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llvm-mirror/lib/Target/TargetMachine.cpp
Chandler Carruth 11c412fd2c Teach LLVM about a PIE option which, when enabled on top of PIC, makes
optimizations which are valid for position independent code being linked
into a single executable, but not for such code being linked into
a shared library.

I discussed the design of this with Eric Christopher, and the decision
was to support an optional bit rather than a completely separate
relocation model. Fundamentally, this is still PIC relocation, its just
that certain optimizations are only valid under a PIC relocation model
when the resulting code won't be in a shared library. The simplest path
to here is to expose a single bit option in the TargetOptions. If folks
have different/better designs, I'm all ears. =]

I've included the first optimization based upon this: changing TLS
models to the *Exec models when PIE is enabled. This is the LLVM
component of PR12380 and is all of the hard work.

llvm-svn: 154294
2012-04-08 17:51:45 +00:00

131 lines
3.6 KiB
C++

//===-- TargetMachine.cpp - General Target Information ---------------------==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file describes the general parts of a Target machine.
//
//===----------------------------------------------------------------------===//
#include "llvm/GlobalValue.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCCodeGenInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/CommandLine.h"
using namespace llvm;
//---------------------------------------------------------------------------
// Command-line options that tend to be useful on more than one back-end.
//
namespace llvm {
bool HasDivModLibcall;
bool AsmVerbosityDefault(false);
}
static cl::opt<bool>
DataSections("fdata-sections",
cl::desc("Emit data into separate sections"),
cl::init(false));
static cl::opt<bool>
FunctionSections("ffunction-sections",
cl::desc("Emit functions into separate sections"),
cl::init(false));
//---------------------------------------------------------------------------
// TargetMachine Class
//
TargetMachine::TargetMachine(const Target &T,
StringRef TT, StringRef CPU, StringRef FS,
const TargetOptions &Options)
: TheTarget(T), TargetTriple(TT), TargetCPU(CPU), TargetFS(FS),
CodeGenInfo(0), AsmInfo(0),
MCRelaxAll(false),
MCNoExecStack(false),
MCSaveTempLabels(false),
MCUseLoc(true),
MCUseCFI(true),
MCUseDwarfDirectory(false),
Options(Options) {
}
TargetMachine::~TargetMachine() {
delete CodeGenInfo;
delete AsmInfo;
}
/// getRelocationModel - Returns the code generation relocation model. The
/// choices are static, PIC, and dynamic-no-pic, and target default.
Reloc::Model TargetMachine::getRelocationModel() const {
if (!CodeGenInfo)
return Reloc::Default;
return CodeGenInfo->getRelocationModel();
}
/// getCodeModel - Returns the code model. The choices are small, kernel,
/// medium, large, and target default.
CodeModel::Model TargetMachine::getCodeModel() const {
if (!CodeGenInfo)
return CodeModel::Default;
return CodeGenInfo->getCodeModel();
}
TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {
bool isLocal = GV->hasLocalLinkage();
bool isDeclaration = GV->isDeclaration();
// FIXME: what should we do for protected and internal visibility?
// For variables, is internal different from hidden?
bool isHidden = GV->hasHiddenVisibility();
if (getRelocationModel() == Reloc::PIC_ &&
!Options.PositionIndependentExecutable) {
if (isLocal || isHidden)
return TLSModel::LocalDynamic;
else
return TLSModel::GeneralDynamic;
} else {
if (!isDeclaration || isHidden)
return TLSModel::LocalExec;
else
return TLSModel::InitialExec;
}
}
/// getOptLevel - Returns the optimization level: None, Less,
/// Default, or Aggressive.
CodeGenOpt::Level TargetMachine::getOptLevel() const {
if (!CodeGenInfo)
return CodeGenOpt::Default;
return CodeGenInfo->getOptLevel();
}
bool TargetMachine::getAsmVerbosityDefault() {
return AsmVerbosityDefault;
}
void TargetMachine::setAsmVerbosityDefault(bool V) {
AsmVerbosityDefault = V;
}
bool TargetMachine::getFunctionSections() {
return FunctionSections;
}
bool TargetMachine::getDataSections() {
return DataSections;
}
void TargetMachine::setFunctionSections(bool V) {
FunctionSections = V;
}
void TargetMachine::setDataSections(bool V) {
DataSections = V;
}