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, 3 insertions, 2 deletions

diff --git a/source/slang/slang-parameter-binding.cpp b/source/slang/slang-parameter-binding.cpp
index 89e633857..4b91056fc 100644
--- a/source/slang/slang-parameter-binding.cpp
+++ b/source/slang/slang-parameter-binding.cpp
@@ -1821,11 +1821,12 @@ static RefPtr<TypeLayout> processSimpleEntryPointParameter(
             // We need to compute whether an entry point consumes
             // any sample-rate inputs, and along with explicitly
             // `sample`-qualified parameters, we also need to
-            // detect use of `SV_SampleIndex` as an input.
+            // detect use of `SV_SampleIndex` and
+            // `SV_VulkanSamplePosition` as an input.
             //
             if (state.directionMask & kEntryPointParameterDirection_Input)
             {
-                if (sn == "sv_sampleindex")
+                if (sn == "sv_sampleindex" || sn == "sv_vulkansampleposition")
                 {
                     state.isSampleRate = true;
                 }