Re: Allow passing arrays in registers on AArch64

[Ramana Radhakrishnan <ramana dot gcc at googlemail dot com>]

On Tue, Feb 4, 2014 at 2:12 AM, Michael Hudson-Doyle
<michael.hudson@linaro.org> wrote:
> Ping?  I'm attaching a marginally cleaner version of the test.  I've had
> a look at integrating this into aapcs64.exp but got defeated in the
> end.  If go-torture-execute took a list of sources as c-torture-execute
> does, then I think adding something like this to aapcs64.exp would work:
>
> # Test passing arrays by value
> set src $srcdir/$subdir/test_array.go
> if {[runtest_file_p $runtests $src]} {
>     go-torture-execute [list $src $srcdir/$subdir/abitest.S $srcdir/$subdir/_test_array_c.c] \
>         $additional_flags
> }
>
> but it doesn't.  I also think that some stuff needs to be set up before
> go-torture-execute can be called that I don't really understand and I
> also also don't know how to avoid executing this test if gccgo hasn't
> been built.

Putting in a shell script like that is a bad idea, the dejagnu
infrastructure can take care of all the transport and target bits for
this. This will fail if someone were to try testing this on qemu while
the rest of the testsuite might work.

However what happens if in aarch64.exp

you do a

load_lib go-dg.exp

and essentially run the tests similar to testsuite/go.dg/dg.exp  ?
That will take care of any cross-testing issues I hope with this using
dejagnu.

If that fails I think we should just drop the test as the go testsuite
will catch this.

>
> All that said, is there any chance of getting the original ABI fix
> committed?  It would be nice to have it in 4.9.


I cannot approve or disapprove this patch but looking at the fix and
the ABI issue under question here, I agree that this should be fixed
for 4.9 and documented in the release notes. Your latest patch should
also take Yufeng's suggestion under consideration about merging the
condition in the if block.


Cheers,
Ramana

>
> Cheers,
> mwh
>
> Michael Hudson-Doyle <michael.hudson@linaro.org> writes:
>
>> Richard Earnshaw <rearnsha@arm.com> writes:
>>
>>> On 17/01/14 23:56, Michael Hudson-Doyle wrote:
>>>> Ian Lance Taylor <iant@golang.org> writes:
>>>>
>>>>> On Fri, Jan 17, 2014 at 11:32 AM, Michael Hudson-Doyle
>>>>> <michael.hudson@canonical.com> wrote:
>>>>>>
>>>>>> On 18 Jan 2014 07:50, "Yufeng Zhang" <Yufeng.Zhang@arm.com> wrote:
>>>>>>>
>>>>>>> Also can you please try to add some new test(s)?  It may not be that
>>>>>>> straightforward to add non-C/C++ tests, but give it a try.
>>>>>>
>>>>>> Can you give some hints? Like at least where in the tree such a test would
>>>>>> go? I don't know this code at all.
>>>>>
>>>>> There is already a test in libgo, of course.
>>>>>
>>>>> I think it would be pretty hard to write a test that doesn't something
>>>>> like what libgo does.  The problem is that GCC is entirely consistent
>>>>> with and without your patch.  You could add a Go test that passes an
>>>>> array in gcc/testsuite/go.go-torture/execute/ easily enough, but it
>>>>> would be quite hard to add a test that doesn't pass whether or not
>>>>> your patch is applied.
>>>>
>>>> I think it would have to be a code generation test, i.e. that compiling
>>>> something like
>>>>
>>>> func second(e [2]int64) int64 {
>>>>         return e[1]
>>>> }
>>>>
>>>> does not access memory or something along those lines.  I'll have a look
>>>> next week.
>>>>
>>>> Cheers,
>>>> mwh
>>>>
>>>
>>> Michael,
>>>
>>> Can you have a look at how the tests in gcc.target/aarch64/aapcs64 work;
>>> it ought to be possible to write a test (though not in C) to catch this.
>>
>> Yeah, I had found those tests.  It would be much easier if I could write
>> this in C :-)
>>
>>> The tests work by calling a wrapper function written in assembler --
>>> that wrapper stores out all the registers used for parameter passing and
>>> then calls back into the test's validator with the register dump
>>> available.  Code can then check that values are passed in the places
>>> expected.  This gives the compiler the separation between caller and
>>> callee that's needed to test this feature.
>>
>> Right, that much makes sense.  I'm not sure I completely understand all
>> the preprocessor trickery involved but the output of it seems clear
>> enough.
>>
>>> My preferred languages for these tests would be (in approximate order)
>>> c, c++, fortran, java, ada, go.  That order is based on which languages
>>> are tested most by users.
>>
>> Well of course it cannot be done in C or C++.  A commenter on the PR
>> said that while fortran does allow passing arrays by value, it's all
>> handled in the frontend.  No idea about Java.  Ada has arrays by value
>> but I don't know it even slightly.  So it's the last one on your list
>> but here's a diff that adds hack at a test in Go:
>>
>> diff --git a/gcc/testsuite/gcc.target/aarch64/aapcs64/abitest.S b/gcc/testsuite/gcc.target/aarch64/aapcs64/abitest.S
>> index 86ce7be..365cd91 100644
>> --- a/gcc/testsuite/gcc.target/aarch64/aapcs64/abitest.S
>> +++ b/gcc/testsuite/gcc.target/aarch64/aapcs64/abitest.S
>> @@ -1,9 +1,12 @@
>>       .global dumpregs
>>       .global myfunc
>> +     .global main.myfunc
>>       .type dumpregs,%function
>>       .type myfunc,%function
>> +     .type main.myfunc,%function
>>  dumpregs:
>>  myfunc:
>> +main.myfunc:
>>        mov    x16, sp
>>        mov    x17, sp
>>        sub    sp,  sp, 352 // 336 for registers and 16 for old sp and lr
>> diff --git a/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array.go b/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array.go
>> new file mode 100644
>> index 0000000..b5e90e4
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array.go
>> @@ -0,0 +1,9 @@
>> +package main
>> +
>> +func myfunc(e [2]int64)
>> +
>> +func main() {
>> +     myfunc([2]int64{40, 50})
>> +}
>> +
>> +
>> diff --git a/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array.sh b/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array.sh
>> new file mode 100755
>> index 0000000..0b3202d
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array.sh
>> @@ -0,0 +1,11 @@
>> +#!/bin/sh
>> +GCC=${GCC:-gcc}
>> +AARCH64HOST=${AARCH64HOST:-localhost}
>> +
>> +set -x
>> +
>> +${GCC}go -g -c test_array.go -o test_array.o
>> +${GCC} -g -c abitest.S -o abitest.o
>> +${GCC} -g -c test_array_c.c -o test_array_c.o
>> +${GCC}go -g abitest.o test_array.o test_array_c.o -o test_array
>> +scp ./test_array ${AARCH64HOST}: && ssh ${AARCH64HOST} ./test_array
>> diff --git a/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array_c.c b/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array_c.c
>> new file mode 100644
>> index 0000000..981d12d
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array_c.c
>> @@ -0,0 +1,19 @@
>> +int which_kind_of_test = 0;
>> +
>> +#include "abitest-common.h"
>> +
>> +void
>> +testfunc (char *stack)
>> +{
>> +  {
>> +    long __x = 40;
>> +    if (memcmp (&__x, stack + X0, sizeof (long)) != 0)
>> +      abort ();
>> +  }
>> +  {
>> +    long __x = 50;
>> +    if (memcmp (&__x, stack + X1, sizeof (long)) != 0)
>> +      abort ();
>> +  }
>> +  return;
>> +}
>>
>> Obviously it's not integrated into the test framework even slightly but
>> on the good side, it fails without my fix and passes with it... Are you
>> able to do the integration part or provide some hints for me?
>>
>> Cheers,
>> mwh
>
>
> diff --git a/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array.go b/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array.go
> new file mode 100644
> index 0000000..c795e88
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array.go
> @@ -0,0 +1,10 @@
> +package main
> +
> +//extern myfunc
> +func myfunc(e [2]int64)
> +
> +func main() {
> +       myfunc([2]int64{40, 50})
> +}
> +
> +
> diff --git a/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array.sh b/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array.sh
> new file mode 100755
> index 0000000..1c41192
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array.sh
> @@ -0,0 +1,8 @@
> +#!/bin/sh
> +GCCGO=${GCCGO:-gccgo}
> +AARCH64HOST=${AARCH64HOST:-localhost}
> +
> +set -x
> +
> +${GCCGO} -g test_array.go abitest.S test_array_c.o -o test_array
> +scp ./test_array ${AARCH64HOST}: && ssh ${AARCH64HOST} ./test_array
> diff --git a/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array_c.c b/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array_c.c
> new file mode 100644
> index 0000000..41066b2
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/aapcs64/test_array_c.c
> @@ -0,0 +1,20 @@
> +int which_kind_of_test = 0;
> +
> +#include "abitest-common.h"
> +
> +void
> +testfunc (char *stack)
> +{
> +  {
> +    long __x = 40;
> +    if (memcmp (&__x, stack + X0, sizeof (long)) != 0)
> +      abort ();
> +  }
> +  {
> +    long __x = 50;
> +    if (memcmp (&__x, stack + X1, sizeof (long)) != 0)
> +      abort ();
> +  }
> +  return;
> +}
> +
>