[flang-commits] [flang] [flang] Improve warnings for invalid arguments when folding host runtime (PR #96807)

[Pete Steinfeld via flang-commits]

================
@@ -633,10 +633,243 @@ static DynamicType BiggerType(DynamicType type) {
   return type;
 }
 
+/// Structure to register intrinsic argument checks that must be performed.
+using ArgumentVerifierFunc = bool (*)(
+    const std::vector<Expr<SomeType>> &, FoldingContext &);
+struct ArgumentVerifier {
+  using Key = std::string_view;
+  // Needed for implicit compare with keys.
+  constexpr operator Key() const { return key; }
+  Key key; // intrinsic name
+  ArgumentVerifierFunc verifier;
+};
+
+static constexpr int lastArg{-1};
+static constexpr int firstArg{0};
+
+static const Expr<SomeType> &getArg(
+    int position, const std::vector<Expr<SomeType>> &args) {
+  if (position == lastArg) {
+    CHECK(!args.empty());
+    return args.back();
+  }
+  CHECK(position >= 0 && static_cast<std::size_t>(position) < args.size());
+  return args[position];
+}
+
+template <typename T>
+static bool IsInRange(const Expr<T> &expr, int lb, int ub) {
+  if (auto scalar{GetScalarConstantValue<T>(expr)}) {
+    auto lbValue{Scalar<T>::FromInteger(value::Integer<8>{lb}).value};
+    auto ubValue{Scalar<T>::FromInteger(value::Integer<8>{ub}).value};
+    return Satisfies(RelationalOperator::LE, lbValue.Compare(*scalar)) &&
+        Satisfies(RelationalOperator::LE, scalar->Compare(ubValue));
+  }
+  return true;
+}
+
+/// Verify that the argument in an intrinsic call belongs to [lb, ub] if is
+/// real.
+template <int lb, int ub>
+static bool VerifyInRangeIfReal(
+    const std::vector<Expr<SomeType>> &args, FoldingContext &context) {
+  if (const auto *someReal =
+          std::get_if<Expr<SomeReal>>(&getArg(firstArg, args).u)) {
+    const bool isInRange{
+        std::visit([&](const auto &x) -> bool { return IsInRange(x, lb, ub); },
+            someReal->u)};
+    if (!isInRange) {
+      context.messages().Say(
+          "argument is out of range [%d., %d.]"_warn_en_US, lb, ub);
----------------
psteinfeld wrote:

The values in Fortran are `REAL`, even though the values that the compiler deals with are `int`.

https://github.com/llvm/llvm-project/pull/96807