Miscellaneous backward autodiff fixes. (#2665)

* Fix differentiable type registration

* Fix use of non-differentiable return value in a differentiable func.

* Fix use of primal inst that does not dominate the diff block.

* Fix primal inst hoisting, and add missing type legalization logic.

* Make `detach` defined on all differentiable T.

---------

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

1 files changed, 24 insertions, 0 deletions

diff --git a/source/slang/slang-ir-autodiff.cpp b/source/slang/slang-ir-autodiff.cpp
index 97cdb644e..b630b798d 100644
--- a/source/slang/slang-ir-autodiff.cpp
+++ b/source/slang/slang-ir-autodiff.cpp
@@ -563,6 +563,30 @@ bool isDifferentiableType(DifferentiableTypeConformanceContext& context, IRInst*
     return false;
 }
 
+bool canInstBeStored(IRInst* inst)
+{
+    if (as<IRBasicType>(inst->getDataType()))
+        return true;
+
+    switch (inst->getDataType()->getOp())
+    {
+    case kIROp_StructType:
+    case kIROp_OptionalType:
+    case kIROp_TupleType:
+    case kIROp_ArrayType:
+    case kIROp_DifferentialPairType:
+    case kIROp_InterfaceType:
+    case kIROp_AnyValueType:
+    case kIROp_ClassType:
+    case kIROp_FloatType:
+    case kIROp_VectorType:
+    case kIROp_MatrixType:
+        return true;
+    default:
+        return false;
+    }
+}
+
 struct AutoDiffPass : public InstPassBase
 {
     DiagnosticSink* getSink()