--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/Target/TargetLoweringObjectFile.cpp	Thu Dec 12 13:56:28 2013 +0900
@@ -0,0 +1,335 @@
+//===-- llvm/Target/TargetLoweringObjectFile.cpp - Object File Info -------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements classes used to handle lowerings specific to common
+// object file formats.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Target/TargetLoweringObjectFile.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/Support/Dwarf.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/Mangler.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetOptions.h"
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+//                              Generic Code
+//===----------------------------------------------------------------------===//
+
+/// Initialize - this method must be called before any actual lowering is
+/// done.  This specifies the current context for codegen, and gives the
+/// lowering implementations a chance to set up their default sections.
+void TargetLoweringObjectFile::Initialize(MCContext &ctx,
+                                          const TargetMachine &TM) {
+  Ctx = &ctx;
+  InitMCObjectFileInfo(TM.getTargetTriple(),
+                       TM.getRelocationModel(), TM.getCodeModel(), *Ctx);
+}
+  
+TargetLoweringObjectFile::~TargetLoweringObjectFile() {
+}
+
+static bool isSuitableForBSS(const GlobalVariable *GV, bool NoZerosInBSS) {
+  const Constant *C = GV->getInitializer();
+
+  // Must have zero initializer.
+  if (!C->isNullValue())
+    return false;
+
+  // Leave constant zeros in readonly constant sections, so they can be shared.
+  if (GV->isConstant())
+    return false;
+
+  // If the global has an explicit section specified, don't put it in BSS.
+  if (!GV->getSection().empty())
+    return false;
+
+  // If -nozero-initialized-in-bss is specified, don't ever use BSS.
+  if (NoZerosInBSS)
+    return false;
+
+  // Otherwise, put it in BSS!
+  return true;
+}
+
+/// IsNullTerminatedString - Return true if the specified constant (which is
+/// known to have a type that is an array of 1/2/4 byte elements) ends with a
+/// nul value and contains no other nuls in it.  Note that this is more general
+/// than ConstantDataSequential::isString because we allow 2 & 4 byte strings.
+static bool IsNullTerminatedString(const Constant *C) {
+  // First check: is we have constant array terminated with zero
+  if (const ConstantDataSequential *CDS = dyn_cast<ConstantDataSequential>(C)) {
+    unsigned NumElts = CDS->getNumElements();
+    assert(NumElts != 0 && "Can't have an empty CDS");
+    
+    if (CDS->getElementAsInteger(NumElts-1) != 0)
+      return false; // Not null terminated.
+    
+    // Verify that the null doesn't occur anywhere else in the string.
+    for (unsigned i = 0; i != NumElts-1; ++i)
+      if (CDS->getElementAsInteger(i) == 0)
+        return false;
+    return true;
+  }
+
+  // Another possibility: [1 x i8] zeroinitializer
+  if (isa<ConstantAggregateZero>(C))
+    return cast<ArrayType>(C->getType())->getNumElements() == 1;
+
+  return false;
+}
+
+/// Return the MCSymbol for the specified global value.  This
+/// symbol is the main label that is the address of the global.
+MCSymbol *TargetLoweringObjectFile::getSymbol(Mangler &M, 
+                                              const GlobalValue *GV) const {
+  SmallString<60> NameStr;
+  M.getNameWithPrefix(NameStr, GV, false);
+  return Ctx->GetOrCreateSymbol(NameStr.str());
+}
+
+
+MCSymbol *TargetLoweringObjectFile::
+getCFIPersonalitySymbol(const GlobalValue *GV, Mangler *Mang,
+                        MachineModuleInfo *MMI) const {
+  return getSymbol(*Mang, GV);
+}
+
+void TargetLoweringObjectFile::emitPersonalityValue(MCStreamer &Streamer,
+                                                    const TargetMachine &TM,
+                                                    const MCSymbol *Sym) const {
+}
+
+
+/// getKindForGlobal - This is a top-level target-independent classifier for
+/// a global variable.  Given an global variable and information from TM, it
+/// classifies the global in a variety of ways that make various target
+/// implementations simpler.  The target implementation is free to ignore this
+/// extra info of course.
+SectionKind TargetLoweringObjectFile::getKindForGlobal(const GlobalValue *GV,
+                                                       const TargetMachine &TM){
+  assert(!GV->isDeclaration() && !GV->hasAvailableExternallyLinkage() &&
+         "Can only be used for global definitions");
+
+  Reloc::Model ReloModel = TM.getRelocationModel();
+
+  // Early exit - functions should be always in text sections.
+  const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
+  if (GVar == 0)
+    return SectionKind::getText();
+
+  // Handle thread-local data first.
+  if (GVar->isThreadLocal()) {
+    if (isSuitableForBSS(GVar, TM.Options.NoZerosInBSS))
+      return SectionKind::getThreadBSS();
+    return SectionKind::getThreadData();
+  }
+
+  // Variables with common linkage always get classified as common.
+  if (GVar->hasCommonLinkage())
+    return SectionKind::getCommon();
+
+  // Variable can be easily put to BSS section.
+  if (isSuitableForBSS(GVar, TM.Options.NoZerosInBSS)) {
+    if (GVar->hasLocalLinkage())
+      return SectionKind::getBSSLocal();
+    else if (GVar->hasExternalLinkage())
+      return SectionKind::getBSSExtern();
+    return SectionKind::getBSS();
+  }
+
+  const Constant *C = GVar->getInitializer();
+
+  // If the global is marked constant, we can put it into a mergable section,
+  // a mergable string section, or general .data if it contains relocations.
+  if (GVar->isConstant()) {
+    // If the initializer for the global contains something that requires a
+    // relocation, then we may have to drop this into a writable data section
+    // even though it is marked const.
+    switch (C->getRelocationInfo()) {
+    case Constant::NoRelocation:
+      // If the global is required to have a unique address, it can't be put
+      // into a mergable section: just drop it into the general read-only
+      // section instead.
+      if (!GVar->hasUnnamedAddr())
+        return SectionKind::getReadOnly();
+        
+      // If initializer is a null-terminated string, put it in a "cstring"
+      // section of the right width.
+      if (ArrayType *ATy = dyn_cast<ArrayType>(C->getType())) {
+        if (IntegerType *ITy =
+              dyn_cast<IntegerType>(ATy->getElementType())) {
+          if ((ITy->getBitWidth() == 8 || ITy->getBitWidth() == 16 ||
+               ITy->getBitWidth() == 32) &&
+              IsNullTerminatedString(C)) {
+            if (ITy->getBitWidth() == 8)
+              return SectionKind::getMergeable1ByteCString();
+            if (ITy->getBitWidth() == 16)
+              return SectionKind::getMergeable2ByteCString();
+
+            assert(ITy->getBitWidth() == 32 && "Unknown width");
+            return SectionKind::getMergeable4ByteCString();
+          }
+        }
+      }
+
+      // Otherwise, just drop it into a mergable constant section.  If we have
+      // a section for this size, use it, otherwise use the arbitrary sized
+      // mergable section.
+      switch (TM.getDataLayout()->getTypeAllocSize(C->getType())) {
+      case 4:  return SectionKind::getMergeableConst4();
+      case 8:  return SectionKind::getMergeableConst8();
+      case 16: return SectionKind::getMergeableConst16();
+      default: return SectionKind::getMergeableConst();
+      }
+
+    case Constant::LocalRelocation:
+      // In static relocation model, the linker will resolve all addresses, so
+      // the relocation entries will actually be constants by the time the app
+      // starts up.  However, we can't put this into a mergable section, because
+      // the linker doesn't take relocations into consideration when it tries to
+      // merge entries in the section.
+      if (ReloModel == Reloc::Static)
+        return SectionKind::getReadOnly();
+
+      // Otherwise, the dynamic linker needs to fix it up, put it in the
+      // writable data.rel.local section.
+      return SectionKind::getReadOnlyWithRelLocal();
+
+    case Constant::GlobalRelocations:
+      // In static relocation model, the linker will resolve all addresses, so
+      // the relocation entries will actually be constants by the time the app
+      // starts up.  However, we can't put this into a mergable section, because
+      // the linker doesn't take relocations into consideration when it tries to
+      // merge entries in the section.
+      if (ReloModel == Reloc::Static)
+        return SectionKind::getReadOnly();
+
+      // Otherwise, the dynamic linker needs to fix it up, put it in the
+      // writable data.rel section.
+      return SectionKind::getReadOnlyWithRel();
+    }
+  }
+
+  // Okay, this isn't a constant.  If the initializer for the global is going
+  // to require a runtime relocation by the dynamic linker, put it into a more
+  // specific section to improve startup time of the app.  This coalesces these
+  // globals together onto fewer pages, improving the locality of the dynamic
+  // linker.
+  if (ReloModel == Reloc::Static)
+    return SectionKind::getDataNoRel();
+
+  switch (C->getRelocationInfo()) {
+  case Constant::NoRelocation:
+    return SectionKind::getDataNoRel();
+  case Constant::LocalRelocation:
+    return SectionKind::getDataRelLocal();
+  case Constant::GlobalRelocations:
+    return SectionKind::getDataRel();
+  }
+  llvm_unreachable("Invalid relocation");
+}
+
+/// SectionForGlobal - This method computes the appropriate section to emit
+/// the specified global variable or function definition.  This should not
+/// be passed external (or available externally) globals.
+const MCSection *TargetLoweringObjectFile::
+SectionForGlobal(const GlobalValue *GV, SectionKind Kind, Mangler *Mang,
+                 const TargetMachine &TM) const {
+  // Select section name.
+  if (GV->hasSection())
+    return getExplicitSectionGlobal(GV, Kind, Mang, TM);
+
+
+  // Use default section depending on the 'type' of global
+  return SelectSectionForGlobal(GV, Kind, Mang, TM);
+}
+
+
+// Lame default implementation. Calculate the section name for global.
+const MCSection *
+TargetLoweringObjectFile::SelectSectionForGlobal(const GlobalValue *GV,
+                                                 SectionKind Kind,
+                                                 Mangler *Mang,
+                                                 const TargetMachine &TM) const{
+  assert(!Kind.isThreadLocal() && "Doesn't support TLS");
+
+  if (Kind.isText())
+    return getTextSection();
+
+  if (Kind.isBSS() && BSSSection != 0)
+    return BSSSection;
+
+  if (Kind.isReadOnly() && ReadOnlySection != 0)
+    return ReadOnlySection;
+
+  return getDataSection();
+}
+
+/// getSectionForConstant - Given a mergable constant with the
+/// specified size and relocation information, return a section that it
+/// should be placed in.
+const MCSection *
+TargetLoweringObjectFile::getSectionForConstant(SectionKind Kind) const {
+  if (Kind.isReadOnly() && ReadOnlySection != 0)
+    return ReadOnlySection;
+
+  return DataSection;
+}
+
+/// getTTypeGlobalReference - Return an MCExpr to use for a
+/// reference to the specified global variable from exception
+/// handling information.
+const MCExpr *TargetLoweringObjectFile::
+getTTypeGlobalReference(const GlobalValue *GV, Mangler *Mang,
+                        MachineModuleInfo *MMI, unsigned Encoding,
+                        MCStreamer &Streamer) const {
+  const MCSymbolRefExpr *Ref =
+    MCSymbolRefExpr::Create(getSymbol(*Mang, GV), getContext());
+
+  return getTTypeReference(Ref, Encoding, Streamer);
+}
+
+const MCExpr *TargetLoweringObjectFile::
+getTTypeReference(const MCSymbolRefExpr *Sym, unsigned Encoding,
+                  MCStreamer &Streamer) const {
+  switch (Encoding & 0x70) {
+  default:
+    report_fatal_error("We do not support this DWARF encoding yet!");
+  case dwarf::DW_EH_PE_absptr:
+    // Do nothing special
+    return Sym;
+  case dwarf::DW_EH_PE_pcrel: {
+    // Emit a label to the streamer for the current position.  This gives us
+    // .-foo addressing.
+    MCSymbol *PCSym = getContext().CreateTempSymbol();
+    Streamer.EmitLabel(PCSym);
+    const MCExpr *PC = MCSymbolRefExpr::Create(PCSym, getContext());
+    return MCBinaryExpr::CreateSub(Sym, PC, getContext());
+  }
+  }
+}
+
+const MCExpr *TargetLoweringObjectFile::getDebugThreadLocalSymbol(const MCSymbol *Sym) const {
+  // FIXME: It's not clear what, if any, default this should have - perhaps a
+  // null return could mean 'no location' & we should just do that here.
+  return MCSymbolRefExpr::Create(Sym, *Ctx);
+}