Updating branches/google/stable to r178511stable

git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/google/stable@178655 91177308-0d34-0410-b5e6-96231b3b80d8

8 files changed, 208 insertions, 33 deletions

diff --git a/lib/CodeGen/AsmPrinter/CMakeLists.txt b/lib/CodeGen/AsmPrinter/CMakeLists.txt
index 58fe2ed9d3..8d15c069c6 100644
--- a/lib/CodeGen/AsmPrinter/CMakeLists.txt
+++ b/lib/CodeGen/AsmPrinter/CMakeLists.txt
@@ -9,6 +9,7 @@ add_llvm_library(LLVMAsmPrinter
   DwarfCompileUnit.cpp
   DwarfDebug.cpp
   DwarfException.cpp
+  ErlangGCPrinter.cpp
   OcamlGCPrinter.cpp
   Win64Exception.cpp
   )
diff --git a/lib/CodeGen/AsmPrinter/DIE.cpp b/lib/CodeGen/AsmPrinter/DIE.cpp
index 4ded2818ed..57e0acda89 100644
--- a/lib/CodeGen/AsmPrinter/DIE.cpp
+++ b/lib/CodeGen/AsmPrinter/DIE.cpp
@@ -112,6 +112,17 @@ DIE::~DIE() {
     delete Children[i];
 }
 
+/// Climb up the parent chain to get the compile unit DIE this DIE belongs to.
+DIE *DIE::getCompileUnit() const{
+  DIE *p = getParent();
+  while (p) {
+    if (p->getTag() == dwarf::DW_TAG_compile_unit)
+      return p;
+    p = p->getParent();
+  }
+  llvm_unreachable("We should not have orphaned DIEs.");
+}
+
 #ifndef NDEBUG
 void DIE::print(raw_ostream &O, unsigned IncIndent) {
   IndentCount += IncIndent;
@@ -133,7 +144,7 @@ void DIE::print(raw_ostream &O, unsigned IncIndent) {
     O << "Size: " << Size << "\n";
   }
 
-  const SmallVector<DIEAbbrevData, 8> &Data = Abbrev.getData();
+  const SmallVectorImpl<DIEAbbrevData> &Data = Abbrev.getData();
 
   IndentCount += 2;
   for (unsigned i = 0, N = Data.size(); i < N; ++i) {
@@ -313,7 +324,7 @@ void DIEEntry::print(raw_ostream &O) {
 ///
 unsigned DIEBlock::ComputeSize(AsmPrinter *AP) {
   if (!Size) {
-    const SmallVector<DIEAbbrevData, 8> &AbbrevData = Abbrev.getData();
+    const SmallVectorImpl<DIEAbbrevData> &AbbrevData = Abbrev.getData();
     for (unsigned i = 0, N = Values.size(); i < N; ++i)
       Size += Values[i]->SizeOf(AP, AbbrevData[i].getForm());
   }
@@ -332,7 +343,7 @@ void DIEBlock::EmitValue(AsmPrinter *Asm, unsigned Form) const {
   case dwarf::DW_FORM_block:  Asm->EmitULEB128(Size); break;
   }
 
-  const SmallVector<DIEAbbrevData, 8> &AbbrevData = Abbrev.getData();
+  const SmallVectorImpl<DIEAbbrevData> &AbbrevData = Abbrev.getData();
   for (unsigned i = 0, N = Values.size(); i < N; ++i)
     Values[i]->EmitValue(Asm, AbbrevData[i].getForm());
 }
diff --git a/lib/CodeGen/AsmPrinter/DIE.h b/lib/CodeGen/AsmPrinter/DIE.h
index 35d7959ac1..18b6966e18 100644
--- a/lib/CodeGen/AsmPrinter/DIE.h
+++ b/lib/CodeGen/AsmPrinter/DIE.h
@@ -66,7 +66,7 @@ namespace llvm {
 
     /// Data - Raw data bytes for abbreviation.
     ///
-    SmallVector<DIEAbbrevData, 8> Data;
+    SmallVector<DIEAbbrevData, 12> Data;
 
   public:
     DIEAbbrev(uint16_t T, uint16_t C) : Tag(T), ChildrenFlag(C), Data() {}
@@ -75,7 +75,7 @@ namespace llvm {
     uint16_t getTag() const { return Tag; }
     unsigned getNumber() const { return Number; }
     uint16_t getChildrenFlag() const { return ChildrenFlag; }
-    const SmallVector<DIEAbbrevData, 8> &getData() const { return Data; }
+    const SmallVectorImpl<DIEAbbrevData> &getData() const { return Data; }
     void setTag(uint16_t T) { Tag = T; }
     void setChildrenFlag(uint16_t CF) { ChildrenFlag = CF; }
     void setNumber(unsigned N) { Number = N; }
@@ -133,7 +133,7 @@ namespace llvm {
 
     /// Attribute values.
     ///
-    SmallVector<DIEValue*, 32> Values;
+    SmallVector<DIEValue*, 12> Values;
 
     // Private data for print()
     mutable unsigned IndentCount;
@@ -150,8 +150,11 @@ namespace llvm {
     unsigned getOffset() const { return Offset; }
     unsigned getSize() const { return Size; }
     const std::vector<DIE *> &getChildren() const { return Children; }
-    const SmallVector<DIEValue*, 32> &getValues() const { return Values; }
+    const SmallVectorImpl<DIEValue*> &getValues() const { return Values; }
     DIE *getParent() const { return Parent; }
+    /// Climb up the parent chain to get the compile unit DIE this DIE belongs
+    /// to.
+    DIE *getCompileUnit() const;
     void setTag(unsigned Tag) { Abbrev.setTag(Tag); }
     void setOffset(unsigned O) { Offset = O; }
     void setSize(unsigned S) { Size = S; }
@@ -232,9 +235,10 @@ namespace llvm {
     ///
     static unsigned BestForm(bool IsSigned, uint64_t Int) {
       if (IsSigned) {
-        if ((char)Int == (signed)Int)   return dwarf::DW_FORM_data1;
-        if ((short)Int == (signed)Int)  return dwarf::DW_FORM_data2;
-        if ((int)Int == (signed)Int)    return dwarf::DW_FORM_data4;
+        const int64_t SignedInt = Int;
+        if ((char)Int == SignedInt)     return dwarf::DW_FORM_data1;
+        if ((short)Int == SignedInt)    return dwarf::DW_FORM_data2;
+        if ((int)Int == SignedInt)      return dwarf::DW_FORM_data4;
       } else {
         if ((unsigned char)Int == Int)  return dwarf::DW_FORM_data1;
         if ((unsigned short)Int == Int) return dwarf::DW_FORM_data2;
diff --git a/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 01f15e52e8..1c743c2414 100644
--- a/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -35,7 +35,7 @@ using namespace llvm;
 CompileUnit::CompileUnit(unsigned UID, unsigned L, DIE *D, AsmPrinter *A,
                          DwarfDebug *DW, DwarfUnits *DWU)
   : UniqueID(UID), Language(L), CUDie(D), Asm(A), DD(DW), DU(DWU),
-    IndexTyDie(0) {
+    IndexTyDie(0), DebugInfoOffset(0) {
   DIEIntegerOne = new (DIEValueAllocator) DIEInteger(1);
 }
 
diff --git a/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h b/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
index 77bf6a9e50..2b180c6cc3 100644
--- a/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
+++ b/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
@@ -87,6 +87,9 @@ class CompileUnit {
   /// corresponds to the MDNode mapped with the subprogram DIE.
   DenseMap<DIE *, const MDNode *> ContainingTypeMap;
 
+  /// Offset of the CUDie from beginning of debug info section.
+  unsigned DebugInfoOffset;
+
   /// getLowerBoundDefault - Return the default lower bound for an array. If the
   /// DWARF version doesn't handle the language, return -1.
   int64_t getDefaultLowerBound() const;
@@ -103,6 +106,7 @@ public:
   unsigned getUniqueID()            const { return UniqueID; }
   unsigned getLanguage()            const { return Language; }
   DIE* getCUDie()                   const { return CUDie.get(); }
+  unsigned getDebugInfoOffset()     const { return DebugInfoOffset; }
   const StringMap<DIE*> &getGlobalNames() const { return GlobalNames; }
   const StringMap<DIE*> &getGlobalTypes() const { return GlobalTypes; }
 
@@ -120,6 +124,7 @@ public:
     return AccelTypes;
   }
 
+  void setDebugInfoOffset(unsigned DbgInfoOff) { DebugInfoOffset = DbgInfoOff; }
   /// hasContent - Return true if this compile unit has something to write out.
   ///
   bool hasContent() const { return !CUDie->getChildren().empty(); }
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 30bfa78989..585a92a92f 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -352,11 +352,16 @@ DIE *DwarfDebug::updateSubprogramScopeDIE(CompileUnit *SPCU,
   // If we're updating an abstract DIE, then we will be adding the children and
   // object pointer later on. But what we don't want to do is process the
   // concrete DIE twice.
-  if (DIE *AbsSPDIE = AbstractSPDies.lookup(SPNode)) {
+  DIE *AbsSPDIE = AbstractSPDies.lookup(SPNode);
+  if (AbsSPDIE) {
+    bool InSameCU = (AbsSPDIE->getCompileUnit() == SPCU->getCUDie());
     // Pick up abstract subprogram DIE.
     SPDie = new DIE(dwarf::DW_TAG_subprogram);
+    // If AbsSPDIE belongs to a different CU, use DW_FORM_ref_addr instead of
+    // DW_FORM_ref4.
     SPCU->addDIEEntry(SPDie, dwarf::DW_AT_abstract_origin,
-                      dwarf::DW_FORM_ref4, AbsSPDIE);
+                      InSameCU ? dwarf::DW_FORM_ref4 : dwarf::DW_FORM_ref_addr,
+                      AbsSPDIE);
     SPCU->addDie(SPDie);
   } else {
     DISubprogram SPDecl = SP.getFunctionDeclaration();
@@ -716,13 +721,6 @@ CompileUnit *DwarfDebug::constructCompileUnit(const MDNode *N) {
   if (!FirstCU)
     FirstCU = NewCU;
 
-  if (useSplitDwarf()) {
-    // This should be a unique identifier when we want to build .dwp files.
-    NewCU->addUInt(Die, dwarf::DW_AT_GNU_dwo_id, dwarf::DW_FORM_data8, 0);
-    // Now construct the skeleton CU associated.
-    constructSkeletonCU(N);
-  }
-
   InfoHolder.addUnit(NewCU);
 
   CUMap.insert(std::make_pair(N, NewCU));
@@ -789,6 +787,14 @@ void DwarfDebug::beginModule() {
     DIArray RetainedTypes = CUNode.getRetainedTypes();
     for (unsigned i = 0, e = RetainedTypes.getNumElements(); i != e; ++i)
       CU->getOrCreateTypeDIE(RetainedTypes.getElement(i));
+    // If we're splitting the dwarf out now that we've got the entire
+    // CU then construct a skeleton CU based upon it.
+    if (useSplitDwarf()) {
+    // This should be a unique identifier when we want to build .dwp files.
+      CU->addUInt(CU->getCUDie(), dwarf::DW_AT_GNU_dwo_id, dwarf::DW_FORM_data8, 0);
+      // Now construct the skeleton CU associated.
+      constructSkeletonCU(CUNode);
+    }
   }
 
   // Tell MMI that we have debug info.
@@ -1666,8 +1672,8 @@ DwarfUnits::computeSizeAndOffset(DIE *Die, unsigned Offset) {
   // Start the size with the size of abbreviation code.
   Offset += MCAsmInfo::getULEB128Size(AbbrevNumber);
 
-  const SmallVector<DIEValue*, 32> &Values = Die->getValues();
-  const SmallVector<DIEAbbrevData, 8> &AbbrevData = Abbrev->getData();
+  const SmallVectorImpl<DIEValue*> &Values = Die->getValues();
+  const SmallVectorImpl<DIEAbbrevData> &AbbrevData = Abbrev->getData();
 
   // Size the DIE attribute values.
   for (unsigned i = 0, N = Values.size(); i < N; ++i)
@@ -1692,15 +1698,19 @@ DwarfUnits::computeSizeAndOffset(DIE *Die, unsigned Offset) {
 
 // Compute the size and offset of all the DIEs.
 void DwarfUnits::computeSizeAndOffsets() {
-  for (SmallVector<CompileUnit *, 1>::iterator I = CUs.begin(),
+  // Offset from the beginning of debug info section.
+  unsigned AccuOffset = 0;
+  for (SmallVectorImpl<CompileUnit *>::iterator I = CUs.begin(),
          E = CUs.end(); I != E; ++I) {
+    (*I)->setDebugInfoOffset(AccuOffset);
     unsigned Offset =
       sizeof(int32_t) + // Length of Compilation Unit Info
       sizeof(int16_t) + // DWARF version number
       sizeof(int32_t) + // Offset Into Abbrev. Section
       sizeof(int8_t);   // Pointer Size (in bytes)
 
-    computeSizeAndOffset((*I)->getCUDie(), Offset);
+    unsigned EndOffset = computeSizeAndOffset((*I)->getCUDie(), Offset);
+    AccuOffset += EndOffset;
   }
 }
 
@@ -1757,8 +1767,8 @@ void DwarfDebug::emitDIE(DIE *Die, std::vector<DIEAbbrev *> *Abbrevs) {
                                 dwarf::TagString(Abbrev->getTag()));
   Asm->EmitULEB128(AbbrevNumber);
 
-  const SmallVector<DIEValue*, 32> &Values = Die->getValues();
-  const SmallVector<DIEAbbrevData, 8> &AbbrevData = Abbrev->getData();
+  const SmallVectorImpl<DIEValue*> &Values = Die->getValues();
+  const SmallVectorImpl<DIEAbbrevData> &AbbrevData = Abbrev->getData();
 
   // Emit the DIE attribute values.
   for (unsigned i = 0, N = Values.size(); i < N; ++i) {
@@ -1774,6 +1784,13 @@ void DwarfDebug::emitDIE(DIE *Die, std::vector<DIEAbbrev *> *Abbrevs) {
       DIEEntry *E = cast<DIEEntry>(Values[i]);
       DIE *Origin = E->getEntry();
       unsigned Addr = Origin->getOffset();
+      if (Form == dwarf::DW_FORM_ref_addr) {
+        // For DW_FORM_ref_addr, output the offset from beginning of debug info
+        // section. Origin->getOffset() returns the offset from start of the
+        // compile unit.
+        DwarfUnits &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;
+        Addr += Holder.getCUOffset(Origin->getCompileUnit());
+      }
       Asm->EmitInt32(Addr);
       break;
     }
@@ -1839,7 +1856,7 @@ void DwarfUnits::emitUnits(DwarfDebug *DD,
                            const MCSection *ASection,
                            const MCSymbol *ASectionSym) {
   Asm->OutStreamer.SwitchSection(USection);
-  for (SmallVector<CompileUnit *, 1>::iterator I = CUs.begin(),
+  for (SmallVectorImpl<CompileUnit *>::iterator I = CUs.begin(),
          E = CUs.end(); I != E; ++I) {
     CompileUnit *TheCU = *I;
     DIE *Die = TheCU->getCUDie();
@@ -1871,6 +1888,19 @@ void DwarfUnits::emitUnits(DwarfDebug *DD,
   }
 }
 
+/// For a given compile unit DIE, returns offset from beginning of debug info.
+unsigned DwarfUnits::getCUOffset(DIE *Die) {
+  assert(Die->getTag() == dwarf::DW_TAG_compile_unit  &&
+         "Input DIE should be compile unit in getCUOffset.");
+  for (SmallVectorImpl<CompileUnit *>::iterator I = CUs.begin(),
+       E = CUs.end(); I != E; ++I) {
+    CompileUnit *TheCU = *I;
+    if (TheCU->getCUDie() == Die)
+      return TheCU->getDebugInfoOffset();
+  }
+  llvm_unreachable("The compile unit DIE should belong to CUs in DwarfUnits.");
+}
+
 // Emit the debug info section.
 void DwarfDebug::emitDebugInfo() {
   DwarfUnits &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;
@@ -2255,7 +2285,7 @@ void DwarfDebug::emitDebugLoc() {
   if (DotDebugLocEntries.empty())
     return;
 
-  for (SmallVector<DotDebugLocEntry, 4>::iterator
+  for (SmallVectorImpl<DotDebugLocEntry>::iterator
          I = DotDebugLocEntries.begin(), E = DotDebugLocEntries.end();
        I != E; ++I) {
     DotDebugLocEntry &Entry = *I;
@@ -2269,7 +2299,7 @@ void DwarfDebug::emitDebugLoc() {
   unsigned char Size = Asm->getDataLayout().getPointerSize();
   Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("debug_loc", 0));
   unsigned index = 1;
-  for (SmallVector<DotDebugLocEntry, 4>::iterator
+  for (SmallVectorImpl<DotDebugLocEntry>::iterator
          I = DotDebugLocEntries.begin(), E = DotDebugLocEntries.end();
        I != E; ++I, ++index) {
     DotDebugLocEntry &Entry = *I;
@@ -2362,7 +2392,7 @@ void DwarfDebug::emitDebugRanges() {
   Asm->OutStreamer.SwitchSection(
     Asm->getObjFileLowering().getDwarfRangesSection());
   unsigned char Size = Asm->getDataLayout().getPointerSize();
-  for (SmallVector<const MCSymbol *, 8>::iterator
+  for (SmallVectorImpl<const MCSymbol *>::iterator
          I = DebugRangeSymbols.begin(), E = DebugRangeSymbols.end();
        I != E; ++I) {
     if (*I)
@@ -2420,13 +2450,13 @@ void DwarfDebug::emitDebugInlineInfo() {
   Asm->OutStreamer.AddComment("Address Size (in bytes)");
   Asm->EmitInt8(Asm->getDataLayout().getPointerSize());
 
-  for (SmallVector<const MDNode *, 4>::iterator I = InlinedSPNodes.begin(),
+  for (SmallVectorImpl<const MDNode *>::iterator I = InlinedSPNodes.begin(),
          E = InlinedSPNodes.end(); I != E; ++I) {
 
     const MDNode *Node = *I;
     DenseMap<const MDNode *, SmallVector<InlineInfoLabels, 4> >::iterator II
       = InlineInfo.find(Node);
-    SmallVector<InlineInfoLabels, 4> &Labels = II->second;
+    SmallVectorImpl<InlineInfoLabels> &Labels = II->second;
     DISubprogram SP(Node);
     StringRef LName = SP.getLinkageName();
     StringRef Name = SP.getName();
@@ -2445,7 +2475,7 @@ void DwarfDebug::emitDebugInlineInfo() {
                            DwarfStrSectionSym);
     Asm->EmitULEB128(Labels.size(), "Inline count");
 
-    for (SmallVector<InlineInfoLabels, 4>::iterator LI = Labels.begin(),
+    for (SmallVectorImpl<InlineInfoLabels>::iterator LI = Labels.begin(),
            LE = Labels.end(); LI != LE; ++LI) {
       if (Asm->isVerbose()) Asm->OutStreamer.AddComment("DIE offset");
       Asm->EmitInt32(LI->second->getOffset());
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.h b/lib/CodeGen/AsmPrinter/DwarfDebug.h
index 771bc362cb..81e345e628 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -274,6 +274,10 @@ public:
 
   /// \brief Returns the address pool.
   AddrPool *getAddrPool() { return &AddressPool; }
+
+  /// \brief for a given compile unit DIE, returns offset from beginning of
+  /// debug info.
+  unsigned getCUOffset(DIE *Die);
 };
 
 /// \brief Collects and handles dwarf debug information.
diff --git a/lib/CodeGen/AsmPrinter/ErlangGCPrinter.cpp b/lib/CodeGen/AsmPrinter/ErlangGCPrinter.cpp
new file mode 100644
index 0000000000..a8fb66dcf1
--- /dev/null
+++ b/lib/CodeGen/AsmPrinter/ErlangGCPrinter.cpp
@@ -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);
+    }
+  }
+}