// 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.
+//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "internalize"
#include "llvm/Transforms/IPO.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.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");
cl::desc("A list of symbol names to preserve"),
cl::CommaSeparated);
-static cl::list<std::string>
-DSOList("internalize-dso-list", cl::value_desc("list"),
- cl::desc("A list of symbol names need for a dso symbol table"),
- cl::CommaSeparated);
-
namespace {
class InternalizePass : public ModulePass {
std::set<std::string> ExternalNames;
- std::set<std::string> DSONames;
public:
static char ID; // Pass identification, replacement for typeid
explicit InternalizePass();
- explicit InternalizePass(ArrayRef<const char *> ExportList,
- ArrayRef<const char *> DSOList);
+ explicit InternalizePass(ArrayRef<const char *> ExportList);
void LoadFile(const char *Filename);
- virtual bool runOnModule(Module &M);
+ bool maybeInternalize(GlobalValue &GV,
+ const std::set<const Comdat *> &ExternalComdats);
+ void checkComdatVisibility(GlobalValue &GV,
+ std::set<const Comdat *> &ExternalComdats);
+ bool runOnModule(Module &M) override;
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
- AU.addPreserved<CallGraph>();
+ AU.addPreserved<CallGraphWrapperPass>();
}
};
} // end anonymous namespace
INITIALIZE_PASS(InternalizePass, "internalize",
"Internalize Global Symbols", false, false)
-InternalizePass::InternalizePass()
- : ModulePass(ID) {
+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());
- DSONames.insert(DSOList.begin(), DSOList.end());
}
-InternalizePass::InternalizePass(ArrayRef<const char *> ExportList,
- ArrayRef<const char *> DSOList)
- : ModulePass(ID){
+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);
}
- for(ArrayRef<const char *>::const_iterator itr = DSOList.begin();
- itr != DSOList.end(); itr++) {
- DSONames.insert(*itr);
- }
}
void InternalizePass::LoadFile(const char *Filename) {
}
}
-static bool shouldInternalize(const GlobalValue &GV,
- const std::set<std::string> &ExternalNames,
- const std::set<std::string> &DSONames) {
+static bool isExternallyVisible(const GlobalValue &GV,
+ const std::set<std::string> &ExternalNames) {
// Function must be defined here
if (GV.isDeclaration())
- return false;
+ return true;
// Available externally is really just a "declaration with a body".
if (GV.hasAvailableExternallyLinkage())
- return false;
+ return true;
- // Already has internal linkage
- if (GV.hasLocalLinkage())
- return false;
+ // Assume that dllexported symbols are referenced elsewhere
+ if (GV.hasDLLExportStorageClass())
+ return true;
// Marked to keep external?
- if (ExternalNames.count(GV.getName()))
- return false;
-
- // Not needed for the symbol table?
- if (!DSONames.count(GV.getName()))
+ if (!GV.hasLocalLinkage() && ExternalNames.count(GV.getName()))
return true;
- // Not a linkonce. Someone can depend on it being on the symbol table.
- if (!GV.hasLinkOnceLinkage())
- return false;
+ return false;
+}
- // The address is not important, we can hide it.
- if (GV.hasUnnamedAddr())
- return true;
+// Internalize GV if it is possible to do so, i.e. it is not externally visible
+// and is not a member of an externally visible comdat.
+bool InternalizePass::maybeInternalize(
+ GlobalValue &GV, const std::set<const Comdat *> &ExternalComdats) {
+ if (Comdat *C = GV.getComdat()) {
+ if (ExternalComdats.count(C))
+ return false;
+
+ // If a comdat is not externally visible we can drop it.
+ if (auto GO = dyn_cast<GlobalObject>(&GV))
+ GO->setComdat(nullptr);
+
+ if (GV.hasLocalLinkage())
+ return false;
+ } else {
+ if (GV.hasLocalLinkage())
+ return false;
+
+ if (isExternallyVisible(GV, ExternalNames))
+ return false;
+ }
- // FIXME: Check if the address is used.
- return false;
+ GV.setVisibility(GlobalValue::DefaultVisibility);
+ GV.setLinkage(GlobalValue::InternalLinkage);
+ return true;
+}
+
+// If GV is part of a comdat and is externally visible, keep track of its
+// comdat so that we don't internalize any of its members.
+void InternalizePass::checkComdatVisibility(
+ GlobalValue &GV, std::set<const Comdat *> &ExternalComdats) {
+ Comdat *C = GV.getComdat();
+ if (!C)
+ return;
+
+ if (isExternallyVisible(GV, ExternalNames))
+ ExternalComdats.insert(C);
}
bool InternalizePass::runOnModule(Module &M) {
- CallGraph *CG = getAnalysisIfAvailable<CallGraph>();
- CallGraphNode *ExternalNode = CG ? CG->getExternalCallingNode() : 0;
- bool Changed = false;
+ CallGraphWrapperPass *CGPass = getAnalysisIfAvailable<CallGraphWrapperPass>();
+ CallGraph *CG = CGPass ? &CGPass->getCallGraph() : nullptr;
+ CallGraphNode *ExternalNode = CG ? CG->getExternalCallingNode() : nullptr;
SmallPtrSet<GlobalValue *, 8> Used;
collectUsedGlobalVariables(M, Used, false);
+ // Collect comdat visiblity information for the module.
+ std::set<const Comdat *> ExternalComdats;
+ if (!M.getComdatSymbolTable().empty()) {
+ for (Function &F : M)
+ checkComdatVisibility(F, ExternalComdats);
+ for (GlobalVariable &GV : M.globals())
+ checkComdatVisibility(GV, ExternalComdats);
+ for (GlobalAlias &GA : M.aliases())
+ checkComdatVisibility(GA, ExternalComdats);
+ }
+
// 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
// 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;
+ for (GlobalValue *V : Used) {
ExternalNames.insert(V->getName());
}
// Mark all functions not in the api as internal.
- // FIXME: maybe use private linkage?
- for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
- if (!shouldInternalize(*I, ExternalNames, DSONames))
+ for (Function &I : M) {
+ if (!maybeInternalize(I, ExternalComdats))
continue;
- I->setLinkage(GlobalValue::InternalLinkage);
-
if (ExternalNode)
// Remove a callgraph edge from the external node to this function.
- ExternalNode->removeOneAbstractEdgeTo((*CG)[I]);
+ ExternalNode->removeOneAbstractEdgeTo((*CG)[&I]);
- Changed = true;
++NumFunctions;
- DEBUG(dbgs() << "Internalizing func " << I->getName() << "\n");
+ DEBUG(dbgs() << "Internalizing func " << I.getName() << "\n");
}
// Never internalize the llvm.used symbol. It is used to implement
// Mark all global variables with initializers that are not in the api as
// internal as well.
- // FIXME: maybe use private linkage?
for (Module::global_iterator I = M.global_begin(), E = M.global_end();
I != E; ++I) {
- if (!shouldInternalize(*I, ExternalNames, DSONames))
+ if (!maybeInternalize(*I, ExternalComdats))
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, DSONames))
+ if (!maybeInternalize(*I, ExternalComdats))
continue;
- I->setLinkage(GlobalValue::InternalLinkage);
- Changed = true;
++NumAliases;
DEBUG(dbgs() << "Internalized alias " << I->getName() << "\n");
}
- return Changed;
+ // We do not keep track of whether this pass changed the module because
+ // it adds unnecessary complexity:
+ // 1) This pass will generally be near the start of the pass pipeline, so
+ // there will be no analyses to invalidate.
+ // 2) This pass will most likely end up changing the module and it isn't worth
+ // worrying about optimizing the case where the module is unchanged.
+ return true;
}
-ModulePass *llvm::createInternalizePass() {
- return new InternalizePass();
-}
+ModulePass *llvm::createInternalizePass() { return new InternalizePass(); }
-ModulePass *llvm::createInternalizePass(ArrayRef<const char *> ExportList,
- ArrayRef<const char *> DSOList) {
- return new InternalizePass(ExportList, DSOList);
+ModulePass *llvm::createInternalizePass(ArrayRef<const char *> ExportList) {
+ return new InternalizePass(ExportList);
}
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