[flang][Evaluate] Fold DBLE

[rogfer01]

Summary

We can reuse the folding of REAL.

[rogfer01]

I was wondering why similar intrinsics SNGL and FLOAT work already but they seem to be lowered earlier to REAL, does this make sense?

(Also this is my first patch for flang, so if I'm missing something very obvious please let me know. Thanks!)

[jeanPerier]

Thanks for the patch.

I was wondering why similar intrinsics SNGL and FLOAT work already but they seem to be lowered earlier to REAL, does this make sense?

Yes, SNGL is a specific intrinsic (defined in section 16.8 in Fortran 2018 standard), while DBLE is a generic intrinsic (defined in section 16.9). Intrinsic procedure call resolution (Probe in lib/Evaluate/intrinsics.cpp) replaces specific names by the related generic names. So SGNL is replaced by REAL there, but DBLE is not. So your patch in folding makes sense to me.

flang/test/Evaluate/fold-dble.f90

8

test_folding.py is testing that parameters names text_xxx (with xxx being any string) folds to .true.. Your test currently checks that dble is folded, but not that it is folded correctly. To make your test more thorough, you could add to the module definitions:

logical, parameter :: test_dble_1 = ntotal_f == real(nx*ny*nz, kind(0.0D0))
logical, parameter :: test_dble_2 = kind(dble(nx)) == kind(0.0D0)

[rogfer01]

Yes, SNGL is a specific intrinsic (defined in section 16.8 in Fortran 2018 standard), while DBLE is a generic intrinsic (defined in section 16.9). Intrinsic procedure call resolution (Probe in lib/Evaluate/intrinsics.cpp) replaces specific names by the related generic names. So SGNL is replaced by REAL there, but DBLE is not. So your patch in folding makes sense to me.

OK. Thanks a lot for the clarification, @jeanPerier.

[rogfer01]

ChangeLog:

• Improve the test with assertions verified by test_folding.py as suggested

flang/lib/Evaluate/fold-real.cpp

Expr<Type<TypeCategory::Real, KIND>> FoldIntrinsicFunction(
   } else if (name == "min") {
     return FoldMINorMAX(context, std::move(funcRef), Ordering::Less);
   } else if (name == "minval") {
     return FoldMaxvalMinval<T>(
         context, std::move(funcRef), RelationalOperator::LT, T::Scalar::HUGE());
   } else if (name == "product") {
     auto one{Scalar<T>::FromInteger(value::Integer<8>{1}).value};
     return FoldProduct<T>(context, std::move(funcRef), one);
-  } else if (name == "real") {
+  } else if (name == "real" || name == "dble") {
     if (auto *expr{args[0].value().UnwrapExpr()}) {
       return ToReal<KIND>(context, std::move(*expr));
     }
   } else if (name == "scale") {
     if (const auto *byExpr{UnwrapExpr<Expr<SomeInteger>>(args[1])}) {
       return std::visit(
           [&](const auto &byVal) {
             using TBY = ResultType<decltype(byVal)>;

flang/test/Evaluate/fold-dble.f90

+! RUN: %python %S/test_folding.py %s %flang_fc1
+! Tests folding of DBLE()
+module ft_data
+  integer nx, ny, nz
+  parameter (nx=64, ny=64, nz=64, maxdim=64)
+  double precision ntotal_f
+  parameter (ntotal_f =  dble(nx)*ny*nz)
+  logical, parameter :: test_dble_1 = ntotal_f == real(nx*ny*nz, kind(0.0D0))
+  logical, parameter :: test_dble_2 = kind(dble(nx)) == kind(0.0D0)
+end module ft_data