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.
---
 tests/autodiff/dynamic-dispatch-bwd-diff.slang               | 2 ++
 tests/autodiff/dynamic-dispatch-generic-2.slang              | 3 +++
 tests/autodiff/dynamic-object-bwd-diff.slang                 | 4 ++++
 tests/autodiff/material2/DiffuseMaterial.slang               | 1 +
 tests/autodiff/material2/GlossyMaterial.slang                | 1 +
 tests/autodiff/material2/MxLayeredMaterial.slang             | 1 +
 tests/autodiff/member-func-extension-custom-derivative.slang | 1 +
 tests/autodiff/nondiff-call.slang                            | 1 +
 8 files changed, 14 insertions(+)

(limited to 'tests/autodiff')

diff --git a/tests/autodiff/dynamic-dispatch-bwd-diff.slang b/tests/autodiff/dynamic-dispatch-bwd-diff.slang
index 5945c22cd..9941aa7b1 100644
--- a/tests/autodiff/dynamic-dispatch-bwd-diff.slang
+++ b/tests/autodiff/dynamic-dispatch-bwd-diff.slang
@@ -17,6 +17,7 @@ struct A : IInterface
 {
     float a;
     [BackwardDifferentiable]
+    [NoDiffThis]
     float calc(float x) { return a*x*x; }
 };
 
@@ -24,6 +25,7 @@ struct B : IInterface
 {
     float a;
     [BackwardDifferentiable]
+    [NoDiffThis]
     float calc(float x) { return a*x*x*x; }
 };
 
diff --git a/tests/autodiff/dynamic-dispatch-generic-2.slang b/tests/autodiff/dynamic-dispatch-generic-2.slang
index bbf7c7da1..97cb5f42c 100644
--- a/tests/autodiff/dynamic-dispatch-generic-2.slang
+++ b/tests/autodiff/dynamic-dispatch-generic-2.slang
@@ -16,7 +16,9 @@ interface IInterface
 struct A : IInterface
 {
     float z;
+
     [ForwardDifferentiable]
+    [NoDiffThis]
     float calc(float x) { return x * x * x; }
 };
 
@@ -25,6 +27,7 @@ struct B : IInterface
     float z;
 
     [ForwardDifferentiable]
+    [NoDiffThis]
     float calc(float x) { return x * x + z; }
 };
 
diff --git a/tests/autodiff/dynamic-object-bwd-diff.slang b/tests/autodiff/dynamic-object-bwd-diff.slang
index a10c48f9b..a80025d52 100644
--- a/tests/autodiff/dynamic-object-bwd-diff.slang
+++ b/tests/autodiff/dynamic-object-bwd-diff.slang
@@ -26,7 +26,9 @@ struct C : IInterface2
 struct A : IInterface
 {
     float a;
+
     [BackwardDifferentiable]
+    [NoDiffThis]
     float calc(IInterface2 i2, float x)
     {
         float b = no_diff(i2.innerCalc(x));
@@ -37,7 +39,9 @@ struct A : IInterface
 struct B : IInterface
 {
     float a;
+
     [BackwardDifferentiable]
+    [NoDiffThis]
     float calc(IInterface2 i2, float x)
     {
         float b = no_diff(i2.innerCalc(x));
diff --git a/tests/autodiff/material2/DiffuseMaterial.slang b/tests/autodiff/material2/DiffuseMaterial.slang
index 1422ee30c..a5c0aaa30 100644
--- a/tests/autodiff/material2/DiffuseMaterial.slang
+++ b/tests/autodiff/material2/DiffuseMaterial.slang
@@ -16,6 +16,7 @@ public struct DiffuseMaterial : IMaterial
     }
 
     [BackwardDifferentiable]
+    [NoDiffThis]
     public DiffuseMaterialInstance setupMaterialInstance(out MaterialInstanceData miData)
     {
         float3 albedo = getAlbedo(baseColor);
diff --git a/tests/autodiff/material2/GlossyMaterial.slang b/tests/autodiff/material2/GlossyMaterial.slang
index 1070c6e63..12fbc5f73 100644
--- a/tests/autodiff/material2/GlossyMaterial.slang
+++ b/tests/autodiff/material2/GlossyMaterial.slang
@@ -30,6 +30,7 @@ public struct GlossyMaterial : IMaterial
     }
 
     [BackwardDifferentiable]
+    [NoDiffThis]
     public GlossyMaterialInstance setupMaterialInstance(out MaterialInstanceData miData)
     {
         float3 albedo = getAlbedo(baseColor);
diff --git a/tests/autodiff/material2/MxLayeredMaterial.slang b/tests/autodiff/material2/MxLayeredMaterial.slang
index fabfde80c..9e88d2ce9 100644
--- a/tests/autodiff/material2/MxLayeredMaterial.slang
+++ b/tests/autodiff/material2/MxLayeredMaterial.slang
@@ -52,6 +52,7 @@ public struct MxLayeredMaterial : IMaterial
     }
 
     [Differentiable]
+    [NoDiffThis]
     public UsedMaterialInstance setupMaterialInstance(out MaterialInstanceData miData)
     {
         float3 albedo = getAlbedo(baseColor);
diff --git a/tests/autodiff/member-func-extension-custom-derivative.slang b/tests/autodiff/member-func-extension-custom-derivative.slang
index 8752dfff5..72fbcf9a1 100644
--- a/tests/autodiff/member-func-extension-custom-derivative.slang
+++ b/tests/autodiff/member-func-extension-custom-derivative.slang
@@ -32,6 +32,7 @@ struct Foo<T : IDifferentiable>
 extension<T : IDifferentiable> Foo<T>
 {
     [ForwardDerivativeOf(doThing)]
+    [NoDiffThis]
     DifferentialPair<T> diff_doThing()
     {
         return diffPair(value, T.dzero());
diff --git a/tests/autodiff/nondiff-call.slang b/tests/autodiff/nondiff-call.slang
index d62de1b78..79d9b9f15 100644
--- a/tests/autodiff/nondiff-call.slang
+++ b/tests/autodiff/nondiff-call.slang
@@ -35,6 +35,7 @@ struct A
     float o;
 
     [ForwardDifferentiable]
+    [NoDiffThis]
     float doSomethingDifferentiable(float b)
     {
         return o + b;
-- 
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