From a670bafc121c20168624f70a388dbe8556402c7f Mon Sep 17 00:00:00 2001
From: kaizhangNV <149626564+kaizhangNV@users.noreply.github.com>
Date: Wed, 9 Jul 2025 11:25:29 -0500
Subject: no_diff diagnostics improvement (#7655)

close #6286.

This PR is to improve the diagnostics for no_diff usage.

In a differentiable function, any calls to a non-diff function with constant arguments should not require no_diff attribute.
This PR adds this extra check at `checkAutoDiffUsages` where it checks the differentiability on IR.

In a differentiable method, we will force to use `[NoDiffThis]` attribute if there is access to non-differentiable `This` type. Once this access is detected we will report a warning to bring users attention that this access won't generate any derivative, they have to use `[NoDiffThis]` to suppress that warning.
This PR adds this check at type checking stage, because it's the easiest way to find out all the `This` accesses.
---
 source/slang/diff.meta.slang | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'source/slang/diff.meta.slang')

diff --git a/source/slang/diff.meta.slang b/source/slang/diff.meta.slang
index 542983049..b22d91595 100644
--- a/source/slang/diff.meta.slang
+++ b/source/slang/diff.meta.slang
@@ -992,10 +992,12 @@ struct DiffTensorView
 
     [BackwardDerivative(__load_backward)]
     [ForwardDerivative(__load_forward)]
+    [NoDiffThis]
     T load(uint i) { return primal.load(i); }
 
     [BackwardDerivative(__load_backward)]
     [ForwardDerivative(__load_forward)]
+    [NoDiffThis]
     __generic<let N : int>
     T load(vector<uint, N> i) { return primal.load(i); }
 
@@ -1026,10 +1028,12 @@ struct DiffTensorView
 
     [BackwardDerivative(__store_backward)]
     [ForwardDerivative(__store_forward)]
+    [NoDiffThis]
     void store(uint x, T val) { primal.store(x, val); }
 
     [BackwardDerivative(__store_backward)]
     [ForwardDerivative(__store_forward)]
+    [NoDiffThis]
     __generic<let N : int>
     void store(vector<uint, N> x, T val) { primal.store(x, val); }
 
@@ -1135,10 +1139,12 @@ struct DiffTensorView
 
     [BackwardDerivative(__loadOnce_backward)]
     [ForwardDerivative(__loadOnce_forward)]
+    [NoDiffThis]
     T loadOnce(uint i) { return primal.load(i); }
 
     [BackwardDerivative(__loadOnce_backward)]
     [ForwardDerivative(__loadOnce_forward)]
+    [NoDiffThis]
     __generic<let N : int>
     T loadOnce(vector<uint, N> i) { return primal.load(i); }
 
@@ -1168,10 +1174,12 @@ struct DiffTensorView
 
     [BackwardDerivative(__storeOnce_backward)]
     [ForwardDerivative(__storeOnce_forward)]
+    [NoDiffThis]
     void storeOnce(uint x, T val) { primal.store(x, val); }
 
     [BackwardDerivative(__storeOnce_backward)]
     [ForwardDerivative(__storeOnce_forward)]
+    [NoDiffThis]
     __generic<let N : int>
     void storeOnce(vector<uint, N> x, T val) { primal.store(x, val); }
 
-- 
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