From 83a42cb76feb1f702ff730040f359cabc01c571a Mon Sep 17 00:00:00 2001
From: Ellie Hermaszewska <ellieh@nvidia.com>
Date: Fri, 4 Apr 2025 15:25:20 +0800
Subject: Do no fail on missing no_diff annotation on non-differentiable
 (inputs and output) function outputs (#6737)

Closes https://github.com/shader-slang/slang/issues/6632
---
 source/slang/slang-ir-autodiff.cpp | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

(limited to 'source/slang/slang-ir-autodiff.cpp')

diff --git a/source/slang/slang-ir-autodiff.cpp b/source/slang/slang-ir-autodiff.cpp
index afd698e8b..f70e30b72 100644
--- a/source/slang/slang-ir-autodiff.cpp
+++ b/source/slang/slang-ir-autodiff.cpp
@@ -147,6 +147,20 @@ bool isNoDiffType(IRType* paramType)
     return false;
 }
 
+// Return true if the result type and all the parameter types are no_diff
+bool isNeverDiffFuncType(IRFuncType* const funcType)
+{
+    const auto resultType = funcType->getResultType();
+    if (!isNoDiffType(resultType))
+        return false;
+    for (const auto p : funcType->getParamTypes())
+    {
+        if (!isNoDiffType(p))
+            return false;
+    }
+    return true;
+}
+
 IRInst* lookupForwardDerivativeReference(IRInst* primalFunction)
 {
     if (auto jvpDefinition = primalFunction->findDecoration<IRForwardDerivativeDecoration>())
-- 
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