Autodiff through simple dynamic dispatch. (#2527)

* Autodiff through simple dynamic dispatch.

* Revert changes.

* Fix.

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

1 files changed, 40 insertions, 0 deletions

diff --git a/source/slang/slang-ast-val.cpp b/source/slang/slang-ast-val.cpp
index 87e89ef18..a0f0552c6 100644
--- a/source/slang/slang-ast-val.cpp
+++ b/source/slang/slang-ast-val.cpp
@@ -1516,4 +1516,44 @@ Val* WitnessLookupIntVal::tryFold(ASTBuilder* astBuilder, SubtypeWitness* witnes
     return witnessResult;
 }
 
+
+bool DifferentiateVal::_equalsValOverride(Val* val)
+{
+    if (auto other = as<DifferentiateVal>(val))
+    {
+        return other->astNodeType == astNodeType && other->func == func;
+    }
+    return false;
+}
+
+void DifferentiateVal::_toTextOverride(StringBuilder& out)
+{
+    out << "DifferentiateVal(";
+    out << func;
+    out << ")";
+}
+
+HashCode DifferentiateVal::_getHashCodeOverride()
+{
+    HashCode result = (HashCode)astNodeType;
+    result = combineHash(result, func.getHashCode());
+    return result;
+}
+
+Val* DifferentiateVal::_substituteImplOverride(ASTBuilder* astBuilder, SubstitutionSet subst, int* ioDiff)
+{
+    int diff = 0;
+    auto newFunc = func.substituteImpl(astBuilder, subst, &diff);
+    *ioDiff += diff;
+    if (diff)
+    {
+        auto result = as<DifferentiateVal>(astBuilder->createByNodeType(astNodeType));
+        result->func = newFunc;
+        return result;
+    }
+    // Nothing found: don't substitute.
+    return this;
+}
+
+
 } // namespace Slang