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, 21 insertions, 0 deletions

diff --git a/source/slang/slang-type-layout.cpp b/source/slang/slang-type-layout.cpp
index 22aa3f304..293dce7c6 100644
--- a/source/slang/slang-type-layout.cpp
+++ b/source/slang/slang-type-layout.cpp
@@ -722,6 +722,9 @@ static LayoutResourceKind _getHLSLLayoutResourceKind(ShaderParameterKind kind)
 {
     switch (kind)
     {
+        case ShaderParameterKind::SubpassInput:
+            return LayoutResourceKind::InputAttachmentIndex;
+
         case ShaderParameterKind::ConstantBuffer:
             return LayoutResourceKind::ConstantBuffer;
 
@@ -778,6 +781,13 @@ struct GLSLObjectLayoutRulesImpl : ObjectLayoutRulesImpl
             }
         }
 
+        switch (kind)
+        {
+        case ShaderParameterKind::SubpassInput:
+            return SimpleLayoutInfo(LayoutResourceKind::InputAttachmentIndex, slotCount);
+        default:
+            break;
+        }
         return SimpleLayoutInfo(LayoutResourceKind::DescriptorTableSlot, slotCount);
     }
 };
@@ -4089,6 +4099,17 @@ static TypeLayoutResult _createTypeLayout(
             type,
             rules);
     }
+    else if (as<SubpassInputType>(type))
+    {
+        // SubpassInputType fills 2 slots, 'shader resource' and 'input_attachment_index'
+        auto objLayout1 = rules->GetObjectLayout(ShaderParameterKind::Texture, context.objectLayoutOptions);
+        auto objLayout2 = rules->GetObjectLayout(ShaderParameterKind::SubpassInput, context.objectLayoutOptions);
+        objLayout1.layoutInfos.add(objLayout2.layoutInfos.getFirst());
+        return createSimpleTypeLayout(
+            objLayout1,
+            type,
+            rules);
+    }
     else if (auto textureType = as<TextureType>(type))
     {
         // TODO: the logic here should really be defined by the rules,