Reuse higher-order `ResolveInvoke` logic to resolve func refs in `[*DerivativeOf]` attribs. (#2688)

* Reuse higher-order `ResolveInvoke` logic to resolve func refs in [*DerivativeOf] attribs.

* Add diff implementation matrix versions of binary and ternary intrinsics.

* Add diff impl for legacy intrinsics.

* Fix diagnostics of using non-differentiable function in a diff operator.

* Add diff implementation for `determinant`.

---------

Co-authored-by: Yong He <yhe@nvidia.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/source/slang/slang-ast-support-types.cpp b/source/slang/slang-ast-support-types.cpp
index aa0513569..3feed7541 100644
--- a/source/slang/slang-ast-support-types.cpp
+++ b/source/slang/slang-ast-support-types.cpp
@@ -36,11 +36,16 @@ void removeModifier(ModifiableSyntaxNode* syntax, Modifier* toRemove)
     }
 }
 
-Expr* getInnerMostExprFromHigherOrderExpr(Expr* expr)
+Expr* getInnerMostExprFromHigherOrderExpr(Expr* expr, FunctionDifferentiableLevel& outLevel)
 {
     HashSet<Expr*> workListSet;
+    outLevel = FunctionDifferentiableLevel::None;
     while (auto higherOrder = as<HigherOrderInvokeExpr>(expr))
     {
+        if (as<BackwardDifferentiateExpr>(expr))
+            outLevel = FunctionDifferentiableLevel::Backward;
+        else if (as<ForwardDifferentiateExpr>(expr) && outLevel == FunctionDifferentiableLevel::None)
+            outLevel = FunctionDifferentiableLevel::Forward;
         if (workListSet.Add(higherOrder))
         {
             expr = higherOrder->baseFunction;