Fix diagnostics for [PreferRecompute] (#5159)

* Fix diagnostics for [PreferRecompute]

* Update dont-warn-on-simple-prefer-recompute.slang

* Update slang-ir-autodiff.cpp

* Update dont-warn-on-simple-prefer-recompute.slang

* Update warn-on-prefer-recompute-side-effects.slang

1 files changed, 8 insertions, 2 deletions

diff --git a/source/slang/slang-ir-autodiff.cpp b/source/slang/slang-ir-autodiff.cpp
index 6c729ea63..bed6a68e4 100644
--- a/source/slang/slang-ir-autodiff.cpp
+++ b/source/slang/slang-ir-autodiff.cpp
@@ -2416,9 +2416,15 @@ void checkAutodiffPatterns(
         if (auto func = as<IRFunc>(inst))
         {
             if (func->sourceLoc.isValid() && // Don't diagnose for synthesized functions
-                func->findDecoration<IRPreferRecomputeDecoration>() &&
-                !func->findDecoration<IRNoSideEffectDecoration>())
+                func->findDecoration<IRPreferRecomputeDecoration>())
             {
+                // If we don't have any side-effect behavior, we should warn (note: read-none is a stronger 
+                // guarantee than no-side-effect)
+                //
+                if (func->findDecoration<IRNoSideEffectDecoration>() ||
+                    func->findDecoration<IRReadNoneDecoration>())
+                    continue;
+
                 auto preferRecomputeDecor = func->findDecoration<IRPreferRecomputeDecoration>();
                 auto sideEffectBehavior = as<IRIntLit>(preferRecomputeDecor->getOperand(0))->getValue();