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//==-LTOInternalize.cpp - LLVM Link Time Optimizer Internalization Utility -==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines a helper to run the internalization part of LTO.
//
//===----------------------------------------------------------------------===//
#include "llvm/LTO/legacy/UpdateCompilerUsed.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Mangler.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetSubtargetInfo.h"
#include "llvm/Transforms/IPO/Internalize.h"
using namespace llvm;
namespace {
// Helper class that collects AsmUsed and user supplied libcalls.
class PreserveLibCallsAndAsmUsed {
public:
PreserveLibCallsAndAsmUsed(const StringSet<> &AsmUndefinedRefs,
const TargetMachine &TM,
SmallPtrSetImpl<const GlobalValue *> &LLVMUsed)
: AsmUndefinedRefs(AsmUndefinedRefs), TM(TM), LLVMUsed(LLVMUsed) {}
void findInModule(const Module &TheModule) {
initializeLibCalls(TheModule);
for (const Function &F : TheModule)
findLibCallsAndAsm(F);
for (const GlobalVariable &GV : TheModule.globals())
findLibCallsAndAsm(GV);
for (const GlobalAlias &GA : TheModule.aliases())
findLibCallsAndAsm(GA);
}
private:
// Inputs
const StringSet<> &AsmUndefinedRefs;
const TargetMachine &TM;
// Temps
llvm::Mangler Mangler;
StringSet<> Libcalls;
// Output
SmallPtrSetImpl<const GlobalValue *> &LLVMUsed;
// Collect names of runtime library functions. User-defined functions with the
// same names are added to llvm.compiler.used to prevent them from being
// deleted by optimizations.
void initializeLibCalls(const Module &TheModule) {
TargetLibraryInfoImpl TLII(Triple(TM.getTargetTriple()));
TargetLibraryInfo TLI(TLII);
// TargetLibraryInfo has info on C runtime library calls on the current
// target.
for (unsigned I = 0, E = static_cast<unsigned>(LibFunc::NumLibFuncs);
I != E; ++I) {
LibFunc::Func F = static_cast<LibFunc::Func>(I);
if (TLI.has(F))
Libcalls.insert(TLI.getName(F));
}
SmallPtrSet<const TargetLowering *, 1> TLSet;
for (const Function &F : TheModule) {
const TargetLowering *Lowering =
TM.getSubtargetImpl(F)->getTargetLowering();
if (Lowering && TLSet.insert(Lowering).second)
// TargetLowering has info on library calls that CodeGen expects to be
// available, both from the C runtime and compiler-rt.
for (unsigned I = 0, E = static_cast<unsigned>(RTLIB::UNKNOWN_LIBCALL);
I != E; ++I)
if (const char *Name =
Lowering->getLibcallName(static_cast<RTLIB::Libcall>(I)))
Libcalls.insert(Name);
}
}
void findLibCallsAndAsm(const GlobalValue &GV) {
// There are no restrictions to apply to declarations.
if (GV.isDeclaration())
return;
// There is nothing more restrictive than private linkage.
if (GV.hasPrivateLinkage())
return;
// Conservatively append user-supplied runtime library functions to
// llvm.compiler.used. These could be internalized and deleted by
// optimizations like -globalopt, causing problems when later optimizations
// add new library calls (e.g., llvm.memset => memset and printf => puts).
// Leave it to the linker to remove any dead code (e.g. with -dead_strip).
if (isa<Function>(GV) && Libcalls.count(GV.getName()))
LLVMUsed.insert(&GV);
SmallString<64> Buffer;
TM.getNameWithPrefix(Buffer, &GV, Mangler);
if (AsmUndefinedRefs.count(Buffer))
LLVMUsed.insert(&GV);
}
};
} // namespace anonymous
void llvm::updateCompilerUsed(Module &TheModule, const TargetMachine &TM,
const StringSet<> &AsmUndefinedRefs) {
SmallPtrSet<const GlobalValue *, 8> UsedValues;
PreserveLibCallsAndAsmUsed(AsmUndefinedRefs, TM, UsedValues)
.findInModule(TheModule);
if (UsedValues.empty())
return;
llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(TheModule.getContext());
std::vector<Constant *> UsedValuesList;
for (const auto *GV : UsedValues) {
Constant *c =
ConstantExpr::getBitCast(const_cast<GlobalValue *>(GV), i8PTy);
UsedValuesList.push_back(c);
}
GlobalVariable *LLVMUsed = TheModule.getGlobalVariable("llvm.compiler.used");
if (LLVMUsed) {
ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
for (auto &V : Inits->operands())
UsedValuesList.push_back(cast<Constant>(&V));
LLVMUsed->eraseFromParent();
}
llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, UsedValuesList.size());
LLVMUsed = new llvm::GlobalVariable(
TheModule, ATy, false, llvm::GlobalValue::AppendingLinkage,
llvm::ConstantArray::get(ATy, UsedValuesList), "llvm.compiler.used");
LLVMUsed->setSection("llvm.metadata");
}
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