[PATCH 0/2] MR784: tests: Check that derivatives are still computed after discarding.

[Giovanni Mascellani (＠giomasce)]

A couple of follow-ups to !774.

[PATCH 1/2] tests: Avoid using a different UAV for SM<6 and SM>=6.

[Giovanni Mascellani]

From: Giovanni Mascellani

---
 tests/hlsl/discard.shader_test | 20 +++++---------------
 1 file changed, 5 insertions(+), 15 deletions(-)

diff --git a/tests/hlsl/discard.shader_test b/tests/hlsl/discard.shader_test
index cf53bf482..69272b587 100644
--- a/tests/hlsl/discard.shader_test
+++ b/tests/hlsl/discard.shader_test
@@ -19,12 +19,6 @@ probe all rgba (1, 2, 3, 4)
 [require]
 shader model >= 5.0

-[uav 0]
-format r32 float
-size (2d, 2, 1)
-
-0.0 0.0
-
 [uav 1]
 format r32 float
 size (2d, 2, 1)
@@ -34,7 +28,7 @@ size (2d, 2, 1)
 % Check that side effects stop happening after discard
 [pixel shader]
 uniform float4 x;
-RWTexture2D<float> y;
+RWTexture2D<float> y : register(u1);

float4 main(float4 pos : sv_position) : sv_target
 {
@@ -51,14 +45,10 @@ float4 main(float4 pos : sv_position) : sv_target
 uniform 0 float4 1 2 3 4
 todo(glsl) draw quad
 probe all rgba (1, 2, 3, 4)
-if(sm<6) probe uav 1 (0, 0) r (1.0)
-if(sm<6) probe uav 1 (1, 0) r (1.0)
-if(sm>=6) probe uav 0 (0, 0) r (1.0)
-if(sm>=6) probe uav 0 (1, 0) r (1.0)
+probe uav 1 (0, 0) r (1.0)
+probe uav 1 (1, 0) r (1.0)
 uniform 0 float4 9 8 7 6
 todo(glsl) draw quad
 probe all rgba (1, 2, 3, 4)
-if(sm<6) probe uav 1 (0, 0) r (2.0)
-if(sm<6) probe uav 1 (1, 0) r (1.0)
-if(sm>=6) probe uav 0 (0, 0) r (2.0)
-if(sm>=6) probe uav 0 (1, 0) r (1.0)
+probe uav 1 (0, 0) r (2.0)
+probe uav 1 (1, 0) r (1.0)

[PATCH 2/2] tests: Check that derivatives are still computed after discarding.

[Giovanni Mascellani]

From: Giovanni Mascellani

---
 tests/hlsl/discard.shader_test | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/tests/hlsl/discard.shader_test b/tests/hlsl/discard.shader_test
index 69272b587..152a3a0d3 100644
--- a/tests/hlsl/discard.shader_test
+++ b/tests/hlsl/discard.shader_test
@@ -16,6 +16,30 @@ uniform 0 float4 9 8 7 6
 todo(sm<4 | glsl) draw quad
 probe all rgba (1, 2, 3, 4)

+[require]
+shader model >= 3.0
+
+% Check that derivatives are still computed after discarding
+% other pixels in the same quad
+[pixel shader todo(sm<4)]
+float4 main(float4 pos : sv_position) : sv_target
+{
+    if (frac((floor(pos.x) + floor(pos.y)) / 2) == 0.5)
+        discard;
+    return float4(ddx(pos.x), ddx(pos.y), ddy(pos.x), ddy(pos.y));
+}
+
+[test]
+todo(sm<4 | glsl) draw quad
+probe (0, 0) rgba (1, 0, 0, 1)
+probe (1, 0) rgba (1, 2, 3, 4)
+probe (0, 1) rgba (1, 2, 3, 4)
+probe (1, 1) rgba (1, 0, 0, 1)
+probe (2, 0) rgba (1, 0, 0, 1)
+probe (3, 0) rgba (1, 2, 3, 4)
+probe (2, 1) rgba (1, 2, 3, 4)
+probe (3, 1) rgba (1, 0, 0, 1)
+
 [require]
 shader model >= 5.0

[PATCH 0/2] MR784: tests: Check that derivatives are still computed after discarding. - approved

[Giovanni Mascellani (＠giomasce)]

This merge request was approved by Giovanni Mascellani.

[Henri Verbeet (＠hverbeet)]

Is the test working as intended? I would have expected this to require enabling the VK_EXT_shader_demote_to_helper_invocation for the Vulkan runner, as well as passing VKD3D_SHADER_SPIRV_EXTENSION_EXT_DEMOTE_TO_HELPER_INVOCATION in the SPIR-V target info for vkd3d_shader_compile().

[Giovanni Mascellani (＠giomasce)]

On Mon Apr 15 14:01:04 2024 +0000, Henri Verbeet wrote:
> Is the test working as intended? I would have expected this to require
> enabling the VK_EXT_shader_demote_to_helper_invocation for the Vulkan
> runner, as well as passing
> VKD3D_SHADER_SPIRV_EXTENSION_EXT_DEMOTE_TO_HELPER_INVOCATION in the
> SPIR-V target info for vkd3d_shader_compile().

I can see that the generates shaders have `OpKill` or `OpDemoteToHelperInvocationEXT` depending on whether they're on the Vulkan or D3D12 runner, but in practice the effect seems to be the same on all the drivers I tested. It doesn't look like that the SPIR-V specs tells a lot about what is ought to happen when derivatives are computer after `OpKill`, so I assume it's unspecified and drivers treat that as `OpDemoteToHelperInvocationEXT` anyway.

[Henri Verbeet (＠hverbeet)]

> I can see that the generates shaders have `OpKill` or `OpDemoteToHelperInvocationEXT` depending on whether they're on the Vulkan or D3D12 runner, but in practice the effect seems to be the same on all the drivers I tested. It doesn't look like that the SPIR-V specs tells a lot about what is ought to happen when derivatives are computer after `OpKill`, so I assume it's unspecified and drivers treat that as `OpDemoteToHelperInvocationEXT` anyway.

I suppose, which is perhaps unfortunate. We should probably enable the extension in any case for the Vulkan runner to get defined behaviour though.