[flang-commits] [flang] [flang] Associate named constant actual arguments with their storage (PR #222986)

[Eugene Epshteyn via flang-commits]

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@@ -132,6 +132,29 @@ void CheckImplicitInterfaceArg(evaluate::ActualArgument &arg,
 
 // F'2023 15.5.2.12p1: "Sequence association only applies when the dummy
 // argument is an explicit-shape or assumed-size array."
+// Total size in bytes of a whole object for storage-sequence checks.
+// A named constant has no storage assignment (symbol.size() is zero), so
+// measure it from its type and constant extents instead.
+static std::optional<std::int64_t> ObjectTotalBytes(
+    const Symbol &symbol, evaluate::FoldingContext &foldingContext) {
+  if (std::size_t bytes{symbol.size()}) {
+    return static_cast<std::int64_t>(bytes);
+  }
+  if (const Symbol &ultimate{symbol.GetUltimate()}; IsNamedConstant(ultimate)) {
+    if (auto type{evaluate::DynamicType::From(ultimate)}) {
+      if (auto extents{
+              evaluate::GetConstantExtents(foldingContext, &ultimate)}) {
+        if (auto bytes{evaluate::ToInt64(evaluate::Fold(foldingContext,
+                type->MeasureSizeInBytes(
+                    foldingContext, evaluate::GetRank(*extents) > 0)))}) {
+          return *bytes * evaluate::GetSize(*extents);
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eugeneepshteyn wrote:

Good call — it did not work, and there was no test covering it. The designator folder gets bounds through `GetLBOUND`, which for an explicit lower bound other than 1 requires an explicit upper bound to prove the dimension is not empty. An implied-shape array has no explicit upper bound, so the bound came back unknown, `FoldDesignator` gave up, and both storage sequence checks were silently skipped.

Fixed in `GetLowerBoundHelper` by taking the extent from the initializer for implied-shape named constants, with `(*)`, `(0:*)` and `(0:*,*)` cases — both conforming and too-short — added to `flang/test/Semantics/call-parameter-seq-assoc.f90`.

The same gap also kept omitted-bound sections of such constants from being constant expressions, so `size(p(:))`, `ubound(p(:),1)` and array expressions over them were rejected in constant contexts. The same change fixes that, covered by a new `flang/test/Evaluate/fold-implied-shape-section.f90`. (Should this perhaps be a separate PR?)

https://github.com/llvm/llvm-project/pull/222986