WholeProgramDevirt.cpp File Reference

#include "llvm/Transforms/IPO/WholeProgramDevirt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BasicAliasAnalysis.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/ModuleSummaryAnalysis.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TypeMetadataUtils.h"
#include "llvm/Bitcode/BitcodeReader.h"
#include "llvm/Bitcode/BitcodeWriter.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/ModuleSummaryIndexYAML.h"
#include "llvm/IR/PassManager.h"
#include "llvm/IR/ProfDataUtils.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Errc.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/GlobPattern.h"
#include "llvm/Support/TimeProfiler.h"
#include "llvm/TargetParser/Triple.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/IPO/FunctionAttrs.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/CallPromotionUtils.h"
#include "llvm/Transforms/Utils/Evaluator.h"
#include <algorithm>
#include <cmath>
#include <cstddef>
#include <map>
#include <set>
#include <string>

Go to the source code of this file.

Classes
struct	llvm::DenseMapInfo< VTableSlot >
struct	llvm::DenseMapInfo< VTableSlotSummary >

Namespaces
namespace	llvm
	This is an optimization pass for GlobalISel generic memory operations.

Macros
#define	DEBUG_TYPE   "wholeprogramdevirt"

Enumerations
enum	WPDCheckMode { None , Trap , Fallback }
	Mechanism to add runtime checking of devirtualization decisions, optionally trapping or falling back to indirect call on any that are not correct. More...

Functions
	STATISTIC (NumDevirtTargets, "Number of whole program devirtualization targets")
	STATISTIC (NumSingleImpl, "Number of single implementation devirtualizations")
	STATISTIC (NumBranchFunnel, "Number of branch funnels")
	STATISTIC (NumUniformRetVal, "Number of uniform return value optimizations")
	STATISTIC (NumUniqueRetVal, "Number of unique return value optimizations")
	STATISTIC (NumVirtConstProp1Bit, "Number of 1 bit virtual constant propagations")
	STATISTIC (NumVirtConstProp, "Number of virtual constant propagations")
static bool	mustBeUnreachableFunction (ValueInfo TheFnVI)
static bool	typeIDVisibleToRegularObj (StringRef TypeID, function_ref< bool(StringRef)> IsVisibleToRegularObj)
static bool	skipUpdateDueToValidation (GlobalVariable &GV, function_ref< bool(StringRef)> IsVisibleToRegularObj)
static Error	checkCombinedSummaryForTesting (ModuleSummaryIndex *Summary)
static bool	addCalls (VTableSlotInfo &SlotInfo, const ValueInfo &Callee)

Variables
static cl::opt< PassSummaryAction >	llvm::ClSummaryAction ("wholeprogramdevirt-summary-action", cl::desc("What to do with the summary when running this pass"), cl::values(clEnumValN(PassSummaryAction::None, "none", "Do nothing"), clEnumValN(PassSummaryAction::Import, "import", "Import typeid resolutions from summary and globals"), clEnumValN(PassSummaryAction::Export, "export", "Export typeid resolutions to summary and globals")), cl::Hidden)
static cl::opt< std::string >	llvm::ClReadSummary ("wholeprogramdevirt-read-summary", cl::desc("Read summary from given bitcode or YAML file before running pass"), cl::Hidden)
static cl::opt< std::string >	llvm::ClWriteSummary ("wholeprogramdevirt-write-summary", cl::desc("Write summary to given bitcode or YAML file after running pass. " "Output file format is deduced from extension: *.bc means writing " "bitcode, otherwise YAML"), cl::Hidden)
static cl::opt< bool >	llvm::ClDevirtualizeSpeculatively ("devirtualize-speculatively", cl::desc("Enable speculative devirtualization optimization"), cl::init(false))
static cl::opt< unsigned >	llvm::ClThreshold ("wholeprogramdevirt-branch-funnel-threshold", cl::Hidden, cl::init(10), cl::desc("Maximum number of call targets per " "call site to enable branch funnels"))
static cl::opt< bool >	llvm::PrintSummaryDevirt ("wholeprogramdevirt-print-index-based", cl::Hidden, cl::desc("Print index-based devirtualization messages"))
static cl::opt< bool >	llvm::WholeProgramVisibility ("whole-program-visibility", cl::Hidden, cl::desc("Enable whole program visibility"))
	Provide a way to force enable whole program visibility in tests.
static cl::opt< bool >	llvm::DisableWholeProgramVisibility ("disable-whole-program-visibility", cl::Hidden, cl::desc("Disable whole program visibility (overrides enabling options)"))
	Provide a way to force disable whole program for debugging or workarounds, when enabled via the linker.
static cl::list< std::string >	llvm::SkipFunctionNames ("wholeprogramdevirt-skip", cl::desc("Prevent function(s) from being devirtualized"), cl::Hidden, cl::CommaSeparated)
	Provide way to prevent certain function from being devirtualized.
static cl::opt< bool >	WholeProgramDevirtKeepUnreachableFunction ("wholeprogramdevirt-keep-unreachable-function", cl::desc("Regard unreachable functions as possible devirtualize targets."), cl::Hidden, cl::init(true))
	With Clang, a pure virtual class's deleting destructor is emitted as a llvm.trap intrinsic followed by an unreachable IR instruction.
static cl::opt< unsigned >	WholeProgramDevirtCutoff ("wholeprogramdevirt-cutoff", cl::desc("Max number of devirtualizations for devirt module pass"), cl::init(0))
	If explicitly specified, the devirt module pass will stop transformation once the total number of devirtualizations reach the cutoff value.
static cl::opt< WPDCheckMode >	DevirtCheckMode ("wholeprogramdevirt-check", cl::Hidden, cl::desc("Type of checking for incorrect devirtualizations"), cl::values(clEnumValN(WPDCheckMode::None, "none", "No checking"), clEnumValN(WPDCheckMode::Trap, "trap", "Trap when incorrect"), clEnumValN(WPDCheckMode::Fallback, "fallback", "Fallback to indirect when incorrect")))

Macro Definition Documentation

DEBUG_TYPE

#define DEBUG_TYPE   "wholeprogramdevirt"

Definition at line 123 of file WholeProgramDevirt.cpp.

Enumeration Type Documentation

WPDCheckMode

enum WPDCheckMode

Mechanism to add runtime checking of devirtualization decisions, optionally trapping or falling back to indirect call on any that are not correct.

Trapping mode is useful for debugging undefined behavior leading to failures with WPD. Fallback mode is useful for ensuring safety when whole program visibility may be compromised.

Enumerator
None
Trap
Fallback

Definition at line 235 of file WholeProgramDevirt.cpp.

Function Documentation

addCalls()

bool addCalls ( VTableSlotInfo & SlotInfo, const ValueInfo & Callee )

static

Definition at line 1304 of file WholeProgramDevirt.cpp.

References llvm::CalleeInfo::Hot, and P.

checkCombinedSummaryForTesting()

Error checkCombinedSummaryForTesting ( ModuleSummaryIndex * Summary )

static

Definition at line 999 of file WholeProgramDevirt.cpp.

References ClSummaryAction, llvm::createStringError(), llvm::ModuleSummaryIndex::getRegularLTOModuleName(), llvm::Import, and llvm::invalid_argument.

mustBeUnreachableFunction()

bool mustBeUnreachableFunction ( ValueInfo TheFnVI )

static

Definition at line 438 of file WholeProgramDevirt.cpp.

References llvm::dyn_cast(), llvm::ValueInfo::getSummaryList(), and WholeProgramDevirtKeepUnreachableFunction.

skipUpdateDueToValidation()

bool skipUpdateDueToValidation ( GlobalVariable & GV, function_ref< bool(StringRef)> IsVisibleToRegularObj )

static

Definition at line 852 of file WholeProgramDevirt.cpp.

References llvm::dyn_cast(), llvm::GlobalObject::getMetadata(), and typeIDVisibleToRegularObj().

Referenced by llvm::updateVCallVisibilityInModule().

STATISTIC() [1/7]

STATISTIC	(	NumBranchFunnel	,
		"Number of branch funnels"	)

STATISTIC() [2/7]

STATISTIC	(	NumDevirtTargets	,
		"Number of whole program devirtualization targets"	)

STATISTIC() [3/7]

STATISTIC	(	NumSingleImpl	,
		"Number of single implementation devirtualizations"	)

STATISTIC() [4/7]

STATISTIC	(	NumUniformRetVal	,
		"Number of uniform return value optimizations"	)

STATISTIC() [5/7]

STATISTIC	(	NumUniqueRetVal	,
		"Number of unique return value optimizations"	)

STATISTIC() [6/7]

STATISTIC	(	NumVirtConstProp	,
		"Number of virtual constant propagations"	)

STATISTIC() [7/7]

STATISTIC	(	NumVirtConstProp1Bit	,
		"Number of 1 bit virtual constant propagations"	)

typeIDVisibleToRegularObj()

bool typeIDVisibleToRegularObj ( StringRef TypeID, function_ref< bool(StringRef)> IsVisibleToRegularObj )

static

Definition at line 828 of file WholeProgramDevirt.cpp.

Referenced by llvm::getVisibleToRegularObjVtableGUIDs(), and skipUpdateDueToValidation().

Variable Documentation

DevirtCheckMode

cl::opt< WPDCheckMode > DevirtCheckMode("wholeprogramdevirt-check", cl::Hidden, cl::desc("Type of checking for incorrect devirtualizations"), cl::values(clEnumValN(WPDCheckMode::None, "none", "No checking"), clEnumValN(WPDCheckMode::Trap, "trap", "Trap when incorrect"), clEnumValN(WPDCheckMode::Fallback, "fallback", "Fallback to indirect when incorrect"))) ( "wholeprogramdevirt-check" , cl::Hidden , cl::desc("Type of checking for incorrect devirtualizations") , cl::values(clEnumValN(WPDCheckMode::None, "none", "No checking"), clEnumValN(WPDCheckMode::Trap, "trap", "Trap when incorrect"), clEnumValN(WPDCheckMode::Fallback, "fallback", "Fallback to indirect when incorrect"))  )

static

WholeProgramDevirtCutoff

cl::opt< unsigned > WholeProgramDevirtCutoff("wholeprogramdevirt-cutoff", cl::desc("Max number of devirtualizations for devirt module pass"), cl::init(0)) ( "wholeprogramdevirt-cutoff" , cl::desc("Max number of devirtualizations for devirt module pass") , cl::init(0)  )

static

If explicitly specified, the devirt module pass will stop transformation once the total number of devirtualizations reach the cutoff value.

Setting this option to 0 explicitly will do 0 devirtualization.

WholeProgramDevirtKeepUnreachableFunction

cl::opt< bool > WholeProgramDevirtKeepUnreachableFunction("wholeprogramdevirt-keep-unreachable-function", cl::desc("Regard unreachable functions as possible devirtualize targets."), cl::Hidden, cl::init(true)) ( "wholeprogramdevirt-keep-unreachable-function" , cl::desc("Regard unreachable functions as possible devirtualize targets.") , cl::Hidden , cl::init(true)  )

static

With Clang, a pure virtual class's deleting destructor is emitted as a llvm.trap intrinsic followed by an unreachable IR instruction.

In the context of whole program devirtualization, the deleting destructor of a pure virtual class won't be invoked by the source code so safe to skip as a devirtualize target.

However, not all unreachable functions are safe to skip. In some cases, the program intends to run such functions and terminate, for instance, a unit test may run a death test. A non-test program might (or allowed to) invoke such functions to report failures (whether/when it's a good practice or not is a different topic).

This option is enabled to keep an unreachable function as a possible devirtualize target to conservatively keep the program behavior.

TODO: Make a pure virtual class's deleting destructor precisely identifiable in Clang's codegen for more devirtualization in LLVM.

Referenced by mustBeUnreachableFunction().