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, 10 insertions, 15 deletions

diff --git a/source/slang/slang-check-expr.cpp b/source/slang/slang-check-expr.cpp
index 2803b5959..bebaa63a2 100644
--- a/source/slang/slang-check-expr.cpp
+++ b/source/slang/slang-check-expr.cpp
@@ -1971,31 +1971,26 @@ namespace Slang
 
                 if (auto higherOrderInvoke = as<DifferentiateExpr>(invoke->functionExpr))
                 {
-                    if (auto funcDeclExpr = as<DeclRefExpr>(getInnerMostExprFromHigherOrderExpr(higherOrderInvoke)))
+                    FunctionDifferentiableLevel requiredLevel;
+                    if (auto funcDeclExpr = as<DeclRefExpr>(
+                            getInnerMostExprFromHigherOrderExpr(higherOrderInvoke, requiredLevel)))
                     {
                         auto funcDecl = as<FunctionDeclBase>(funcDeclExpr->declRef.getDecl());
                         if (funcDecl)
                         {
-                            DifferentiateExpr* forwardDiff = nullptr;
-                            DifferentiateExpr* backwardDiff = nullptr;
-                            for (auto node = as<DifferentiateExpr>(invoke->functionExpr); node; node = as<DifferentiateExpr>(node->baseFunction))
+                            if (requiredLevel == FunctionDifferentiableLevel::Forward &&
+                                !getShared()->isDifferentiableFunc(funcDecl))
                             {
-                                if (auto fwd = as<ForwardDifferentiateExpr>(node))
-                                    forwardDiff = fwd;
-                                if (auto bwd = as<BackwardDifferentiateExpr>(node))
-                                    backwardDiff = bwd;
+                                getSink()->diagnose(funcDeclExpr, Diagnostics::functionNotMarkedAsDifferentiable, funcDecl, "forward");
                             }
-                            if (forwardDiff && !getShared()->isDifferentiableFunc(funcDecl))
+                            if (requiredLevel == FunctionDifferentiableLevel::Backward &&
+                                !getShared()->isBackwardDifferentiableFunc(funcDecl))
                             {
-                                getSink()->diagnose(forwardDiff, Diagnostics::functionNotMarkedAsDifferentiable, funcDecl, "forward");
-                            }
-                            if (backwardDiff && !getShared()->isBackwardDifferentiableFunc(funcDecl))
-                            {
-                                getSink()->diagnose(forwardDiff, Diagnostics::functionNotMarkedAsDifferentiable, funcDecl, "backward");
+                                getSink()->diagnose(funcDeclExpr, Diagnostics::functionNotMarkedAsDifferentiable, funcDecl, "backward");
                             }
                             if (!isEffectivelyStatic(funcDecl) && !isGlobalDecl(funcDecl))
                             {
-                                getSink()->diagnose(forwardDiff, Diagnostics::nonStaticMemberFunctionNotAllowedAsDiffOperand, funcDecl);
+                                getSink()->diagnose(invoke->functionExpr, Diagnostics::nonStaticMemberFunctionNotAllowedAsDiffOperand, funcDecl);
                             }
                         }
                     }