[flang][openacc] Skeleton for OpenACC construct lowering

[clementval]

Summary

This patch introduce the basic infrastructure to be able to lower
OpenACC constructs to the future OpenACC dialect.

[clementval]

Format in test

[SouraVX]

flang/include/flang/Lower/OpenACC.h

2

Nit: OpenACC Directives ?

flang/lib/Lower/OpenACC.cpp

2

Same Nit: OpenACC ?

[clementval]

Address comments

flang/include/flang/Lower/OpenACC.h

2

Yes this should be OpenACC directives. Just updated.

flang/lib/Lower/OpenACC.cpp

2

Also updated

[ichoyjx]

flang/include/flang/Lower/PFTBuilder.h

135

We may need EndLoopDirective for OpenACC also because for combined constructs, the end * loop is optional.

flang/test/Lower/pre-fir-tree05.f90

29

What is the second <<End OpenACCConstruct>> here?

[clementval]

flang/include/flang/Lower/PFTBuilder.h

135

Right we might add a OpenACCEndCombinedDirective. Since it is not in the current parser, do you mind if we had this in a follow up patch together with the parsing part and some parsing tests?

flang/test/Lower/pre-fir-tree05.f90

29

That's the end of the loop block. Similar to pre-fir-tree03.f90 this is output for the !$omp do on line 32 check at line 41.

[schweitz]

flang/include/flang/Lower/OpenACC.h

9

We've been adding a comment to all the files in Lower that they are following the MLIR coding conventions as a reminder.

[clementval]

flang/include/flang/Lower/OpenACC.h

9

I have seen that in other file but wasn't sure if I should add it or not. I'll push a commit with this as a NFC.

flang/include/flang/Lower/OpenACC.h

+//===-- Lower/OpenACC.h -- lower OpenACC directives -------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FORTRAN_LOWER_OPENACC_H
+#define FORTRAN_LOWER_OPENACC_H
+
+namespace Fortran {
+namespace parser {
+struct OpenACCConstruct;
+} // namespace parser
+
+namespace lower {
+
+class AbstractConverter;
+
+namespace pft {
+struct Evaluation;
+} // namespace pft
+
+void genOpenACCConstruct(AbstractConverter &, pft::Evaluation &,
+                         const parser::OpenACCConstruct &);
+
+} // namespace lower
+} // namespace Fortran
+
+#endif // FORTRAN_LOWER_OPENACC_H

flang/include/flang/Lower/PFTBuilder.h

using Constructs =
     std::tuple<parser::AssociateConstruct, parser::BlockConstruct,
                parser::CaseConstruct, parser::ChangeTeamConstruct,
                parser::CriticalConstruct, parser::DoConstruct,
                parser::IfConstruct, parser::SelectRankConstruct,
                parser::SelectTypeConstruct, parser::WhereConstruct,
                parser::ForallConstruct>;
 
 using Directives =
-    std::tuple<parser::CompilerDirective, parser::OpenMPConstruct,
-               parser::OmpEndLoopDirective>;
+    std::tuple<parser::CompilerDirective, parser::OpenACCConstruct,
+               parser::OpenMPConstruct, parser::OmpEndLoopDirective>;
 
 template <typename A>
 static constexpr bool isActionStmt{common::HasMember<A, ActionStmts>};
 
 template <typename A>
 static constexpr bool isOtherStmt{common::HasMember<A, OtherStmts>};
 
 template <typename A>

flang/lib/Lower/CMakeLists.txt

 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-error -Wno-unused-parameter")
 get_property(dialect_libs GLOBAL PROPERTY MLIR_DIALECT_LIBS)
 
 add_flang_library(FortranLower
   CharacterExpr.cpp
   CharacterRuntime.cpp
   Coarray.cpp
   ComplexExpr.cpp
   ConvertType.cpp
   ConvertExpr.cpp
   DoLoopHelper.cpp
   FIRBuilder.cpp
   IntrinsicCall.cpp
   IO.cpp
   Mangler.cpp
+  OpenACC.cpp
   OpenMP.cpp
   PFTBuilder.cpp
 
   DEPENDS
   FIROptimizer
   ${dialect_libs}
 
   LINK_LIBS

flang/lib/Lower/OpenACC.cpp

+//===-- OpenMP.cpp -- OpenACC directive lowering --------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "flang/Lower/OpenACC.h"
+#include "flang/Lower/Bridge.h"
+#include "flang/Lower/FIRBuilder.h"
+#include "flang/Lower/PFTBuilder.h"
+#include "flang/Parser/parse-tree.h"
+#include "llvm/Frontend/OpenACC/ACC.h.inc"
+
+#define TODO() llvm_unreachable("not yet implemented")
+
+void Fortran::lower::genOpenACCConstruct(
+    Fortran::lower::AbstractConverter &absConv,
+    Fortran::lower::pft::Evaluation &eval,
+    const Fortran::parser::OpenACCConstruct &accConstruct) {
+
+  std::visit(
+      common::visitors{
+          [&](const Fortran::parser::OpenACCBlockConstruct &blockConstruct) {
+            TODO();
+          },
+          [&](const Fortran::parser::OpenACCCombinedConstruct
+                  &combinedConstruct) { TODO(); },
+          [&](const Fortran::parser::OpenACCLoopConstruct &loopConstruct) {
+            TODO();
+          },
+          [&](const Fortran::parser::OpenACCStandaloneConstruct
+                  &standaloneConstruct) { TODO(); },
+          [&](const Fortran::parser::OpenACCRoutineConstruct
+                  &routineConstruct) { TODO(); },
+          [&](const Fortran::parser::OpenACCCacheConstruct &cacheConstruct) {
+            TODO();
+          },
+          [&](const Fortran::parser::OpenACCWaitConstruct &waitConstruct) {
+            TODO();
+          },
+          [&](const Fortran::parser::OpenACCAtomicConstruct &atomicConstruct) {
+            TODO();
+          },
+      },
+      accConstruct.u);
+}

flang/test/Lower/pre-fir-tree05.f90

+! RUN: %f18 -fdebug-pre-fir-tree -fparse-only -fopenacc %s | FileCheck %s
+
+! Test structure of the Pre-FIR tree with OpenACC construct
+
+! CHECK: Subroutine foo
+subroutine foo()
+  ! CHECK-NEXT: <<OpenACCConstruct>>
+  ! CHECK-NEXT: <<OpenACCConstruct>>
+  !$acc parallel
+  !$acc loop
+  ! CHECK-NEXT: <<DoConstruct>>
+  ! CHECK-NEXT: NonLabelDoStmt
+  do i=1,5
+    ! CHECK-NEXT: PrintStmt
+    print *, "hey"
+    ! CHECK-NEXT: <<DoConstruct>>
+    ! CHECK-NEXT: NonLabelDoStmt
+    do j=1,5
+      ! CHECK-NEXT: PrintStmt
+      print *, "hello", i, j
+    ! CHECK-NEXT: EndDoStmt
+    ! CHECK-NEXT: <<End DoConstruct>>
+    end do
+  ! CHECK-NEXT: EndDoStmt
+  ! CHECK-NEXT: <<End DoConstruct>>
+  end do
+  !$acc end parallel
+  ! CHECK-NEXT: <<End OpenACCConstruct>>
+  ! CHECK-NEXT: <<End OpenACCConstruct>>
+  ! CHECK-NEXT: ContinueStmt
+end subroutine
+! CHECK-NEXT: EndSubroutine foo
+