#include "llvm/Transforms/Scalar/JumpThreading.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/GuardUtils.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LazyValueInfo.h"
#include "llvm/Analysis/Loads.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DomTreeUpdater.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.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/PassManager.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Use.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/Pass.h"
#include "llvm/Support/BlockFrequency.h"
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
#include "llvm/Transforms/Utils/ValueMapper.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <iterator>
#include <memory>
#include <utility>

Macros
#define	DEBUG_TYPE "jump-threading"

Functions
	STATISTIC (NumThreads, "Number of jumps threaded")

	STATISTIC (NumFolds, "Number of terminators folded")

	STATISTIC (NumDupes, "Number of branch blocks duplicated to eliminate phi")

	INITIALIZE_PASS_BEGIN (JumpThreading, "jump-threading", "Jump Threading", false, false) INITIALIZE_PASS_END(JumpThreading

static void	updatePredecessorProfileMetadata (PHINode PN, BasicBlock BB)

static void	ReplaceFoldableUses (Instruction Cond, Value ToVal)

static unsigned	getJumpThreadDuplicationCost (BasicBlock BB, Instruction StopAt, unsigned Threshold)
	Return the cost of duplicating a piece of this block from first non-phi and before StopAt instruction to thread across it. More...

static Constant *	getKnownConstant (Value *Val, ConstantPreference Preference)
	getKnownConstant - Helper method to determine if we can thread over a terminator with the given value as its condition, and if so what value to use for that. More...

static unsigned	GetBestDestForJumpOnUndef (BasicBlock *BB)
	GetBestDestForBranchOnUndef - If we determine that the specified block ends in an undefined jump, decide which block is best to revector to. More...

static bool	hasAddressTakenAndUsed (BasicBlock *BB)

static bool	isOpDefinedInBlock (Value Op, BasicBlock BB)
	Return true if Op is an instruction defined in the given block. More...

static BasicBlock *	FindMostPopularDest (BasicBlock BB, const SmallVectorImpl< std::pair< BasicBlock , BasicBlock *>> &PredToDestList)
	FindMostPopularDest - The specified list contains multiple possible threadable destinations. More...

static void	AddPHINodeEntriesForMappedBlock (BasicBlock PHIBB, BasicBlock OldPred, BasicBlock NewPred, DenseMap< Instruction , Value *> &ValueMap)
	AddPHINodeEntriesForMappedBlock - We're adding 'NewPred' as a new predecessor to the PHIBB block. More...

Variables
static cl::opt< unsigned >	BBDuplicateThreshold ("jump-threading-threshold", cl::desc("Max block size to duplicate for jump threading"), cl::init(6), cl::Hidden)

static cl::opt< unsigned >	ImplicationSearchThreshold ("jump-threading-implication-search-threshold", cl::desc("The number of predecessors to search for a stronger " "condition to use to thread over a weaker condition"), cl::init(3), cl::Hidden)

static cl::opt< bool >	PrintLVIAfterJumpThreading ("print-lvi-after-jump-threading", cl::desc("Print the LazyValueInfo cache after JumpThreading"), cl::init(false), cl::Hidden)

jump	threading

jump Jump	Threading

jump Jump	false

Macro Definition Documentation

◆ DEBUG_TYPE

#define DEBUG_TYPE "jump-threading"

Definition at line 83 of file JumpThreading.cpp.

Function Documentation

◆ AddPHINodeEntriesForMappedBlock()

static void AddPHINodeEntriesForMappedBlock	(	BasicBlock *	PHIBB,
		BasicBlock *	OldPred,
		BasicBlock *	NewPred,
		DenseMap< Instruction , Value > &	ValueMap
	)

static

AddPHINodeEntriesForMappedBlock - We're adding 'NewPred' as a new predecessor to the PHIBB block.

If it has PHI nodes, add entries for NewPred using the entries from OldPred (suitably mapped).

Definition at line 1884 of file JumpThreading.cpp.

References llvm::DenseMapBase< DenseMap< KeyT, ValueT, KeyInfoT, BucketT >, KeyT, ValueT, KeyInfoT, BucketT >::end(), llvm::DenseMapBase< DenseMap< KeyT, ValueT, KeyInfoT, BucketT >, KeyT, ValueT, KeyInfoT, BucketT >::find(), I, and llvm::BasicBlock::phis().

Referenced by llvm::JumpThreadingPass::DuplicateCondBranchOnPHIIntoPred(), and llvm::JumpThreadingPass::ThreadEdge().

◆ FindMostPopularDest()

static BasicBlock* FindMostPopularDest	(	BasicBlock *	BB,
		const SmallVectorImpl< std::pair< BasicBlock , BasicBlock >> &	PredToDestList
	)

static

FindMostPopularDest - The specified list contains multiple possible threadable destinations.

Pick the one that occurs the most frequently in the list.

Definition at line 1509 of file JumpThreading.cpp.

References assert(), llvm::DenseMapBase< DerivedT, KeyT, ValueT, KeyInfoT, BucketT >::begin(), llvm::SmallVectorImpl< T >::clear(), llvm::SmallVectorBase::empty(), llvm::DenseMapBase< DenseMap< KeyT, ValueT, KeyInfoT, BucketT >, KeyT, ValueT, KeyInfoT, BucketT >::end(), llvm::Instruction::getNumSuccessors(), llvm::Instruction::getSuccessor(), llvm::BasicBlock::getTerminator(), llvm::is_contained(), and llvm::SmallVectorTemplateBase< T >::push_back().

Referenced by llvm::JumpThreadingPass::ProcessThreadableEdges().

◆ GetBestDestForJumpOnUndef()

static unsigned GetBestDestForJumpOnUndef ( BasicBlock * BB )

static

GetBestDestForBranchOnUndef - If we determine that the specified block ends in an undefined jump, decide which block is best to revector to.

Since we can pick an arbitrary destination, we pick the successor with the fewest predecessors. This should reduce the in-degree of the others.

Definition at line 948 of file JumpThreading.cpp.

References llvm::Instruction::getNumSuccessors(), llvm::Instruction::getSuccessor(), llvm::BasicBlock::getTerminator(), and llvm::pred_size().

Referenced by llvm::JumpThreadingPass::ProcessBlock(), and llvm::JumpThreadingPass::ProcessThreadableEdges().

◆ getJumpThreadDuplicationCost()

static unsigned getJumpThreadDuplicationCost	(	BasicBlock *	BB,
		Instruction *	StopAt,
		unsigned	Threshold
	)

static

Return the cost of duplicating a piece of this block from first non-phi and before StopAt instruction to thread across it.

Stop scanning the block when exceeding the threshold. If duplication is impossible, returns ~0U.

Ignore PHI nodes, these will be flattened when duplication happens.

Definition at line 460 of file JumpThreading.cpp.

References assert(), llvm::BasicBlock::getFirstNonPHI(), llvm::Instruction::getParent(), llvm::BasicBlock::getTerminator(), I, and Size.

Referenced by llvm::JumpThreadingPass::DuplicateCondBranchOnPHIIntoPred(), llvm::JumpThreadingPass::ThreadEdge(), and llvm::JumpThreadingPass::ThreadGuard().

◆ getKnownConstant()

static Constant* getKnownConstant	(	Value *	Val,
		ConstantPreference	Preference
	)

static

getKnownConstant - Helper method to determine if we can thread over a terminator with the given value as its condition, and if so what value to use for that.

What kind of value this is depends on whether we want an integer or a block address, but an undef is always accepted. Returns null if Val is null or not an appropriate constant.

Definition at line 557 of file JumpThreading.cpp.

References llvm::dyn_cast(), llvm::Value::stripPointerCasts(), and llvm::jumpthreading::WantBlockAddress.

Referenced by llvm::JumpThreadingPass::ComputeValueKnownInPredecessorsImpl(), and llvm::JumpThreadingPass::ProcessBlock().

◆ hasAddressTakenAndUsed()

static bool hasAddressTakenAndUsed ( BasicBlock * BB )

static

Definition at line 966 of file JumpThreading.cpp.

References llvm::BlockAddress::get(), llvm::BasicBlock::hasAddressTaken(), llvm::Constant::removeDeadConstantUsers(), and llvm::Value::use_empty().

Referenced by llvm::JumpThreadingPass::ProcessBlock().

◆ INITIALIZE_PASS_BEGIN()

INITIALIZE_PASS_BEGIN	(	JumpThreading	,
		"jump-threading"	,
		"Jump Threading"	,
		false	,
		false
	)

◆ isOpDefinedInBlock()

static bool isOpDefinedInBlock	(	Value *	Op,
		BasicBlock *	BB
	)

static

Return true if Op is an instruction defined in the given block.

Definition at line 1261 of file JumpThreading.cpp.

Referenced by llvm::JumpThreadingPass::SimplifyPartiallyRedundantLoad().

◆ ReplaceFoldableUses()

static void ReplaceFoldableUses	(	Instruction *	Cond,
		Value *	ToVal
	)

static

Definition at line 435 of file JumpThreading.cpp.

References assert(), llvm::Instruction::eraseFromParent(), llvm::Instruction::getParent(), llvm::Value::getType(), I, llvm::isGuaranteedToTransferExecutionToSuccessor(), llvm::Instruction::mayHaveSideEffects(), llvm::replaceNonLocalUsesWith(), llvm::reverse(), and llvm::Value::use_empty().

Referenced by llvm::JumpThreadingPass::ProcessBlock(), and llvm::JumpThreadingPass::ProcessThreadableEdges().

◆ STATISTIC() [1/3]

STATISTIC	(	NumThreads	,
		"Number of jumps threaded"
	)

◆ STATISTIC() [2/3]

STATISTIC	(	NumFolds	,
		"Number of terminators folded"
	)

◆ STATISTIC() [3/3]

STATISTIC	(	NumDupes	,
		"Number of branch blocks duplicated to eliminate phi"
	)

◆ updatePredecessorProfileMetadata()

static void updatePredecessorProfileMetadata	(	PHINode *	PN,
		BasicBlock *	BB
	)

static

Definition at line 205 of file JumpThreading.cpp.

References llvm::AMDGPUISD::BFI, llvm::dbgs(), llvm::dyn_cast(), llvm::Instruction::extractProfMetadata(), F(), llvm::BranchProbability::getBranchProbability(), llvm::BranchProbability::getCompl(), llvm::BasicBlock::getContext(), llvm::PHINode::getIncomingBlock(), llvm::PHINode::getIncomingValue(), llvm::Value::getName(), llvm::BranchProbability::getNumerator(), llvm::PHINode::getNumIncomingValues(), llvm::Instruction::getParent(), llvm::BranchInst::getSuccessor(), llvm::BasicBlock::getTerminator(), llvm::ConstantInt::getType(), llvm::Function::hasProfileData(), llvm::BranchInst::isConditional(), llvm::Type::isIntegerTy(), llvm::ConstantInt::isOne(), llvm::DomTreeUpdater::Lazy, llvm::LLVMContext::MD_prof, PrintLVIAfterJumpThreading, llvm::SmallVectorTemplateBase< T >::push_back(), llvm::DominatorTreeBase< NodeT, IsPostDom >::reset(), llvm::JumpThreadingPass::runImpl(), runOnFunction(), and llvm::Instruction::setMetadata().

Referenced by llvm::JumpThreadingPass::ProcessBlock().

Variable Documentation

◆ BBDuplicateThreshold

cl::opt<unsigned> BBDuplicateThreshold("jump-threading-threshold", cl::desc("Max block size to duplicate for jump threading"), cl::init(6), cl::Hidden)

static

Referenced by llvm::JumpThreadingPass::JumpThreadingPass().

◆ false

jump Jump false

Definition at line 158 of file JumpThreading.cpp.

◆ ImplicationSearchThreshold

cl::opt<unsigned> ImplicationSearchThreshold("jump-threading-implication-search-threshold", cl::desc("The number of predecessors to search for a stronger " "condition to use to thread over a weaker condition"), cl::init(3), cl::Hidden)

static

Referenced by llvm::JumpThreadingPass::ProcessImpliedCondition().

◆ PrintLVIAfterJumpThreading

cl::opt<bool> PrintLVIAfterJumpThreading("print-lvi-after-jump-threading", cl::desc("Print the LazyValueInfo cache after JumpThreading"), cl::init(false), cl::Hidden)

static

Referenced by updatePredecessorProfileMetadata().

◆ threading

jump threading

Definition at line 158 of file JumpThreading.cpp.

◆ Threading

jump Jump Threading

Definition at line 158 of file JumpThreading.cpp.

Macros

Functions

Variables

Macro Definition Documentation

◆ DEBUG_TYPE

Function Documentation

◆ AddPHINodeEntriesForMappedBlock()

◆ FindMostPopularDest()

◆ GetBestDestForJumpOnUndef()

◆ getJumpThreadDuplicationCost()

◆ getKnownConstant()

◆ hasAddressTakenAndUsed()

◆ INITIALIZE_PASS_BEGIN()

◆ isOpDefinedInBlock()

◆ ReplaceFoldableUses()

◆ STATISTIC() [1/3]

◆ STATISTIC() [2/3]

◆ STATISTIC() [3/3]

◆ updatePredecessorProfileMetadata()

Variable Documentation

◆ BBDuplicateThreshold

◆ false

◆ ImplicationSearchThreshold

◆ PrintLVIAfterJumpThreading

◆ threading

◆ Threading