1 files changed, 158 insertions, 0 deletions
diff --git a/lib/Target/ARM64/MCTargetDesc/ARM64ELFStreamer.cpp b/lib/Target/ARM64/MCTargetDesc/ARM64ELFStreamer.cpp
new file mode 100644
index 0000000000..97a34938af
--- /dev/null
+++ b/lib/Target/ARM64/MCTargetDesc/ARM64ELFStreamer.cpp
@@ -0,0 +1,158 @@
+//===- lib/MC/ARM64ELFStreamer.cpp - ELF Object Output for ARM64 ----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file assembles .s files and emits AArch64 ELF .o object files. Different
+// from generic ELF streamer in emitting mapping symbols ($x and $d) to delimit
+// regions of data and code.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/MC/MCELFStreamer.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/Twine.h"
+#include "llvm/MC/MCAsmBackend.h"
+#include "llvm/MC/MCAssembler.h"
+#include "llvm/MC/MCCodeEmitter.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCELF.h"
+#include "llvm/MC/MCELFStreamer.h"
+#include "llvm/MC/MCELFSymbolFlags.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCObjectStreamer.h"
+#include "llvm/MC/MCSection.h"
+#include "llvm/MC/MCSectionELF.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCValue.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ELF.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+namespace {
+
+/// Extend the generic ELFStreamer class so that it can emit mapping symbols at
+/// the appropriate points in the object files. These symbols are defined in the
+/// AArch64 ELF ABI:
+///    infocenter.arm.com/help/topic/com.arm.doc.ihi0056a/IHI0056A_aaelf64.pdf
+///
+/// In brief: $x or $d should be emitted at the start of each contiguous region
+/// of A64 code or data in a section. In practice, this emission does not rely
+/// on explicit assembler directives but on inherent properties of the
+/// directives doing the emission (e.g. ".byte" is data, "add x0, x0, x0" an
+/// instruction).
+///
+/// As a result this system is orthogonal to the DataRegion infrastructure used
+/// by MachO. Beware!
+class ARM64ELFStreamer : public MCELFStreamer {
+public:
+  ARM64ELFStreamer(MCContext &Context, MCAsmBackend &TAB, raw_ostream &OS,
+                   MCCodeEmitter *Emitter)
+      : MCELFStreamer(Context, TAB, OS, Emitter), MappingSymbolCounter(0),
+        LastEMS(EMS_None) {}
+
+  ~ARM64ELFStreamer() {}
+
+  virtual void ChangeSection(const MCSection *Section,
+                             const MCExpr *Subsection) {
+    // We have to keep track of the mapping symbol state of any sections we
+    // use. Each one should start off as EMS_None, which is provided as the
+    // default constructor by DenseMap::lookup.
+    LastMappingSymbols[getPreviousSection().first] = LastEMS;
+    LastEMS = LastMappingSymbols.lookup(Section);
+
+    MCELFStreamer::ChangeSection(Section, Subsection);
+  }
+
+  /// This function is the one used to emit instruction data into the ELF
+  /// streamer. We override it to add the appropriate mapping symbol if
+  /// necessary.
+  virtual void EmitInstruction(const MCInst &Inst, const MCSubtargetInfo &STI) {
+    EmitA64MappingSymbol();
+    MCELFStreamer::EmitInstruction(Inst, STI);
+  }
+
+  /// This is one of the functions used to emit data into an ELF section, so the
+  /// ARM64 streamer overrides it to add the appropriate mapping symbol ($d)
+  /// if necessary.
+  virtual void EmitBytes(StringRef Data) {
+    EmitDataMappingSymbol();
+    MCELFStreamer::EmitBytes(Data);
+  }
+
+  /// This is one of the functions used to emit data into an ELF section, so the
+  /// ARM64 streamer overrides it to add the appropriate mapping symbol ($d)
+  /// if necessary.
+  virtual void EmitValueImpl(const MCExpr *Value, unsigned Size) {
+    EmitDataMappingSymbol();
+    MCELFStreamer::EmitValueImpl(Value, Size);
+  }
+
+private:
+  enum ElfMappingSymbol {
+    EMS_None,
+    EMS_A64,
+    EMS_Data
+  };
+
+  void EmitDataMappingSymbol() {
+    if (LastEMS == EMS_Data)
+      return;
+    EmitMappingSymbol("$d");
+    LastEMS = EMS_Data;
+  }
+
+  void EmitA64MappingSymbol() {
+    if (LastEMS == EMS_A64)
+      return;
+    EmitMappingSymbol("$x");
+    LastEMS = EMS_A64;
+  }
+
+  void EmitMappingSymbol(StringRef Name) {
+    MCSymbol *Start = getContext().CreateTempSymbol();
+    EmitLabel(Start);
+
+    MCSymbol *Symbol = getContext().GetOrCreateSymbol(
+        Name + "." + Twine(MappingSymbolCounter++));
+
+    MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
+    MCELF::SetType(SD, ELF::STT_NOTYPE);
+    MCELF::SetBinding(SD, ELF::STB_LOCAL);
+    SD.setExternal(false);
+    Symbol->setSection(*getCurrentSection().first);
+
+    const MCExpr *Value = MCSymbolRefExpr::Create(Start, getContext());
+    Symbol->setVariableValue(Value);
+  }
+
+  int64_t MappingSymbolCounter;
+
+  DenseMap<const MCSection *, ElfMappingSymbol> LastMappingSymbols;
+  ElfMappingSymbol LastEMS;
+
+  /// @}
+};
+}
+
+namespace llvm {
+MCELFStreamer *createARM64ELFStreamer(MCContext &Context, MCAsmBackend &TAB,
+                                      raw_ostream &OS, MCCodeEmitter *Emitter,
+                                      bool RelaxAll, bool NoExecStack) {
+  ARM64ELFStreamer *S = new ARM64ELFStreamer(Context, TAB, OS, Emitter);
+  if (RelaxAll)
+    S->getAssembler().setRelaxAll(true);
+  if (NoExecStack)
+    S->getAssembler().setNoExecStack(true);
+  return S;
+}
+}