[RISCV] Add bare-bones RISC-V MCTargetDesc

This is enough to compile and link but doesn't yet do anything particularly 
useful. Once an ASM parser and printer are added in the next two patches, the 
whole thing can be usefully tested.

Differential Revision: https://reviews.llvm.org/D23562

llvm-svn: 285770

1 files changed, 51 insertions, 0 deletions

diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp
new file mode 100644
index 00000000000..def20dd48e4
--- /dev/null
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp
@@ -0,0 +1,51 @@
+//===-- RISCVELFObjectWriter.cpp - RISCV ELF Writer -----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "MCTargetDesc/RISCVMCTargetDesc.h"
+#include "llvm/MC/MCELFObjectWriter.h"
+#include "llvm/MC/MCFixup.h"
+#include "llvm/Support/ErrorHandling.h"
+
+using namespace llvm;
+
+namespace {
+class RISCVELFObjectWriter : public MCELFObjectTargetWriter {
+public:
+  RISCVELFObjectWriter(uint8_t OSABI, bool Is64Bit);
+
+  ~RISCVELFObjectWriter() override;
+
+protected:
+  unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
+                        const MCFixup &Fixup, bool IsPCRel) const override;
+};
+}
+
+RISCVELFObjectWriter::RISCVELFObjectWriter(uint8_t OSABI, bool Is64Bit)
+    : MCELFObjectTargetWriter(Is64Bit, OSABI, ELF::EM_RISCV,
+                              /*HasRelocationAddend*/ false) {}
+
+RISCVELFObjectWriter::~RISCVELFObjectWriter() {}
+
+unsigned RISCVELFObjectWriter::getRelocType(MCContext &Ctx,
+                                            const MCValue &Target,
+                                            const MCFixup &Fixup,
+                                            bool IsPCRel) const {
+  // Determine the type of the relocation
+  switch ((unsigned)Fixup.getKind()) {
+  default:
+    llvm_unreachable("invalid fixup kind!");
+  }
+}
+
+MCObjectWriter *llvm::createRISCVELFObjectWriter(raw_pwrite_stream &OS,
+                                                 uint8_t OSABI, bool Is64Bit) {
+  MCELFObjectTargetWriter *MOTW = new RISCVELFObjectWriter(OSABI, Is64Bit);
+  return createELFObjectWriter(MOTW, OS, /*IsLittleEndian*/ true);
+}