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, 5 insertions, 0 deletions

diff --git a/source/slang/slang-emit-spirv.cpp b/source/slang/slang-emit-spirv.cpp
index aa4c3bec8..6b42896d0 100644
--- a/source/slang/slang-emit-spirv.cpp
+++ b/source/slang/slang-emit-spirv.cpp
@@ -6182,6 +6182,11 @@ struct SPIRVEmitContext : public SourceEmitterBase, public SPIRVEmitSharedContex
                     requireSPIRVCapability(SpvCapabilitySampleRateShading);
                     return getBuiltinGlobalVar(inst->getFullType(), SpvBuiltInSampleId, inst);
                 }
+                else if (semanticName == "sv_vulkansampleposition")
+                {
+                    requireSPIRVCapability(SpvCapabilitySampleRateShading);
+                    return getBuiltinGlobalVar(inst->getFullType(), SpvBuiltInSamplePosition, inst);
+                }
                 else if (semanticName == "sv_stencilref")
                 {
                     requireSPIRVCapability(SpvCapabilityStencilExportEXT);