LoopSimplify.cpp File Reference (original) (raw)

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

◆ DEBUG_TYPE

#define DEBUG_TYPE "loop-simplify"

◆ addBlockAndPredsToSet()

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 155 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()

◆ INITIALIZE_PASS_BEGIN()

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

◆ insertUniqueBackedgeBlock()

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 355 of file LoopSimplify.cpp.

References llvm::PHINode::addIncoming(), assert(), llvm::cast(), llvm::BasicBlock::Create(), llvm::BranchInst::Create(), llvm::PHINode::Create(), llvm::dbgs(), llvm::Instruction::eraseFromParent(), F, llvm::PHINode::getIncomingBlock(), llvm::PHINode::getIncomingValue(), llvm::ilist_node_impl< OptionsT >::getIterator(), llvm::Instruction::getMetadata(), 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()

◆ separateNestedLoop()

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 212 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::LoopInfoBase< BlockT, LoopT >::changeTopLevelLoop(), 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::LoopBase< BlockT, LoopT >::replaceChildLoopWith(), llvm::size(), and llvm::SplitBlockPredecessors().