[LoongArch 3/n] Add target stub for LoongArch

[SixWeining]

Summary

This patch registers the 'loongarch32' and 'loongarch64' targets. Also adds a
simple testcase to check the output of llc --vesion containing the targets.

Depends on D115773

[SixWeining]

update

llvm/CODE_OWNERS.TXT

 E: [e-mail]
 D: VLIW Instruction Scheduling, Packetization
 
 N: Chris Lattner
 E: [e-mail]
 W: http://nondot.org/~sabre/
 D: Everything not covered by someone else
 
+N: Weining Lu
+E: [e-mail]
+D: LoongArch backend (lib/Target/LoongArch/*)
+
 N: David Majnemer
 E: [e-mail]
 D: IR Constant Folder, InstCombine
 
 N: Dylan McKay
 E: [e-mail]
 D: AVR Backend
 

llvm/docs/CompilerWriterInfo.rst

 ------
 * `RISC-V User-Level ISA Specification <https://riscv.org/specifications/>`_
 
 C-SKY
 ------
 * `C-SKY Architecture User Guide <https://github.com/c-sky/csky-doc/blob/master/CSKY%20Architecture%20user_guide.pdf>`_
 * `C-SKY V2 ABI <https://github.com/c-sky/csky-doc/blob/master/C-SKY_V2_CPU_Applications_Binary_Interface_Standards_Manual.pdf>`_
 
+LoongArch
+---------
+* `LoongArch Reference Manual - Volume 1: Basic Architecture <https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html>`_
+* `LoongArch ELF ABI specification <https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html>`_
+
 SPARC
 -----
 
 * `SPARC standards <http://sparc.org/standards>`_
 * `SPARC V9 ABI <http://sparc.org/standards/64.psabi.1.35.ps.Z>`_
 * `SPARC V8 ABI <http://sparc.org/standards/psABI3rd.pdf>`_
 
 SystemZ

llvm/lib/Target/LoongArch/CMakeLists.txt

+add_llvm_component_group(LoongArch)
+
+add_llvm_target(LoongArchCodeGen
+  LoongArchTargetMachine.cpp
+
+  LINK_COMPONENTS
+  Analysis
+  AsmPrinter
+  CodeGen
+  Core
+  MC
+  LoongArchDesc
+  LoongArchInfo
+  SelectionDAG
+  Support
+  Target
+  GlobalISel
+
+  ADD_TO_COMPONENT
+  LoongArch
+  )
+
+add_subdirectory(MCTargetDesc)
+add_subdirectory(TargetInfo)

llvm/lib/Target/LoongArch/LoongArchTargetMachine.h

+//=- LoongArchTargetMachine.h - Define TargetMachine for LoongArch -*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the LoongArch specific subclass of TargetMachine.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_LOONGARCH_LOONGARCHTARGETMACHINE_H
+#define LLVM_LIB_TARGET_LOONGARCH_LOONGARCHTARGETMACHINE_H
+
+#include "llvm/Target/TargetMachine.h"
+
+namespace llvm {
+
+class LoongArchTargetMachine : public LLVMTargetMachine {
+
+public:
+  LoongArchTargetMachine(const Target &T, const Triple &TT, StringRef CPU,
+                         StringRef FS, const TargetOptions &Options,
+                         Optional<Reloc::Model> RM,
+                         Optional<CodeModel::Model> CM, CodeGenOpt::Level OL,
+                         bool JIT);
+  ~LoongArchTargetMachine() override;
+};
+
+} // end namespace llvm
+
+#endif // LLVM_LIB_TARGET_LOONGARCH_LOONGARCHTARGETMACHINE_H

llvm/lib/Target/LoongArch/LoongArchTargetMachine.cpp

+//===-- LoongArchTargetMachine.cpp - Define TargetMachine for LoongArch ---===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Implements the info about LoongArch target spec.
+//
+//===----------------------------------------------------------------------===//
+
+#include "LoongArchTargetMachine.h"
+#include "TargetInfo/LoongArchTargetInfo.h"
+#include "llvm/MC/TargetRegistry.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "loongarch"
+
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeLoongArchTarget() {
+  // Register the target.
+  RegisterTargetMachine<LoongArchTargetMachine> X(getTheLA32Target());
+  RegisterTargetMachine<LoongArchTargetMachine> Y(getTheLA64Target());
+}
+
+// FIXME: This is just a placeholder to make current commit buildable. Body of
+// this function will be filled in later commits.
+static std::string computeDataLayout(const Triple &TT) {
+  std::string Ret;
+  Ret += "e";
+  return Ret;
+}
+
+static Reloc::Model getEffectiveRelocModel(const Triple &TT,
+                                           Optional<Reloc::Model> RM) {
+  if (!RM.hasValue())
+    return Reloc::Static;
+  return *RM;
+}
+
+LoongArchTargetMachine::LoongArchTargetMachine(
+    const Target &T, const Triple &TT, StringRef CPU, StringRef FS,
+    const TargetOptions &Options, Optional<Reloc::Model> RM,
+    Optional<CodeModel::Model> CM, CodeGenOpt::Level OL, bool JIT)
+    : LLVMTargetMachine(T, computeDataLayout(TT), TT, CPU, FS, Options,
+                        getEffectiveRelocModel(TT, RM),
+                        getEffectiveCodeModel(CM, CodeModel::Small), OL) {
+  initAsmInfo();
+}
+
+LoongArchTargetMachine::~LoongArchTargetMachine() = default;

llvm/lib/Target/LoongArch/MCTargetDesc/CMakeLists.txt

+add_llvm_component_library(LLVMLoongArchDesc
+  LoongArchMCTargetDesc.cpp
+
+  LINK_COMPONENTS
+  MC
+  LoongArchInfo
+  Support
+
+  ADD_TO_COMPONENT
+  LoongArch
+  )

llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCTargetDesc.cpp

+//===-- LoongArchMCTargetDesc.cpp - LoongArch Target Descriptions ---------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file provides LoongArch specific target descriptions.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/Compiler.h"
+
+// FIXME: This is just a placeholder to make current commit buildable. Body of
+// this function will be filled in later commits.
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeLoongArchTargetMC() {}

llvm/lib/Target/LoongArch/TargetInfo/CMakeLists.txt

+add_llvm_component_library(LLVMLoongArchInfo
+  LoongArchTargetInfo.cpp
+
+  LINK_COMPONENTS
+  Support
+
+  ADD_TO_COMPONENT
+  LoongArch
+  )

llvm/lib/Target/LoongArch/TargetInfo/LoongArchTargetInfo.h

+//===-- LoongArchTargetInfo.h - LoongArch Target Implementation -*- 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 LLVM_LIB_TARGET_LOONGARCH_TARGETINFO_LOONGARCHTARGETINFO_H
+#define LLVM_LIB_TARGET_LOONGARCH_TARGETINFO_LOONGARCHTARGETINFO_H
+
+namespace llvm {
+
+class Target;
+
+Target &getTheLA32Target();
+Target &getTheLA64Target();
+
+} // namespace llvm
+
+#endif // LLVM_LIB_TARGET_LOONGARCH_TARGETINFO_LOONGARCHTARGETINFO_H

llvm/lib/Target/LoongArch/TargetInfo/LoongArchTargetInfo.cpp

+//===-- LoongArchTargetInfo.cpp - LoongArch Target Implementation ---------===//
+//
+// 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 "TargetInfo/LoongArchTargetInfo.h"
+#include "llvm/MC/TargetRegistry.h"
+using namespace llvm;
+
+Target &llvm::getTheLA32Target() {
+  static Target TheLA32Target;
+  return TheLA32Target;
+}
+
+Target &llvm::getTheLA64Target() {
+  static Target TheLA64Target;
+  return TheLA64Target;
+}
+
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeLoongArchTargetInfo() {
+  RegisterTarget<Triple::loongarch32, /*HasJIT=*/false> X(
+      getTheLA32Target(), "loongarch32", "LoongArch (32-bit)", "LoongArch");
+  RegisterTarget<Triple::loongarch64, /*HasJIT=*/false> Y(
+      getTheLA64Target(), "loongarch64", "LoongArch (64-bit)", "LoongArch");
+}

llvm/test/CodeGen/LoongArch/lit.local.cfg

+if not 'LoongArch' in config.root.targets:
+    config.unsupported = True

llvm/test/CodeGen/LoongArch/target_support.ll

+; RUN: llc --version | FileCheck %s
+; CHECK:    loongarch32 - LoongArch (32-bit)
+; CHECK:    loongarch64 - LoongArch (64-bit)