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llvm/tools/lto/LTOModule.cpp
Daniel Dunbar 3c2d4bf97f Pass target triple string in to TargetMachine constructor. 
This is not just a matter of passing in the target triple from the module;
currently backends are making decisions based on the build and host
architecture. The goal is to migrate to making these decisions based off of the
triple (in conjunction with the feature string). Thus most clients pass in the
target triple, or the host triple if that is empty.

This has one important change in the way behavior of the JIT and llc.

For the JIT, it was previously selecting the Target based on the host
(naturally), but it was setting the target machine features based on the triple
from the module. Now it is setting the target machine features based on the
triple of the host.

For LLC, -march was previously only used to select the target, the target
machine features were initialized from the module's triple (which may have been
empty). Now the target triple is taken from the module, or the host's triple is
used if that is empty. Then the triple is adjusted to match -march.

The take away is that -march for llc is now used in conjunction with the host
triple to initialize the subtarget. If users want more deterministic behavior
from llc, they should use -mtriple, or set the triple in the input module.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77946 91177308-0d34-0410-b5e6-96231b3b80d8
2009-08-03 04:03:51 +00:00

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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/Host.h"
#include "llvm/System/Path.h"
#include "llvm/System/Process.h"
#include "llvm/Target/SubtargetFeature.h"
#include "llvm/Target/TargetAsmInfo.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 == 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) {
InitializeAllTargets();
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)
{
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,
/*FallbackToHost=*/false,
/*RequireJIT=*/false,
errMsg);
if ( march == NULL )
return NULL;
// construct LTModule, hand over ownership of module and target
std::string FeatureStr = getFeatureString(Triple.c_str());
TargetMachine* target = march->createTargetMachine(*m, Triple, 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 (def->getName().startswith("llvm."))
return;
// string is owned by _defines
const char* symbolName = ::strdup(mangler.getMangledName(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) == 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 (decl->getName().startswith("llvm."))
return;
// ignore all aliases
if (isa<GlobalAlias>(decl))
return;
std::string name = mangler.getMangledName(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 ) {
_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->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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