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, 10 insertions, 11 deletions

diff --git a/source/slang/slang-emit-spirv.cpp b/source/slang/slang-emit-spirv.cpp
index 51a71d65c..1a4d80ae1 100644
--- a/source/slang/slang-emit-spirv.cpp
+++ b/source/slang/slang-emit-spirv.cpp
@@ -2230,6 +2230,16 @@ struct SPIRVEmitContext
                     isDescirptorSetDecorated = true;
                 }
                 break;
+            case LayoutResourceKind::InputAttachmentIndex:
+                {
+                    emitOpDecorateInputAttachmentIndex(
+                        getSection(SpvLogicalSectionID::Annotations),
+                        nullptr,
+                        varInst,
+                        SpvLiteralInteger::from32((int32_t)index)
+                    );
+                }
+                break;
             default:
                 break;
             }
@@ -3576,17 +3586,6 @@ struct SPIRVEmitContext
                 );
             }
             break;
-        case kIROp_GLSLInputAttachmentIndexDecoration:
-            {
-                const auto c = cast<IRGLSLInputAttachmentIndexDecoration>(decoration);
-                emitOpDecorateInputAttachmentIndex(
-                    getSection(SpvLogicalSectionID::Annotations),
-                    decoration,
-                    dstID,
-                    SpvLiteralInteger::from32(int32_t(c->getIndex()->getValue()))
-                );
-            }
-            break;
 
         case kIROp_VulkanHitAttributesDecoration:
         case kIROp_VulkanCallablePayloadDecoration: