Support `IDifferentiablePtrType` (#5031)

* initial diff-ref-type interface

* Initial support for `IDifferentiablePtrType`

* Fix unused vars

* More tests + fix switch case fallthrough.

* Update slang-ir-autodiff.cpp

* Update diff-ptr-type-loop.slang

* Add optimization to allow more complex pair types

* Update slang-ir-autodiff-primal-hoist.cpp

* Update diff-ptr-type-loop.slang

* Update slang-ir-autodiff-primal-hoist.cpp

* More fixes to address reviews

* Update slang-check-expr.cpp

* Optimizations + rename `differentiableRefInterfaceType` -> `differentiablePtrInterfaceType`

* Move pair logic to ir-builder, unify the type dictionaries.

---------

Co-authored-by: Yong He <yonghe@outlook.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/source/slang/slang-check-conformance.cpp b/source/slang/slang-check-conformance.cpp
index ffa037996..9d9047e41 100644
--- a/source/slang/slang-check-conformance.cpp
+++ b/source/slang/slang-check-conformance.cpp
@@ -274,9 +274,14 @@ namespace Slang
         return isInterfaceType(type);
     }
 
-    bool SemanticsVisitor::isTypeDifferentiable(Type* type)
+    SubtypeWitness* SemanticsVisitor::isTypeDifferentiable(Type* type)
     {
-        return isSubtype(type, m_astBuilder->getDiffInterfaceType(), IsSubTypeOptions::None);
+        if (auto valueWitness = isSubtype(type, m_astBuilder->getDiffInterfaceType(), IsSubTypeOptions::None))
+            return valueWitness;
+        else if (auto ptrWitness = isSubtype(type, m_astBuilder->getDifferentiableRefInterfaceType(), IsSubTypeOptions::None))
+            return ptrWitness;
+        
+        return nullptr;
     }
 
     bool SemanticsVisitor::doesTypeHaveTag(Type* type, TypeTag tag)