Implement HLSL resource bindings and default type `float4` to `SubpassInput<T>` (#4462)

* Add case to `emitVectorReshape` for `vector<>` type, `scalar` value

1. Add new case
2. Add test

* fix warning

* fix warning

* Implement HLSL resource bindings and default type `float4` to `SubpassInput<T>`

fixes: #4440

1. Removed GLSLInputAttachmentIndexLayout modifier and the somewhat 'hacky' binding model 'Input Attachment' previously relied upon. This was changed to work with the slang-type-layout rules system. This change allows Slang automatic bindings, HLSL bindings, GLSL bindings, and translation of GLSL to and from HLSL bindings to work.
2. Added default argument `float4` to SubpassInput<T>.
3. Merged glsl.meta and hlsl.meta SubpassInput logic.

* fix InputAttachment attribute checks

fix InputAttachment attribute checks for HLSL and GLSL syntax

* remove unused var

* validate attribute correctly

Attributes do not have type information. We must check the type expression to validate attribute usage.

* remove hacky validation

type based validation before types are fully resolved is quite hacky and unstable to changes and wrapped types

* fix warning

* remove redundant `!= nullptr`

* remove extra `!= nullptr`

* fix some warnings/errors

* subpass capability to limit to dxc & remove default values in some functions

* revert logic to previous logic

revert logic to return if we have a binding regardless of if a VarDecl is given the binding

1 files changed, 6 insertions, 11 deletions

diff --git a/source/slang/slang-emit-glsl.cpp b/source/slang/slang-emit-glsl.cpp
index b6c3c0d67..7cf478c36 100644
--- a/source/slang/slang-emit-glsl.cpp
+++ b/source/slang/slang-emit-glsl.cpp
@@ -751,6 +751,11 @@ bool GLSLSourceEmitter::_emitGLSLLayoutQualifierWithBindingKinds(LayoutResourceK
             m_writer->emit("layout(shaderRecordEXT)\n");
             break;
 
+        case LayoutResourceKind::InputAttachmentIndex:
+            m_writer->emit("layout(input_attachment_index = ");
+            m_writer->emit(index);
+            m_writer->emit(")\n");
+            break;
     }
     return true;
 }
@@ -1338,7 +1343,7 @@ void GLSLSourceEmitter::_emitGLSLPerVertexVaryingFragmentInput(IRGlobalParam* pa
 
     emitSemantics(param, false);
 
-    emitLayoutSemantics(param);
+    emitLayoutSemantics(param, "register");
 
     m_writer->emit(";\n\n");
 }
@@ -2825,16 +2830,6 @@ void GLSLSourceEmitter::emitVarDecorationsImpl(IRInst* varDecl)
         break;
     }
 
-    // non raytracing decorations
-    for (auto decoration : varDecl->getDecorations())
-    {        
-        if (auto glslInputAttachment = as<IRGLSLInputAttachmentIndexDecoration>(decoration))
-        {
-            m_writer->emit(toSlice("layout(input_attachment_index = "));
-            m_writer->emit(glslInputAttachment->getIndex()->getValue());
-            m_writer->emit(toSlice(")\n"));
-        }
-    }
 }
 
 void GLSLSourceEmitter::emitMatrixLayoutModifiersImpl(IRVarLayout* layout)