//===========- DirectiveCommonGen.cpp - Directive common info generator -=====//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// OpenMPCommonGen generates utility information from the single OpenMP source
// of truth in llvm/lib/Frontend/OpenMP.
//
//===----------------------------------------------------------------------===//

#include "mlir/TableGen/GenInfo.h"

#include "llvm/ADT/Twine.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/TableGen/DirectiveEmitter.h"
#include "llvm/TableGen/Error.h"
#include "llvm/TableGen/Record.h"

using llvm::Clause;
using llvm::EnumVal;
using llvm::raw_ostream;
using llvm::RecordKeeper;

// LLVM has multiple places (Clang, Flang, MLIR) where information about
// the directives (OpenMP/OpenACC), and clauses are needed. It is good software
// engineering to keep the common information in a single place to avoid
// duplication, reduce engineering effort and prevent mistakes.
// Currently that common place is llvm/include/llvm/Frontend/OpenMP/OMP.td for
// OpenMP and llvm/include/llvm/Frontend/OpenACC/ACC.td for OpenACC.
// We plan to use this tablegen source to generate all the required
// declarations, functions etc.
//
// Some OpenMP/OpenACC clauses accept only a fixed set of values as inputs.
// These can be represented as a Enum Attributes (EnumAttrDef) in MLIR
// ODS. The emitDecls function below currently generates these enumerations. The
// name of the enumeration is specified in the enumClauseValue field of
// Clause record in OMP.td. This name can be used to specify the type of the
// OpenMP operation's operand. The allowedClauseValues field provides the list
// of ClauseValues which are part of the enumeration.
static bool emitDecls(const RecordKeeper &records, llvm::StringRef dialect,
                      raw_ostream &os) {
  // A dialect must be selected for the generated attributes.
  if (dialect.empty()) {
    llvm::PrintFatalError("a dialect must be selected for the directives via "
                          "'--directives-dialect'");
  }

  const auto directiveLanguages =
      records.getAllDerivedDefinitions("DirectiveLanguage");
  assert(!directiveLanguages.empty() && "DirectiveLanguage missing.");

  for (const Clause c : records.getAllDerivedDefinitions("Clause")) {
    const auto &clauseVals = c.getClauseVals();
    if (clauseVals.empty())
      continue;

    const auto enumName = c.getEnumName();
    assert(!enumName.empty() && "enumClauseValue field not set.");

    std::vector<std::string> cvDefs;
    for (const auto &it : llvm::enumerate(clauseVals)) {
      const EnumVal val{it.value()};
      if (!val.isUserVisible())
        continue;

      std::string name = val.getFormattedName();
      std::string enumValName(name.length(), ' ');
      llvm::transform(name, enumValName.begin(), llvm::toLower);
      enumValName[0] = llvm::toUpper(enumValName[0]);
      std::string cvDef{(enumName + llvm::Twine(name)).str()};
      os << "def " << cvDef << " : I32EnumAttrCase<\"" << enumValName << "\", "
         << it.index() << ", \"" << name << "\">;\n";
      cvDefs.push_back(cvDef);
    }

    os << "def " << enumName << ": I32EnumAttr<\n";
    os << "  \"Clause" << enumName << "\",\n";
    os << "  \"" << enumName << " Clause\",\n";
    os << "  [";
    llvm::interleaveComma(cvDefs, os);
    os << "]> {\n";
    os << "    let cppNamespace = \"::mlir::"
       << directiveLanguages[0]->getValueAsString("cppNamespace") << "\";\n";
    os << "    let genSpecializedAttr = 0;\n";
    os << "}\n";
    llvm::SmallString<16> mnemonic;
    llvm::transform(enumName, std::back_inserter(mnemonic), llvm::toLower);
    os << "def " << enumName << "Attr : EnumAttr<" << dialect << "_Dialect, "
       << enumName << ", \"" << mnemonic << "\">;\n";
  }
  return false;
}

static llvm::cl::OptionCategory
    directiveGenCat("Options for gen-directive-decl");
static llvm::cl::opt<std::string>
    dialect("directives-dialect",
            llvm::cl::desc("Generate directives for this dialect"),
            llvm::cl::cat(directiveGenCat), llvm::cl::CommaSeparated);

// Registers the generator to mlir-tblgen.
static mlir::GenRegistration genDirectiveDecls(
    "gen-directive-decl",
    "Generate declarations for directives (OpenMP/OpenACC etc.)",
    [](const RecordKeeper &records, raw_ostream &os) {
      return emitDecls(records, dialect, os);
    });