From 86675155eb79532039ba79655ed14a76998e9f85 Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Wed, 15 Feb 2023 17:18:00 -0800
Subject: Treat user defined backward derivative function as non
 differentiable. (#2650)

Co-authored-by: Yong He <yhe@nvidia.com>
---
 source/slang/slang-ir-check-differentiability.cpp | 5 -----
 source/slang/slang-lower-to-ir.cpp                | 2 --
 2 files changed, 7 deletions(-)

(limited to 'source')

diff --git a/source/slang/slang-ir-check-differentiability.cpp b/source/slang/slang-ir-check-differentiability.cpp
index e7d5a0e5c..a3f7ae7c0 100644
--- a/source/slang/slang-ir-check-differentiability.cpp
+++ b/source/slang/slang-ir-check-differentiability.cpp
@@ -165,7 +165,6 @@ public:
 
         HashSet<IRInst*> produceDiffSet;
         HashSet<IRInst*> expectDiffSet;
-        int differentiableInputs = 0;
         int differentiableOutputs = 0;
         for (auto param : funcInst->getFirstBlock()->getParams())
         {
@@ -173,8 +172,6 @@ public:
             {
                 if (as<IROutTypeBase>(param->getFullType()))
                     differentiableOutputs++;
-                if (!as<IROutType>(param->getFullType()))
-                    differentiableInputs++;
                 produceDiffSet.Add(param);
             }
         }
@@ -186,8 +183,6 @@ public:
 
         if (differentiableOutputs == 0)
             sink->diagnose(funcInst, Diagnostics::differentiableFuncMustHaveOutput);
-        if (differentiableInputs == 0)
-            sink->diagnose(funcInst, Diagnostics::differentiableFuncMustHaveInput);
 
         DifferentiableLevel requiredDiffLevel = DifferentiableLevel::Forward;
         if (isBackwardDifferentiableFunc(funcInst))
diff --git a/source/slang/slang-lower-to-ir.cpp b/source/slang/slang-lower-to-ir.cpp
index 9cf6aedf4..957f74d40 100644
--- a/source/slang/slang-lower-to-ir.cpp
+++ b/source/slang/slang-lower-to-ir.cpp
@@ -8436,8 +8436,6 @@ struct DeclLoweringVisitor : DeclVisitor<DeclLoweringVisitor, LoweredValInfo>
                 else
                 {
                     originalSubBuilder->addUserDefinedBackwardDerivativeDecoration(originalFuncVal, derivativeFuncVal.val);
-                    getBuilder()->addForwardDifferentiableDecoration(irFunc);
-                    getBuilder()->addBackwardDifferentiableDecoration(irFunc);
                 }
             }
             subContext->irBuilder->setInsertInto(irFunc);
-- 
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