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, 1 deletions

diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index deb8c55eb..8e78ff084 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -10204,7 +10204,8 @@ namespace Slang
             bool isDiffParam = (!param->findModifier<NoDiffModifier>());
             if (isDiffParam)
             {
-                if (auto pairType = as<DifferentialPairType>(visitor->getDifferentialPairType(param->getType())))
+                auto diffPair = visitor->getDifferentialPairType(param->getType());
+                if (auto pairType = as<DifferentialPairType>(diffPair))
                 {
                     arg->type.type = pairType;
                     arg->type.isLeftValue = true;
@@ -10225,6 +10226,11 @@ namespace Slang
                         direction = ParameterDirection::kParameterDirection_InOut;
                     }
                 }
+                else if (auto refPairType = as<DifferentialPtrPairType>(diffPair))
+                {
+                    // no need to change direction of ref-pairs.
+                    arg->type.type = refPairType;
+                }
                 else
                 {
                     isDiffParam = false;