[flang-commits] [flang] [flang][Evaluate] Add `ExtractSubstring` to evaluate/tools.h (PR #81265)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-flang-semantics

Author: Krzysztof Parzyszek (kparzysz)

<details>
<summary>Changes</summary>

There are utility functions to extract a DataRef, optionally traversing into a substring, but there is no function to get the subscript itself. This patch adds one.

---
Full diff: https://github.com/llvm/llvm-project/pull/81265.diff


1 Files Affected:

- (modified) flang/include/flang/Evaluate/tools.h (+23) 


``````````diff
diff --git a/flang/include/flang/Evaluate/tools.h b/flang/include/flang/Evaluate/tools.h
index d257da1a709642..e9999974944e88 100644
--- a/flang/include/flang/Evaluate/tools.h
+++ b/flang/include/flang/Evaluate/tools.h
@@ -430,6 +430,29 @@ template <typename A> std::optional<CoarrayRef> ExtractCoarrayRef(const A &x) {
   }
 }
 
+struct ExtractSubstringHelper {
+  template <typename T> static std::optional<Substring> visit(T &&) {
+    return std::nullopt;
+  }
+
+  static std::optional<Substring> visit(const Substring &e) { return e; }
+
+  template <typename T>
+  static std::optional<Substring> visit(const Designator<T> &e) {
+    return std::visit([](auto &&s) { return visit(s); }, e.u);
+  }
+
+  template <typename T>
+  static std::optional<Substring> visit(const Expr<T> &e) {
+    return std::visit([](auto &&s) { return visit(s); }, e.u);
+  }
+};
+
+template <typename A>
+std::optional<Substring> ExtractSubstring(const A &x) {
+  return ExtractSubstringHelper::visit(x);
+}
+
 // If an expression is simply a whole symbol data designator,
 // extract and return that symbol, else null.
 template <typename A> const Symbol *UnwrapWholeSymbolDataRef(const A &x) {

``````````

</details>


https://github.com/llvm/llvm-project/pull/81265