[RISCV] Add stub backend

This contains just enough for lib/Target/RISCV to compile. Notably a basic 
RISCVTargetMachine and RISCVTargetInfo. At this point you can attempt llc 
-march=riscv32 myinput.ll and will find it fails due to the lack of 
MCAsmInfo.

See http://lists.llvm.org/pipermail/llvm-dev/2016-August/103748.html for 
further discussion

Differential Revision: https://reviews.llvm.org/D23560

llvm-svn: 285712

Author: asb

llvm/CMakeLists.txt

@@ -279,6 +279,7 @@ set(LLVM_ALL_TARGETS
   MSP430
   NVPTX
   PowerPC
+  RISCV
   Sparc
   SystemZ
   X86

llvm/CODE_OWNERS.TXT

@@ -17,6 +17,10 @@ E: mail@justinbogner.com
 D: InstrProfiling and related parts of ProfileData
 D: SelectionDAG (lib/CodeGen/SelectionDAG/*)
 
+N: Alex Bradbury
+E: asb@lowrisc.org
+D: RISC-V backend (lib/Target/RISCV/*)
+
 N: Chandler Carruth
 E: chandlerc@gmail.com
 E: chandlerc@google.com

llvm/docs/CompilerWriterInfo.rst

@@ -83,6 +83,10 @@ AMDGPU
 * `AMD Compute Resources <http://developer.amd.com/tools/heterogeneous-computing/amd-accelerated-parallel-processing-app-sdk/documentation/>`_
 * `AMDGPU Compute Application Binary Interface <https://github.com/RadeonOpenCompute/ROCm-ComputeABI-Doc/blob/master/AMDGPU-ABI.md>`__
 
+RISC-V
+------
+* `RISC-V User-Level ISA Specification <https://riscv.org/specifications/>`_
+
 SPARC
 -----
 

llvm/lib/Target/LLVMBuild.txt

@@ -30,6 +30,7 @@ subdirectories =
  NVPTX
  Mips
  PowerPC
+ RISCV
  Sparc
  SystemZ
  WebAssembly

llvm/lib/Target/RISCV/CMakeLists.txt

@@ -0,0 +1,5 @@
+add_llvm_target(RISCVCodeGen
+  RISCVTargetMachine.cpp
+  )
+
+add_subdirectory(TargetInfo)

llvm/lib/Target/RISCV/LLVMBuild.txt

@@ -0,0 +1,31 @@
+;===- ./lib/Target/RISCV/LLVMBuild.txt -------------------------*- Conf -*--===;
+;
+;                     The LLVM Compiler Infrastructure
+;
+; This file is distributed under the University of Illinois Open Source
+; License. See LICENSE.TXT for details.
+;
+;===------------------------------------------------------------------------===;
+;
+; 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 = RISCV
+parent = Target
+
+[component_1]
+type = Library
+name = RISCVCodeGen
+parent = RISCV
+required_libraries = Core CodeGen RISCVInfo Support Target
+add_to_library_groups = RISCV

llvm/lib/Target/RISCV/RISCVTargetMachine.cpp

@@ -0,0 +1,58 @@
+//===-- RISCVTargetMachine.cpp - Define TargetMachine for RISCV -----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Implements the info about RISCV target spec.
+//
+//===----------------------------------------------------------------------===//
+
+#include "RISCVTargetMachine.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
+#include "llvm/CodeGen/TargetPassConfig.h"
+#include "llvm/IR/LegacyPassManager.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Support/FormattedStream.h"
+#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Target/TargetOptions.h"
+using namespace llvm;
+
+extern "C" void LLVMInitializeRISCVTarget() {
+  RegisterTargetMachine<RISCVTargetMachine> X(getTheRISCV32Target());
+  RegisterTargetMachine<RISCVTargetMachine> Y(getTheRISCV64Target());
+}
+
+static std::string computeDataLayout(const Triple &TT) {
+  if (TT.isArch64Bit()) {
+    return "e-m:e-i64:64-n32:64-S128";
+  } else {
+    assert(TT.isArch32Bit() && "only RV32 and RV64 are currently supported");
+    return "e-m:e-i64:64-n32-S128";
+  }
+}
+
+static Reloc::Model getEffectiveRelocModel(const Triple &TT,
+                                           Optional<Reloc::Model> RM) {
+  if (!RM.hasValue())
+    return Reloc::Static;
+  return *RM;
+}
+
+RISCVTargetMachine::RISCVTargetMachine(const Target &T, const Triple &TT,
+                                       StringRef CPU, StringRef FS,
+                                       const TargetOptions &Options,
+                                       Optional<Reloc::Model> RM,
+                                       CodeModel::Model CM,
+                                       CodeGenOpt::Level OL)
+    : LLVMTargetMachine(T, computeDataLayout(TT), TT, CPU, FS, Options,
+                        getEffectiveRelocModel(TT, RM), CM, OL),
+      TLOF(make_unique<TargetLoweringObjectFileELF>()) {}
+
+TargetPassConfig *RISCVTargetMachine::createPassConfig(PassManagerBase &PM) {
+  return new TargetPassConfig(this, PM);
+}

llvm/lib/Target/RISCV/RISCVTargetMachine.h

@@ -0,0 +1,41 @@
+//===-- RISCVTargetMachine.h - Define TargetMachine for RISCV ---*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the RISCV specific subclass of TargetMachine.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_RISCV_RISCVTARGETMACHINE_H
+#define LLVM_LIB_TARGET_RISCV_RISCVTARGETMACHINE_H
+
+#include "llvm/CodeGen/SelectionDAGTargetInfo.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/IR/DataLayout.h"
+
+namespace llvm {
+class RISCVTargetMachine : public LLVMTargetMachine {
+  std::unique_ptr<TargetLoweringObjectFile> TLOF;
+
+public:
+  RISCVTargetMachine(const Target &T, const Triple &TT, StringRef CPU,
+                     StringRef FS, const TargetOptions &Options,
+                     Optional<Reloc::Model> RM, CodeModel::Model CM,
+                     CodeGenOpt::Level OL);
+
+  TargetPassConfig *createPassConfig(PassManagerBase &PM) override;
+
+  TargetLoweringObjectFile *getObjFileLowering() const override {
+    return TLOF.get();
+  }
+};
+Target &getTheRISCV32Target();
+Target &getTheRISCV64Target();
+}
+
+#endif

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

@@ -0,0 +1,3 @@
+add_llvm_library(LLVMRISCVInfo
+  RISCVTargetInfo.cpp
+  )

llvm/lib/Target/RISCV/TargetInfo/LLVMBuild.txt

@@ -0,0 +1,23 @@
+;===- ./lib/Target/RISCV/TargetInfo/LLVMBuild.txt --------------*- Conf -*--===;
+;
+;                     The LLVM Compiler Infrastructure
+;
+; This file is distributed under the University of Illinois Open Source
+; License. See LICENSE.TXT for details.
+;
+;===------------------------------------------------------------------------===;
+;
+; 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 = RISCVInfo
+parent = RISCV
+required_libraries = Support
+add_to_library_groups = RISCV

llvm/lib/Target/RISCV/TargetInfo/RISCVTargetInfo.cpp

@@ -0,0 +1,35 @@
+//===-- RISCVTargetInfo.cpp - RISCV Target Implementation -----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/TargetRegistry.h"
+using namespace llvm;
+
+namespace llvm {
+Target &getTheRISCV32Target() {
+  static Target TheRISCV32Target;
+  return TheRISCV32Target;
+}
+
+Target &getTheRISCV64Target() {
+  static Target TheRISCV64Target;
+  return TheRISCV64Target;
+}
+}
+
+extern "C" void LLVMInitializeRISCVTargetInfo() {
+  RegisterTarget<Triple::riscv32> X(getTheRISCV32Target(), "riscv32",
+                                    "32-bit RISC-V");
+  RegisterTarget<Triple::riscv64> Y(getTheRISCV64Target(), "riscv64",
+                                    "64-bit RISC-V");
+}
+
+// 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 LLVMInitializeRISCVTargetMC() {}