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//===-Config.h - LLVM Link Time Optimizer Configuration -------------------===//
// 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 defines the lto::Config data structure, which allows clients to
// configure LTO.
#include "llvm/ADT/DenseSet.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/Passes/PassBuilder.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Target/TargetOptions.h"
#include <functional>
namespace llvm {
class Error;
class Module;
class ModuleSummaryIndex;
class raw_pwrite_stream;
namespace lto {
/// LTO configuration. A linker can configure LTO by setting fields in this data
/// structure and passing it to the lto::LTO constructor.
struct Config {
// Note: when adding fields here, consider whether they need to be added to
// computeCacheKey in LTO.cpp.
std::string CPU;
TargetOptions Options;
std::vector<std::string> MAttrs;
Optional<Reloc::Model> RelocModel = Reloc::PIC_;
Optional<CodeModel::Model> CodeModel = None;
CodeGenOpt::Level CGOptLevel = CodeGenOpt::Default;
CodeGenFileType CGFileType = CGFT_ObjectFile;
unsigned OptLevel = 2;
bool DisableVerify = false;
/// Use the new pass manager
bool UseNewPM = false;
/// Flag to indicate that the optimizer should not assume builtins are present
/// on the target.
bool Freestanding = false;
/// Disable entirely the optimizer, including importing for ThinLTO
bool CodeGenOnly = false;
/// Run PGO context sensitive IR instrumentation.
bool RunCSIRInstr = false;
/// If this field is set, the set of passes run in the middle-end optimizer
/// will be the one specified by the string. Only works with the new pass
/// manager as the old one doesn't have this ability.
std::string OptPipeline;
// If this field is set, it has the same effect of specifying an AA pipeline
// identified by the string. Only works with the new pass manager, in
// conjunction OptPipeline.
std::string AAPipeline;
/// Setting this field will replace target triples in input files with this
/// triple.
std::string OverrideTriple;
/// Setting this field will replace unspecified target triples in input files
/// with this triple.
std::string DefaultTriple;
/// Context Sensitive PGO profile path.
std::string CSIRProfile;
/// Sample PGO profile path.
std::string SampleProfile;
/// Name remapping file for profile data.
std::string ProfileRemapping;
/// The directory to store .dwo files.
std::string DwoDir;
/// The name for the split debug info file used for the DW_AT_[GNU_]dwo_name
/// attribute in the skeleton CU. This should generally only be used when
/// running an individual backend directly via thinBackend(), as otherwise
/// all objects would use the same .dwo file. Not used as output path.
std::string SplitDwarfFile;
/// The path to write a .dwo file to. This should generally only be used when
/// running an individual backend directly via thinBackend(), as otherwise
/// all .dwo files will be written to the same path. Not used in skeleton CU.
std::string SplitDwarfOutput;
/// Optimization remarks file path.
std::string RemarksFilename = "";
/// Optimization remarks pass filter.
std::string RemarksPasses = "";
/// Whether to emit optimization remarks with hotness informations.
bool RemarksWithHotness = false;
/// The format used for serializing remarks (default: YAML).
std::string RemarksFormat = "";
/// Whether to emit the pass manager debuggging informations.
bool DebugPassManager = false;
/// Statistics output file path.
std::string StatsFile;
bool ShouldDiscardValueNames = true;
DiagnosticHandlerFunction DiagHandler;
/// If this field is set, LTO will write input file paths and symbol
/// resolutions here in llvm-lto2 command line flag format. This can be
/// used for testing and for running the LTO pipeline outside of the linker
/// with llvm-lto2.
std::unique_ptr<raw_ostream> ResolutionFile;
/// Tunable parameters for passes in the default pipelines.
PipelineTuningOptions PTO;
/// The following callbacks deal with tasks, which normally represent the
/// entire optimization and code generation pipeline for what will become a
/// single native object file. Each task has a unique identifier between 0 and
/// getMaxTasks()-1, which is supplied to the callback via the Task parameter.
/// A task represents the entire pipeline for ThinLTO and regular
/// (non-parallel) LTO, but a parallel code generation task will be split into
/// N tasks before code generation, where N is the parallelism level.
/// LTO may decide to stop processing a task at any time, for example if the
/// module is empty or if a module hook (see below) returns false. For this
/// reason, the client should not expect to receive exactly getMaxTasks()
/// native object files.
/// A module hook may be used by a linker to perform actions during the LTO
/// pipeline. For example, a linker may use this function to implement
/// -save-temps. If this function returns false, any further processing for
/// that task is aborted.
/// Module hooks must be thread safe with respect to the linker's internal
/// data structures. A module hook will never be called concurrently from
/// multiple threads with the same task ID, or the same module.
/// Note that in out-of-process backend scenarios, none of the hooks will be
/// called for ThinLTO tasks.
using ModuleHookFn = std::function<bool(unsigned Task, const Module &)>;
/// This module hook is called after linking (regular LTO) or loading
/// (ThinLTO) the module, before modifying it.
ModuleHookFn PreOptModuleHook;
/// This hook is called after promoting any internal functions
/// (ThinLTO-specific).
ModuleHookFn PostPromoteModuleHook;
/// This hook is called after internalizing the module.
ModuleHookFn PostInternalizeModuleHook;
/// This hook is called after importing from other modules (ThinLTO-specific).
ModuleHookFn PostImportModuleHook;
/// This module hook is called after optimization is complete.
ModuleHookFn PostOptModuleHook;
/// This module hook is called before code generation. It is similar to the
/// PostOptModuleHook, but for parallel code generation it is called after
/// splitting the module.
ModuleHookFn PreCodeGenModuleHook;
/// A combined index hook is called after all per-module indexes have been
/// combined (ThinLTO-specific). It can be used to implement -save-temps for
/// the combined index.
/// If this function returns false, any further processing for ThinLTO tasks
/// is aborted.
/// It is called regardless of whether the backend is in-process, although it
/// is not called from individual backend processes.
using CombinedIndexHookFn = std::function<bool(
const ModuleSummaryIndex &Index,
const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols)>;
CombinedIndexHookFn CombinedIndexHook;
/// This is a convenience function that configures this Config object to write
/// temporary files named after the given OutputFileName for each of the LTO
/// phases to disk. A client can use this function to implement -save-temps.
/// FIXME: Temporary files derived from ThinLTO backends are currently named
/// after the input file name, rather than the output file name, when
/// UseInputModulePath is set to true.
/// Specifically, it (1) sets each of the above module hooks and the combined
/// index hook to a function that calls the hook function (if any) that was
/// present in the appropriate field when the addSaveTemps function was
/// called, and writes the module to a bitcode file with a name prefixed by
/// the given output file name, and (2) creates a resolution file whose name
/// is prefixed by the given output file name and sets ResolutionFile to its
/// file handle.
Error addSaveTemps(std::string OutputFileName,
bool UseInputModulePath = false);
struct LTOLLVMDiagnosticHandler : public DiagnosticHandler {
DiagnosticHandlerFunction *Fn;
LTOLLVMDiagnosticHandler(DiagnosticHandlerFunction *DiagHandlerFn)
: Fn(DiagHandlerFn) {}
bool handleDiagnostics(const DiagnosticInfo &DI) override {
return true;
/// A derived class of LLVMContext that initializes itself according to a given
/// Config object. The purpose of this class is to tie ownership of the
/// diagnostic handler to the context, as opposed to the Config object (which
/// may be ephemeral).
// FIXME: This should not be required as diagnostic handler is not callback.
struct LTOLLVMContext : LLVMContext {
LTOLLVMContext(const Config &C) : DiagHandler(C.DiagHandler) {
std::make_unique<LTOLLVMDiagnosticHandler>(&DiagHandler), true);
DiagnosticHandlerFunction DiagHandler;