RE: [PATCH 09/11] test/ring: disable problematic tests for RISC-V

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

<snip>

> 
> When compiling for RISC-V in debug mode the large amount of inlining in
> test_ring_basic_ex() and test_ring_with_exact_size() (in test_ring.c) leads to
> large loop bodies. This causes 'goto' and 'for' loop PC-relative jumps generated
> by the compiler to go beyond the architecture limitation of +/-1MB offset (the
> 'j <offset>' instruction). This instruction should not be generated by the
> compiler since C language does not limit the maximum distance for 'goto' or
> 'for' loop jumps.
> 
> This only happens in the unit test for ring which tries to perform long loops
> with ring enqueue/dequeue and it seems to be caused by excessive
> __rte_always_inline usage. ring perf test compiles just fine under debug.
> 
> To work around this, disable the offending tests in debug mode.
Is this still required given you have submitted [1]

[1] http://patches.dpdk.org/project/dpdk/patch/20220510115758.457794-1-kda@semihalf.com/

> 
> Signed-off-by: Stanislaw Kardach <kda@semihalf.com>
> Sponsored-by: Frank Zhao <Frank.Zhao@starfivetech.com>
> Sponsored-by: Sam Grove <sam.grove@sifive.com>
> ---
>  app/test/test_ring.c                   | 8 ++++++++
>  config/riscv/meson.build               | 5 +++++
>  doc/guides/rel_notes/release_22_07.rst | 3 ++-
>  3 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/app/test/test_ring.c b/app/test/test_ring.c index
> bde33ab4a1..7d809c147b 100644
> --- a/app/test/test_ring.c
> +++ b/app/test/test_ring.c
> @@ -955,6 +955,7 @@ test_ring_burst_bulk_tests4(unsigned int test_idx)
>  	return -1;
>  }
> 
> +#if !defined(RTE_RISCV_WO_DISABLE_RING_TESTS)
>  /*
>   * Test default, single element, bulk and burst APIs
>   */
> @@ -1189,6 +1190,7 @@ test_ring_with_exact_size(void)
>  	rte_ring_free(exact_sz_r);
>  	return -1;
>  }
> +#endif
> 
>  static int
>  test_ring(void)
> @@ -1200,12 +1202,18 @@ test_ring(void)
>  	if (test_ring_negative_tests() < 0)
>  		goto test_fail;
> 
> +/* Disable the following tests on RISC-V in debug mode. This is a
> +work-around
> + * GCC bug for RISC-V which fails to generate proper jumps for loops
> +with large
> + * bodies.
> + */
> +#if !defined(RTE_RISCV_WO_DISABLE_RING_TESTS)
>  	/* Some basic operations */
>  	if (test_ring_basic_ex() < 0)
>  		goto test_fail;
> 
>  	if (test_ring_with_exact_size() < 0)
>  		goto test_fail;
> +#endif
> 
>  	/* Burst and bulk operations with sp/sc, mp/mc and default.
>  	 * The test cases are split into smaller test cases to diff --git
> a/config/riscv/meson.build b/config/riscv/meson.build index
> 0c16c31fc2..50d0b513bf 100644
> --- a/config/riscv/meson.build
> +++ b/config/riscv/meson.build
> @@ -141,3 +141,8 @@ foreach flag: dpdk_flags  endforeach  message('Using
> machine args: @0@'.format(machine_args))
> 
> +# Enable work-around for ring unit tests in debug mode which fail to
> +link # properly due to bad code generation by GCC.
> +if get_option('optimization') == '0' or get_option('optimization') == 'g'
> +    add_project_arguments('-DRTE_RISCV_WO_DISABLE_RING_TESTS',
> +language: 'c') endif
> diff --git a/doc/guides/rel_notes/release_22_07.rst
> b/doc/guides/rel_notes/release_22_07.rst
> index 453591e568..4d64b68dfd 100644
> --- a/doc/guides/rel_notes/release_22_07.rst
> +++ b/doc/guides/rel_notes/release_22_07.rst
> @@ -76,7 +76,8 @@ New Features
>    * Debug build of ``app/test/dpdk-test`` fails currently on RISC-V due to
>      seemingly invalid loop and goto jump code generation by GCC in
>      ``test_ring.c`` where extensive inlining increases the code size beyond the
> -    capability of the generated instruction (JAL: +/-1MB PC-relative).
> +    capability of the generated instruction (JAL: +/-1MB PC-relative). The
> +    workaround is to disable ``test_ring_basic_ex()`` and
> ``test_ring_with_exact_size()`` on RISC-V on ``-O0`` or ``-Og``.
> 
>  * **Updated Intel iavf driver.**
> 
> --
> 2.30.2