Implement SV_VulkanSamplePosition (#8236)

-Adds semantic SV_VulkanSamplePosition that emits corresponding
gl_SamplePosition and SpvBuiltinSamplePosition
-Adds gl_SamplePosition property to glsl.meta.slang
-Adds SPIRV and GLSL tests for the semantic and property
-Plan is to later implement SV_SamplePosition that follows HLSL range of
-0.5 to +0.5,
and emits GetRenderTargetSamplePosition(SV_SampleIndex) which needs more
complicated IR manipulation for HLSL and Metal

Fixes #7906

---------

Co-authored-by: ArielG-NV <159081215+ArielG-NV@users.noreply.github.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/tests/spirv/sv-vulkan-sample-position.slang b/tests/spirv/sv-vulkan-sample-position.slang
new file mode 100644
index 000000000..853ae03ac
--- /dev/null
+++ b/tests/spirv/sv-vulkan-sample-position.slang
@@ -0,0 +1,21 @@
+//TEST:SIMPLE(filecheck=CHECK-SPIRV): -target spirv -stage fragment -entry main
+//TEST:SIMPLE(filecheck=CHECK-GLSL): -target glsl -stage fragment -entry main
+
+// Test for SV_VulkanSamplePosition support
+
+// CHECK-SPIRV: OpCapability SampleRateShading
+// CHECK-SPIRV-DAG: OpDecorate {{.*}} BuiltIn SamplePosition
+// CHECK-GLSL-DAG: gl_SamplePosition
+
+import glsl;
+
+struct FragmentInput
+{
+    float2 samplePosition : SV_VulkanSamplePosition;
+}
+
+[shader("fragment")]
+float4 main(FragmentInput input) : SV_Target
+{
+    return float4(input.samplePosition.x, gl_SamplePosition.y, 0.0, 1.0);
+}
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