GuardWidening.cpp File Reference

#include "llvm/Transforms/Scalar/GuardWidening.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/GuardUtils.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/MemorySSAUpdater.h"
#include "llvm/Analysis/PostDominators.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/KnownBits.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/GuardUtils.h"
#include "llvm/Transforms/Utils/LoopUtils.h"
#include <functional>

Go to the source code of this file.

Macros
#define	DEBUG_TYPE   "guard-widening"

Functions
	STATISTIC (GuardsEliminated, "Number of eliminated guards")
	STATISTIC (CondBranchEliminated, "Number of eliminated conditional branches")
	STATISTIC (FreezeAdded, "Number of freeze instruction introduced")
static Value *	getCondition (Instruction *I)
static void	setCondition (Instruction *I, Value *NewCond)
static void	eliminateGuard (Instruction *GuardInst, MemorySSAUpdater *MSSAU)
static std::optional< BasicBlock::iterator >	findInsertionPointForWideCondition (Instruction *WCOrGuard)
	Find a point at which the widened condition of Guard should be inserted.
static bool	isSupportedGuardInstruction (const Instruction *Insn)
static std::optional< BasicBlock::iterator >	getFreezeInsertPt (Value *V, const DominatorTree &DT)

Variables
static cl::opt< bool >	WidenBranchGuards ("guard-widening-widen-branch-guards", cl::Hidden, cl::desc("Whether or not we should widen guards " "expressed as branches by widenable conditions"), cl::init(true))

Macro Definition Documentation

DEBUG_TYPE

#define DEBUG_TYPE   "guard-widening"

Definition at line 66 of file GuardWidening.cpp.

Function Documentation

eliminateGuard()

void eliminateGuard ( Instruction * GuardInst, MemorySSAUpdater * MSSAU )

static

Definition at line 106 of file GuardWidening.cpp.

References llvm::Instruction::eraseFromParent(), and llvm::MemorySSAUpdater::removeMemoryAccess().

findInsertionPointForWideCondition()

std::optional< BasicBlock::iterator > findInsertionPointForWideCondition ( Instruction * WCOrGuard )

static

Find a point at which the widened condition of Guard should be inserted.

When it is represented as intrinsic call, we can do it right before the call instruction. However, when we are dealing with widenable branch, we must account for the following situation: widening should not turn a loop-invariant condition into a loop-variant. It means that if widenable.condition() call is invariant (w.r.t. any loop), the new wide condition should stay invariant. Otherwise there can be a miscompile, like the one described at https://github.com/llvm/llvm-project/issues/60234. The safest way to do it is to expand the new condition at WC's block.

Definition at line 123 of file GuardWidening.cpp.

References llvm::cast(), llvm::extractWidenableCondition(), llvm::ilist_node_impl< OptionsT >::getIterator(), and llvm::isGuard().

getCondition()

Value * getCondition ( Instruction * I )

static

Definition at line 79 of file GuardWidening.cpp.

References assert(), llvm::cast(), Cond, llvm::dyn_cast(), I, and llvm::parseWidenableBranch().

Referenced by foldICmpWithDominatingICmp(), handleGuaranteedWellDefinedOps(), llvm::AArch64TTIImpl::isProfitableToSinkOperands(), LLVMGetCondition(), negateICmpIfUsedByBranchOrSelectOnly(), llvm::PredicateSwitch::PredicateSwitch(), shouldInsertFreeze(), and SimplifyCondBranchToCondBranch().

getFreezeInsertPt()

std::optional< BasicBlock::iterator > getFreezeInsertPt ( Value * V, const DominatorTree & DT )

static

Definition at line 604 of file GuardWidening.cpp.

References llvm::any_of(), llvm::DominatorTree::dominates(), llvm::dyn_cast(), llvm::BasicBlock::getFirstNonPHIOrDbgOrAlloca(), llvm::DominatorTreeBase< NodeT, IsPostDom >::getRoot(), and I.

isSupportedGuardInstruction()

bool isSupportedGuardInstruction ( const Instruction * Insn )

static

Definition at line 333 of file GuardWidening.cpp.

References llvm::isGuard(), llvm::isGuardAsWidenableBranch(), and WidenBranchGuards.

setCondition()

void setCondition ( Instruction * I, Value * NewCond )

static

Definition at line 95 of file GuardWidening.cpp.

References assert(), llvm::cast(), llvm::dyn_cast(), and I.

STATISTIC() [1/3]

STATISTIC	(	CondBranchEliminated	,
		"Number of eliminated conditional branches"	)

STATISTIC() [2/3]

STATISTIC	(	FreezeAdded	,
		"Number of freeze instruction introduced"	)

STATISTIC() [3/3]

STATISTIC	(	GuardsEliminated	,
		"Number of eliminated guards"	)

Variable Documentation

WidenBranchGuards

cl::opt< bool > WidenBranchGuards("guard-widening-widen-branch-guards", cl::Hidden, cl::desc("Whether or not we should widen guards " "expressed as branches by widenable conditions"), cl::init(true)) ( "guard-widening-widen-branch-guards" , cl::Hidden , cl::desc("Whether or not we should widen guards " "expressed as branches by widenable conditions") , cl::init(true)  )

static

Referenced by isSupportedGuardInstruction().