LoopSimplifyCFG.cpp File Reference

#include "llvm/Transforms/Scalar/LoopSimplifyCFG.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/DependenceAnalysis.h"
#include "llvm/Analysis/DomTreeUpdater.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopIterator.h"
#include "llvm/Analysis/MemorySSA.h"
#include "llvm/Analysis/MemorySSAUpdater.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Scalar/LoopPassManager.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/LoopUtils.h"
#include <optional>

Go to the source code of this file.

Macros
#define	DEBUG_TYPE   "loop-simplifycfg"

Functions
	STATISTIC (NumTerminatorsFolded, "Number of terminators folded to unconditional branches")
	STATISTIC (NumLoopBlocksDeleted, "Number of loop blocks deleted")
	STATISTIC (NumLoopExitsDeleted, "Number of loop exiting edges deleted")
static BasicBlock *	getOnlyLiveSuccessor (BasicBlock *BB)
	If BB is a switch or a conditional branch, but only one of its successors can be reached from this block in runtime, return this successor.
static void	removeBlockFromLoops (BasicBlock *BB, Loop *FirstLoop, Loop *LastLoop=nullptr)
	Removes BB from all loops from [FirstLoop, LastLoop) in parent chain.
static Loop *	getInnermostLoopFor (SmallPtrSetImpl< BasicBlock * > &BBs, Loop &L, LoopInfo &LI)
	Find innermost loop that contains at least one block from BBs and contains the header of loop L.
static bool	constantFoldTerminators (Loop &L, DominatorTree &DT, LoopInfo &LI, ScalarEvolution &SE, MemorySSAUpdater *MSSAU, bool &IsLoopDeleted)
	Turn branches and switches with known constant conditions into unconditional branches.
static bool	mergeBlocksIntoPredecessors (Loop &L, DominatorTree &DT, LoopInfo &LI, MemorySSAUpdater *MSSAU, ScalarEvolution &SE)
static bool	simplifyLoopCFG (Loop &L, DominatorTree &DT, LoopInfo &LI, ScalarEvolution &SE, MemorySSAUpdater *MSSAU, bool &IsLoopDeleted)

Variables
static cl::opt< bool >	EnableTermFolding ("enable-loop-simplifycfg-term-folding", cl::init(true))

Macro Definition Documentation

DEBUG_TYPE

#define DEBUG_TYPE   "loop-simplifycfg"

Definition at line 36 of file LoopSimplifyCFG.cpp.

Function Documentation

constantFoldTerminators()

static bool constantFoldTerminators ( Loop &  L, DominatorTree &  DT, LoopInfo &  LI, ScalarEvolution &  SE, MemorySSAUpdater *  MSSAU, bool &  IsLoopDeleted  )

static

Turn branches and switches with known constant conditions into unconditional branches.

Definition at line 643 of file LoopSimplifyCFG.cpp.

References EnableTermFolding.

Referenced by simplifyLoopCFG().

getInnermostLoopFor()

static Loop * getInnermostLoopFor ( SmallPtrSetImpl< BasicBlock * > &  BBs, Loop &  L, LoopInfo &  LI  )

static

Find innermost loop that contains at least one block from BBs and contains the header of loop L.

Definition at line 90 of file LoopSimplifyCFG.cpp.

References llvm::LoopBase< BlockT, LoopT >::contains(), llvm::LoopBase< BlockT, LoopT >::getLoopDepth(), llvm::LoopInfoBase< BlockT, LoopT >::getLoopFor(), and llvm::LoopBase< BlockT, LoopT >::getParentLoop().

getOnlyLiveSuccessor()

static BasicBlock * getOnlyLiveSuccessor ( BasicBlock *  BB )

static

If BB is a switch or a conditional branch, but only one of its successors can be reached from this block in runtime, return this successor.

Otherwise, return nullptr.

Definition at line 51 of file LoopSimplifyCFG.cpp.

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

mergeBlocksIntoPredecessors()

static bool mergeBlocksIntoPredecessors ( Loop &  L, DominatorTree &  DT, LoopInfo &  LI, MemorySSAUpdater *  MSSAU, ScalarEvolution &  SE  )

static

Definition at line 661 of file LoopSimplifyCFG.cpp.

References llvm::Block, Blocks, llvm::ScalarEvolution::forgetBlockAndLoopDispositions(), llvm::LoopInfoBase< BlockT, LoopT >::getLoopFor(), llvm::MemorySSAUpdater::getMemorySSA(), llvm::BasicBlock::getSinglePredecessor(), llvm::BasicBlock::getSingleSuccessor(), llvm::MergeBlockIntoPredecessor(), llvm::MemorySSA::verifyMemorySSA(), and llvm::VerifyMemorySSA.

Referenced by simplifyLoopCFG().

removeBlockFromLoops()

static void removeBlockFromLoops ( BasicBlock *  BB, Loop *  FirstLoop, Loop *  LastLoop = nullptr  )

static

Removes BB from all loops from [FirstLoop, LastLoop) in parent chain.

Definition at line 78 of file LoopSimplifyCFG.cpp.

References assert(), llvm::LoopBase< BlockT, LoopT >::contains(), llvm::LoopBase< BlockT, LoopT >::getHeader(), and llvm::LoopBase< BlockT, LoopT >::getParentLoop().

simplifyLoopCFG()

static bool simplifyLoopCFG ( Loop &  L, DominatorTree &  DT, LoopInfo &  LI, ScalarEvolution &  SE, MemorySSAUpdater *  MSSAU, bool &  IsLoopDeleted  )

static

Definition at line 696 of file LoopSimplifyCFG.cpp.

References constantFoldTerminators(), llvm::ScalarEvolution::forgetTopmostLoop(), and mergeBlocksIntoPredecessors().

Referenced by llvm::LoopSimplifyCFGPass::run().

STATISTIC() [1/3]

STATISTIC	(	NumLoopBlocksDeleted	,
		"Number of loop blocks deleted"
	)

STATISTIC() [2/3]

STATISTIC	(	NumLoopExitsDeleted	,
		"Number of loop exiting edges deleted"
	)

STATISTIC() [3/3]

STATISTIC	(	NumTerminatorsFolded	,
		"Number of terminators folded to unconditional branches"
	)

Variable Documentation

EnableTermFolding

cl::opt< bool > EnableTermFolding("enable-loop-simplifycfg-term-folding", cl::init(true)) ( "enable-loop-simplifycfg-term-folding"  , cl::init(true)    )

static

Referenced by constantFoldTerminators().