate the correct immediate but have been unsuccessful,
> resulting in regressions in various parts of the testsuite or making a big mess of the function.
>
> Given that armeb is not a target of major concern I believe the safest route at this stage is to only allow vector constants
> that will obviously work on big-endian, that is the ones that are just a single element duplicated in all lanes.
>
> This patch fixes the execution failures:
> FAIL: gfortran.dg/intrinsic_pack_1.f90
> FAIL: gfortran.dg/c_f_pointer_logical.f03
> FAIL: gcc.dg/torture/pr60183.c
> FAIL: gcc.dg/vect/pr51581-4.c
>
> on armeb-none-eabi.
>
> Ok for trunk?
>
> Thanks,
> Kyrill
>
> 2017-01-06  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>
>     PR target/71270
>     * config/arm/arm.c (neon_valid_immediate): Reject vector constants
>     in big-endian mode when they are not a single duplicated value.

Re: [PATCH][ARM] PR target/71270 fix neon_valid_immediate for big-endian

[Richard Earnshaw (lists)]

On 06/01/17 11:54, Kyrill Tkachov wrote:
> Hi all,
> 
> In this wrong-code issue the RTL tries to load a const_vector:
> (const_vector:V8QI [
>         (const_int 1 [0x1])
>         (const_int 0 [0])
>         (const_int 1 [0x1])
>         (const_int 0 [0])
>         (const_int 1 [0x1])
>         (const_int 0 [0])
>         (const_int 1 [0x1])
>         (const_int 0 [0])
>     ])
> 
> into a NEON register. The logic for that is in neon_valid_immediate
> which does a number of tricks
> to decide what value and of what size to do a VMOV on to load the
> correct vector immediate into the register.
> It goes wrong on big-endian. On both big and little-endian this outputs:
> vmov.i16    d18, #0x1
> 
> This is wrong on big-endian. The vector layout has to be such as if
> loaded from memory.
> I've tried various approaches of fixing neon_valid_immediate to generate
> the correct immediate but have been unsuccessful,
> resulting in regressions in various parts of the testsuite or making a
> big mess of the function.
> 
> Given that armeb is not a target of major concern I believe the safest
> route at this stage is to only allow vector constants
> that will obviously work on big-endian, that is the ones that are just a
> single element duplicated in all lanes.
> 
> This patch fixes the execution failures:
> FAIL: gfortran.dg/intrinsic_pack_1.f90
> FAIL: gfortran.dg/c_f_pointer_logical.f03
> FAIL: gcc.dg/torture/pr60183.c
> FAIL: gcc.dg/vect/pr51581-4.c
> 
> on armeb-none-eabi.
> 
> Ok for trunk?
> 
> Thanks,
> Kyrill
> 
> 2017-01-06  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
> 
>     PR target/71270
>     * config/arm/arm.c (neon_valid_immediate): Reject vector constants
>     in big-endian mode when they are not a single duplicated value.
> 

Ok, but if you plan to close the PR above, please create a new
'enhancement' PR to fix the missed optimization.

R.

> armeb-vec.patch
> 
> 
> diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
> index 45e0a3cd11fa650f456f7382ffbbcd1c932b95eb..2beee8ebe94eeadd6fb1d5b119e3b474e1ab902a 100644
> --- a/gcc/config/arm/arm.c
> +++ b/gcc/config/arm/arm.c
> @@ -11542,6 +11542,12 @@ neon_valid_immediate (rtx op, machine_mode mode, int inverse,
>  	return 18;
>      }
>  
> +  /* The tricks done in the code below apply for little-endian vector layout.
> +     For big-endian vectors only allow vectors of the form { a, a, a..., a }.
> +     FIXME: Implement logic for big-endian vectors.  */
> +  if (BYTES_BIG_ENDIAN && vector && !const_vec_duplicate_p (op))
> +    return -1;
> +
>    /* Splat vector constant out into a byte vector.  */
>    for (i = 0; i < n_elts; i++)
>      {
> 

Re: [PATCH][ARM] PR target/71270 fix neon_valid_immediate for big-endian

[Kyrill Tkachov]

On 20/01/17 14:33, Richard Earnshaw (lists) wrote:
> On 06/01/17 11:54, Kyrill Tkachov wrote:
>> Hi all,
>>
>> In this wrong-code issue the RTL tries to load a const_vector:
>> (const_vector:V8QI [
>>          (const_int 1 [0x1])
>>          (const_int 0 [0])
>>          (const_int 1 [0x1])
>>          (const_int 0 [0])
>>          (const_int 1 [0x1])
>>          (const_int 0 [0])
>>          (const_int 1 [0x1])
>>          (const_int 0 [0])
>>      ])
>>
>> into a NEON register. The logic for that is in neon_valid_immediate
>> which does a number of tricks
>> to decide what value and of what size to do a VMOV on to load the
>> correct vector immediate into the register.
>> It goes wrong on big-endian. On both big and little-endian this outputs:
>> vmov.i16    d18, #0x1
>>
>> This is wrong on big-endian. The vector layout has to be such as if
>> loaded from memory.
>> I've tried various approaches of fixing neon_valid_immediate to generate
>> the correct immediate but have been unsuccessful,
>> resulting in regressions in various parts of the testsuite or making a
>> big mess of the function.
>>
>> Given that armeb is not a target of major concern I believe the safest
>> route at this stage is to only allow vector constants
>> that will obviously work on big-endian, that is the ones that are just a
>> single element duplicated in all lanes.
>>
>> This patch fixes the execution failures:
>> FAIL: gfortran.dg/intrinsic_pack_1.f90
>> FAIL: gfortran.dg/c_f_pointer_logical.f03
>> FAIL: gcc.dg/torture/pr60183.c
>> FAIL: gcc.dg/vect/pr51581-4.c
>>
>> on armeb-none-eabi.
>>
>> Ok for trunk?
>>
>> Thanks,
>> Kyrill
>>
>> 2017-01-06  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>>
>>      PR target/71270
>>      * config/arm/arm.c (neon_valid_immediate): Reject vector constants
>>      in big-endian mode when they are not a single duplicated value.
>>
> Ok, but if you plan to close the PR above, please create a new
> 'enhancement' PR to fix the missed optimization.

Thanks, I've committed it as r244716 and opened PR 79166 to track
the missed optimisation.

Kyrill

> R.
>
>> armeb-vec.patch
>>
>>
>> diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
>> index 45e0a3cd11fa650f456f7382ffbbcd1c932b95eb..2beee8ebe94eeadd6fb1d5b119e3b474e1ab902a 100644
>> --- a/gcc/config/arm/arm.c
>> +++ b/gcc/config/arm/arm.c
>> @@ -11542,6 +11542,12 @@ neon_valid_immediate (rtx op, machine_mode mode, int inverse,
>>   	return 18;
>>       }
>>   
>> +  /* The tricks done in the code below apply for little-endian vector layout.
>> +     For big-endian vectors only allow vectors of the form { a, a, a..., a }.
>> +     FIXME: Implement logic for big-endian vectors.  */
>> +  if (BYTES_BIG_ENDIAN && vector && !const_vec_duplicate_p (op))
>> +    return -1;
>> +
>>     /* Splat vector constant out into a byte vector.  */
>>     for (i = 0; i < n_elts; i++)
>>       {
>>