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llvm-project/llvm/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/ModuleProvider.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/Bitcode/ReaderWriter.h"
#include "llvm/Support/SystemUtils.h"
#include "llvm/Support/Mangler.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/System/Path.h"
#include "llvm/System/Process.h"
#include "llvm/Target/SubtargetFeature.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetMachineRegistry.h"
#include "llvm/Target/TargetAsmInfo.h"
#include <fstream>
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 == NULL )
return false;
return isTargetMatch(buffer, triplePrefix);
}
bool LTOModule::isBitcodeFileForTarget(const char* path,
const char* triplePrefix)
{
MemoryBuffer *buffer = MemoryBuffer::getFile(path);
if (buffer == NULL)
return false;
return isTargetMatch(buffer, triplePrefix);
}
// takes ownership of buffer
bool LTOModule::isTargetMatch(MemoryBuffer* buffer, const char* triplePrefix)
{
OwningPtr<ModuleProvider> mp(getBitcodeModuleProvider(buffer,
getGlobalContext()));
// on success, mp owns buffer and both are deleted at end of this method
if ( !mp ) {
delete buffer;
return false;
}
std::string actualTarget = mp->getModule()->getTargetTriple();
return ( strncmp(actualTarget.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(MemoryBuffer::getFile(path, &errMsg));
if ( !buffer )
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(startPtr, endPtr);
else
return MemoryBuffer::getMemBuffer(startPtr, endPtr);
}
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);
}
/// getFeatureString - Return a string listing the features associated with the
/// target triple.
///
/// FIXME: This is an inelegant way of specifying the features of a
/// subtarget. It would be better if we could encode this information into the
/// IR. See <rdar://5972456>.
std::string getFeatureString(const char *TargetTriple) {
SubtargetFeatures Features;
if (strncmp(TargetTriple, "powerpc-apple-", 14) == 0) {
Features.AddFeature("altivec", true);
} else if (strncmp(TargetTriple, "powerpc64-apple-", 16) == 0) {
Features.AddFeature("64bit", true);
Features.AddFeature("altivec", true);
}
return Features.getString();
}
LTOModule* LTOModule::makeLTOModule(MemoryBuffer* buffer,
std::string& errMsg)
{
// parse bitcode buffer
OwningPtr<Module> m(ParseBitcodeFile(buffer, getGlobalContext(), &errMsg));
if ( !m )
return NULL;
// find machine architecture for this module
const TargetMachineRegistry::entry* march =
TargetMachineRegistry::getClosestStaticTargetForModule(*m, errMsg);
if ( march == NULL )
return NULL;
// construct LTModule, hand over ownership of module and target
std::string FeatureStr = getFeatureString(m->getTargetTriple().c_str());
TargetMachine* target = march->CtorFn(*m, FeatureStr);
return new LTOModule(m.take(), target);
}
const char* LTOModule::getTargetTriple()
{
return _module->getTargetTriple().c_str();
}
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 = ::strdup(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 = ::strdup(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 = ::strdup(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 ( strncmp(def->getNameStart(), "llvm.", 5) == 0 )
return;
// string is owned by _defines
const char* symbolName = ::strdup(mangler.getValueName(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 != NULL) && gv->isConstant() )
attr |= LTO_SYMBOL_PERMISSIONS_RODATA;
else
attr |= LTO_SYMBOL_PERMISSIONS_DATA;
}
// set definition part
if ( def->hasWeakLinkage() || def->hasLinkOnceLinkage() ) {
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() )
attr |= LTO_SYMBOL_SCOPE_DEFAULT;
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, &name[strlen(name)+1]) == 0 )
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 ( strncmp(decl->getNameStart(), "llvm.", 5) == 0 )
return;
// ignore all aliases
if (isa<GlobalAlias>(decl))
return;
const char* name = mangler.getValueName(decl).c_str();
// we already have the symbol
if (_undefines.find(name) != _undefines.end())
return;
NameAndAttributes info;
// string is owned by _undefines
info.name = ::strdup(name);
if (decl->hasExternalWeakLinkage())
info.attributes = LTO_SYMBOL_DEFINITION_WEAKUNDEF;
else
info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
_undefines[name] = info;
}
// Find exeternal 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 ) {
_symbolsParsed = true;
// Use mangler to add GlobalPrefix to names to match linker names.
Mangler mangler(*_module, _target->getTargetAsmInfo()->getGlobalPrefix());
// add chars used in ObjC method names so method names aren't mangled
mangler.markCharAcceptable('[');
mangler.markCharAcceptable(']');
mangler.markCharAcceptable('(');
mangler.markCharAcceptable(')');
mangler.markCharAcceptable('-');
mangler.markCharAcceptable('+');
mangler.markCharAcceptable(' ');
// 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);
}
// 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->getKeyData(), it->getKeyData()+
it->getKeyLength()) == 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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