[fir] Add !fir.len type conversion

[clementval]

Summary

This patch adds the !fir.len type conversion. The type is converted
to the a 32 bits integer.

This patch is part of the upstreaming effort from fir-dev branch.

Co-authored-by: Eric Schweitz <[e-mail]>

[kiranchandramohan]

flang/lib/Optimizer/CodeGen/TypeConverter.h

73

Nit: A comment on why this is 32 bits while some others like character len is 64 or platform-dependent will be good.

[clementval]

Rebase

[clementval]

Get size from the descriptor + rebase

flang/lib/Optimizer/CodeGen/TypeConverter.h

addConversion([&](fir::LogicalType boolTy) {
       return mlir::IntegerType::get(
           &getContext(), kindMapping.getLogicalBitsize(boolTy.getFKind()));
     });
     addConversion(
         [&](fir::PointerType pointer) { return convertPointerLike(pointer); });
     addConversion(
         [&](fir::RecordType derived) { return convertRecordType(derived); });
     addConversion([&](fir::FieldType field) {
       // Convert to i32 because of LLVM GEP indexing restriction.
       return mlir::IntegerType::get(field.getContext(), 32);
     });
+    addConversion([&](fir::LenType field) {
+      // Get size of len paramter from the descriptor.
+      return getModel<Fortran::runtime::typeInfo::TypeParameterValue>()(
+          &getContext());
+    });
     addConversion(
         [&](fir::ComplexType cmplx) { return convertComplexType(cmplx); });
     addConversion(
         [&](fir::RealType real) { return convertRealType(real.getFKind()); });
     addConversion(
         [&](fir::ReferenceType ref) { return convertPointerLike(ref); });
     addConversion([&](fir::SequenceType sequence) {
       return convertSequenceType(sequence);

flang/test/Fir/types-to-llvm.fir

 
 // -----
 
 // Test `!fir.field` conversion
 
 func private @foo0(%arg0: !fir.field)
 // CHECK-LABEL: foo0
 // CHECK-SAME: i32
+
+// -----
+
+// Test `!fir.len` conversion.
+
+func private @foo0(%arg0: !fir.len)
+// CHECK-LABEL: foo0
+// CHECK-SAME: i64