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//===- TargetPassConfig.h - Code Generation pass options --------*- C++ -*-===//
// 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
/// Target-Independent Code Generator Pass Configuration Options pass.
#include "llvm/Pass.h"
#include "llvm/Support/CodeGen.h"
#include <cassert>
#include <string>
namespace llvm {
class LLVMTargetMachine;
struct MachineSchedContext;
class PassConfigImpl;
class ScheduleDAGInstrs;
// The old pass manager infrastructure is hidden in a legacy namespace now.
namespace legacy {
class PassManagerBase;
} // end namespace legacy
using legacy::PassManagerBase;
/// Discriminated union of Pass ID types.
/// The PassConfig API prefers dealing with IDs because they are safer and more
/// efficient. IDs decouple configuration from instantiation. This way, when a
/// pass is overriden, it isn't unnecessarily instantiated. It is also unsafe to
/// refer to a Pass pointer after adding it to a pass manager, which deletes
/// redundant pass instances.
/// However, it is convient to directly instantiate target passes with
/// non-default ctors. These often don't have a registered PassInfo. Rather than
/// force all target passes to implement the pass registry boilerplate, allow
/// the PassConfig API to handle either type.
/// AnalysisID is sadly char*, so PointerIntPair won't work.
class IdentifyingPassPtr {
union {
AnalysisID ID;
Pass *P;
bool IsInstance = false;
IdentifyingPassPtr() : P(nullptr) {}
IdentifyingPassPtr(AnalysisID IDPtr) : ID(IDPtr) {}
IdentifyingPassPtr(Pass *InstancePtr) : P(InstancePtr), IsInstance(true) {}
bool isValid() const { return P; }
bool isInstance() const { return IsInstance; }
AnalysisID getID() const {
assert(!IsInstance && "Not a Pass ID");
return ID;
Pass *getInstance() const {
assert(IsInstance && "Not a Pass Instance");
return P;
/// Target-Independent Code Generator Pass Configuration Options.
/// This is an ImmutablePass solely for the purpose of exposing CodeGen options
/// to the internals of other CodeGen passes.
class TargetPassConfig : public ImmutablePass {
PassManagerBase *PM = nullptr;
AnalysisID StartBefore = nullptr;
AnalysisID StartAfter = nullptr;
AnalysisID StopBefore = nullptr;
AnalysisID StopAfter = nullptr;
unsigned StartBeforeInstanceNum = 0;
unsigned StartBeforeCount = 0;
unsigned StartAfterInstanceNum = 0;
unsigned StartAfterCount = 0;
unsigned StopBeforeInstanceNum = 0;
unsigned StopBeforeCount = 0;
unsigned StopAfterInstanceNum = 0;
unsigned StopAfterCount = 0;
bool Started = true;
bool Stopped = false;
bool AddingMachinePasses = false;
/// Set the StartAfter, StartBefore and StopAfter passes to allow running only
/// a portion of the normal code-gen pass sequence.
/// If the StartAfter and StartBefore pass ID is zero, then compilation will
/// begin at the normal point; otherwise, clear the Started flag to indicate
/// that passes should not be added until the starting pass is seen. If the
/// Stop pass ID is zero, then compilation will continue to the end.
/// This function expects that at least one of the StartAfter or the
/// StartBefore pass IDs is null.
void setStartStopPasses();
LLVMTargetMachine *TM;
PassConfigImpl *Impl = nullptr; // Internal data structures
bool Initialized = false; // Flagged after all passes are configured.
// Target Pass Options
// Targets provide a default setting, user flags override.
bool DisableVerify = false;
/// Default setting for -enable-tail-merge on this target.
bool EnableTailMerge = true;
/// Require processing of functions such that callees are generated before
/// callers.
bool RequireCodeGenSCCOrder = false;
/// Add the actual instruction selection passes. This does not include
/// preparation passes on IR.
bool addCoreISelPasses();
TargetPassConfig(LLVMTargetMachine &TM, PassManagerBase &pm);
// Dummy constructor.
~TargetPassConfig() override;
static char ID;
/// Get the right type of TargetMachine for this target.
template<typename TMC> TMC &getTM() const {
return *static_cast<TMC*>(TM);
void setInitialized() { Initialized = true; }
CodeGenOpt::Level getOptLevel() const;
/// Returns true if one of the `-start-after`, `-start-before`, `-stop-after`
/// or `-stop-before` options is set.
static bool hasLimitedCodeGenPipeline();
/// Returns true if none of the `-stop-before` and `-stop-after` options is
/// set.
static bool willCompleteCodeGenPipeline();
/// If hasLimitedCodeGenPipeline is true, this method
/// returns a string with the name of the options, separated
/// by \p Separator that caused this pipeline to be limited.
getLimitedCodeGenPipelineReason(const char *Separator = "/") const;
void setDisableVerify(bool Disable) { setOpt(DisableVerify, Disable); }
bool getEnableTailMerge() const { return EnableTailMerge; }
void setEnableTailMerge(bool Enable) { setOpt(EnableTailMerge, Enable); }
bool requiresCodeGenSCCOrder() const { return RequireCodeGenSCCOrder; }
void setRequiresCodeGenSCCOrder(bool Enable = true) {
setOpt(RequireCodeGenSCCOrder, Enable);
/// Allow the target to override a specific pass without overriding the pass
/// pipeline. When passes are added to the standard pipeline at the
/// point where StandardID is expected, add TargetID in its place.
void substitutePass(AnalysisID StandardID, IdentifyingPassPtr TargetID);
/// Insert InsertedPassID pass after TargetPassID pass.
void insertPass(AnalysisID TargetPassID, IdentifyingPassPtr InsertedPassID,
bool VerifyAfter = true, bool PrintAfter = true);
/// Allow the target to enable a specific standard pass by default.
void enablePass(AnalysisID PassID) { substitutePass(PassID, PassID); }
/// Allow the target to disable a specific standard pass by default.
void disablePass(AnalysisID PassID) {
substitutePass(PassID, IdentifyingPassPtr());
/// Return the pass substituted for StandardID by the target.
/// If no substitution exists, return StandardID.
IdentifyingPassPtr getPassSubstitution(AnalysisID StandardID) const;
/// Return true if the pass has been substituted by the target or
/// overridden on the command line.
bool isPassSubstitutedOrOverridden(AnalysisID ID) const;
/// Return true if the optimized regalloc pipeline is enabled.
bool getOptimizeRegAlloc() const;
/// Return true if the default global register allocator is in use and
/// has not be overriden on the command line with '-regalloc=...'
bool usingDefaultRegAlloc() const;
/// High level function that adds all passes necessary to go from llvm IR
/// representation to the MI representation.
/// Adds IR based lowering and target specific optimization passes and finally
/// the core instruction selection passes.
/// \returns true if an error occurred, false otherwise.
bool addISelPasses();
/// Add common target configurable passes that perform LLVM IR to IR
/// transforms following machine independent optimization.
virtual void addIRPasses();
/// Add passes to lower exception handling for the code generator.
void addPassesToHandleExceptions();
/// Add pass to prepare the LLVM IR for code generation. This should be done
/// before exception handling preparation passes.
virtual void addCodeGenPrepare();
/// Add common passes that perform LLVM IR to IR transforms in preparation for
/// instruction selection.
virtual void addISelPrepare();
/// addInstSelector - This method should install an instruction selector pass,
/// which converts from LLVM code to machine instructions.
virtual bool addInstSelector() {
return true;
/// This method should install an IR translator pass, which converts from
/// LLVM code to machine instructions with possibly generic opcodes.
virtual bool addIRTranslator() { return true; }
/// This method may be implemented by targets that want to run passes
/// immediately before legalization.
virtual void addPreLegalizeMachineIR() {}
/// This method should install a legalize pass, which converts the instruction
/// sequence into one that can be selected by the target.
virtual bool addLegalizeMachineIR() { return true; }
/// This method may be implemented by targets that want to run passes
/// immediately before the register bank selection.
virtual void addPreRegBankSelect() {}
/// This method should install a register bank selector pass, which
/// assigns register banks to virtual registers without a register
/// class or register banks.
virtual bool addRegBankSelect() { return true; }
/// This method may be implemented by targets that want to run passes
/// immediately before the (global) instruction selection.
virtual void addPreGlobalInstructionSelect() {}
/// This method should install a (global) instruction selector pass, which
/// converts possibly generic instructions to fully target-specific
/// instructions, thereby constraining all generic virtual registers to
/// register classes.
virtual bool addGlobalInstructionSelect() { return true; }
/// Add the complete, standard set of LLVM CodeGen passes.
/// Fully developed targets will not generally override this.
virtual void addMachinePasses();
/// Create an instance of ScheduleDAGInstrs to be run within the standard
/// MachineScheduler pass for this function and target at the current
/// optimization level.
/// This can also be used to plug a new MachineSchedStrategy into an instance
/// of the standard ScheduleDAGMI:
/// return new ScheduleDAGMI(C, make_unique<MyStrategy>(C), /*RemoveKillFlags=*/false)
/// Return NULL to select the default (generic) machine scheduler.
virtual ScheduleDAGInstrs *
createMachineScheduler(MachineSchedContext *C) const {
return nullptr;
/// Similar to createMachineScheduler but used when postRA machine scheduling
/// is enabled.
virtual ScheduleDAGInstrs *
createPostMachineScheduler(MachineSchedContext *C) const {
return nullptr;
/// printAndVerify - Add a pass to dump then verify the machine function, if
/// those steps are enabled.
void printAndVerify(const std::string &Banner);
/// Add a pass to print the machine function if printing is enabled.
void addPrintPass(const std::string &Banner);
/// Add a pass to perform basic verification of the machine function if
/// verification is enabled.
void addVerifyPass(const std::string &Banner);
/// Check whether or not GlobalISel should abort on error.
/// When this is disabled, GlobalISel will fall back on SDISel instead of
/// erroring out.
bool isGlobalISelAbortEnabled() const;
/// Check whether or not a diagnostic should be emitted when GlobalISel
/// uses the fallback path. In other words, it will emit a diagnostic
/// when GlobalISel failed and isGlobalISelAbortEnabled is false.
virtual bool reportDiagnosticWhenGlobalISelFallback() const;
/// Check whether continuous CSE should be enabled in GISel passes.
/// By default, it's enabled for non O0 levels.
virtual bool isGISelCSEEnabled() const;
// Helper to verify the analysis is really immutable.
void setOpt(bool &Opt, bool Val);
/// Methods with trivial inline returns are convenient points in the common
/// codegen pass pipeline where targets may insert passes. Methods with
/// out-of-line standard implementations are major CodeGen stages called by
/// addMachinePasses. Some targets may override major stages when inserting
/// passes is insufficient, but maintaining overriden stages is more work.
/// addPreISelPasses - This method should add any "last minute" LLVM->LLVM
/// passes (which are run just before instruction selector).
virtual bool addPreISel() {
return true;
/// addMachineSSAOptimization - Add standard passes that optimize machine
/// instructions in SSA form.
virtual void addMachineSSAOptimization();
/// Add passes that optimize instruction level parallelism for out-of-order
/// targets. These passes are run while the machine code is still in SSA
/// form, so they can use MachineTraceMetrics to control their heuristics.
/// All passes added here should preserve the MachineDominatorTree,
/// MachineLoopInfo, and MachineTraceMetrics analyses.
virtual bool addILPOpts() {
return false;
/// This method may be implemented by targets that want to run passes
/// immediately before register allocation.
virtual void addPreRegAlloc() { }
/// createTargetRegisterAllocator - Create the register allocator pass for
/// this target at the current optimization level.
virtual FunctionPass *createTargetRegisterAllocator(bool Optimized);
/// addFastRegAlloc - Add the minimum set of target-independent passes that
/// are required for fast register allocation.
virtual void addFastRegAlloc();
/// addOptimizedRegAlloc - Add passes related to register allocation.
/// LLVMTargetMachine provides standard regalloc passes for most targets.
virtual void addOptimizedRegAlloc();
/// addPreRewrite - Add passes to the optimized register allocation pipeline
/// after register allocation is complete, but before virtual registers are
/// rewritten to physical registers.
/// These passes must preserve VirtRegMap and LiveIntervals, and when running
/// after RABasic or RAGreedy, they should take advantage of LiveRegMatrix.
/// When these passes run, VirtRegMap contains legal physreg assignments for
/// all virtual registers.
/// Note if the target overloads addRegAssignAndRewriteOptimized, this may not
/// be honored. This is also not generally used for the the fast variant,
/// where the allocation and rewriting are done in one pass.
virtual bool addPreRewrite() {
return false;
/// This method may be implemented by targets that want to run passes after
/// register allocation pass pipeline but before prolog-epilog insertion.
virtual void addPostRegAlloc() { }
/// Add passes that optimize machine instructions after register allocation.
virtual void addMachineLateOptimization();
/// This method may be implemented by targets that want to run passes after
/// prolog-epilog insertion and before the second instruction scheduling pass.
virtual void addPreSched2() { }
/// addGCPasses - Add late codegen passes that analyze code for garbage
/// collection. This should return true if GC info should be printed after
/// these passes.
virtual bool addGCPasses();
/// Add standard basic block placement passes.
virtual void addBlockPlacement();
/// This pass may be implemented by targets that want to run passes
/// immediately before machine code is emitted.
virtual void addPreEmitPass() { }
/// Targets may add passes immediately before machine code is emitted in this
/// callback. This is called even later than `addPreEmitPass`.
// FIXME: Rename `addPreEmitPass` to something more sensible given its actual
// position and remove the `2` suffix here as this callback is what
// `addPreEmitPass` *should* be but in reality isn't.
virtual void addPreEmitPass2() {}
/// Utilities for targets to add passes to the pass manager.
/// Add a CodeGen pass at this point in the pipeline after checking overrides.
/// Return the pass that was added, or zero if no pass was added.
/// @p printAfter if true and adding a machine function pass add an extra
/// machine printer pass afterwards
/// @p verifyAfter if true and adding a machine function pass add an extra
/// machine verification pass afterwards.
AnalysisID addPass(AnalysisID PassID, bool verifyAfter = true,
bool printAfter = true);
/// Add a pass to the PassManager if that pass is supposed to be run, as
/// determined by the StartAfter and StopAfter options. Takes ownership of the
/// pass.
/// @p printAfter if true and adding a machine function pass add an extra
/// machine printer pass afterwards
/// @p verifyAfter if true and adding a machine function pass add an extra
/// machine verification pass afterwards.
void addPass(Pass *P, bool verifyAfter = true, bool printAfter = true);
/// addMachinePasses helper to create the target-selected or overriden
/// regalloc pass.
virtual FunctionPass *createRegAllocPass(bool Optimized);
/// Add core register alloator passes which do the actual register assignment
/// and rewriting. \returns true if any passes were added.
virtual bool addRegAssignmentFast();
virtual bool addRegAssignmentOptimized();
} // end namespace llvm