blob: 210a2ce00bdf819c4fe373475feb77b3a438aa4c [file] [log] [blame]
//===-ThinLTOCodeGenerator.h - LLVM Link Time Optimizer -------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file declares the ThinLTOCodeGenerator class, similar to the
// LTOCodeGenerator but for the ThinLTO scheme. It provides an interface for
// linker plugin.
#include "llvm-c/lto.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/ADT/Triple.h"
#include "llvm/IR/ModuleSummaryIndex.h"
#include "llvm/LTO/LTO.h"
#include "llvm/Support/CachePruning.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Target/TargetOptions.h"
#include <string>
namespace llvm {
class StringRef;
class LLVMContext;
class TargetMachine;
/// Helper to gather options relevant to the target machine creation
struct TargetMachineBuilder {
Triple TheTriple;
std::string MCpu;
std::string MAttr;
TargetOptions Options;
Optional<Reloc::Model> RelocModel;
CodeGenOpt::Level CGOptLevel = CodeGenOpt::Aggressive;
std::unique_ptr<TargetMachine> create() const;
/// This class define an interface similar to the LTOCodeGenerator, but adapted
/// for ThinLTO processing.
/// The ThinLTOCodeGenerator is not intended to be reuse for multiple
/// compilation: the model is that the client adds modules to the generator and
/// ask to perform the ThinLTO optimizations / codegen, and finally destroys the
/// codegenerator.
class ThinLTOCodeGenerator {
/// Add given module to the code generator.
void addModule(StringRef Identifier, StringRef Data);
* Adds to a list of all global symbols that must exist in the final generated
* code. If a symbol is not listed there, it will be optimized away if it is
* inlined into every usage.
void preserveSymbol(StringRef Name);
* Adds to a list of all global symbols that are cross-referenced between
* ThinLTO files. If the ThinLTO CodeGenerator can ensure that every
* references from a ThinLTO module to this symbol is optimized away, then
* the symbol can be discarded.
void crossReferenceSymbol(StringRef Name);
* Process all the modules that were added to the code generator in parallel.
* Client can access the resulting object files using getProducedBinaries(),
* unless setGeneratedObjectsDirectory() has been called, in which case
* results are available through getProducedBinaryFiles().
void run();
* Return the "in memory" binaries produced by the code generator. This is
* filled after run() unless setGeneratedObjectsDirectory() has been
* called, in which case results are available through
* getProducedBinaryFiles().
std::vector<std::unique_ptr<MemoryBuffer>> &getProducedBinaries() {
return ProducedBinaries;
* Return the "on-disk" binaries produced by the code generator. This is
* filled after run() when setGeneratedObjectsDirectory() has been
* called, in which case results are available through getProducedBinaries().
std::vector<std::string> &getProducedBinaryFiles() {
return ProducedBinaryFiles;
* \defgroup Options setters
* @{
* \defgroup Cache controlling options
* These entry points control the ThinLTO cache. The cache is intended to
* support incremental build, and thus needs to be persistent accross build.
* The client enabled the cache by supplying a path to an existing directory.
* The code generator will use this to store objects files that may be reused
* during a subsequent build.
* To avoid filling the disk space, a few knobs are provided:
* - The pruning interval limit the frequency at which the garbage collector
* will try to scan the cache directory to prune it from expired entries.
* Setting to -1 disable the pruning (default). Setting to 0 will force
* pruning to occur.
* - The pruning expiration time indicates to the garbage collector how old
* an entry needs to be to be removed.
* - Finally, the garbage collector can be instructed to prune the cache till
* the occupied space goes below a threshold.
* @{
struct CachingOptions {
std::string Path; // Path to the cache, empty to disable.
CachePruningPolicy Policy;
/// Provide a path to a directory where to store the cached files for
/// incremental build.
void setCacheDir(std::string Path) { CacheOptions.Path = std::move(Path); }
/// Cache policy: interval (seconds) between two prunes of the cache. Set to a
/// negative value to disable pruning. A value of 0 will force pruning to
/// occur.
void setCachePruningInterval(int Interval) {
if(Interval < 0)
CacheOptions.Policy.Interval = std::chrono::seconds(Interval);
/// Cache policy: expiration (in seconds) for an entry.
/// A value of 0 will be ignored.
void setCacheEntryExpiration(unsigned Expiration) {
if (Expiration)
CacheOptions.Policy.Expiration = std::chrono::seconds(Expiration);
* Sets the maximum cache size that can be persistent across build, in terms
* of percentage of the available space on the disk. Set to 100 to indicate
* no limit, 50 to indicate that the cache size will not be left over
* half the available space. A value over 100 will be reduced to 100, and a
* value of 0 will be ignored.
* The formula looks like:
* AvailableSpace = FreeSpace + ExistingCacheSize
* NewCacheSize = AvailableSpace * P/100
void setMaxCacheSizeRelativeToAvailableSpace(unsigned Percentage) {
if (Percentage)
CacheOptions.Policy.MaxSizePercentageOfAvailableSpace = Percentage;
/// Cache policy: the maximum size for the cache directory in bytes. A value
/// over the amount of available space on the disk will be reduced to the
/// amount of available space. A value of 0 will be ignored.
void setCacheMaxSizeBytes(uint64_t MaxSizeBytes) {
if (MaxSizeBytes)
CacheOptions.Policy.MaxSizeBytes = MaxSizeBytes;
/// Cache policy: the maximum number of files in the cache directory. A value
/// of 0 will be ignored.
void setCacheMaxSizeFiles(unsigned MaxSizeFiles) {
if (MaxSizeFiles)
CacheOptions.Policy.MaxSizeFiles = MaxSizeFiles;
/// Set the path to a directory where to save temporaries at various stages of
/// the processing.
void setSaveTempsDir(std::string Path) { SaveTempsDir = std::move(Path); }
/// Set the path to a directory where to save generated object files. This
/// path can be used by a linker to request on-disk files instead of in-memory
/// buffers. When set, results are available through getProducedBinaryFiles()
/// instead of getProducedBinaries().
void setGeneratedObjectsDirectory(std::string Path) {
SavedObjectsDirectoryPath = std::move(Path);
/// CPU to use to initialize the TargetMachine
void setCpu(std::string Cpu) { TMBuilder.MCpu = std::move(Cpu); }
/// Subtarget attributes
void setAttr(std::string MAttr) { TMBuilder.MAttr = std::move(MAttr); }
/// TargetMachine options
void setTargetOptions(TargetOptions Options) {
TMBuilder.Options = std::move(Options);
/// Enable the Freestanding mode: indicate that the optimizer should not
/// assume builtins are present on the target.
void setFreestanding(bool Enabled) { Freestanding = Enabled; }
/// CodeModel
void setCodePICModel(Optional<Reloc::Model> Model) {
TMBuilder.RelocModel = Model;
/// CodeGen optimization level
void setCodeGenOptLevel(CodeGenOpt::Level CGOptLevel) {
TMBuilder.CGOptLevel = CGOptLevel;
/// IR optimization level: from 0 to 3.
void setOptLevel(unsigned NewOptLevel) {
OptLevel = (NewOptLevel > 3) ? 3 : NewOptLevel;
/// Disable CodeGen, only run the stages till codegen and stop. The output
/// will be bitcode.
void disableCodeGen(bool Disable) { DisableCodeGen = Disable; }
/// Perform CodeGen only: disable all other stages.
void setCodeGenOnly(bool CGOnly) { CodeGenOnly = CGOnly; }
* \defgroup Set of APIs to run individual stages in isolation.
* @{
* Produce the combined summary index from all the bitcode files:
* "thin-link".
std::unique_ptr<ModuleSummaryIndex> linkCombinedIndex();
* Perform promotion and renaming of exported internal functions,
* and additionally resolve weak and linkonce symbols.
* Index is updated to reflect linkage changes from weak resolution.
void promote(Module &Module, ModuleSummaryIndex &Index,
const lto::InputFile &File);
* Compute and emit the imported files for module at \p ModulePath.
void emitImports(Module &Module, StringRef OutputName,
ModuleSummaryIndex &Index,
const lto::InputFile &File);
* Perform cross-module importing for the module identified by
* ModuleIdentifier.
void crossModuleImport(Module &Module, ModuleSummaryIndex &Index,
const lto::InputFile &File);
* Compute the list of summaries needed for importing into module.
void gatherImportedSummariesForModule(
Module &Module, ModuleSummaryIndex &Index,
std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex,
const lto::InputFile &File);
* Perform internalization. Index is updated to reflect linkage changes.
void internalize(Module &Module, ModuleSummaryIndex &Index,
const lto::InputFile &File);
* Perform post-importing ThinLTO optimizations.
void optimize(Module &Module);
* Write temporary object file to SavedObjectDirectoryPath, write symlink
* to Cache directory if needed. Returns the path to the generated file in
* SavedObjectsDirectoryPath.
std::string writeGeneratedObject(int count, StringRef CacheEntryPath,
const MemoryBuffer &OutputBuffer);
/// Helper factory to build a TargetMachine
TargetMachineBuilder TMBuilder;
/// Vector holding the in-memory buffer containing the produced binaries, when
/// SavedObjectsDirectoryPath isn't set.
std::vector<std::unique_ptr<MemoryBuffer>> ProducedBinaries;
/// Path to generated files in the supplied SavedObjectsDirectoryPath if any.
std::vector<std::string> ProducedBinaryFiles;
/// Vector holding the input buffers containing the bitcode modules to
/// process.
std::vector<std::unique_ptr<lto::InputFile>> Modules;
/// Set of symbols that need to be preserved outside of the set of bitcode
/// files.
StringSet<> PreservedSymbols;
/// Set of symbols that are cross-referenced between bitcode files.
StringSet<> CrossReferencedSymbols;
/// Control the caching behavior.
CachingOptions CacheOptions;
/// Path to a directory to save the temporary bitcode files.
std::string SaveTempsDir;
/// Path to a directory to save the generated object files.
std::string SavedObjectsDirectoryPath;
/// Flag to enable/disable CodeGen. When set to true, the process stops after
/// optimizations and a bitcode is produced.
bool DisableCodeGen = false;
/// Flag to indicate that only the CodeGen will be performed, no cross-module
/// importing or optimization.
bool CodeGenOnly = false;
/// Flag to indicate that the optimizer should not assume builtins are present
/// on the target.
bool Freestanding = false;
/// IR Optimization Level [0-3].
unsigned OptLevel = 3;