From d48cd130aacbab34bb98d51bb237ad38ff37348c Mon Sep 17 00:00:00 2001
From: kaizhangNV <149626564+kaizhangNV@users.noreply.github.com>
Date: Thu, 2 Jan 2025 14:29:57 -0600
Subject: Correct IR generation for no-diff pointer type (#5976)

* Correct IR generation for no-diff pointer type

Close #5805

There is an issue on checking whether a pointer type parameter
is no_diff, we should first check whether this parameter is
an Attribute type first, then check the data type.

In the back-propagate pass, for the pointer type parameter, we should
load this parameter to a temp variable, then pass it to the primal
function call. Otherwise, the temp variable will no be initialized,
which will cause the following calculation wrong.
---
 source/slang/slang-ir-autodiff.cpp | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

(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 5c05b0811..4edd8eabe 100644
--- a/source/slang/slang-ir-autodiff.cpp
+++ b/source/slang/slang-ir-autodiff.cpp
@@ -126,13 +126,22 @@ static IRInst* _getDiffTypeWitnessFromPairType(
 
 bool isNoDiffType(IRType* paramType)
 {
-    while (auto ptrType = as<IRPtrTypeBase>(paramType))
-        paramType = ptrType->getValueType();
-    while (auto attrType = as<IRAttributedType>(paramType))
+    while (paramType)
     {
-        if (attrType->findAttr<IRNoDiffAttr>())
+        if (auto attrType = as<IRAttributedType>(paramType))
         {
-            return true;
+            if (attrType->findAttr<IRNoDiffAttr>())
+                return true;
+
+            paramType = attrType->getBaseType();
+        }
+        else if (auto ptrType = as<IRPtrTypeBase>(paramType))
+        {
+            paramType = ptrType->getValueType();
+        }
+        else
+        {
+            return false;
         }
     }
     return false;
-- 
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