Small fixes around repro loading/autodiff (#2585)

* #include an absolute path didn't work - because paths were taken to always be relative.

* Work around for some issue seen with a repro.

* Small improvement in doing IDifferentable check.

1 files changed, 8 insertions, 3 deletions

diff --git a/source/slang/slang-ir-autodiff.cpp b/source/slang/slang-ir-autodiff.cpp
index 53e2ed0be..94417ea00 100644
--- a/source/slang/slang-ir-autodiff.cpp
+++ b/source/slang/slang-ir-autodiff.cpp
@@ -309,10 +309,15 @@ IRInst* AutoDiffSharedContext::findDifferentiableInterface()
             // TODO: This seems like a particularly dangerous way to look for an interface.
             // See if we can lower IDifferentiable to a separate IR inst.
             //
-            if (globalInst->getOp() == kIROp_InterfaceType &&
-                as<IRInterfaceType>(globalInst)->findDecoration<IRNameHintDecoration>()->getName() == "IDifferentiable")
+            if (auto intf = as<IRInterfaceType>(globalInst))
             {
-                return globalInst;
+                if (auto decor = intf->findDecoration<IRNameHintDecoration>())
+                {
+                    if (decor->getName() == toSlice("IDifferentiable"))
+                    {
+                        return globalInst;
+                    }
+                }
             }
         }
     }