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

[Simon Camphausen]

================
@@ -37,6 +37,106 @@ struct SCFToEmitCPass : public impl::SCFToEmitCBase<SCFToEmitCPass> {
   void runOnOperation() override;
 };
 
+// Lower scf::for to emitc::for, implementing return values using
+// emitc::variable's updated within 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 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();
+
+  auto insertionPoint = rewriter.saveInsertionPoint();
----------------
simon-camp wrote:

```c++
OpBuilder::InsertionGuard guard(rewriter);
...
```

You can use a guard instead of save/restore pairs.

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