Implement 8.14-8.19 of OpenGL-GLSL specification

The following PR implements 8.14-8.19 of the [OpenGL-GLSL specification](https://registry.khronos.org/OpenGL/specs/gl/GLSLangSpec.4.60.pdf).

Fully implements all functions and built-in type's, resolves https://github.com/shader-slang/slang/issues/3692 for GLSL & SPRI-V targets.

_Notes:_
Testing Tools:
* Fragment shaders cannot test computational results. Only OpCodes are checked for proper emitting.

Implementation Notes:
* SubpassInput requires an unknown image format.
* SubpassInput is disjoint from TextureType: __SubpassImpl (.slang) & SubpassInputType (Compiler) to reduce code generation required.
* SubpassInput required an additional input layout modifier, input_attachment_index, this was added as a new parameter binding attribute. Since the following qualifiers can overlap with different resources (`layout(input_attachment_index = 0, binding = 0, set = 0)`) input_attachment_index is checked for overlapping resource bindings separately from other qualifiers with `LayoutResourceKind::InputAttachmentIndex`.
* `GLSLInputAttachmentIndexLayoutModifier` was added to enforce function parameters only accepting `in` decorated variables.
* `in` decorated variables needed to have emitting modified to allow directly emitting the variable into function calls if used as a parameter, normally Slang has a "global variable" shadow as a "global parameter" through a copy. This does not work and is solved using `GlobalVariableShadowingGlobalParameterDecoration` to build a relationship of "global variable" to "global parameter", we then resolve this relationship and replace "global variable" uses later in compile.
* `AtomicCounterMemory` memory-constraint requires `OpCapability AtomicStorage`, `AtomicStorage` is invalid for Vulkan targets. glslang outputs for `barrier`, `memoryBarrier`, and `groupMemoryBarrier` `AtomicCounterMemory` as a memory constraint. This compiles as valid SPIR-V for Vulkan since `OpCapability AtomicStorage` is not declared. This behavior of glslang is undefined as per [3.31.Capability of the SPIR-V specification](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#_capability). We will omit `AtomicCounterMemory` from our barrier calls.

1 files changed, 27 insertions, 0 deletions

diff --git a/source/slang/slang-lower-to-ir.cpp b/source/slang/slang-lower-to-ir.cpp
index 1e324b4a4..2d9ecf574 100644
--- a/source/slang/slang-lower-to-ir.cpp
+++ b/source/slang/slang-lower-to-ir.cpp
@@ -2204,6 +2204,16 @@ void addVarDecorations(
             builder->addDecoration(inst, kIROp_GLSLLocationDecoration,
                 builder->getIntValue(builder->getIntType(), stringToInt(glslLocationMod->valToken.getContent())));
         }
+        else if (auto glslInputAttachmentMod = as<GLSLInputAttachmentIndexLayoutModifier>(mod))
+        {
+            auto subpassType = as<IRSubpassInputType>(inst->getDataType());
+
+            if (!subpassType)
+                context->getSink()->diagnose(inst, Diagnostics::InputAttachmentIndexOnlyAllowedOnSubpass);
+
+            builder->addDecoration(inst, kIROp_GLSLInputAttachmentIndexDecoration,
+                builder->getIntValue(builder->getIntType(), stringToInt(glslInputAttachmentMod->valToken.getContent())));
+        }
         else if (auto glslOffsetMod = as<GLSLOffsetLayoutAttribute>(mod))
         {
             builder->addDecoration(inst, kIROp_GLSLOffsetDecoration,
@@ -3546,6 +3556,21 @@ struct ExprLoweringContext
         // TODO: also need to handle this-type substitution here?
     }
 
+    void validateInvokeExprArgsWithFunctionModifiers(
+        InvokeExpr* expr,
+        FunctionDeclBase* decl,
+        List<IRInst*>& irArgs)
+    {
+        if (auto glslRequireShaderInputParameter = decl->findModifier<GLSLRequireShaderInputParameterAttribute>())
+        {
+            if (!irArgs[glslRequireShaderInputParameter->parameterNumber]->findDecoration<IRGlobalInputDecoration>())
+            {
+                this->context->getSink()->diagnose(expr, Diagnostics::requireInputDecoratedVarForParameter, decl, glslRequireShaderInputParameter->parameterNumber);
+            }
+            return;
+        }
+    }
+
     /// Lower an invoke expr, and attempt to fuse a store of the expr's result into destination.
     /// If the store is fused, returns LoweredValInfo::None. Otherwise, returns the IR val representing the RValue.
     LoweredValInfo visitInvokeExprImpl(InvokeExpr* expr, LoweredValInfo destination, const TryClauseEnvironment& tryEnv)
@@ -3663,6 +3688,8 @@ struct ExprLoweringContext
             auto funcType = funcTypeInfo.type;
             addDirectCallArgs(expr, funcDeclRef, &irArgs, &argFixups);
 
+            validateInvokeExprArgsWithFunctionModifiers(expr, as<FunctionDeclBase>(funcDeclRef.getDecl()), irArgs);
+
             LoweredValInfo result;
             if (funcTypeInfo.returnViaLastRefParam)
             {