Re: [PATCH 3/3] tests/tcg/s390x: Test VSTRS

[Claudio Fontana]

On 8/7/23 10:08, Ilya Leoshkevich wrote:
> On Sun, 2023-08-06 at 13:05 +0200, Claudio Fontana wrote:
>> On 8/5/23 01:03, Ilya Leoshkevich wrote:
>>> Add a small test to prevent regressions.
>>>
>>> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
>>> ---
>>>  tests/tcg/s390x/Makefile.target |  1 +
>>>  tests/tcg/s390x/vxeh2_vstrs.c   | 88
>>> +++++++++++++++++++++++++++++++++
>>>  2 files changed, 89 insertions(+)
>>>  create mode 100644 tests/tcg/s390x/vxeh2_vstrs.c
>>>
>>> diff --git a/tests/tcg/s390x/Makefile.target
>>> b/tests/tcg/s390x/Makefile.target
>>> index 1fc98099070..8ba36e5985b 100644
>>> --- a/tests/tcg/s390x/Makefile.target
>>> +++ b/tests/tcg/s390x/Makefile.target
>>> @@ -73,6 +73,7 @@ ifneq ($(CROSS_CC_HAS_Z15),)
>>>  Z15_TESTS=vxeh2_vs
>>>  Z15_TESTS+=vxeh2_vcvt
>>>  Z15_TESTS+=vxeh2_vlstr
>>> +Z15_TESTS+=vxeh2_vstrs
>>>  $(Z15_TESTS): CFLAGS+=-march=z15 -O2
>>>  TESTS+=$(Z15_TESTS)
>>>  endif
>>> diff --git a/tests/tcg/s390x/vxeh2_vstrs.c
>>> b/tests/tcg/s390x/vxeh2_vstrs.c
>>> new file mode 100644
>>> index 00000000000..313ec1d728f
>>> --- /dev/null
>>> +++ b/tests/tcg/s390x/vxeh2_vstrs.c
>>> @@ -0,0 +1,88 @@
>>> +/*
>>> + * Test the VSTRS instruction.
>>> + *
>>> + * SPDX-License-Identifier: GPL-2.0-or-later
>>> + */
>>> +#include <assert.h>
>>> +#include <stdint.h>
>>> +#include <stdio.h>
>>> +#include <stdlib.h>
>>> +#include "vx.h"
>>> +
>>> +static inline __attribute__((__always_inline__)) int
>>> +vstrs(S390Vector *v1, const S390Vector *v2, const S390Vector *v3,
>>> +      const S390Vector *v4, const uint8_t m5, const uint8_t m6)
>>> +{
>>> +    int cc;
>>> +
>>> +    asm("vstrs %[v1],%[v2],%[v3],%[v4],%[m5],%[m6]\n"
>>> +        "ipm %[cc]"
>>> +        : [v1] "=v" (v1->v)
>>> +        , [cc] "=r" (cc)
>>> +        : [v2] "v" (v2->v)
>>> +        , [v3] "v" (v3->v)
>>> +        , [v4] "v" (v4->v)
>>> +        , [m5] "i" (m5)
>>> +        , [m6]  "i" (m6)
>>> +        : "cc");
>>> +
>>> +    return (cc >> 28) & 3;
>> Following the POp, I am puzzled by the use of an "int" to contain the
>> register result of the IPM instruction, should it not be a 64bit
>> variable?
>> bits 0-31 are left unchanged / are uninteresting, is that enough to
>> avoid having to use a properly sized variable?
> 
> The compiler understands that if the type is int, then the asm block
> will not touch the upper 32 bits of the register that's assigned to it.
> This observation is used not only in the QEMU tests, but also all over
> arch/s390 in the Linux kernel.

Thank you,

Claudio

>>
>> I see that this is done elsewhere in the tests (sometimes a 64bit
>> variable is used, sometimes just 'int'), so I assume it's probably
>> fine.
>>
>> Otherwise lgtm,
>>
>> Claudio
> 
> [...]
>>
>