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llvm-mirror/tools/lto/LTOModule.cpp

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//===-- LTOModule.cpp - LLVM Link Time Optimizer --------------------------===//
//
// 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 Link Time Optimization library. This library is
// intended to be used by linker to optimize code at link time.
//
//===----------------------------------------------------------------------===//
#include "LTOModule.h"
#include "llvm/Constants.h"
#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Bitcode/ReaderWriter.h"
#include "llvm/Support/SystemUtils.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/system_error.h"
#include "llvm/Target/Mangler.h"
#include "llvm/Target/SubtargetFeature.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegistry.h"
#include "llvm/Target/TargetSelect.h"
using namespace llvm;
bool LTOModule::isBitcodeFile(const void *mem, size_t length) {
return llvm::sys::IdentifyFileType((char*)mem, length)
== llvm::sys::Bitcode_FileType;
}
bool LTOModule::isBitcodeFile(const char *path) {
return llvm::sys::Path(path).isBitcodeFile();
}
bool LTOModule::isBitcodeFileForTarget(const void *mem, size_t length,
const char *triplePrefix) {
MemoryBuffer *buffer = makeBuffer(mem, length);
if (!buffer)
return false;
return isTargetMatch(buffer, triplePrefix);
}
bool LTOModule::isBitcodeFileForTarget(const char *path,
const char *triplePrefix) {
OwningPtr<MemoryBuffer> buffer;
if (MemoryBuffer::getFile(path, buffer))
return false;
return isTargetMatch(buffer.take(), triplePrefix);
}
// Takes ownership of buffer.
bool LTOModule::isTargetMatch(MemoryBuffer *buffer, const char *triplePrefix) {
std::string Triple = getBitcodeTargetTriple(buffer, getGlobalContext());
delete buffer;
return (strncmp(Triple.c_str(), triplePrefix,
strlen(triplePrefix)) == 0);
}
LTOModule::LTOModule(Module *m, TargetMachine *t)
: _module(m), _target(t), _symbolsParsed(false)
{
}
LTOModule *LTOModule::makeLTOModule(const char *path,
std::string &errMsg) {
OwningPtr<MemoryBuffer> buffer;
if (error_code ec = MemoryBuffer::getFile(path, buffer)) {
errMsg = ec.message();
return NULL;
}
return makeLTOModule(buffer.get(), errMsg);
}
/// makeBuffer - Create a MemoryBuffer from a memory range. MemoryBuffer
/// requires the byte past end of the buffer to be a zero. We might get lucky
/// and already be that way, otherwise make a copy. Also if next byte is on a
/// different page, don't assume it is readable.
MemoryBuffer *LTOModule::makeBuffer(const void *mem, size_t length) {
const char *startPtr = (char*)mem;
const char *endPtr = startPtr+length;
if (((uintptr_t)endPtr & (sys::Process::GetPageSize()-1)) == 0 ||
*endPtr != 0)
return MemoryBuffer::getMemBufferCopy(StringRef(startPtr, length));
return MemoryBuffer::getMemBuffer(StringRef(startPtr, length));
}
LTOModule *LTOModule::makeLTOModule(const void *mem, size_t length,
std::string &errMsg) {
OwningPtr<MemoryBuffer> buffer(makeBuffer(mem, length));
if (!buffer)
return NULL;
return makeLTOModule(buffer.get(), errMsg);
}
LTOModule *LTOModule::makeLTOModule(MemoryBuffer *buffer,
std::string &errMsg) {
InitializeAllTargets();
// parse bitcode buffer
OwningPtr<Module> m(ParseBitcodeFile(buffer, getGlobalContext(), &errMsg));
if (!m)
return NULL;
std::string Triple = m->getTargetTriple();
if (Triple.empty())
Triple = sys::getHostTriple();
// find machine architecture for this module
const Target *march = TargetRegistry::lookupTarget(Triple, errMsg);
if (!march)
return NULL;
// construct LTModule, hand over ownership of module and target
SubtargetFeatures Features;
Features.getDefaultSubtargetFeatures("" /* cpu */, llvm::Triple(Triple));
std::string FeatureStr = Features.getString();
TargetMachine *target = march->createTargetMachine(Triple, FeatureStr);
return new LTOModule(m.take(), target);
}
const char *LTOModule::getTargetTriple() {
return _module->getTargetTriple().c_str();
}
void LTOModule::setTargetTriple(const char *triple) {
_module->setTargetTriple(triple);
}
void LTOModule::addDefinedFunctionSymbol(Function *f, Mangler &mangler) {
// add to list of defined symbols
addDefinedSymbol(f, mangler, true);
// add external symbols referenced by this function.
for (Function::iterator b = f->begin(); b != f->end(); ++b) {
for (BasicBlock::iterator i = b->begin(); i != b->end(); ++i) {
for (unsigned count = 0, total = i->getNumOperands();
count != total; ++count) {
findExternalRefs(i->getOperand(count), mangler);
}
}
}
}
// Get string that data pointer points to.
bool LTOModule::objcClassNameFromExpression(Constant *c, std::string &name) {
if (ConstantExpr *ce = dyn_cast<ConstantExpr>(c)) {
Constant *op = ce->getOperand(0);
if (GlobalVariable *gvn = dyn_cast<GlobalVariable>(op)) {
Constant *cn = gvn->getInitializer();
if (ConstantArray *ca = dyn_cast<ConstantArray>(cn)) {
if (ca->isCString()) {
name = ".objc_class_name_" + ca->getAsString();
return true;
}
}
}
}
return false;
}
// Parse i386/ppc ObjC class data structure.
void LTOModule::addObjCClass(GlobalVariable *clgv) {
if (ConstantStruct *c = dyn_cast<ConstantStruct>(clgv->getInitializer())) {
// second slot in __OBJC,__class is pointer to superclass name
std::string superclassName;
if (objcClassNameFromExpression(c->getOperand(1), superclassName)) {
NameAndAttributes info;
if (_undefines.find(superclassName.c_str()) == _undefines.end()) {
const char *symbolName = ::strdup(superclassName.c_str());
info.name = symbolName;
info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
// string is owned by _undefines
_undefines[info.name] = info;
}
}
// third slot in __OBJC,__class is pointer to class name
std::string className;
if (objcClassNameFromExpression(c->getOperand(2), className)) {
const char *symbolName = ::strdup(className.c_str());
NameAndAttributes info;
info.name = symbolName;
info.attributes = (lto_symbol_attributes)
(LTO_SYMBOL_PERMISSIONS_DATA |
LTO_SYMBOL_DEFINITION_REGULAR |
LTO_SYMBOL_SCOPE_DEFAULT);
_symbols.push_back(info);
_defines[info.name] = 1;
}
}
}
// Parse i386/ppc ObjC category data structure.
void LTOModule::addObjCCategory(GlobalVariable *clgv) {
if (ConstantStruct *c = dyn_cast<ConstantStruct>(clgv->getInitializer())) {
// second slot in __OBJC,__category is pointer to target class name
std::string targetclassName;
if (objcClassNameFromExpression(c->getOperand(1), targetclassName)) {
NameAndAttributes info;
if (_undefines.find(targetclassName.c_str()) == _undefines.end()) {
const char *symbolName = ::strdup(targetclassName.c_str());
info.name = symbolName;
info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
// string is owned by _undefines
_undefines[info.name] = info;
}
}
}
}
// Parse i386/ppc ObjC class list data structure.
void LTOModule::addObjCClassRef(GlobalVariable *clgv) {
std::string targetclassName;
if (objcClassNameFromExpression(clgv->getInitializer(), targetclassName)) {
NameAndAttributes info;
if (_undefines.find(targetclassName.c_str()) == _undefines.end()) {
const char *symbolName = ::strdup(targetclassName.c_str());
info.name = symbolName;
info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
// string is owned by _undefines
_undefines[info.name] = info;
}
}
}
void LTOModule::addDefinedDataSymbol(GlobalValue *v, Mangler &mangler) {
// Add to list of defined symbols.
addDefinedSymbol(v, mangler, false);
// Special case i386/ppc ObjC data structures in magic sections:
// The issue is that the old ObjC object format did some strange
// contortions to avoid real linker symbols. For instance, the
// ObjC class data structure is allocated statically in the executable
// that defines that class. That data structures contains a pointer to
// its superclass. But instead of just initializing that part of the
// struct to the address of its superclass, and letting the static and
// dynamic linkers do the rest, the runtime works by having that field
// instead point to a C-string that is the name of the superclass.
// At runtime the objc initialization updates that pointer and sets
// it to point to the actual super class. As far as the linker
// knows it is just a pointer to a string. But then someone wanted the
// linker to issue errors at build time if the superclass was not found.
// So they figured out a way in mach-o object format to use an absolute
// symbols (.objc_class_name_Foo = 0) and a floating reference
// (.reference .objc_class_name_Bar) to cause the linker into erroring when
// a class was missing.
// The following synthesizes the implicit .objc_* symbols for the linker
// from the ObjC data structures generated by the front end.
if (v->hasSection() /* && isTargetDarwin */) {
// special case if this data blob is an ObjC class definition
if (v->getSection().compare(0, 15, "__OBJC,__class,") == 0) {
if (GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
addObjCClass(gv);
}
}
// special case if this data blob is an ObjC category definition
else if (v->getSection().compare(0, 18, "__OBJC,__category,") == 0) {
if (GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
addObjCCategory(gv);
}
}
// special case if this data blob is the list of referenced classes
else if (v->getSection().compare(0, 18, "__OBJC,__cls_refs,") == 0) {
if (GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
addObjCClassRef(gv);
}
}
}
// add external symbols referenced by this data.
for (unsigned count = 0, total = v->getNumOperands();
count != total; ++count) {
findExternalRefs(v->getOperand(count), mangler);
}
}
void LTOModule::addDefinedSymbol(GlobalValue *def, Mangler &mangler,
bool isFunction) {
// ignore all llvm.* symbols
if (def->getName().startswith("llvm."))
return;
// string is owned by _defines
const char *symbolName = ::strdup(mangler.getNameWithPrefix(def).c_str());
// set alignment part log2() can have rounding errors
uint32_t align = def->getAlignment();
uint32_t attr = align ? CountTrailingZeros_32(def->getAlignment()) : 0;
// set permissions part
if (isFunction)
attr |= LTO_SYMBOL_PERMISSIONS_CODE;
else {
GlobalVariable *gv = dyn_cast<GlobalVariable>(def);
if (gv && gv->isConstant())
attr |= LTO_SYMBOL_PERMISSIONS_RODATA;
else
attr |= LTO_SYMBOL_PERMISSIONS_DATA;
}
// set definition part
if (def->hasWeakLinkage() || def->hasLinkOnceLinkage() ||
def->hasLinkerPrivateWeakLinkage() ||
def->hasLinkerPrivateWeakDefAutoLinkage())
attr |= LTO_SYMBOL_DEFINITION_WEAK;
else if (def->hasCommonLinkage())
attr |= LTO_SYMBOL_DEFINITION_TENTATIVE;
else
attr |= LTO_SYMBOL_DEFINITION_REGULAR;
// set scope part
if (def->hasHiddenVisibility())
attr |= LTO_SYMBOL_SCOPE_HIDDEN;
else if (def->hasProtectedVisibility())
attr |= LTO_SYMBOL_SCOPE_PROTECTED;
else if (def->hasExternalLinkage() || def->hasWeakLinkage() ||
def->hasLinkOnceLinkage() || def->hasCommonLinkage() ||
def->hasLinkerPrivateWeakLinkage())
attr |= LTO_SYMBOL_SCOPE_DEFAULT;
else if (def->hasLinkerPrivateWeakDefAutoLinkage())
attr |= LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN;
else
attr |= LTO_SYMBOL_SCOPE_INTERNAL;
// add to table of symbols
NameAndAttributes info;
info.name = symbolName;
info.attributes = (lto_symbol_attributes)attr;
_symbols.push_back(info);
_defines[info.name] = 1;
}
void LTOModule::addAsmGlobalSymbol(const char *name) {
// only add new define if not already defined
if (_defines.count(name))
return;
// string is owned by _defines
const char *symbolName = ::strdup(name);
uint32_t attr = LTO_SYMBOL_DEFINITION_REGULAR;
attr |= LTO_SYMBOL_SCOPE_DEFAULT;
NameAndAttributes info;
info.name = symbolName;
info.attributes = (lto_symbol_attributes)attr;
_symbols.push_back(info);
_defines[info.name] = 1;
}
void LTOModule::addPotentialUndefinedSymbol(GlobalValue *decl,
Mangler &mangler) {
// ignore all llvm.* symbols
if (decl->getName().startswith("llvm."))
return;
// ignore all aliases
if (isa<GlobalAlias>(decl))
return;
std::string name = mangler.getNameWithPrefix(decl);
// we already have the symbol
if (_undefines.find(name) != _undefines.end())
return;
NameAndAttributes info;
// string is owned by _undefines
info.name = ::strdup(name.c_str());
if (decl->hasExternalWeakLinkage())
info.attributes = LTO_SYMBOL_DEFINITION_WEAKUNDEF;
else
info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
_undefines[name] = info;
}
// Find external symbols referenced by VALUE. This is a recursive function.
void LTOModule::findExternalRefs(Value *value, Mangler &mangler) {
if (GlobalValue *gv = dyn_cast<GlobalValue>(value)) {
if (!gv->hasExternalLinkage())
addPotentialUndefinedSymbol(gv, mangler);
// If this is a variable definition, do not recursively process
// initializer. It might contain a reference to this variable
// and cause an infinite loop. The initializer will be
// processed in addDefinedDataSymbol().
return;
}
// GlobalValue, even with InternalLinkage type, may have operands with
// ExternalLinkage type. Do not ignore these operands.
if (Constant *c = dyn_cast<Constant>(value)) {
// Handle ConstantExpr, ConstantStruct, ConstantArry etc.
for (unsigned i = 0, e = c->getNumOperands(); i != e; ++i)
findExternalRefs(c->getOperand(i), mangler);
}
}
void LTOModule::lazyParseSymbols() {
if (_symbolsParsed)
return;
_symbolsParsed = true;
// Use mangler to add GlobalPrefix to names to match linker names.
MCContext Context(*_target->getMCAsmInfo(), NULL);
Mangler mangler(Context, *_target->getTargetData());
// add functions
for (Module::iterator f = _module->begin(); f != _module->end(); ++f) {
if (f->isDeclaration())
addPotentialUndefinedSymbol(f, mangler);
else
addDefinedFunctionSymbol(f, mangler);
}
// add data
for (Module::global_iterator v = _module->global_begin(),
e = _module->global_end(); v != e; ++v) {
if (v->isDeclaration())
addPotentialUndefinedSymbol(v, mangler);
else
addDefinedDataSymbol(v, mangler);
}
// add asm globals
const std::string &inlineAsm = _module->getModuleInlineAsm();
const std::string glbl = ".globl";
std::string asmSymbolName;
std::string::size_type pos = inlineAsm.find(glbl, 0);
while (pos != std::string::npos) {
// eat .globl
pos = pos + 6;
// skip white space between .globl and symbol name
std::string::size_type pbegin = inlineAsm.find_first_not_of(' ', pos);
if (pbegin == std::string::npos)
break;
// find end-of-line
std::string::size_type pend = inlineAsm.find_first_of('\n', pbegin);
if (pend == std::string::npos)
break;
asmSymbolName.assign(inlineAsm, pbegin, pend - pbegin);
addAsmGlobalSymbol(asmSymbolName.c_str());
// search next .globl
pos = inlineAsm.find(glbl, pend);
}
// add aliases
for (Module::alias_iterator i = _module->alias_begin(),
e = _module->alias_end(); i != e; ++i) {
if (i->isDeclaration())
addPotentialUndefinedSymbol(i, mangler);
else
addDefinedDataSymbol(i, mangler);
}
// make symbols for all undefines
for (StringMap<NameAndAttributes>::iterator it=_undefines.begin();
it != _undefines.end(); ++it) {
// if this symbol also has a definition, then don't make an undefine
// because it is a tentative definition
if (_defines.count(it->getKey()) == 0) {
NameAndAttributes info = it->getValue();
_symbols.push_back(info);
}
}
}
uint32_t LTOModule::getSymbolCount() {
lazyParseSymbols();
return _symbols.size();
}
lto_symbol_attributes LTOModule::getSymbolAttributes(uint32_t index) {
lazyParseSymbols();
if (index < _symbols.size())
return _symbols[index].attributes;
else
return lto_symbol_attributes(0);
}
const char *LTOModule::getSymbolName(uint32_t index) {
lazyParseSymbols();
if (index < _symbols.size())
return _symbols[index].name;
else
return NULL;
}
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