[flang] add -flang-experimental-polymorphism flag to flang-new

[DavidTruby]

Summary

This flag enables Fortran 2003 polymorphism. It is marked experimental
and not included in --help.

[tblah]

Looks good to me, thanks!

[awarzynski]

LGTM, thanks David!

Could you also add a test in https://github.com/llvm/llvm-project/blob/main/flang/test/Driver/frontend-forwarding.f90?

[clementval]

Looks ok to me. Note that some of the polymorphic TODOs will only be removed when HLFIR is in place.

Looks like you have a clang-format issue.

clang/include/clang/Driver/Options.td

 //===----------------------------------------------------------------------===//
 // FLangOption + NoXarchOption
 //===----------------------------------------------------------------------===//
 
 def flang_experimental_hlfir : Flag<["-"], "flang-experimental-hlfir">,
   Flags<[FlangOption, FC1Option, FlangOnlyOption, NoXarchOption, HelpHidden]>,
   HelpText<"Use HLFIR lowering (experimental)">;
 
+def flang_experimental_polymorphism : Flag<["-"], "flang-experimental-polymorphism">,
+  Flags<[FlangOption, FC1Option, FlangOnlyOption, NoXarchOption, HelpHidden]>,
+  HelpText<"Enable Fortran 2003 polymorphism (experimental)">;
+  
+
 //===----------------------------------------------------------------------===//
 // FLangOption + CoreOption + NoXarchOption
 //===----------------------------------------------------------------------===//
 
 def Xflang : Separate<["-"], "Xflang">,
   HelpText<"Pass <arg> to the flang compiler">, MetaVarName<"<arg>">,
   Flags<[FlangOption, FlangOnlyOption, NoXarchOption, CoreOption]>,
   Group<CompileOnly_Group>;

clang/lib/Driver/ToolChains/Flang.cpp

Arg *stackArrays =
       Args.getLastArg(options::OPT_Ofast, options::OPT_fstack_arrays,
                       options::OPT_fno_stack_arrays);
   if (stackArrays &&
       !stackArrays->getOption().matches(options::OPT_fno_stack_arrays))
     CmdArgs.push_back("-fstack-arrays");
 
   if (Args.hasArg(options::OPT_flang_experimental_hlfir))
     CmdArgs.push_back("-flang-experimental-hlfir");
+  if (Args.hasArg(options::OPT_flang_experimental_polymorphism))
+    CmdArgs.push_back("-flang-experimental-polymorphism");
   if (shouldLoopVersion(Args))
     CmdArgs.push_back("-fversion-loops-for-stride");
 }
 
 void Flang::addPicOptions(const ArgList &Args, ArgStringList &CmdArgs) const {
   // ParsePICArgs parses -fPIC/-fPIE and their variants and returns a tuple of
   // (RelocationModel, PICLevel, IsPIE).
   llvm::Reloc::Model RelocationModel;

flang/lib/Frontend/CompilerInvocation.cpp

bool CompilerInvocation::createFromArgs(
   }
 
   // -flang-experimental-hlfir
   if (args.hasArg(clang::driver::options::OPT_flang_experimental_hlfir) ||
       args.hasArg(clang::driver::options::OPT_emit_hlfir)) {
     res.loweringOpts.setLowerToHighLevelFIR(true);
   }
 
+  if (args.hasArg(clang::driver::options::OPT_flang_experimental_polymorphism)) {
+    res.loweringOpts.setPolymorphicTypeImpl(true);
+  }
+
   success &= parseFrontendArgs(res.getFrontendOpts(), args, diags);
   parseTargetArgs(res.getTargetOpts(), args);
   parsePreprocessorArgs(res.getPreprocessorOpts(), args);
   parseCodeGenArgs(res.getCodeGenOpts(), args, diags);
   success &= parseDebugArgs(res.getCodeGenOpts(), args, diags);
   success &= parseSemaArgs(res, args, diags);
   success &= parseDialectArgs(res, args, diags);
   success &= parseDiagArgs(res, args, diags);

flang/test/Driver/driver-help-hidden.f90

 ! CHECK-NEXT: -ffp-contract=<value> Form fused FP ops (e.g. FMAs)
 ! CHECK-NEXT: -ffree-form            Process source files in free form
 ! CHECK-NEXT: -fimplicit-none        No implicit typing allowed unless overridden by IMPLICIT statements
 ! CHECK-NEXT: -finput-charset=<value> Specify the default character set for source files
 ! CHECK-NEXT: -fintrinsic-modules-path <dir>
 ! CHECK-NEXT:                        Specify where to find the compiled intrinsic modules
 ! CHECK-NEXT: -flang-experimental-hlfir
 ! CHECK-NEXT:                        Use HLFIR lowering (experimental)
+! CHECK-NEXT: -flang-experimental-polymorphism
+! CHECK-NEXT:                        Enable Fortran 2003 polymorphism (experimental)
 ! CHECK-NEXT: -flarge-sizes          Use INTEGER(KIND=8) for the result type in size-related intrinsics
 ! CHECK-NEXT: -flogical-abbreviations Enable logical abbreviations
 ! CHECK-NEXT: -flto=<value> Set LTO mode
 ! CHECK-NEXT: -flto Enable LTO in 'full' mode
 ! CHECK-NEXT: -fno-automatic         Implies the SAVE attribute for non-automatic local objects in subprograms unless RECURSIVE
 ! CHECK-NEXT: -fno-color-diagnostics  Disable colors in diagnostics
 ! CHECK-NEXT: -fno-integrated-as     Disable the integrated assembler
 ! CHECK-NEXT: -fno-signed-zeros      Allow optimizations that ignore the sign of floating point zeros

flang/test/Driver/flang-experimental-polymorphism-flag.f90

+! Test -flang-experimental-hlfir flag
+! RUN: %flang_fc1 -flang-experimental-polymorphism -emit-fir -o - %s | FileCheck %s
+! RUN: not %flang_fc1 -emit-fir -o - %s 2>&1 | FileCheck %s --check-prefix NO-POLYMORPHISM
+
+! CHECK: func.func @_QPtest(%{{.*}}: !fir.class<none> {fir.bindc_name = "poly"})
+subroutine test(poly)
+  class(*) :: poly
+end subroutine test
+
+! NO-POLYMORPHISM: not yet implemented: support for polymorphic types

flang/test/Driver/frontend-forwarding.f90

 ! RUN:     -ffp-contract=fast \
 ! RUN:     -fno-honor-nans \
 ! RUN:     -fapprox-func \
 ! RUN:     -fno-signed-zeros \
 ! RUN:     -fassociative-math \
 ! RUN:     -freciprocal-math \
 ! RUN:     -fpass-plugin=Bye%pluginext \
 ! RUN:     -fversion-loops-for-stride \
-! RUN:     -mllvm -print-before-all\
+! RUN:     -flang-experimental-polymorphism \
 ! RUN:     -mllvm -print-before-all \
 ! RUN:     -save-temps=obj \
 ! RUN:     -P \
 ! RUN:   | FileCheck %s
 
 ! CHECK: "-P"
 ! CHECK: "-finput-charset=utf-8"
 ! CHECK: "-fdefault-double-8"
 ! CHECK: "-fdefault-integer-8"
 ! CHECK: "-fdefault-real-8"
 ! CHECK: "-flarge-sizes"
 ! CHECK: "-ffp-contract=fast"
 ! CHECK: "-menable-no-nans"
 ! CHECK: "-fapprox-func"
 ! CHECK: "-fno-signed-zeros"
 ! CHECK: "-mreassociate"
 ! CHECK: "-freciprocal-math"
 ! CHECK: "-fconvert=little-endian"
 ! CHECK: "-fpass-plugin=Bye
-! CHECK: "-fversion-loops-for-stride"  
+! CHECK: "-flang-experimental-polymorphism"
+! CHECK: "-fversion-loops-for-stride"
 ! CHECK: "-mllvm" "-print-before-all"
 ! CHECK: "-save-temps=obj"