[Mlir-commits] [mlir] [MLIR, LLVM]: Add an IR utility to perform slice walking (PR #103053)

[Tobias Gysi]

================
@@ -0,0 +1,99 @@
+//===- SliceSupport.h - Helpers for performing IR slicing -------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_IR_SLICESUPPORT_H
+#define MLIR_IR_SLICESUPPORT_H
+
+#include "mlir/IR/ValueRange.h"
+
+namespace mlir {
+
+/// A class to signal how to proceed with the walk of the backward slice:
+/// - Interrupt: Stops the walk.
+/// - AdvanceTo: Continues the walk to user-specified values.
+/// - Skip: Continues the walk, but skips the predecessors of the current value.
+class WalkContinuation {
+public:
+  enum class WalkAction {
+    /// Stops the walk.
+    Interrupt,
+    /// Continues the walk to user-specified values.
+    AdvanceTo,
+    /// Continues the walk, but skips the predecessors of the current value.
+    Skip
+  };
+
+  WalkContinuation(WalkAction action, mlir::ValueRange nextValues)
+      : action(action), nextValues(nextValues) {}
+
+  /// Allows diagnostics to interrupt the walk.
+  explicit WalkContinuation(mlir::Diagnostic &&)
+      : action(WalkAction::Interrupt) {}
+
+  /// Allows diagnostics to interrupt the walk.
+  explicit WalkContinuation(mlir::InFlightDiagnostic &&)
+      : action(WalkAction::Interrupt) {}
+
+  /// Creates a continuation that interrupts the walk.
+  static WalkContinuation interrupt() {
+    return WalkContinuation(WalkAction::Interrupt, {});
+  }
+
+  /// Creates a continuation that adds the user-specified `nextValues` to the
+  /// work list and advances the walk. Unlike advance, this function does not
+  /// add the control flow predecessor values to the work list.
----------------
gysit wrote:

```suggestion
  /// work list and advances the walk.
```
nit: this is not needed anymore.

https://github.com/llvm/llvm-project/pull/103053