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llvm-mirror/lib/LTO/UpdateCompilerUsed.cpp
David Blaikie e01dc73ad2 Fix a bunch more layering of CodeGen headers that are in Target
All these headers already depend on CodeGen headers so moving them into
CodeGen fixes the layering (since CodeGen depends on Target, not the
other way around).

llvm-svn: 318490
2017-11-17 01:07:10 +00:00

129 lines
4.2 KiB
C++

//==-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/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Mangler.h"
#include "llvm/Transforms/IPO/Internalize.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
using namespace llvm;
namespace {
// Helper class that collects AsmUsed and user supplied libcalls.
class PreserveLibCallsAndAsmUsed {
public:
PreserveLibCallsAndAsmUsed(const StringSet<> &AsmUndefinedRefs,
const TargetMachine &TM,
std::vector<GlobalValue *> &LLVMUsed)
: AsmUndefinedRefs(AsmUndefinedRefs), TM(TM), LLVMUsed(LLVMUsed) {}
void findInModule(Module &TheModule) {
initializeLibCalls(TheModule);
for (Function &F : TheModule)
findLibCallsAndAsm(F);
for (GlobalVariable &GV : TheModule.globals())
findLibCallsAndAsm(GV);
for (GlobalAlias &GA : TheModule.aliases())
findLibCallsAndAsm(GA);
}
private:
// Inputs
const StringSet<> &AsmUndefinedRefs;
const TargetMachine &TM;
// Temps
llvm::Mangler Mangler;
StringSet<> Libcalls;
// Output
std::vector<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 F = static_cast<LibFunc>(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(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.push_back(&GV);
return;
}
SmallString<64> Buffer;
TM.getNameWithPrefix(Buffer, &GV, Mangler);
if (AsmUndefinedRefs.count(Buffer))
LLVMUsed.push_back(&GV);
}
};
} // namespace anonymous
void llvm::updateCompilerUsed(Module &TheModule, const TargetMachine &TM,
const StringSet<> &AsmUndefinedRefs) {
std::vector<GlobalValue *> UsedValues;
PreserveLibCallsAndAsmUsed(AsmUndefinedRefs, TM, UsedValues)
.findInModule(TheModule);
if (UsedValues.empty())
return;
appendToCompilerUsed(TheModule, UsedValues);
}