[Mesa-dev] [PATCH] radv: do not lower UBO/SSBO access to offsets

[Jason Ekstrand]

On Thu, Mar 28, 2019 at 9:29 AM Jason Ekstrand <jason at jlekstrand.net> wrote:

> I did some benchmarking of Assassin's Creed Odyssey today on ANV.
> Disabling the SSBO optimization possibilities in ANV that moving to derefs
> unlocks (I just moved the lowering super-early; moving back to index/offset
> would be insane) drops the perf of ACO by 20%.  You want SSBO derefs. :D
>

Or not.... Aparently the benchmark numbers aren't as reproducible as one
would like.  In any case, if you put the lowering after optimization, you
should see a more noticable (and positive) vkpipeline-db result.

--Jason


> On Thu, Mar 28, 2019 at 9:08 AM Jason Ekstrand <jason at jlekstrand.net>
> wrote:
>
>> On Wed, Mar 27, 2019 at 4:13 AM Samuel Pitoiset <
>> samuel.pitoiset at gmail.com> wrote:
>>
>>> This helps few compute shaders, mostly for F12017.
>>>
>>> 27670 shaders in 14347 tests
>>> Totals:
>>> SGPRS: 1231173 -> 1231173 (0.00 %)
>>> VGPRS: 866056 -> 865928 (-0.01 %)
>>> Spilled SGPRs: 24201 -> 24201 (0.00 %)
>>> Code Size: 46137040 -> 46144868 (0.02 %) bytes
>>> Max Waves: 232287 -> 232302 (0.01 %)
>>>
>>> Totals from affected shaders:
>>> SGPRS: 24624 -> 24624 (0.00 %)
>>> VGPRS: 25960 -> 25832 (-0.49 %)
>>> Spilled SGPRs: 0 -> 0 (0.00 %)
>>> Code Size: 2922632 -> 2930460 (0.27 %) bytes
>>> Max Waves: 1216 -> 1231 (1.23 %)
>>>
>>> Suggested-by: <Jason Ekstrand jason at jlekstrand.net>
>>> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
>>> ---
>>>  src/amd/common/ac_nir_to_llvm.c | 8 ++++++++
>>>  src/amd/vulkan/radv_shader.c    | 5 ++++-
>>>  2 files changed, 12 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/src/amd/common/ac_nir_to_llvm.c
>>> b/src/amd/common/ac_nir_to_llvm.c
>>> index b25cc6a0a84..c46d98e6dd9 100644
>>> --- a/src/amd/common/ac_nir_to_llvm.c
>>> +++ b/src/amd/common/ac_nir_to_llvm.c
>>> @@ -3275,6 +3275,14 @@ static void visit_intrinsic(struct ac_nir_context
>>> *ctx,
>>>         case nir_intrinsic_vulkan_resource_reindex:
>>>                 result = visit_vulkan_resource_reindex(ctx, instr);
>>>                 break;
>>> +       case nir_intrinsic_load_vulkan_descriptor: {
>>> +               LLVMValueRef values[2] = {
>>> +                       get_src(ctx, instr->src[0]),
>>> +                       ctx->ac.i32_0,
>>> +               };
>>> +               result = ac_build_gather_values(&ctx->ac, values, 2);
>>> +               break;
>>> +       }
>>>         case nir_intrinsic_store_ssbo:
>>>                 visit_store_ssbo(ctx, instr);
>>>                 break;
>>> diff --git a/src/amd/vulkan/radv_shader.c b/src/amd/vulkan/radv_shader.c
>>> index 19a807df199..2751302e8b9 100644
>>> --- a/src/amd/vulkan/radv_shader.c
>>> +++ b/src/amd/vulkan/radv_shader.c
>>> @@ -220,7 +220,6 @@ radv_shader_compile_to_nir(struct radv_device
>>> *device,
>>>                         }
>>>                 }
>>>                 const struct spirv_to_nir_options spirv_options = {
>>> -                       .lower_ubo_ssbo_access_to_offsets = true,
>>>                         .caps = {
>>>                                 .descriptor_array_dynamic_indexing =
>>> true,
>>>                                 .device_group = true,
>>> @@ -306,6 +305,10 @@ radv_shader_compile_to_nir(struct radv_device
>>> *device,
>>>                 NIR_PASS_V(nir, nir_lower_system_values);
>>>                 NIR_PASS_V(nir, nir_lower_clip_cull_distance_arrays);
>>>                 NIR_PASS_V(nir, nir_lower_frexp);
>>> +
>>> +               NIR_PASS_V(nir, nir_lower_explicit_io,
>>> +                         nir_var_mem_ubo | nir_var_mem_ssbo,
>>> +                         nir_address_format_32bit_index_offset);
>>>
>>
>> If you actually want to get SSBO access optimization, you need to call
>> this *after* your first call to your main optimization loop.  Otherwise,
>> the change is basically just a no-op which just shuffles around the way
>> address calculations are done a bit.
>>
>> --Jason
>>
>>
>>>         }
>>>
>>>         /* Vulkan uses the separate-shader linking model */
>>> --
>>> 2.21.0
>>>
>>> _______________________________________________
>>> mesa-dev mailing list
>>> mesa-dev at lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/mesa-dev
>>
>>
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