LoopSimplify.cpp File Reference

#include "llvm/Transforms/Utils/LoopSimplify.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BasicAliasAnalysis.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/MemorySSA.h"
#include "llvm/Analysis/MemorySSAUpdater.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/InitializePasses.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/LoopUtils.h"

Go to the source code of this file.

Macros
#define	DEBUG_TYPE   "loop-simplify"

Functions
	STATISTIC (NumNested, "Number of nested loops split out")
static void	placeSplitBlockCarefully (BasicBlock *NewBB, SmallVectorImpl< BasicBlock * > &SplitPreds, Loop *L)
static void	addBlockAndPredsToSet (BasicBlock *InputBB, BasicBlock *StopBlock, SmallPtrSetImpl< BasicBlock * > &Blocks)
	Add the specified block, and all of its predecessors, to the specified set, if it's not already in there.
static PHINode *	findPHIToPartitionLoops (Loop *L, DominatorTree *DT, AssumptionCache *AC)
	The first part of loop-nestification is to find a PHI node that tells us how to partition the loops.
static Loop *	separateNestedLoop (Loop *L, BasicBlock *Preheader, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE, bool PreserveLCSSA, AssumptionCache *AC, MemorySSAUpdater *MSSAU)
	If this loop has multiple backedges, try to pull one of them out into a nested loop.
static BasicBlock *	insertUniqueBackedgeBlock (Loop *L, BasicBlock *Preheader, DominatorTree *DT, LoopInfo *LI, MemorySSAUpdater *MSSAU)
	This method is called when the specified loop has more than one backedge in it.
static bool	simplifyHeaderPHIs (Loop *L, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE, AssumptionCache *AC, bool PreserveLCSSA)
	Replace PHI nodes in the loop header that simplify to a single value.
static bool	simplifyOneLoop (Loop *L, SmallVectorImpl< Loop * > &Worklist, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE, AssumptionCache *AC, MemorySSAUpdater *MSSAU, bool PreserveLCSSA, const TargetTransformInfo *TTI)
	Simplify one loop and queue further loops for simplification.
	INITIALIZE_PASS_BEGIN (LoopSimplify, "loop-simplify", "Canonicalize natural loops", false, false) INITIALIZE_PASS_END(LoopSimplify

Variables
loop	simplify
loop Canonicalize natural	loops
loop Canonicalize natural	false

Macro Definition Documentation

DEBUG_TYPE

#define DEBUG_TYPE   "loop-simplify"

Definition at line 74 of file LoopSimplify.cpp.

Function Documentation

addBlockAndPredsToSet()

void addBlockAndPredsToSet ( BasicBlock * InputBB, BasicBlock * StopBlock, SmallPtrSetImpl< BasicBlock * > & Blocks )

static

Add the specified block, and all of its predecessors, to the specified set, if it's not already in there.

Stop predecessor traversal when we reach StopBlock.

Definition at line 156 of file LoopSimplify.cpp.

References llvm::append_range(), llvm::SmallVectorTemplateCommon< T, typename >::empty(), llvm::SmallPtrSetImpl< PtrType >::insert(), llvm::SmallVectorImpl< T >::pop_back_val(), llvm::predecessors(), and llvm::SmallVectorTemplateBase< T, bool >::push_back().

Referenced by separateNestedLoop().

findPHIToPartitionLoops()

PHINode * findPHIToPartitionLoops ( Loop * L, DominatorTree * DT, AssumptionCache * AC )

static

The first part of loop-nestification is to find a PHI node that tells us how to partition the loops.

Definition at line 171 of file LoopSimplify.cpp.

References llvm::cast(), DL, llvm::Instruction::eraseFromParent(), llvm::PHINode::getIncomingBlock(), llvm::PHINode::getIncomingValue(), llvm::PHINode::getNumIncomingValues(), I, llvm::isa(), llvm::Value::replaceAllUsesWith(), llvm::simplifyInstruction(), and V.

Referenced by separateNestedLoop().

INITIALIZE_PASS_BEGIN()

INITIALIZE_PASS_BEGIN	(	LoopSimplify	,
		"loop-simplify"	,
		"Canonicalize natural loops"	,
		false	,
		false	)

References INITIALIZE_PASS_DEPENDENCY.

insertUniqueBackedgeBlock()

BasicBlock * insertUniqueBackedgeBlock ( Loop * L, BasicBlock * Preheader, DominatorTree * DT, LoopInfo * LI, MemorySSAUpdater * MSSAU )

static

This method is called when the specified loop has more than one backedge in it.

If this occurs, revector all of these backedges to target a new basic block and have that block branch to the loop header. This ensures that loops have exactly one backedge.

Definition at line 353 of file LoopSimplify.cpp.

References llvm::PHINode::addIncoming(), assert(), llvm::cast(), llvm::BasicBlock::Create(), llvm::PHINode::Create(), llvm::UncondBrInst::Create(), llvm::dbgs(), llvm::Instruction::eraseFromParent(), F, llvm::PHINode::getIncomingBlock(), llvm::PHINode::getIncomingValue(), llvm::ilist_node_impl< OptionsT >::getIterator(), llvm::Value::getName(), llvm::PHINode::getNumIncomingValues(), llvm::BasicBlock::getTerminator(), llvm::Value::getType(), I, llvm::isa(), IV, LLVM_DEBUG, P, llvm::predecessors(), llvm::PHINode::removeIncomingValueIf(), llvm::Value::replaceAllUsesWith(), llvm::Instruction::replaceSuccessorWith(), llvm::Instruction::setDebugLoc(), llvm::PHINode::setIncomingBlock(), llvm::PHINode::setIncomingValue(), llvm::Instruction::setMetadata(), llvm::DominatorTreeBase< NodeT, IsPostDom >::splitBlock(), and llvm::MemorySSAUpdater::updatePhisWhenInsertingUniqueBackedgeBlock().

Referenced by simplifyOneLoop().

placeSplitBlockCarefully()

void placeSplitBlockCarefully ( BasicBlock * NewBB, SmallVectorImpl< BasicBlock * > & SplitPreds, Loop * L )

static

Definition at line 81 of file LoopSimplify.cpp.

References llvm::Function::end(), llvm::ilist_node_impl< OptionsT >::getIterator(), llvm::BasicBlock::getParent(), llvm::is_contained(), llvm::BasicBlock::moveAfter(), and Pred.

Referenced by llvm::InsertPreheaderForLoop(), and separateNestedLoop().

separateNestedLoop()

Loop * separateNestedLoop ( Loop * L, BasicBlock * Preheader, DominatorTree * DT, LoopInfo * LI, ScalarEvolution * SE, bool PreserveLCSSA, AssumptionCache * AC, MemorySSAUpdater * MSSAU )

static

If this loop has multiple backedges, try to pull one of them out into a nested loop.

This is important for code that looks like this:

Loop: ... br cond, Loop, Next ... br cond2, Loop, Out

To identify this common case, we look at the PHI nodes in the header of the loop. PHI nodes with unchanging values on one backedge correspond to values that change in the "outer" loop, but not in the "inner" loop.

If we are able to separate out a loop, return the new outer loop that was created.

Definition at line 213 of file LoopSimplify.cpp.

References addBlockAndPredsToSet(), llvm::LoopBase< BlockT, LoopT >::addBlockEntry(), llvm::LoopBase< BlockT, LoopT >::addChildLoop(), llvm::LoopInfoBase< BlockT, LoopT >::AllocateLoop(), assert(), llvm::LoopInfoBase< BlockT, LoopT >::changeLoopFor(), llvm::SmallPtrSetImpl< PtrType >::count(), llvm::dbgs(), llvm::DominatorTree::dominates(), llvm::dyn_cast(), findPHIToPartitionLoops(), llvm::ScalarEvolution::forgetLoop(), llvm::formDedicatedExitBlocks(), llvm::formLCSSA(), llvm::PHINode::getIncomingBlock(), llvm::PHINode::getIncomingValue(), llvm::PHINode::getNumIncomingValues(), llvm::BasicBlock::getTerminator(), I, II, llvm::isa(), llvm::Loop::isRecursivelyLCSSAForm(), LLVM_DEBUG, P, placeSplitBlockCarefully(), llvm::predecessors(), llvm::SmallVectorTemplateBase< T, bool >::push_back(), llvm::LoopInfoBase< BlockT, LoopT >::replaceLoop(), llvm::size(), and llvm::SplitBlockPredecessors().

Referenced by simplifyOneLoop().

simplifyHeaderPHIs()

bool simplifyHeaderPHIs ( Loop * L, DominatorTree * DT, LoopInfo * LI, ScalarEvolution * SE, AssumptionCache * AC, bool PreserveLCSSA )

static

Replace PHI nodes in the loop header that simplify to a single value.

Definition at line 473 of file LoopSimplify.cpp.

References Changed, DL, llvm::dyn_cast(), llvm::Instruction::eraseFromParent(), llvm::ScalarEvolution::forgetValue(), I, llvm::Value::replaceAllUsesWith(), llvm::LoopInfo::replacementPreservesLCSSAForm(), llvm::simplifyInstruction(), and V.

Referenced by simplifyOneLoop().

simplifyOneLoop()

bool simplifyOneLoop ( Loop * L, SmallVectorImpl< Loop * > & Worklist, DominatorTree * DT, LoopInfo * LI, ScalarEvolution * SE, AssumptionCache * AC, MemorySSAUpdater * MSSAU, bool PreserveLCSSA, const TargetTransformInfo * TTI )

static

Simplify one loop and queue further loops for simplification.

Definition at line 494 of file LoopSimplify.cpp.

References assert(), Changed, llvm::DominatorTreeBase< NodeT, IsPostDom >::changeImmediateDominator(), llvm::changeToUnreachable(), Cond, llvm::dbgs(), llvm::dyn_cast(), llvm::DominatorTreeBase< NodeT, IsPostDom >::eraseNode(), llvm::foldBranchToCommonDest(), llvm::formDedicatedExitBlocks(), llvm::CondBrInst::getCondition(), llvm::MemorySSAUpdater::getMemorySSA(), llvm::DominatorTreeBase< NodeT, IsPostDom >::getNode(), llvm::ilist_detail::node_parent_access< NodeTy, ParentTy >::getParent(), llvm::CondBrInst::getSuccessor(), llvm::BasicBlock::getTerminator(), I, llvm::SetVector< T, Vector, Set, N >::insert(), llvm::InsertPreheaderForLoop(), insertUniqueBackedgeBlock(), LLVM_DEBUG, P, llvm::pred_empty(), llvm::predecessors(), llvm::SmallVectorTemplateBase< T, bool >::push_back(), llvm::LoopInfoBase< BlockT, LoopT >::removeBlock(), llvm::MemorySSAUpdater::removeBlocks(), llvm::BasicBlock::removePredecessor(), separateNestedLoop(), simplifyHeaderPHIs(), llvm::successors(), llvm::VerifyMemorySSA, and llvm::MemorySSA::verifyMemorySSA().

Referenced by llvm::simplifyLoop().

STATISTIC()

STATISTIC	(	NumNested	,
		"Number of nested loops split out"	)

Variable Documentation

false

loop Canonicalize natural false

Definition at line 797 of file LoopSimplify.cpp.

loops

loop Canonicalize natural loops

Definition at line 796 of file LoopSimplify.cpp.

simplify

loop simplify

Definition at line 796 of file LoopSimplify.cpp.