On Fri, Feb 23, 2018 at 1:40 AM, Iago Toral <ito...@igalia.com> wrote:
> On Thu, 2018-02-22 at 11:22 -0800, Gustavo Lima Chaves wrote:
> > v2:
> > An attempt to support SpvExecutionModeStencilRefReplacingEXT's
> > behavior
> > also follows, with the interpretation to said mode being we prevent
> > writes to the built-in FragStencilRefEXT variable when the execution
> > mode isn't set.
> >
> > v3:
> > A more cautious reading of 1db44252d01bf7539452ccc2b5210c74b8dcd573
> > led
> > me to a missing change that would stop (what I later discovered were)
> > GPU hangs on the CTS test written to exercize this.
> > ---
> > src/compiler/shader_info.h | 2 ++
> > src/compiler/spirv/spirv_to_nir.c | 4 ++++
> > src/compiler/spirv/vtn_variables.c | 4 ++++
> > src/intel/vulkan/anv_extensions.py | 2 ++
> > src/intel/vulkan/anv_pipeline.c | 1 +
> > src/intel/vulkan/genX_pipeline.c | 1 +
> > 6 files changed, 14 insertions(+)
> >
> > diff --git a/src/compiler/shader_info.h b/src/compiler/shader_info.h
> > index 6de707f672..f99cbc27a7 100644
> > --- a/src/compiler/shader_info.h
> > +++ b/src/compiler/shader_info.h
> > @@ -162,6 +162,8 @@ typedef struct shader_info {
> >
> > bool pixel_center_integer;
> >
> > + bool outputs_stencil;
> > +
> > /** gl_FragDepth layout for ARB_conservative_depth. */
> > enum gl_frag_depth_layout depth_layout;
> > } fs;
> > diff --git a/src/compiler/spirv/spirv_to_nir.c
> > b/src/compiler/spirv/spirv_to_nir.c
> > index e00dcafa12..dcb8b31967 100644
> > --- a/src/compiler/spirv/spirv_to_nir.c
> > +++ b/src/compiler/spirv/spirv_to_nir.c
> > @@ -3395,6 +3395,10 @@ vtn_handle_execution_mode(struct vtn_builder
> > *b, struct vtn_value *entry_point,
> > case SpvExecutionModeContractionOff:
> > break; /* OpenCL */
> >
> > + case SpvExecutionModeStencilRefReplacingEXT:
> > + b->shader->info.fs.outputs_stencil = true;
> > + break;
> > +
> > default:
> > vtn_fail("Unhandled execution mode");
> > }
> > diff --git a/src/compiler/spirv/vtn_variables.c
> > b/src/compiler/spirv/vtn_variables.c
> > index 36976798e9..42f915d434 100644
> > --- a/src/compiler/spirv/vtn_variables.c
> > +++ b/src/compiler/spirv/vtn_variables.c
> > @@ -1373,6 +1373,10 @@ apply_var_decoration(struct vtn_builder *b,
> > nir_variable *nir_var,
> > case SpvBuiltInFragCoord:
> > nir_var->data.pixel_center_integer = b-
> > >pixel_center_integer;
> > break;
> > + case SpvBuiltInFragStencilRefEXT:
> > + if (!b->shader->info.fs.outputs_stencil)
> > + nir_var->data.read_only = true;
> > + break;
>
> From the SPIR-V spec:
>
> FragStencilRefEXT must only decorate output variable whose type is
> an arbitrary-sized integer type scalar.
>
> If it is an output variable, I don't think we should make it read-only
> in any case.
>
Thanks for doing the spec archeology. I suspected that was the case.
> More over, from ARB_shader_stencil_export (which is the base GL
> extension this is trying to replicate):
>
> "1) Should gl_FragStencilRefARB be initialized to the current stencil
> reference value on input to the fragment shader?
>
> RESOLVED: No. gl_FragStencilRefARB is write-only. If the current
> stencil reference value is required in a shader, the application should
> place it in a uniform."
>
> In other words, this is an output-only variable and it is not expected
> to be read. If we see a SpvBuiltInFragStencilRefEXT decoration then my
> understanding is that we should also have
> SpvExecutionModeStencilRefReplacingEXT, so if we didn't have that I
> think we have incorrect SPIR-V, and in that case, instead of marking
> the variable as read-only, we should maybe just drop a warning instead.
>
Thanks for checking. I've filed an issue against the Vulkan spec for this:
https://gitlab.khronos.org/vulkan/vulkan/issues/1173
For now, let's proceed under the assumption that the Vulkan extension
follows the GL extension and does not require gl_FragStencilRefARB to be
initialized with the API stencil reference value.
--Jason
> > default:
> > break;
> > }
> > diff --git a/src/intel/vulkan/anv_extensions.py
> > b/src/intel/vulkan/anv_extensions.py
> > index 581921e62a..cd90c6ae52 100644
> > --- a/src/intel/vulkan/anv_extensions.py
> > +++ b/src/intel/vulkan/anv_extensions.py
> > @@ -86,6 +86,8 @@ EXTENSIONS = [
> > Extension('VK_KHX_multiview', 1, True),
> > Extension('VK_EXT_debug_report', 8, True),
> > Extension('VK_EXT_external_memory_dma_buf', 1, True),
> > + Extension('VK_EXT_shader_stencil_export', 1,
> > + 'device->info.gen >= 9'),
> > ]
> >
> > class VkVersion:
> > diff --git a/src/intel/vulkan/anv_pipeline.c
> > b/src/intel/vulkan/anv_pipeline.c
> > index e16a7a1994..ed63fa42cd 100644
> > --- a/src/intel/vulkan/anv_pipeline.c
> > +++ b/src/intel/vulkan/anv_pipeline.c
> > @@ -143,6 +143,7 @@ anv_shader_compile_to_nir(struct anv_pipeline
> > *pipeline,
> > .multiview = true,
> > .variable_pointers = true,
> > .storage_16bit = device->instance->physicalDevice.info.gen
> > >= 8,
> > + .stencil_export = device->instance->physicalDevice.info.gen
> > >= 9,
> > },
> > };
> >
> > diff --git a/src/intel/vulkan/genX_pipeline.c
> > b/src/intel/vulkan/genX_pipeline.c
> > index 89cbe293b8..683a4607e6 100644
> > --- a/src/intel/vulkan/genX_pipeline.c
> > +++ b/src/intel/vulkan/genX_pipeline.c
> > @@ -1600,6 +1600,7 @@ emit_3dstate_ps_extra(struct anv_pipeline
> > *pipeline,
> > ps.PixelShaderHasUAV = true;
> >
> > #if GEN_GEN >= 9
> > + ps.PixelShaderComputesStencil = wm_prog_data-
> > >computed_stencil;
> > ps.PixelShaderPullsBary = wm_prog_data->pulls_bary;
> > ps.InputCoverageMaskState = wm_prog_data->uses_sample_mask ?
> > ICMS_INNER_CONSERVATIVE :
> > ICMS_NONE;
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