Index: llvm/CODE_OWNERS.TXT
===================================================================
--- llvm/CODE_OWNERS.TXT
+++ llvm/CODE_OWNERS.TXT
@@ -232,3 +232,7 @@
 N: Martin Storsjö
 E: martin@martin.st
 D: MinGW
+
+N: Zi Xuan Wu (Zeson)
+E: zixuan.wu@linux.alibaba.com
+D: C-SKY backend (lib/Target/CSKY/*)
Index: llvm/docs/CompilerWriterInfo.rst
===================================================================
--- llvm/docs/CompilerWriterInfo.rst
+++ llvm/docs/CompilerWriterInfo.rst
@@ -102,6 +102,11 @@
 ------
 * `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>`_
+
 SPARC
 -----
 
Index: llvm/lib/Target/CSKY/CMakeLists.txt
===================================================================
--- /dev/null
+++ llvm/lib/Target/CSKY/CMakeLists.txt
@@ -0,0 +1,5 @@
+add_llvm_target(CSKYCodeGen
+  CSKYTargetMachine.cpp
+  )
+
+add_subdirectory(TargetInfo)
Index: llvm/lib/Target/CSKY/CSKYTargetMachine.h
===================================================================
--- /dev/null
+++ llvm/lib/Target/CSKY/CSKYTargetMachine.h
@@ -0,0 +1,38 @@
+//===--- CSKYTargetMachine.h - Define TargetMachine for CSKY ----*- 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 CSKY specific subclass of TargetMachine.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_CSKY_CSKYTARGETMACHINE_H
+#define LLVM_LIB_TARGET_CSKY_CSKYTARGETMACHINE_H
+
+#include "llvm/IR/DataLayout.h"
+#include "llvm/Target/TargetMachine.h"
+
+namespace llvm {
+
+class CSKYTargetMachine : public LLVMTargetMachine {
+  std::unique_ptr<TargetLoweringObjectFile> TLOF;
+
+public:
+  CSKYTargetMachine(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);
+
+  TargetPassConfig *createPassConfig(PassManagerBase &PM) override;
+
+  TargetLoweringObjectFile *getObjFileLowering() const override {
+    return TLOF.get();
+  }
+};
+} // namespace llvm
+
+#endif
Index: llvm/lib/Target/CSKY/CSKYTargetMachine.cpp
===================================================================
--- /dev/null
+++ llvm/lib/Target/CSKY/CSKYTargetMachine.cpp
@@ -0,0 +1,68 @@
+//===--- CSKYTargetMachine.cpp - Define TargetMachine for CSKY ------------===//
+//
+// 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 CSKY target spec.
+//
+//===----------------------------------------------------------------------===//
+
+#include "CSKYTargetMachine.h"
+#include "TargetInfo/CSKYTargetInfo.h"
+#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
+#include "llvm/CodeGen/TargetPassConfig.h"
+#include "llvm/Support/TargetRegistry.h"
+
+using namespace llvm;
+
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeCSKYTarget() {
+  RegisterTargetMachine<CSKYTargetMachine> X(getTheCSKYTarget());
+}
+
+static std::string computeDataLayout(const Triple &TT) {
+  std::string Ret;
+
+  // Only support little endian for now.
+  // TODO: Add support for big endian.
+  Ret += "e";
+
+  // CSKY is always 32-bit target with the CSKYv2 ABI as prefer now.
+  // It's a 4-byte aligned stack with ELF mangling only.
+  Ret += "-m:e-S32-p:32:32-i32:32:32-i64:32:32-f32:32:32-f64:32:32-v64:32:32"
+         "-v128:32:32-a:0:32-Fi32-n32";
+
+  return Ret;
+}
+
+CSKYTargetMachine::CSKYTargetMachine(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,
+                        !RM.hasValue() ? Reloc::Static : *RM,
+                        getEffectiveCodeModel(CM, CodeModel::Small), OL),
+      TLOF(std::make_unique<TargetLoweringObjectFileELF>()) {
+  initAsmInfo();
+}
+
+namespace {
+class CSKYPassConfig : public TargetPassConfig {
+public:
+  CSKYPassConfig(CSKYTargetMachine &TM, PassManagerBase &PM)
+      : TargetPassConfig(TM, PM) {}
+
+  CSKYTargetMachine &getCSKYTargetMachine() const {
+    return getTM<CSKYTargetMachine>();
+  }
+};
+
+} // namespace
+
+TargetPassConfig *CSKYTargetMachine::createPassConfig(PassManagerBase &PM) {
+  return new CSKYPassConfig(*this, PM);
+}
Index: llvm/lib/Target/CSKY/LLVMBuild.txt
===================================================================
--- /dev/null
+++ llvm/lib/Target/CSKY/LLVMBuild.txt
@@ -0,0 +1,30 @@
+;===----- ./lib/Target/CSKY/LLVMBuild.txt ----------------------*- Conf -*--===;
+;
+; 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 is an LLVMBuild description file for the components in this subdirectory.
+;
+; For more information on the LLVMBuild system, please see:
+;
+;   http://llvm.org/docs/LLVMBuild.html
+;
+;===------------------------------------------------------------------------===;
+
+[common]
+subdirectories = TargetInfo
+
+[component_0]
+type = TargetGroup
+name = CSKY
+parent = Target
+
+[component_1]
+type = Library
+name = CSKYCodeGen
+parent = CSKY
+required_libraries = Core CodeGen CSKYInfo Support Target
+add_to_library_groups = CSKY
Index: llvm/lib/Target/CSKY/TargetInfo/CMakeLists.txt
===================================================================
--- /dev/null
+++ llvm/lib/Target/CSKY/TargetInfo/CMakeLists.txt
@@ -0,0 +1,3 @@
+add_llvm_library(LLVMCSKYInfo
+  CSKYTargetInfo.cpp
+  )
Index: llvm/lib/Target/CSKY/TargetInfo/CSKYTargetInfo.h
===================================================================
--- /dev/null
+++ llvm/lib/Target/CSKY/TargetInfo/CSKYTargetInfo.h
@@ -0,0 +1,20 @@
+//===-- CSKYTargetInfo.cpp - CSKY 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_CSKY_TARGETINFO_CSKYTARGETINFO_H
+#define LLVM_LIB_TARGET_CSKY_TARGETINFO_CSKYTARGETINFO_H
+
+namespace llvm {
+
+class Target;
+
+Target &getTheCSKYTarget();
+
+} // namespace llvm
+
+#endif // LLVM_LIB_TARGET_CSKY_TARGETINFO_CSKYTARGETINFO_H
Index: llvm/lib/Target/CSKY/TargetInfo/CSKYTargetInfo.cpp
===================================================================
--- /dev/null
+++ llvm/lib/Target/CSKY/TargetInfo/CSKYTargetInfo.cpp
@@ -0,0 +1,25 @@
+//===-- CSKYTargetInfo.cpp - CSKY 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/CSKYTargetInfo.h"
+#include "llvm/Support/TargetRegistry.h"
+using namespace llvm;
+
+Target &llvm::getTheCSKYTarget() {
+  static Target TheCSKYTarget;
+  return TheCSKYTarget;
+}
+
+extern "C" void LLVMInitializeCSKYTargetInfo() {
+  RegisterTarget<Triple::csky> X(getTheCSKYTarget(), "csky", "C-SKY", "CSKY");
+}
+
+// FIXME: Temporary stub - this function must be defined for linking
+// to succeed and will be called unconditionally by llc, so must be a no-op.
+// Remove once this function is properly implemented.
+extern "C" void LLVMInitializeCSKYTargetMC() {}
Index: llvm/lib/Target/CSKY/TargetInfo/LLVMBuild.txt
===================================================================
--- /dev/null
+++ llvm/lib/Target/CSKY/TargetInfo/LLVMBuild.txt
@@ -0,0 +1,22 @@
+;===-- ./lib/Target/CSKY/TargetInfo/LLVMBuild.txt --------------*- Conf -*--===;
+;
+; 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 is an LLVMBuild description file for the components in this subdirectory.
+;
+; For more information on the LLVMBuild system, please see:
+;
+;   http://llvm.org/docs/LLVMBuild.html
+;
+;===------------------------------------------------------------------------===;
+
+[component_0]
+type = Library
+name = CSKYInfo
+parent = CSKY
+required_libraries = Support
+add_to_library_groups = CSKY
Index: llvm/lib/Target/LLVMBuild.txt
===================================================================
--- llvm/lib/Target/LLVMBuild.txt
+++ llvm/lib/Target/LLVMBuild.txt
@@ -24,6 +24,7 @@
  ARM
  AVR
  BPF
+ CSKY
  Hexagon
  Lanai
  MSP430