llvm-project/llvm/lib/Transforms/IPO/Internalize.cpp

224 lines
7.7 KiB
C++

//===-- Internalize.cpp - Mark functions internal -------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass loops over all of the functions and variables in the input module.
// If the function or variable is not in the list of external names given to
// the pass it is marked as internal.
//
// This transformation would not be legal in a regular compilation, but it gets
// extra information from the linker about what is safe.
//
// For example: Internalizing a function with external linkage. Only if we are
// told it is only used from within this module, it is safe to do it.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/IPO.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/GlobalStatus.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
#include <fstream>
#include <set>
using namespace llvm;
#define DEBUG_TYPE "internalize"
STATISTIC(NumAliases , "Number of aliases internalized");
STATISTIC(NumFunctions, "Number of functions internalized");
STATISTIC(NumGlobals , "Number of global vars internalized");
// APIFile - A file which contains a list of symbols that should not be marked
// external.
static cl::opt<std::string>
APIFile("internalize-public-api-file", cl::value_desc("filename"),
cl::desc("A file containing list of symbol names to preserve"));
// APIList - A list of symbols that should not be marked internal.
static cl::list<std::string>
APIList("internalize-public-api-list", cl::value_desc("list"),
cl::desc("A list of symbol names to preserve"),
cl::CommaSeparated);
namespace {
class InternalizePass : public ModulePass {
std::set<std::string> ExternalNames;
public:
static char ID; // Pass identification, replacement for typeid
explicit InternalizePass();
explicit InternalizePass(ArrayRef<const char *> ExportList);
void LoadFile(const char *Filename);
bool runOnModule(Module &M) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
AU.addPreserved<CallGraphWrapperPass>();
}
};
} // end anonymous namespace
char InternalizePass::ID = 0;
INITIALIZE_PASS(InternalizePass, "internalize",
"Internalize Global Symbols", false, false)
InternalizePass::InternalizePass() : ModulePass(ID) {
initializeInternalizePassPass(*PassRegistry::getPassRegistry());
if (!APIFile.empty()) // If a filename is specified, use it.
LoadFile(APIFile.c_str());
ExternalNames.insert(APIList.begin(), APIList.end());
}
InternalizePass::InternalizePass(ArrayRef<const char *> ExportList)
: ModulePass(ID) {
initializeInternalizePassPass(*PassRegistry::getPassRegistry());
for(ArrayRef<const char *>::const_iterator itr = ExportList.begin();
itr != ExportList.end(); itr++) {
ExternalNames.insert(*itr);
}
}
void InternalizePass::LoadFile(const char *Filename) {
// Load the APIFile...
std::ifstream In(Filename);
if (!In.good()) {
errs() << "WARNING: Internalize couldn't load file '" << Filename
<< "'! Continuing as if it's empty.\n";
return; // Just continue as if the file were empty
}
while (In) {
std::string Symbol;
In >> Symbol;
if (!Symbol.empty())
ExternalNames.insert(Symbol);
}
}
static bool shouldInternalize(const GlobalValue &GV,
const std::set<std::string> &ExternalNames) {
// Function must be defined here
if (GV.isDeclaration())
return false;
// Available externally is really just a "declaration with a body".
if (GV.hasAvailableExternallyLinkage())
return false;
// Assume that dllexported symbols are referenced elsewhere
if (GV.hasDLLExportStorageClass())
return false;
// Already has internal linkage
if (GV.hasLocalLinkage())
return false;
// Marked to keep external?
if (ExternalNames.count(GV.getName()))
return false;
return true;
}
bool InternalizePass::runOnModule(Module &M) {
CallGraphWrapperPass *CGPass = getAnalysisIfAvailable<CallGraphWrapperPass>();
CallGraph *CG = CGPass ? &CGPass->getCallGraph() : 0;
CallGraphNode *ExternalNode = CG ? CG->getExternalCallingNode() : 0;
bool Changed = false;
SmallPtrSet<GlobalValue *, 8> Used;
collectUsedGlobalVariables(M, Used, false);
// We must assume that globals in llvm.used have a reference that not even
// the linker can see, so we don't internalize them.
// For llvm.compiler.used the situation is a bit fuzzy. The assembler and
// linker can drop those symbols. If this pass is running as part of LTO,
// one might think that it could just drop llvm.compiler.used. The problem
// is that even in LTO llvm doesn't see every reference. For example,
// we don't see references from function local inline assembly. To be
// conservative, we internalize symbols in llvm.compiler.used, but we
// keep llvm.compiler.used so that the symbol is not deleted by llvm.
for (SmallPtrSet<GlobalValue *, 8>::iterator I = Used.begin(), E = Used.end();
I != E; ++I) {
GlobalValue *V = *I;
ExternalNames.insert(V->getName());
}
// Mark all functions not in the api as internal.
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
if (!shouldInternalize(*I, ExternalNames))
continue;
I->setLinkage(GlobalValue::InternalLinkage);
if (ExternalNode)
// Remove a callgraph edge from the external node to this function.
ExternalNode->removeOneAbstractEdgeTo((*CG)[I]);
Changed = true;
++NumFunctions;
DEBUG(dbgs() << "Internalizing func " << I->getName() << "\n");
}
// Never internalize the llvm.used symbol. It is used to implement
// attribute((used)).
// FIXME: Shouldn't this just filter on llvm.metadata section??
ExternalNames.insert("llvm.used");
ExternalNames.insert("llvm.compiler.used");
// Never internalize anchors used by the machine module info, else the info
// won't find them. (see MachineModuleInfo.)
ExternalNames.insert("llvm.global_ctors");
ExternalNames.insert("llvm.global_dtors");
ExternalNames.insert("llvm.global.annotations");
// Never internalize symbols code-gen inserts.
// FIXME: We should probably add this (and the __stack_chk_guard) via some
// type of call-back in CodeGen.
ExternalNames.insert("__stack_chk_fail");
ExternalNames.insert("__stack_chk_guard");
// Mark all global variables with initializers that are not in the api as
// internal as well.
for (Module::global_iterator I = M.global_begin(), E = M.global_end();
I != E; ++I) {
if (!shouldInternalize(*I, ExternalNames))
continue;
I->setLinkage(GlobalValue::InternalLinkage);
Changed = true;
++NumGlobals;
DEBUG(dbgs() << "Internalized gvar " << I->getName() << "\n");
}
// Mark all aliases that are not in the api as internal as well.
for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
I != E; ++I) {
if (!shouldInternalize(*I, ExternalNames))
continue;
I->setLinkage(GlobalValue::InternalLinkage);
Changed = true;
++NumAliases;
DEBUG(dbgs() << "Internalized alias " << I->getName() << "\n");
}
return Changed;
}
ModulePass *llvm::createInternalizePass() { return new InternalizePass(); }
ModulePass *llvm::createInternalizePass(ArrayRef<const char *> ExportList) {
return new InternalizePass(ExportList);
}