[WebAssembly] Experimental ELF writer support

This creates the initial infrastructure for writing ELF output files. It
doesn't yet have any implementation for encoding instructions.

Differential Revision: http://reviews.llvm.org/D15555

llvm-svn: 255869

1 files changed, 58 insertions, 0 deletions

diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyELFObjectWriter.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyELFObjectWriter.cpp
new file mode 100644
index 00000000000..54953b4033d
--- /dev/null
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyELFObjectWriter.cpp
@@ -0,0 +1,58 @@
+//===-- WebAssemblyELFObjectWriter.cpp - WebAssembly ELF Writer -----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief This file handles ELF-specific object emission, converting LLVM's
+/// internal fixups into the appropriate relocations.
+///
+//===----------------------------------------------------------------------===//
+
+#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
+#include "llvm/MC/MCELFObjectWriter.h"
+#include "llvm/MC/MCFixup.h"
+#include "llvm/Support/ErrorHandling.h"
+using namespace llvm;
+
+namespace {
+class WebAssemblyELFObjectWriter final : public MCELFObjectTargetWriter {
+public:
+  WebAssemblyELFObjectWriter(bool Is64Bit, uint8_t OSABI);
+
+  ~WebAssemblyELFObjectWriter() override;
+
+protected:
+  unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
+                        bool IsPCRel) const override;
+};
+} // end anonymous namespace
+
+// FIXME: Use EM_NONE as a temporary hack. Should we decide to pursue ELF
+// writing seriously, we should email generic-abi@googlegroups.com and ask
+// for our own ELF code.
+WebAssemblyELFObjectWriter::WebAssemblyELFObjectWriter(bool Is64Bit,
+                                                       uint8_t OSABI)
+    : MCELFObjectTargetWriter(Is64Bit, OSABI, ELF::EM_NONE,
+                              /*HasRelocationAddend=*/true) {}
+
+WebAssemblyELFObjectWriter::~WebAssemblyELFObjectWriter() {}
+
+unsigned WebAssemblyELFObjectWriter::GetRelocType(const MCValue &Target,
+                                                  const MCFixup &Fixup,
+                                                  bool IsPCRel) const {
+  // FIXME: Do we need our own relocs?
+  return Fixup.getKind();
+}
+
+MCObjectWriter *llvm::createWebAssemblyELFObjectWriter(raw_pwrite_stream &OS,
+                                                       bool Is64Bit,
+                                                       uint8_t OSABI) {
+  MCELFObjectTargetWriter *MOTW =
+      new WebAssemblyELFObjectWriter(Is64Bit, OSABI);
+  return createELFObjectWriter(MOTW, OS, /*IsLittleEndian=*/true);
+}