Adds a warning for using `[PreferRecompute]` on methods that may contain side effects (#4707)

* Adds a warning for using prefer-recompute on methods that contain side effects

* Rename `SideEffects` -> `SideEffectBehavior`

---------

Co-authored-by: Yong He <yonghe@outlook.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/tests/autodiff/warn-on-prefer-recompute-side-effects.slang b/tests/autodiff/warn-on-prefer-recompute-side-effects.slang
new file mode 100644
index 000000000..38543e67f
--- /dev/null
+++ b/tests/autodiff/warn-on-prefer-recompute-side-effects.slang
@@ -0,0 +1,47 @@
+//TEST:SIMPLE(filecheck=CHECK): -target hlsl -line-directive-mode none
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+groupshared float s_shared;
+
+[BackwardDifferentiable]
+[PreferRecompute]
+float get_thread_5_value(float v, uint group_thread_id)
+{
+    if(group_thread_id == 5)
+    {
+        s_shared = detach(v);
+        // CHECK: tests/autodiff/warn-on-prefer-recompute-side-effects.slang(10): warning 42050: get_thread_5_value has [PreferRecompute] and may have side effects. side effects may execute multiple times. use [PreferRecompute(SideEffectBehavior.Allow)], or mark function with [NoSideEffect]
+        // CHECK: float get_thread_5_value(float v, uint group_thread_id)
+        // CHECK:       ^~~~~~~~~~~~~~~~~~
+    }
+    GroupMemoryBarrierWithGroupSync();
+    return s_shared;
+}
+
+[BackwardDifferentiable]
+[PreferRecompute(SideEffectBehavior.Allow)] // Suppress warning here
+float get_thread_6_value(float v, uint group_thread_id)
+{
+    if (group_thread_id == 6)
+    {
+        s_shared = detach(v);
+        // CHECK-NOT: warning 42050
+
+    }
+    GroupMemoryBarrierWithGroupSync();
+    return s_shared;
+}
+
+[shader("compute")]
+[numthreads(128, 1, 1)]
+void computeMain(uint3 group_thread_id: SV_GroupThreadID, uint3 dispatch_thread_id: SV_DispatchThreadID)
+{
+    DifferentialPair<float> value = diffPair(3.f, 0.f);
+
+    bwd_diff(get_thread_5_value)(value, group_thread_id.x, 1.0f);
+    bwd_diff(get_thread_6_value)(value, group_thread_id.x, 1.0f);
+
+    outputBuffer[dispatch_thread_id.x] = value.d;
+}
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