[Mlir-commits] [mlir] [mlir][vector] Fix for WarpOpScfForOp failure when scf.for has results that are unused. (PR #141853)

[Charitha Saumya]

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@@ -1554,22 +1554,37 @@ struct WarpOpScfForOp : public WarpDistributionPattern {
     llvm::SmallSetVector<Value, 32> escapingValues;
     SmallVector<Type> inputTypes;
     SmallVector<Type> distTypes;
+    auto collectEscapingValues = [&](Value value) {
+      if (!escapingValues.insert(value))
+        return;
+      Type distType = value.getType();
+      if (auto vecType = dyn_cast<VectorType>(distType)) {
+        AffineMap map = distributionMapFn(value);
+        distType = getDistributedType(vecType, map, warpOp.getWarpSize());
+      }
+      inputTypes.push_back(value.getType());
+      distTypes.push_back(distType);
+    };
+
     mlir::visitUsedValuesDefinedAbove(
         forOp.getBodyRegion(), [&](OpOperand *operand) {
           Operation *parent = operand->get().getParentRegion()->getParentOp();
           if (warpOp->isAncestor(parent)) {
-            if (!escapingValues.insert(operand->get()))
-              return;
-            Type distType = operand->get().getType();
-            if (auto vecType = dyn_cast<VectorType>(distType)) {
-              AffineMap map = distributionMapFn(operand->get());
-              distType = getDistributedType(vecType, map, warpOp.getWarpSize());
-            }
-            inputTypes.push_back(operand->get().getType());
-            distTypes.push_back(distType);
+            collectEscapingValues(operand->get());
           }
         });
 
+    // Any forOp result that is not already yielded by the warpOp
+    // region is also considered escaping and must be returned by the
+    // original warpOp.
+    for (OpResult forResult : forOp.getResults()) {
+      // Check if this forResult is already yielded by the yield op.
+      if (llvm::is_contained(yield->getOperands(), forResult)) {
+        continue;
+      }
+      collectEscapingValues(forResult);
+    }
+
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charithaintc wrote:

I agree the existing logic is bit confusing. I am also not sure why the forOp results are yielded instead of the iterArgs directly. Maybe code owners have some insights on this?

But overall the logic will be similar apart from this part (even for a refactored version). This pattern is anyway bit complex since it has a lot of moving parts. :-) 

https://github.com/llvm/llvm-project/pull/141853