--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/CodeGen/AsmPrinter/ErlangGCPrinter.cpp	Thu Dec 12 13:56:28 2013 +0900
@@ -0,0 +1,120 @@
+//===-- ErlangGCPrinter.cpp - Erlang/OTP frametable emitter -----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the compiler plugin that is used in order to emit
+// garbage collection information in a convenient layout for parsing and
+// loading in the Erlang/OTP runtime.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/AsmPrinter.h"
+#include "llvm/CodeGen/GCs.h"
+#include "llvm/CodeGen/GCMetadataPrinter.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instruction.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Metadata.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCSectionELF.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/Target/TargetLoweringObjectFile.h"
+#include "llvm/Target/TargetMachine.h"
+
+using namespace llvm;
+
+namespace {
+
+  class ErlangGCPrinter : public GCMetadataPrinter {
+  public:
+    void beginAssembly(AsmPrinter &AP);
+    void finishAssembly(AsmPrinter &AP);
+  };
+
+}
+
+static GCMetadataPrinterRegistry::Add<ErlangGCPrinter>
+X("erlang", "erlang-compatible garbage collector");
+
+void llvm::linkErlangGCPrinter() { }
+
+void ErlangGCPrinter::beginAssembly(AsmPrinter &AP) { }
+
+void ErlangGCPrinter::finishAssembly(AsmPrinter &AP) {
+  MCStreamer &OS = AP.OutStreamer;
+  unsigned IntPtrSize = AP.TM.getDataLayout()->getPointerSize();
+
+  // Put this in a custom .note section.
+  AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getContext()
+    .getELFSection(".note.gc", ELF::SHT_PROGBITS, 0,
+                   SectionKind::getDataRel()));
+
+  // For each function...
+  for (iterator FI = begin(), FE = end(); FI != FE; ++FI) {
+    GCFunctionInfo &MD = **FI;
+
+    /** A compact GC layout. Emit this data structure:
+     *
+     * struct {
+     *   int16_t PointCount;
+     *   void *SafePointAddress[PointCount];
+     *   int16_t StackFrameSize; (in words)
+     *   int16_t StackArity;
+     *   int16_t LiveCount;
+     *   int16_t LiveOffsets[LiveCount];
+     * } __gcmap_<FUNCTIONNAME>;
+     **/
+
+    // Align to address width.
+    AP.EmitAlignment(IntPtrSize == 4 ? 2 : 3);
+
+    // Emit PointCount.
+    OS.AddComment("safe point count");
+    AP.EmitInt16(MD.size());
+
+    // And each safe point...
+    for (GCFunctionInfo::iterator PI = MD.begin(), PE = MD.end(); PI != PE;
+         ++PI) {
+      // Emit the address of the safe point.
+      OS.AddComment("safe point address");
+      MCSymbol *Label = PI->Label;
+      AP.EmitLabelPlusOffset(Label/*Hi*/, 0/*Offset*/, 4/*Size*/);
+    }
+
+    // Stack information never change in safe points! Only print info from the
+    // first call-site.
+    GCFunctionInfo::iterator PI = MD.begin();
+
+    // Emit the stack frame size.
+    OS.AddComment("stack frame size (in words)");
+    AP.EmitInt16(MD.getFrameSize() / IntPtrSize);
+
+    // Emit stack arity, i.e. the number of stacked arguments.
+    unsigned RegisteredArgs = IntPtrSize == 4 ? 5 : 6;
+    unsigned StackArity = MD.getFunction().arg_size() > RegisteredArgs ?
+                          MD.getFunction().arg_size() - RegisteredArgs : 0;
+    OS.AddComment("stack arity");
+    AP.EmitInt16(StackArity);
+
+    // Emit the number of live roots in the function.
+    OS.AddComment("live root count");
+    AP.EmitInt16(MD.live_size(PI));
+
+    // And for each live root...
+    for (GCFunctionInfo::live_iterator LI = MD.live_begin(PI),
+                                       LE = MD.live_end(PI);
+                                       LI != LE; ++LI) {
+      // Emit live root's offset within the stack frame.
+      OS.AddComment("stack index (offset / wordsize)");
+      AP.EmitInt16(LI->StackOffset / IntPtrSize);
+    }
+  }
+}