[flang] Add OpenACC flag to bbc

[clementval]

Summary

Add -fopenacc flag to the bbc tool.

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

[awarzynski]

Same comment as for https://reviews.llvm.org/D121118 - this change could be avoided and flang-new could be used for OpenACC tests instead.

[clementval]

Rebase + add flang_fc1 run line

flang/test/Lower/OpenACC/pre-fir-tree01.f90

+! RUN: bbc -fopenacc -pft-test -o %t %s | FileCheck %s
+! RUN: %flang_fc1 -fopenacc -fdebug-dump-pft -o %t %s | FileCheck %s
+
+! Test structure of the Pre-FIR tree with OpenACC
+
+subroutine sub1(a, b, n)
+  real :: a(:), b(:)
+  integer :: n, i
+  !$acc parallel loop present(a, b)
+  do i = 1, n
+    b(i) = exp(a(i))
+  end do
+end subroutine
+
+! CHECK-LABEL: Subroutine sub1
+! CHECK:       <<OpenACCConstruct>>
+! CHECK:       <<DoConstruct>>
+! CHECK:       <<End OpenACCConstruct>>

flang/tools/bbc/bbc.cpp

static llvm::cl::opt<bool> pftDumpTest(
     "pft-test",
     llvm::cl::desc("parse the input, create a PFT, dump it, and exit"),
     llvm::cl::init(false));
 
 static llvm::cl::opt<bool> enableOpenMP("fopenmp",
                                         llvm::cl::desc("enable openmp"),
                                         llvm::cl::init(false));
 
+static llvm::cl::opt<bool> enableOpenACC("fopenacc",
+                                         llvm::cl::desc("enable openacc"),
+                                         llvm::cl::init(false));
+
 #define FLANG_EXCLUDE_CODEGEN
 #include "flang/Tools/CLOptions.inc"
 
 //===----------------------------------------------------------------------===//
 
 using ProgramName = std::string;
 
 // Print the module without the "module { ... }" wrapper.
options.predefinitions.emplace_back(
       "__flang_patchlevel__"s, std::string{FLANG_VERSION_PATCHLEVEL_STRING});
 
   // enable parsing of OpenMP
   if (enableOpenMP) {
     options.features.Enable(Fortran::common::LanguageFeature::OpenMP);
     options.predefinitions.emplace_back("_OPENMP", "201511");
   }
 
+  // enable parsing of OpenACC
+  if (enableOpenACC) {
+    options.features.Enable(Fortran::common::LanguageFeature::OpenACC);
+    options.predefinitions.emplace_back("_OPENACC", "201911");
+  }
+
   Fortran::common::IntrinsicTypeDefaultKinds defaultKinds;
   Fortran::parser::AllSources allSources;
   Fortran::parser::AllCookedSources allCookedSources(allSources);
   Fortran::semantics::SemanticsContext semanticsContext{
       defaultKinds, options.features, allCookedSources};
 
   return mlir::failed(convertFortranSourceToMLIR(
       inputFilename, options, programPrefix, semanticsContext, passPipe));
 }