[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

1 files changed, 58 insertions, 0 deletions

diff --git a/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp b/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp
new file mode 100644
index 00000000000..afbbe004186
--- /dev/null
+++ b/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);
+}