Imported Upstream version 5.18.0.161

Former-commit-id: 4db48158d3a35497b8f118ab21b5f08ac3d86d98

external/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyELFObjectWriter.cpp

@@ -0,0 +1,68 @@
+//===-- 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/MC/MCObjectWriter.h"
+#include "llvm/Support/ErrorHandling.h"
+using namespace llvm;
+
+namespace {
+class WebAssemblyELFObjectWriter final : public MCELFObjectTargetWriter {
+public:
+  WebAssemblyELFObjectWriter(bool Is64Bit, uint8_t OSABI);
+
+protected:
+  unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
+                        const MCFixup &Fixup, bool IsPCRel) const override;
+};
+} // end anonymous namespace
+
+WebAssemblyELFObjectWriter::WebAssemblyELFObjectWriter(bool Is64Bit,
+                                                       uint8_t OSABI)
+    : MCELFObjectTargetWriter(Is64Bit, OSABI, ELF::EM_WEBASSEMBLY,
+                              /*HasRelocationAddend=*/false) {}
+
+unsigned WebAssemblyELFObjectWriter::getRelocType(MCContext &Ctx,
+                                                  const MCValue &Target,
+                                                  const MCFixup &Fixup,
+                                                  bool IsPCRel) const {
+  // WebAssembly functions are not allocated in the address space. To resolve a
+  // pointer to a function, we must use a special relocation type.
+  if (const MCSymbolRefExpr *SyExp =
+          dyn_cast<MCSymbolRefExpr>(Fixup.getValue()))
+    if (SyExp->getKind() == MCSymbolRefExpr::VK_WebAssembly_FUNCTION)
+      return ELF::R_WEBASSEMBLY_FUNCTION;
+
+  switch (Fixup.getKind()) {
+  case FK_Data_4:
+    assert(!is64Bit() && "4-byte relocations only supported on wasm32");
+    return ELF::R_WEBASSEMBLY_DATA;
+  case FK_Data_8:
+    assert(is64Bit() && "8-byte relocations only supported on wasm64");
+    return ELF::R_WEBASSEMBLY_DATA;
+  default:
+    llvm_unreachable("unimplemented fixup kind");
+  }
+}
+
+std::unique_ptr<MCObjectWriter>
+llvm::createWebAssemblyELFObjectWriter(raw_pwrite_stream &OS,
+                                       bool Is64Bit,
+                                       uint8_t OSABI) {
+  auto MOTW = llvm::make_unique<WebAssemblyELFObjectWriter>(Is64Bit, OSABI);
+  return createELFObjectWriter(std::move(MOTW), OS, /*IsLittleEndian=*/true);
+}