1 files changed, 92 insertions, 0 deletions
diff --git a/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp b/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp
new file mode 100644
index 000000000000..2846ec5e9337
--- /dev/null
+++ b/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp
@@ -0,0 +1,92 @@
+//===-- WebAssemblyWasmObjectWriter.cpp - WebAssembly Wasm 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 Wasm-specific object emission, converting LLVM's
+/// internal fixups into the appropriate relocations.
+///
+//===----------------------------------------------------------------------===//
+
+#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
+#include "MCTargetDesc/WebAssemblyFixupKinds.h"
+#include "llvm/MC/MCFixup.h"
+#include "llvm/MC/MCSymbolWasm.h"
+#include "llvm/MC/MCWasmObjectWriter.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/Wasm.h"
+using namespace llvm;
+
+namespace {
+class WebAssemblyWasmObjectWriter final : public MCWasmObjectTargetWriter {
+public:
+  explicit WebAssemblyWasmObjectWriter(bool Is64Bit);
+
+private:
+  unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
+                        const MCFixup &Fixup, bool IsPCRel) const override;
+};
+} // end anonymous namespace
+
+WebAssemblyWasmObjectWriter::WebAssemblyWasmObjectWriter(bool Is64Bit)
+    : MCWasmObjectTargetWriter(Is64Bit) {}
+
+// Test whether the given expression computes a function address.
+static bool IsFunctionExpr(const MCExpr *Expr) {
+  if (const MCSymbolRefExpr *SyExp =
+          dyn_cast<MCSymbolRefExpr>(Expr))
+    return cast<MCSymbolWasm>(SyExp->getSymbol()).isFunction();
+
+  if (const MCBinaryExpr *BinOp =
+          dyn_cast<MCBinaryExpr>(Expr))
+    return IsFunctionExpr(BinOp->getLHS()) != IsFunctionExpr(BinOp->getRHS());
+
+  if (const MCUnaryExpr *UnOp =
+          dyn_cast<MCUnaryExpr>(Expr))
+    return IsFunctionExpr(UnOp->getSubExpr());
+
+  return false;
+}
+
+unsigned WebAssemblyWasmObjectWriter::getRelocType(MCContext &Ctx,
+                                                   const MCValue &Target,
+                                                   const MCFixup &Fixup,
+                                                   bool IsPCRel) const {
+  // WebAssembly functions are not allocated in the data address space. To
+  // resolve a pointer to a function, we must use a special relocation type.
+  bool IsFunction = IsFunctionExpr(Fixup.getValue());
+
+  assert(!IsPCRel);
+  switch (unsigned(Fixup.getKind())) {
+  case WebAssembly::fixup_code_sleb128_i32:
+    if (IsFunction)
+      return wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB;
+    return wasm::R_WEBASSEMBLY_GLOBAL_ADDR_SLEB;
+  case WebAssembly::fixup_code_sleb128_i64:
+    llvm_unreachable("fixup_sleb128_i64 not implemented yet");
+  case WebAssembly::fixup_code_uleb128_i32:
+    if (IsFunction)
+      return wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB;
+    return wasm::R_WEBASSEMBLY_GLOBAL_ADDR_LEB;
+  case FK_Data_4:
+    if (IsFunction)
+      return wasm::R_WEBASSEMBLY_TABLE_INDEX_I32;
+    return wasm::R_WEBASSEMBLY_GLOBAL_ADDR_I32;
+  case FK_Data_8:
+    llvm_unreachable("FK_Data_8 not implemented yet");
+  default:
+    llvm_unreachable("unimplemented fixup kind");
+  }
+}
+
+MCObjectWriter *llvm::createWebAssemblyWasmObjectWriter(raw_pwrite_stream &OS,
+                                                        bool Is64Bit) {
+  MCWasmObjectTargetWriter *MOTW = new WebAssemblyWasmObjectWriter(Is64Bit);
+  return createWasmObjectWriter(MOTW, OS);
+}