LLVM  4.0.0
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llvm::Loop Class Reference

Represents a single loop in the control flow graph. More...

#include <LoopInfo.h>

Inheritance diagram for llvm::Loop:
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Collaboration diagram for llvm::Loop:
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Classes

class  LocRange
 A range representing the start and end location of a loop. More...
 

Public Member Functions

 Loop ()
 
bool isLoopInvariant (const Value *V) const
 Return true if the specified value is loop invariant. More...
 
bool hasLoopInvariantOperands (const Instruction *I) const
 Return true if all the operands of the specified instruction are loop invariant. More...
 
bool makeLoopInvariant (Value *V, bool &Changed, Instruction *InsertPt=nullptr) const
 If the given value is an instruction inside of the loop and it can be hoisted, do so to make it trivially loop-invariant. More...
 
bool makeLoopInvariant (Instruction *I, bool &Changed, Instruction *InsertPt=nullptr) const
 If the given instruction is inside of the loop and it can be hoisted, do so to make it trivially loop-invariant. More...
 
PHINodegetCanonicalInductionVariable () const
 Check to see if the loop has a canonical induction variable: an integer recurrence that starts at 0 and increments by one each time through the loop. More...
 
bool isLCSSAForm (DominatorTree &DT) const
 Return true if the Loop is in LCSSA form. More...
 
bool isRecursivelyLCSSAForm (DominatorTree &DT, const LoopInfo &LI) const
 Return true if this Loop and all inner subloops are in LCSSA form. More...
 
bool isLoopSimplifyForm () const
 Return true if the Loop is in the form that the LoopSimplify form transforms loops to, which is sometimes called normal form. More...
 
bool isSafeToClone () const
 Return true if the loop body is safe to clone in practice. More...
 
bool isAnnotatedParallel () const
 Returns true if the loop is annotated parallel. More...
 
MDNodegetLoopID () const
 Return the llvm.loop loop id metadata node for this loop if it is present. More...
 
void setLoopID (MDNode *LoopID) const
 Set the llvm.loop loop id metadata for this loop. More...
 
bool hasDedicatedExits () const
 Return true if no exit block for the loop has a predecessor that is outside the loop. More...
 
void getUniqueExitBlocks (SmallVectorImpl< BasicBlock * > &ExitBlocks) const
 Return all unique successor blocks of this loop. More...
 
BasicBlockgetUniqueExitBlock () const
 If getUniqueExitBlocks would return exactly one block, return that block. More...
 
void dump () const
 
void dumpVerbose () const
 
DebugLoc getStartLoc () const
 Return the debug location of the start of this loop. More...
 
LocRange getLocRange () const
 Return the source code span of the loop. More...
 
StringRef getName () const
 
- Public Member Functions inherited from llvm::LoopBase< N, M >
 LoopBase ()
 This creates an empty loop. More...
 
 ~LoopBase ()
 
unsigned getLoopDepth () const
 Return the nesting level of this loop. More...
 
BlockT * getHeader () const
 
LoopT * getParentLoop () const
 
void setParentLoop (LoopT *L)
 This is a raw interface for bypassing addChildLoop. More...
 
bool contains (const LoopT *L) const
 Return true if the specified loop is contained within in this loop. More...
 
bool contains (const BlockT *BB) const
 Return true if the specified basic block is in this loop. More...
 
template<class InstT >
bool contains (const InstT *Inst) const
 Return true if the specified instruction is in this loop. More...
 
const std::vector< LoopT * > & getSubLoops () const
 Return the loops contained entirely within this loop. More...
 
std::vector< LoopT * > & getSubLoopsVector ()
 
iterator begin () const
 
iterator end () const
 
reverse_iterator rbegin () const
 
reverse_iterator rend () const
 
bool empty () const
 
const std::vector< BlockT * > & getBlocks () const
 Get a list of the basic blocks which make up this loop. More...
 
block_iterator block_begin () const
 
block_iterator block_end () const
 
iterator_range< block_iteratorblocks () const
 
unsigned getNumBlocks () const
 Get the number of blocks in this loop in constant time. More...
 
void invalidate ()
 Invalidate the loop, indicating that it is no longer a loop. More...
 
bool isInvalid ()
 Return true if this loop is no longer valid. More...
 
bool isLoopExiting (const BlockT *BB) const
 True if terminator in the block can branch to another block that is outside of the current loop. More...
 
bool isLoopLatch (const BlockT *BB) const
 
unsigned getNumBackEdges () const
 Calculate the number of back edges to the loop header. More...
 
void getExitingBlocks (SmallVectorImpl< BlockT * > &ExitingBlocks) const
 Return all blocks inside the loop that have successors outside of the loop. More...
 
BlockT * getExitingBlock () const
 If getExitingBlocks would return exactly one block, return that block. More...
 
void getExitBlocks (SmallVectorImpl< BlockT * > &ExitBlocks) const
 Return all of the successor blocks of this loop. More...
 
BlockT * getExitBlock () const
 If getExitBlocks would return exactly one block, return that block. More...
 
void getExitEdges (SmallVectorImpl< Edge > &ExitEdges) const
 Return all pairs of (inside_block,outside_block). More...
 
BlockT * getLoopPreheader () const
 If there is a preheader for this loop, return it. More...
 
BlockT * getLoopPredecessor () const
 If the given loop's header has exactly one unique predecessor outside the loop, return it. More...
 
BlockT * getLoopLatch () const
 If there is a single latch block for this loop, return it. More...
 
void getLoopLatches (SmallVectorImpl< BlockT * > &LoopLatches) const
 Return all loop latch blocks of this loop. More...
 
void addBasicBlockToLoop (BlockT *NewBB, LoopInfoBase< BlockT, LoopT > &LI)
 This method is used by other analyses to update loop information. More...
 
void replaceChildLoopWith (LoopT *OldChild, LoopT *NewChild)
 This is used when splitting loops up. More...
 
void addChildLoop (LoopT *NewChild)
 Add the specified loop to be a child of this loop. More...
 
LoopT * removeChildLoop (iterator I)
 This removes the specified child from being a subloop of this loop. More...
 
void addBlockEntry (BlockT *BB)
 This adds a basic block directly to the basic block list. More...
 
void reverseBlock (unsigned from)
 interface to reverse Blocks[from, end of loop] in this loop More...
 
void reserveBlocks (unsigned size)
 interface to do reserve() for Blocks More...
 
void moveToHeader (BlockT *BB)
 This method is used to move BB (which must be part of this loop) to be the loop header of the loop (the block that dominates all others). More...
 
void removeBlockFromLoop (BlockT *BB)
 This removes the specified basic block from the current loop, updating the Blocks as appropriate. More...
 
void verifyLoop () const
 Verify loop structure. More...
 
void verifyLoopNest (DenseSet< const LoopT * > *Loops) const
 Verify loop structure of this loop and all nested loops. More...
 
void print (raw_ostream &OS, unsigned Depth=0, bool Verbose=false) const
 Print loop with all the BBs inside it. More...
 

Friends

class LoopInfoBase< BasicBlock, Loop >
 

Additional Inherited Members

- Public Types inherited from llvm::LoopBase< N, M >
typedef std::vector< LoopT * >
::const_iterator 
iterator
 
typedef std::vector< LoopT * >
::const_reverse_iterator 
reverse_iterator
 
typedef std::vector< BlockT * >
::const_iterator 
block_iterator
 
typedef std::pair< const
BlockT *, const BlockT * > 
Edge
 Edge type. More...
 
- Protected Member Functions inherited from llvm::LoopBase< N, M >
 LoopBase (BlockT *BB)
 

Detailed Description

Represents a single loop in the control flow graph.

Note that not all SCCs in the CFG are neccessarily loops.

Definition at line 368 of file LoopInfo.h.

Constructor & Destructor Documentation

llvm::Loop::Loop ( )
inline

Definition at line 391 of file LoopInfo.h.

Member Function Documentation

LLVM_DUMP_METHOD void Loop::dump ( ) const

Definition at line 408 of file LoopInfo.cpp.

References llvm::dbgs(), and llvm::LoopBase< N, M >::print().

LLVM_DUMP_METHOD void Loop::dumpVerbose ( ) const

Definition at line 412 of file LoopInfo.cpp.

References llvm::dbgs(), and llvm::LoopBase< N, M >::print().

PHINode * Loop::getCanonicalInductionVariable ( ) const

Check to see if the loop has a canonical induction variable: an integer recurrence that starts at 0 and increments by one each time through the loop.

If so, return the phi node that corresponds to it.

The IndVarSimplify pass transforms loops to have a canonical induction variable.

Definition at line 110 of file LoopInfo.cpp.

References llvm::MCID::Add, assert(), llvm::BasicBlock::begin(), llvm::LoopBase< N, M >::contains(), llvm::LoopBase< N, M >::getHeader(), llvm::PHINode::getIncomingValueForBlock(), H, I, llvm::pred_begin(), llvm::pred_end(), and std::swap().

Loop::LocRange Loop::getLocRange ( ) const

Return the source code span of the loop.

Definition at line 311 of file LoopInfo.cpp.

References llvm::LoopBase< N, M >::getHeader(), getLoopID(), llvm::LoopBase< N, M >::getLoopPreheader(), i, and L.

Referenced by getStartLoc().

MDNode * Loop::getLoopID ( ) const

Return the llvm.loop loop id metadata node for this loop if it is present.

If this loop contains the same llvm.loop metadata on each branch to the header then the node is returned. If any latch instruction does not contain llvm.loop or or if multiple latches contain different nodes then 0 is returned.

Definition at line 212 of file LoopInfo.cpp.

References llvm::LoopBase< N, M >::blocks(), llvm::LoopBase< N, M >::getHeader(), llvm::LoopBase< N, M >::getLoopLatch(), llvm::Instruction::getMetadata(), llvm::MDNode::getNumOperands(), llvm::MDNode::getOperand(), H, isLoopSimplifyForm(), llvm::LLVMContext::MD_loop, llvm::Successor, and llvm::TerminatorInst::successors().

Referenced by AddRuntimeUnrollDisableMetaData(), llvm::addStringMetadataToLoop(), CloneLoopBlocks(), llvm::findStringMetadataForLoop(), getLocRange(), GetUnrollMetadataForLoop(), isAnnotatedParallel(), and SetLoopAlreadyUnrolled().

StringRef llvm::Loop::getName ( ) const
inline

Definition at line 501 of file LoopInfo.h.

DebugLoc Loop::getStartLoc ( ) const

Return the debug location of the start of this loop.

This looks for a BB terminating instruction with a known debug location by looking at the preheader and header blocks. If it cannot find a terminating instruction with location information, it returns an unknown location.

Definition at line 307 of file LoopInfo.cpp.

References getLocRange(), and llvm::Loop::LocRange::getStart().

Referenced by computeUnrollCount(), createMissedAnalysis(), llvm::LoopAccessReport::emitAnalysis(), llvm::OptimizationRemarkEmitter::emitOptimizationRemark(), llvm::OptimizationRemarkEmitter::emitOptimizationRemarkAnalysis(), llvm::OptimizationRemarkEmitter::emitOptimizationRemarkAnalysisAliasing(), llvm::OptimizationRemarkEmitter::emitOptimizationRemarkMissed(), llvm::LoopVectorizePass::processLoop(), and llvm::UnrollLoop().

BasicBlock * Loop::getUniqueExitBlock ( ) const

If getUniqueExitBlocks would return exactly one block, return that block.

Otherwise return null.

Definition at line 399 of file LoopInfo.cpp.

References getUniqueExitBlocks(), and llvm::SmallVectorTemplateCommon< T >::size().

Referenced by canPeel(), ConnectProlog(), llvm::peelLoop(), and llvm::UnrollRuntimeLoopRemainder().

void Loop::getUniqueExitBlocks ( SmallVectorImpl< BasicBlock * > &  ExitBlocks) const

Return all unique successor blocks of this loop.

These are the blocks outside of the current loop which are branched to. This assumes that loop exits are in canonical form.

Definition at line 358 of file LoopInfo.cpp.

References assert(), llvm::LoopBase< N, M >::blocks(), llvm::SmallVectorImpl< T >::clear(), llvm::LoopBase< N, M >::contains(), hasDedicatedExits(), llvm::is_contained(), llvm::pred_begin(), llvm::SmallVectorTemplateBase< T, isPodLike< T >::value >::push_back(), llvm::succ_begin(), llvm::succ_end(), llvm::Successor, and llvm::successors().

Referenced by getUniqueExitBlock(), llvm::LoopDeletionPass::runImpl(), SimplifyLoopInst(), and sink().

bool Loop::hasDedicatedExits ( ) const

Return true if no exit block for the loop has a predecessor that is outside the loop.

Definition at line 344 of file LoopInfo.cpp.

References llvm::LoopBase< N, M >::contains(), llvm::LoopBase< N, M >::getExitBlocks(), and llvm::predecessors().

Referenced by getUniqueExitBlocks(), isLoopSimplifyForm(), and llvm::LoopDeletionPass::runImpl().

bool Loop::hasLoopInvariantOperands ( const Instruction I) const

Return true if all the operands of the specified instruction are loop invariant.

Definition at line 61 of file LoopInfo.cpp.

References llvm::all_of(), isLoopInvariant(), and llvm::User::operands().

Referenced by llvm::hoistRegion(), and sinkLoopInvariantInstructions().

bool Loop::isAnnotatedParallel ( ) const

Returns true if the loop is annotated parallel.

A parallel loop can be assumed to not contain any dependencies between iterations by the compiler. That is, any loop-carried dependency checking can be skipped completely when parallelizing the loop on the target machine. Thus, if the parallel loop information originates from the programmer, e.g. via the OpenMP parallel for pragma, it is the programmer's responsibility to ensure there are no loop-carried dependencies. The final execution order of the instructions across iterations is not guaranteed, thus, the end result might or might not implement actual concurrent execution of instructions across multiple iterations.

Definition at line 266 of file LoopInfo.cpp.

References llvm::LoopBase< N, M >::blocks(), getLoopID(), I, llvm::LLVMContext::MD_mem_parallel_loop_access, and llvm::MDNode::operands().

bool Loop::isLCSSAForm ( DominatorTree DT) const

Return true if the Loop is in LCSSA form.

Definition at line 174 of file LoopInfo.cpp.

References llvm::all_of(), llvm::LoopBase< N, M >::blocks(), and isBlockInLCSSAForm().

Referenced by analyzeLoopUnrollCost(), llvm::formLCSSA(), and llvm::LoopDeletionPass::runImpl().

bool Loop::isLoopInvariant ( const Value V) const
bool Loop::isLoopSimplifyForm ( ) const

Return true if the Loop is in the form that the LoopSimplify form transforms loops to, which is sometimes called normal form.

Definition at line 190 of file LoopInfo.cpp.

References llvm::LoopBase< N, M >::getLoopLatch(), llvm::LoopBase< N, M >::getLoopPreheader(), and hasDedicatedExits().

Referenced by analyzeLoopUnrollCost(), canPeel(), getLoopID(), isSimplifiedLoopNest(), llvm::LoopVersioning::LoopVersioning(), ReduceLoopStrength(), setLoopID(), tryToUnrollLoop(), and llvm::UnrollRuntimeLoopRemainder().

bool Loop::isRecursivelyLCSSAForm ( DominatorTree DT,
const LoopInfo LI 
) const

Return true if this Loop and all inner subloops are in LCSSA form.

Definition at line 181 of file LoopInfo.cpp.

References llvm::all_of(), llvm::LoopBase< N, M >::blocks(), llvm::LoopInfoBase< N, M >::getLoopFor(), and isBlockInLCSSAForm().

Referenced by llvm::LPPassManager::runOnFunction(), and separateNestedLoop().

bool Loop::isSafeToClone ( ) const

Return true if the loop body is safe to clone in practice.

Definition at line 197 of file LoopInfo.cpp.

References llvm::LoopBase< N, M >::blocks(), and I.

Referenced by llvm::UnrollLoop().

bool Loop::makeLoopInvariant ( Value V,
bool Changed,
Instruction InsertPt = nullptr 
) const

If the given value is an instruction inside of the loop and it can be hoisted, do so to make it trivially loop-invariant.

Return true if the value after any hoisting is loop invariant. This function can be used as a slightly more aggressive replacement for isLoopInvariant.

If InsertPt is specified, it is the point to hoist instructions to. If null, the terminator of the loop preheader is used.

Definition at line 65 of file LoopInfo.cpp.

References I.

Referenced by FindLIVLoopCondition(), makeLoopInvariant(), and simplifyOneLoop().

bool Loop::makeLoopInvariant ( Instruction I,
bool Changed,
Instruction InsertPt = nullptr 
) const

If the given instruction is inside of the loop and it can be hoisted, do so to make it trivially loop-invariant.

Return true if the instruction after any hoisting is loop invariant. This function can be used as a slightly more aggressive replacement for isLoopInvariant.

If InsertPt is specified, it is the point to hoist instructions to. If null, the terminator of the loop preheader is used.

Definition at line 72 of file LoopInfo.cpp.

References llvm::Instruction::dropUnknownNonDebugMetadata(), llvm::LoopBase< N, M >::getLoopPreheader(), llvm::BasicBlock::getTerminator(), llvm::Instruction::isEHPad(), isLoopInvariant(), llvm::isSafeToSpeculativelyExecute(), makeLoopInvariant(), llvm::Instruction::mayReadFromMemory(), llvm::Instruction::moveBefore(), and llvm::User::operands().

void Loop::setLoopID ( MDNode LoopID) const

Set the llvm.loop loop id metadata for this loop.

The LoopID metadata node will be added to each terminator instruction in the loop that branches to the loop header.

The LoopID metadata node should have one or more operands and the first operand should should be the node itself.

Definition at line 246 of file LoopInfo.cpp.

References assert(), llvm::LoopBase< N, M >::blocks(), llvm::LoopBase< N, M >::getHeader(), llvm::LoopBase< N, M >::getLoopLatch(), llvm::MDNode::getNumOperands(), llvm::MDNode::getOperand(), H, isLoopSimplifyForm(), llvm::LLVMContext::MD_loop, llvm::Instruction::setMetadata(), llvm::Successor, and llvm::TerminatorInst::successors().

Referenced by AddRuntimeUnrollDisableMetaData(), llvm::addStringMetadataToLoop(), CloneLoopBlocks(), DisableAllLoopOptsOnLoop(), and SetLoopAlreadyUnrolled().

Friends And Related Function Documentation

friend class LoopInfoBase< BasicBlock, Loop >
friend

Definition at line 509 of file LoopInfo.h.


The documentation for this class was generated from the following files: