Re: [PATCH][libgomp, testsuite, nvptx] Limit recursion in declare_target-{1,2}.f90

[Thomas Schwinge <thomas@codesourcery.com>]

Hi Tom!

On 2022-04-01T13:24:40+0200, Tom de Vries <tdevries@suse.de> wrote:
> When running testcases libgomp.fortran/examples-4/declare_target-{1,2}.f90 on
> an RTX A2000 (sm_86) with driver 510.60.02 and with GOMP_NVPTX_JIT=-O0 I run
> into:
> ...
> FAIL: libgomp.fortran/examples-4/declare_target-1.f90 -O0 \
>   -DGOMP_NVPTX_JIT=-O0 execution test
> FAIL: libgomp.fortran/examples-4/declare_target-2.f90 -O0 \
>   -DGOMP_NVPTX_JIT=-O0 execution test
> ...
>
> Fix this by further limiting recursion depth in the test-cases for nvptx.
>
> Furthermore, make the recursion depth limiting nvptx-specific.

Careful:

> --- a/libgomp/testsuite/libgomp.fortran/examples-4/declare_target-1.f90
> +++ b/libgomp/testsuite/libgomp.fortran/examples-4/declare_target-1.f90
> @@ -1,4 +1,16 @@
>  ! { dg-do run }
> +! { dg-additional-options "-cpp" }
> +! Reduced from 25 to 23, otherwise execution runs out of thread stack on
> +! Nvidia Titan V.
> +! Reduced from 23 to 22, otherwise execution runs out of thread stack on
> +! Nvidia T400 (2GB variant), when run with GOMP_NVPTX_JIT=-O0.
> +! Reduced from 22 to 20, otherwise execution runs out of thread stack on
> +! Nvidia RTX A2000 (6GB variant), when run with GOMP_NVPTX_JIT=-O0.
> +! { dg-additional-options "-DREC_DEPTH=20" { target { offload_target_nvptx } } } */

'offload_target_nvptx' doesn't mean that offloading execution is done on
nvptx, but rather that we're "*compiling* for offload target nvptx"
(emphasis mine).  That means, with such a change we're now getting
different behavior in a system with an AMD GPU, when using a toolchain
that only has GCN offloading configured vs. a toolchain that has GCN and
nvptx offloading configured.  This isn't going to cause any real
problems, of course, but it's confusing, and a bad example of
'offload_target_nvptx'.

'offload_device_nvptx' ought to work: "using nvptx offload device".

But again, to keep things simple, I again suggest to unconditionally
reduce the recursion depth for all configurations, unless there exists an
actual rationale for the original value.


Grüße
 Thomas


> +
> +#ifndef REC_DEPTH
> +#define REC_DEPTH 25
> +#endif
>
>  module e_53_1_mod
>    integer :: THRESHOLD = 20
> @@ -27,9 +39,5 @@ end module
>  program e_53_1
>    use e_53_1_mod, only : fib, fib_wrapper
>    if (fib (15) /= fib_wrapper (15)) stop 1
> -  ! Reduced from 25 to 23, otherwise execution runs out of thread stack on
> -  ! Nvidia Titan V.
> -  ! Reduced from 23 to 22, otherwise execution runs out of thread stack on
> -  ! Nvidia T400 (2GB variant), when run with GOMP_NVPTX_JIT=-O0.
> -  if (fib (22) /= fib_wrapper (22)) stop 2
> +  if (fib (REC_DEPTH) /= fib_wrapper (REC_DEPTH)) stop 2
>  end program

> --- a/libgomp/testsuite/libgomp.fortran/examples-4/declare_target-2.f90
> +++ b/libgomp/testsuite/libgomp.fortran/examples-4/declare_target-2.f90
> @@ -1,16 +1,24 @@
>  ! { dg-do run }
> +! { dg-additional-options "-cpp" }
> +! Reduced from 25 to 23, otherwise execution runs out of thread stack on
> +! Nvidia Titan V.
> +! Reduced from 23 to 22, otherwise execution runs out of thread stack on
> +! Nvidia T400 (2GB variant), when run with GOMP_NVPTX_JIT=-O0.
> +! Reduced from 22 to 18, otherwise execution runs out of thread stack on
> +! Nvidia RTX A2000 (6GB variant), when run with GOMP_NVPTX_JIT=-O0.
> +! { dg-additional-options "-DREC_DEPTH=18" { target { offload_target_nvptx } } } */
> +
> +#ifndef REC_DEPTH
> +#define REC_DEPTH 25
> +#endif
>
>  program e_53_2
>    !$omp declare target (fib)
>    integer :: x, fib
>    !$omp target map(from: x)
> -    ! Reduced from 25 to 23, otherwise execution runs out of thread stack on
> -    ! Nvidia Titan V.
> -    ! Reduced from 23 to 22, otherwise execution runs out of thread stack on
> -    ! Nvidia T400 (2GB variant), when run with GOMP_NVPTX_JIT=-O0.
> -    x = fib (22)
> +    x = fib (REC_DEPTH)
>    !$omp end target
> -  if (x /= fib (22)) stop 1
> +  if (x /= fib (REC_DEPTH)) stop 1
>  end program
>
>  integer recursive function fib (n) result (f)
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