[Mlir-commits] [mlir] [mlir][gpu] Loose the condition to convert scf.parallel to gpu.launch (PR #164978)

[Hsiangkai Wang]

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@@ -625,18 +627,49 @@ ParallelToGpuLaunchLowering::matchAndRewrite(ParallelOp parallelOp,
   bool seenSideeffects = false;
   // Whether we have left a nesting scope (and hence are no longer innermost).
   bool leftNestingScope = false;
+  LocalAliasAnalysis aliasAnalysis;
+  llvm::DenseSet<Value> writtenBuffer;
   while (!worklist.empty()) {
     Operation *op = worklist.pop_back_val();
     // Now walk over the body and clone it.
     // TODO: This is only correct if there either is no further scf.parallel
-    //       nested or this code is side-effect free. Otherwise we might need
-    //       predication. We are overly conservative for now and only allow
-    //       side-effects in the innermost scope.
+    //       nested or this code has side-effect but the memory buffer is not
+    //       alias to inner loop access buffer. Otherwise we might need
+    //       predication.
     if (auto nestedParallel = dyn_cast<ParallelOp>(op)) {
       // Before entering a nested scope, make sure there have been no
-      // sideeffects until now.
-      if (seenSideeffects)
-        return failure();
+      // sideeffects until now or the nested operations do not access the
+      // buffer written by outer scope.
+      if (seenSideeffects) {
+        bool accessesWrittenBuffer = false;
+        nestedParallel.walk([&](Operation *nestedOp) {
+          if (accessesWrittenBuffer)
+            return;
+          if (isMemoryEffectFree(nestedOp))
+            return;
+
+          if (auto memEffectInterface =
+                  dyn_cast<MemoryEffectOpInterface>(nestedOp)) {
+            SmallVector<MemoryEffects::EffectInstance> effects;
+            memEffectInterface.getEffects(effects);
+            for (const auto &effect : effects) {
+              if (isa<MemoryEffects::Read>(effect.getEffect()) ||
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Hsiangkai wrote:

Done.

https://github.com/llvm/llvm-project/pull/164978