Coverage Report

Created: 2017-10-03 07:32

/Users/buildslave/jenkins/sharedspace/clang-stage2-coverage-R@2/llvm/lib/Target/TargetLoweringObjectFile.cpp
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//===-- llvm/Target/TargetLoweringObjectFile.cpp - Object File Info -------===//
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//
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//                     The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements classes used to handle lowerings specific to common
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// object file formats.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Target/TargetLoweringObjectFile.h"
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#include "llvm/BinaryFormat/Dwarf.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/DerivedTypes.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/GlobalVariable.h"
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#include "llvm/IR/Mangler.h"
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#include "llvm/MC/MCAsmInfo.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCStreamer.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetLowering.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetOptions.h"
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#include "llvm/Target/TargetSubtargetInfo.h"
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using namespace llvm;
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//===----------------------------------------------------------------------===//
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//                              Generic Code
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//===----------------------------------------------------------------------===//
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/// Initialize - this method must be called before any actual lowering is
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/// done.  This specifies the current context for codegen, and gives the
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/// lowering implementations a chance to set up their default sections.
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void TargetLoweringObjectFile::Initialize(MCContext &ctx,
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33.4k
                                          const TargetMachine &TM) {
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33.4k
  Ctx = &ctx;
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33.4k
  // `Initialize` can be called more than once.
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33.4k
  delete Mang;
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33.4k
  Mang = new Mangler();
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33.4k
  InitMCObjectFileInfo(TM.getTargetTriple(), TM.isPositionIndependent(), *Ctx,
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33.4k
                       TM.getCodeModel() == CodeModel::Large);
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33.4k
}
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25.0k
TargetLoweringObjectFile::~TargetLoweringObjectFile() {
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25.0k
  delete Mang;
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25.0k
}
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57
779k
static bool isSuitableForBSS(const GlobalVariable *GV, bool NoZerosInBSS) {
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779k
  const Constant *C = GV->getInitializer();
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779k
60
779k
  // Must have zero initializer.
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779k
  if (!C->isNullValue())
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709k
    return false;
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69.8k
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69.8k
  // Leave constant zeros in readonly constant sections, so they can be shared.
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69.8k
  
if (69.8k
GV->isConstant()69.8k
)
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1.11k
    return false;
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68.7k
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68.7k
  // If the global has an explicit section specified, don't put it in BSS.
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68.7k
  
if (68.7k
GV->hasSection()68.7k
)
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75
    return false;
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68.6k
72
68.6k
  // If -nozero-initialized-in-bss is specified, don't ever use BSS.
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68.6k
  
if (68.6k
NoZerosInBSS68.6k
)
74
0
    return false;
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68.6k
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68.6k
  // Otherwise, put it in BSS!
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68.6k
  return true;
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68.6k
}
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/// IsNullTerminatedString - Return true if the specified constant (which is
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/// known to have a type that is an array of 1/2/4 byte elements) ends with a
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/// nul value and contains no other nuls in it.  Note that this is more general
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/// than ConstantDataSequential::isString because we allow 2 & 4 byte strings.
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495k
static bool IsNullTerminatedString(const Constant *C) {
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495k
  // First check: is we have constant array terminated with zero
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495k
  if (const ConstantDataSequential *
CDS495k
= dyn_cast<ConstantDataSequential>(C)) {
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494k
    unsigned NumElts = CDS->getNumElements();
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494k
    assert(NumElts != 0 && "Can't have an empty CDS");
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494k
    
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494k
    if (CDS->getElementAsInteger(NumElts-1) != 0)
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1.18k
      return false; // Not null terminated.
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493k
    
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493k
    // Verify that the null doesn't occur anywhere else in the string.
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17.9M
    
for (unsigned i = 0; 493k
i != NumElts-117.9M
;
++i17.4M
)
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17.4M
      
if (17.4M
CDS->getElementAsInteger(i) == 017.4M
)
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        return false;
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493k
    return true;
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966
  }
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966
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966
  // Another possibility: [1 x i8] zeroinitializer
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966
  
if (966
isa<ConstantAggregateZero>(C)966
)
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962
    return cast<ArrayType>(C->getType())->getNumElements() == 1;
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4
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4
  return false;
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4
}
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MCSymbol *TargetLoweringObjectFile::getSymbolWithGlobalValueBase(
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2.63k
    const GlobalValue *GV, StringRef Suffix, const TargetMachine &TM) const {
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2.63k
  assert(!Suffix.empty());
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2.63k
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2.63k
  SmallString<60> NameStr;
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2.63k
  NameStr += GV->getParent()->getDataLayout().getPrivateGlobalPrefix();
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2.63k
  TM.getNameWithPrefix(NameStr, GV, *Mang);
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2.63k
  NameStr.append(Suffix.begin(), Suffix.end());
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2.63k
  return Ctx->getOrCreateSymbol(NameStr);
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}
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MCSymbol *TargetLoweringObjectFile::getCFIPersonalitySymbol(
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    const GlobalValue *GV, const TargetMachine &TM,
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153
    MachineModuleInfo *MMI) const {
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  return TM.getSymbol(GV);
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}
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void TargetLoweringObjectFile::emitPersonalityValue(MCStreamer &Streamer,
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                                                    const DataLayout &,
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                                                    const MCSymbol *Sym) const {
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}
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/// getKindForGlobal - This is a top-level target-independent classifier for
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/// a global variable.  Given an global variable and information from TM, it
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/// classifies the global in a variety of ways that make various target
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/// implementations simpler.  The target implementation is free to ignore this
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/// extra info of course.
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SectionKind TargetLoweringObjectFile::getKindForGlobal(const GlobalObject *GO,
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1.39M
                                                       const TargetMachine &TM){
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1.39M
  assert(!GO->isDeclaration() && !GO->hasAvailableExternallyLinkage() &&
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1.39M
         "Can only be used for global definitions");
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1.39M
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1.39M
  Reloc::Model ReloModel = TM.getRelocationModel();
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1.39M
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1.39M
  // Early exit - functions should be always in text sections.
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1.39M
  const auto *GVar = dyn_cast<GlobalVariable>(GO);
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1.39M
  if (!GVar)
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595k
    return SectionKind::getText();
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803k
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803k
  // Handle thread-local data first.
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803k
  
if (803k
GVar->isThreadLocal()803k
) {
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    if (isSuitableForBSS(GVar, TM.Options.NoZerosInBSS))
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      return SectionKind::getThreadBSS();
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    return SectionKind::getThreadData();
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  }
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803k
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803k
  // Variables with common linkage always get classified as common.
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803k
  
if (803k
GVar->hasCommonLinkage()803k
)
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23.9k
    return SectionKind::getCommon();
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779k
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779k
  // Variable can be easily put to BSS section.
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779k
  
if (779k
isSuitableForBSS(GVar, TM.Options.NoZerosInBSS)779k
) {
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68.4k
    if (GVar->hasLocalLinkage())
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15.2k
      return SectionKind::getBSSLocal();
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53.2k
    else 
if (53.2k
GVar->hasExternalLinkage()53.2k
)
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      return SectionKind::getBSSExtern();
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    return SectionKind::getBSS();
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47.3k
  }
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711k
  const Constant *C = GVar->getInitializer();
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711k
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711k
  // If the global is marked constant, we can put it into a mergable section,
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711k
  // a mergable string section, or general .data if it contains relocations.
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711k
  if (
GVar->isConstant()711k
) {
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646k
    // If the initializer for the global contains something that requires a
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646k
    // relocation, then we may have to drop this into a writable data section
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646k
    // even though it is marked const.
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646k
    if (
!C->needsRelocation()646k
) {
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628k
      // If the global is required to have a unique address, it can't be put
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628k
      // into a mergable section: just drop it into the general read-only
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628k
      // section instead.
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628k
      if (!GVar->hasGlobalUnnamedAddr())
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        return SectionKind::getReadOnly();
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496k
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496k
      // If initializer is a null-terminated string, put it in a "cstring"
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496k
      // section of the right width.
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496k
      
if (ArrayType *496k
ATy496k
= dyn_cast<ArrayType>(C->getType())) {
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496k
        if (IntegerType *ITy =
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495k
              dyn_cast<IntegerType>(ATy->getElementType())) {
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495k
          if (
(ITy->getBitWidth() == 8 || 495k
ITy->getBitWidth() == 161.65k
||
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1.31k
               ITy->getBitWidth() == 32) &&
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495k
              
IsNullTerminatedString(C)495k
) {
190
493k
            if (ITy->getBitWidth() == 8)
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493k
              return SectionKind::getMergeable1ByteCString();
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515
            
if (515
ITy->getBitWidth() == 16515
)
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              return SectionKind::getMergeable2ByteCString();
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491
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0
            assert(ITy->getBitWidth() == 32 && "Unknown width");
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            return SectionKind::getMergeable4ByteCString();
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          }
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495k
        }
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496k
      }
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2.92k
      // Otherwise, just drop it into a mergable constant section.  If we have
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2.92k
      // a section for this size, use it, otherwise use the arbitrary sized
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      // mergable section.
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2.92k
      switch (
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2.92k
          GVar->getParent()->getDataLayout().getTypeAllocSize(C->getType())) {
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      case 4:  return SectionKind::getMergeableConst4();
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      case 8:  return SectionKind::getMergeableConst8();
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800
      case 16: return SectionKind::getMergeableConst16();
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      case 32: return SectionKind::getMergeableConst32();
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1.81k
      default:
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        return SectionKind::getReadOnly();
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      }
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646k
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18.3k
    } else {
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      // In static, ROPI and RWPI relocation models, the linker will resolve
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      // all addresses, so the relocation entries will actually be constants by
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18.3k
      // the time the app starts up.  However, we can't put this into a
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18.3k
      // mergable section, because the linker doesn't take relocations into
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18.3k
      // consideration when it tries to merge entries in the section.
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18.3k
      if (
ReloModel == Reloc::Static || 18.3k
ReloModel == Reloc::ROPI18.3k
||
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18.3k
          
ReloModel == Reloc::RWPI18.3k
||
ReloModel == Reloc::ROPI_RWPI18.3k
)
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        return SectionKind::getReadOnly();
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18.3k
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18.3k
      // Otherwise, the dynamic linker needs to fix it up, put it in the
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18.3k
      // writable data.rel section.
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18.3k
      return SectionKind::getReadOnlyWithRel();
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18.3k
    }
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646k
  }
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64.2k
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64.2k
  // Okay, this isn't a constant.
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64.2k
  return SectionKind::getData();
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64.2k
}
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/// This method computes the appropriate section to emit the specified global
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/// variable or function definition.  This should not be passed external (or
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/// available externally) globals.
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MCSection *TargetLoweringObjectFile::SectionForGlobal(
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1.34M
    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
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1.34M
  // Select section name.
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1.34M
  if (GO->hasSection())
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4.14k
    return getExplicitSectionGlobal(GO, Kind, TM);
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1.34M
243
1.34M
  
if (auto *1.34M
GVar1.34M
= dyn_cast<GlobalVariable>(GO)) {
244
749k
    auto Attrs = GVar->getAttributes();
245
749k
    if (
(Attrs.hasAttribute("bss-section") && 749k
Kind.isBSS()13
) ||
246
749k
        
(Attrs.hasAttribute("data-section") && 749k
Kind.isData()6
) ||
247
749k
        
(Attrs.hasAttribute("rodata-section") && 749k
Kind.isReadOnly()4
)) {
248
13
       return getExplicitSectionGlobal(GO, Kind, TM);
249
13
    }
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1.34M
  }
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1.34M
252
1.34M
  
if (auto *1.34M
F1.34M
= dyn_cast<Function>(GO)) {
253
595k
    if (F->hasFnAttribute("implicit-section-name"))
254
2
      return getExplicitSectionGlobal(GO, Kind, TM);
255
1.34M
  }
256
1.34M
257
1.34M
  // Use default section depending on the 'type' of global
258
1.34M
  return SelectSectionForGlobal(GO, Kind, TM);
259
1.34M
}
260
261
MCSection *TargetLoweringObjectFile::getSectionForJumpTable(
262
45
    const Function &F, const TargetMachine &TM) const {
263
45
  unsigned Align = 0;
264
45
  return getSectionForConstant(F.getParent()->getDataLayout(),
265
45
                               SectionKind::getReadOnly(), /*C=*/nullptr,
266
45
                               Align);
267
45
}
268
269
bool TargetLoweringObjectFile::shouldPutJumpTableInFunctionSection(
270
4.33k
    bool UsesLabelDifference, const Function &F) const {
271
4.33k
  // In PIC mode, we need to emit the jump table to the same section as the
272
4.33k
  // function body itself, otherwise the label differences won't make sense.
273
4.33k
  // FIXME: Need a better predicate for this: what about custom entries?
274
4.33k
  if (UsesLabelDifference)
275
4.27k
    return true;
276
52
277
52
  // We should also do if the section name is NULL or function is declared
278
52
  // in discardable section
279
52
  // FIXME: this isn't the right predicate, should be based on the MCSection
280
52
  // for the function.
281
52
  return F.isWeakForLinker();
282
52
}
283
284
/// Given a mergable constant with the specified size and relocation
285
/// information, return a section that it should be placed in.
286
MCSection *TargetLoweringObjectFile::getSectionForConstant(
287
    const DataLayout &DL, SectionKind Kind, const Constant *C,
288
7
    unsigned &Align) const {
289
7
  if (
Kind.isReadOnly() && 7
ReadOnlySection != nullptr7
)
290
7
    return ReadOnlySection;
291
0
292
0
  return DataSection;
293
0
}
294
295
/// getTTypeGlobalReference - Return an MCExpr to use for a
296
/// reference to the specified global variable from exception
297
/// handling information.
298
const MCExpr *TargetLoweringObjectFile::getTTypeGlobalReference(
299
    const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
300
22
    MachineModuleInfo *MMI, MCStreamer &Streamer) const {
301
22
  const MCSymbolRefExpr *Ref =
302
22
      MCSymbolRefExpr::create(TM.getSymbol(GV), getContext());
303
22
304
22
  return getTTypeReference(Ref, Encoding, Streamer);
305
22
}
306
307
const MCExpr *TargetLoweringObjectFile::
308
getTTypeReference(const MCSymbolRefExpr *Sym, unsigned Encoding,
309
45
                  MCStreamer &Streamer) const {
310
45
  switch (Encoding & 0x70) {
311
0
  default:
312
0
    report_fatal_error("We do not support this DWARF encoding yet!");
313
22
  case dwarf::DW_EH_PE_absptr:
314
22
    // Do nothing special
315
22
    return Sym;
316
23
  case dwarf::DW_EH_PE_pcrel: {
317
23
    // Emit a label to the streamer for the current position.  This gives us
318
23
    // .-foo addressing.
319
23
    MCSymbol *PCSym = getContext().createTempSymbol();
320
23
    Streamer.EmitLabel(PCSym);
321
23
    const MCExpr *PC = MCSymbolRefExpr::create(PCSym, getContext());
322
23
    return MCBinaryExpr::createSub(Sym, PC, getContext());
323
0
  }
324
0
  }
325
0
}
326
327
1
const MCExpr *TargetLoweringObjectFile::getDebugThreadLocalSymbol(const MCSymbol *Sym) const {
328
1
  // FIXME: It's not clear what, if any, default this should have - perhaps a
329
1
  // null return could mean 'no location' & we should just do that here.
330
1
  return MCSymbolRefExpr::create(Sym, *Ctx);
331
1
}
332
333
void TargetLoweringObjectFile::getNameWithPrefix(
334
    SmallVectorImpl<char> &OutName, const GlobalValue *GV,
335
2.62k
    const TargetMachine &TM) const {
336
2.62k
  Mang->getNameWithPrefix(OutName, GV, /*CannotUsePrivateLabel=*/false);
337
2.62k
}