[Mlir-commits] [mlir] [mlir][emitc] Add a structured for operation (PR #68206)

[Marius Brehler]

================
@@ -37,7 +37,99 @@ struct SCFToEmitCPass : public impl::SCFToEmitCBase<SCFToEmitCPass> {
   void runOnOperation() override;
 };
 
-// Lower scf::if to emitc::if, implementing return values as emitc::variable's
+// Lower scf::for to emitc::for, implementing result values using
+// emitc::variable's updated within the loop body.
+struct ForLowering : public OpRewritePattern<ForOp> {
+  using OpRewritePattern<ForOp>::OpRewritePattern;
+
+  LogicalResult matchAndRewrite(ForOp forOp,
+                                PatternRewriter &rewriter) const override;
+};
+
+// Create an uninitialized emitc::variable op for each result of the given op.
+template <typename T>
+static SmallVector<Value> createVariablesForResults(T op,
+                                                    PatternRewriter &rewriter) {
+  SmallVector<Value> resultVariables;
+
+  if (!op.getNumResults())
+    return resultVariables;
+
+  Location loc = op->getLoc();
+  MLIRContext *context = op.getContext();
+
+  OpBuilder::InsertionGuard guard(rewriter);
+  rewriter.setInsertionPoint(op);
+
+  for (OpResult result : op.getResults()) {
+    Type resultType = result.getType();
+    auto noInit = emitc::OpaqueAttr::get(context, "");
+    auto var = rewriter.create<emitc::VariableOp>(loc, resultType, noInit);
----------------
marbre wrote:

```suggestion
    emitc::OpaqueAttr noInit = emitc::OpaqueAttr::get(context, "");
    emitc::VariableOp var = rewriter.create<emitc::VariableOp>(loc, resultType, noInit);
```

I think `auto` can be avoided here.

https://github.com/llvm/llvm-project/pull/68206