Add GLSL/SPIR-V support got GetAttributeAtVertex (#1733)

This change allows varying fragment shader inputs to be declared in a way that allows the `GetAttributeAtVertex` operation to compile to valid code for both D3D and GLSL/SPIR-V/Vulkan.

The key is that rather than just use ordinary `nointerpolation`-qualified inputs the code must declare these varying inputs with a new `pervertex` qualifier that marks them as *only* being usable with `GetAttributeAtVertex`. The `pervertex`-tagged inputs then translate to GLSL inputs using the `pervertexNV` qualifier

Note that this change does *not* include any enforcement of the requirements around how these qualifiers are used (and the compiler doesn't have enforcement for the existing operations like `EvaluateAttributeAtCentroid`). The underlying problem is that the inerpolation-mode qualifiers and explicit interpolation functions in HLSL constitute a kind of rate-qualified type system, but without any systematic rules. It seems wasteful to encode a bunch of ad hoc rules for this stuff as special cases in the compiler when the clear right answer is to implement a systematic approach to rates.

1 files changed, 11 insertions, 0 deletions

diff --git a/source/slang/slang-emit-c-like.cpp b/source/slang/slang-emit-c-like.cpp
index 522e5ef12..a0fa71fee 100644
--- a/source/slang/slang-emit-c-like.cpp
+++ b/source/slang/slang-emit-c-like.cpp
@@ -158,6 +158,17 @@ void CLikeSourceEmitter::emitDeclarator(DeclaratorInfo* declarator)
         }
         break;
 
+    case DeclaratorInfo::Flavor::LiteralSizedArray:
+        {
+            auto arrayDeclarator = (LiteralSizedArrayDeclaratorInfo*)declarator;
+            emitDeclarator(arrayDeclarator->next);
+            m_writer->emit("[");
+            m_writer->emit(arrayDeclarator->elementCount);
+            m_writer->emit("]");
+        }
+        break;
+
+
     default:
         SLANG_DIAGNOSE_UNEXPECTED(getSink(), SourceLoc(), "unknown declarator flavor");
         break;