[Mlir-commits] [mlir] Adding to execute_region_op some missing support (PR #164159)

[Mehdi Amini]

================
@@ -291,9 +292,103 @@ struct MultiBlockExecuteInliner : public OpRewritePattern<ExecuteRegionOp> {
   }
 };
 
+// Pattern to eliminate ExecuteRegionOp results which forward external
+// values from the region. In case there are multiple yield operations,
+// all of them must have the same operands iin order for the pattern to be
+// applicable.
+struct ExecuteRegionForwardingEliminator
+    : public OpRewritePattern<ExecuteRegionOp> {
+  using OpRewritePattern<ExecuteRegionOp>::OpRewritePattern;
+
+  LogicalResult matchAndRewrite(ExecuteRegionOp op,
+                                PatternRewriter &rewriter) const override {
+    if (op.getNumResults() == 0)
+      return failure();
+
+    SmallVector<Operation *> yieldOps;
+    for (Block &block : op.getRegion()) {
+      if (auto yield = dyn_cast<scf::YieldOp>(block.getTerminator()))
+        yieldOps.push_back(yield.getOperation());
+    }
+
+    if (yieldOps.empty())
+      return failure();
+
+    // Check if all yield operations have the same operands.
+    auto yieldOpsOperands = yieldOps[0]->getOperands();
+    for (auto *yieldOp : yieldOps) {
+      if (yieldOp->getOperands() != yieldOpsOperands)
+        return failure();
+    }
+
+    SmallVector<Value> externalValues;
+    SmallVector<Value> internalValues;
+    SmallVector<Value> opResultsToReplaceWithExternalValues;
+    SmallVector<Value> opResultsToKeep;
+    for (auto [index, yieldedValue] : llvm::enumerate(yieldOpsOperands)) {
+      if (isValueFromInsideRegion(yieldedValue, op)) {
+        internalValues.push_back(yieldedValue);
+        opResultsToKeep.push_back(op.getResult(index));
+      } else {
+        externalValues.push_back(yieldedValue);
+        opResultsToReplaceWithExternalValues.push_back(op.getResult(index));
+      }
+    }
+    // No yeilded external values - nothing to do.
----------------
joker-eph wrote:

```suggestion
    // No yielded external values - nothing to do.
```

https://github.com/llvm/llvm-project/pull/164159