llvm::MustBeExecutedIterator Struct Reference

Must be executed iterators visit stretches of instructions that are guaranteed to be executed together, potentially with other instruction executed in-between. More...

#include "llvm/Analysis/MustExecute.h"

Public Types
typedef const Instruction *	value_type
	Type declarations that make his class an input iterator.
typedef std::ptrdiff_t	difference_type
typedef const Instruction **	pointer
typedef const Instruction *&	reference
typedef std::input_iterator_tag	iterator_category
using	ExplorerTy = MustBeExecutedContextExplorer
	}

Public Member Functions
	MustBeExecutedIterator (const MustBeExecutedIterator &Other)=default
	MustBeExecutedIterator (MustBeExecutedIterator &&Other)
MustBeExecutedIterator &	operator= (MustBeExecutedIterator &&Other)
	~MustBeExecutedIterator ()=default
MustBeExecutedIterator &	operator++ ()
	Pre- and post-increment operators.
MustBeExecutedIterator	operator++ (int)
bool	operator== (const MustBeExecutedIterator &Other) const
	}
bool	operator!= (const MustBeExecutedIterator &Other) const
const Instruction *&	operator* ()
	}
const Instruction *	getCurrentInst () const
bool	count (const Instruction *I) const
	Return true if I was encountered by this iterator already.

Friends
struct	MustBeExecutedContextExplorer

Detailed Description

Must be executed iterators visit stretches of instructions that are guaranteed to be executed together, potentially with other instruction executed in-between.

Given the following code, and assuming all statements are single instructions which transfer execution to the successor (see isGuaranteedToTransferExecutionToSuccessor), there are two possible outcomes. If we start the iterator at A, B, or E, we will visit only A, B, and E. If we start at C or D, we will visit all instructions A-E.

A;
B;
if (...) {
  C;
  D;
}
E;

Below is the example extneded with instructions F and G. Now we assume F might not transfer execution to it's successor G. As a result we get the following visit sets:

Start Instruction | Visit Set A | A, B, E, F B | A, B, E, F C | A, B, C, D, E, F D | A, B, C, D, E, F E | A, B, E, F F | A, B, E, F G | A, B, E, F, G

A;
B;
if (...) {
  C;
  D;
}
E;
F;  // Might not transfer execution to its successor G.
G;

A more complex example involving conditionals, loops, break, and continue is shown below. We again assume all instructions will transmit control to the successor and we assume we can prove the inner loop to be finite. We omit non-trivial branch conditions as the exploration is oblivious to them. Constant branches are assumed to be unconditional in the CFG. The resulting visist sets are shown in the table below.

A;
while (true) {
  B;
  if (...)
    C;
  if (...)
    continue;
  D;
  if (...)
    break;
  do {
    if (...)
      continue;
    E;
  } while (...);
  F;
}
G;

Start Instruction | Visit Set A | A, B B | A, B C | A, B, C D | A, B, D E | A, B, D, E, F F | A, B, D, F G | A, B, D, G

Note that the examples show optimal visist sets but not necessarily the ones derived by the explorer depending on the available CFG analyses (see MustBeExecutedContextExplorer). Also note that we, depending on the options, the visit set can contain instructions from other functions.

Definition at line 271 of file MustExecute.h.

Member Typedef Documentation

difference_type

typedef std::ptrdiff_t llvm::MustBeExecutedIterator::difference_type

Definition at line 275 of file MustExecute.h.

ExplorerTy

using llvm::MustBeExecutedIterator::ExplorerTy = MustBeExecutedContextExplorer

}

Definition at line 281 of file MustExecute.h.

iterator_category

typedef std::input_iterator_tag llvm::MustBeExecutedIterator::iterator_category

Definition at line 278 of file MustExecute.h.

pointer

typedef const Instruction** llvm::MustBeExecutedIterator::pointer

Definition at line 276 of file MustExecute.h.

reference

typedef const Instruction*& llvm::MustBeExecutedIterator::reference

Definition at line 277 of file MustExecute.h.

value_type

typedef const Instruction* llvm::MustBeExecutedIterator::value_type

Type declarations that make his class an input iterator.

{

Definition at line 274 of file MustExecute.h.

Constructor & Destructor Documentation

MustBeExecutedIterator() [1/2]

llvm::MustBeExecutedIterator::MustBeExecutedIterator ( const MustBeExecutedIterator &  Other )

default

MustBeExecutedIterator() [2/2]

llvm::MustBeExecutedIterator::MustBeExecutedIterator ( MustBeExecutedIterator &&  Other )

inline

Definition at line 285 of file MustExecute.h.

~MustBeExecutedIterator()

llvm::MustBeExecutedIterator::~MustBeExecutedIterator ( )

default

Member Function Documentation

count()

bool llvm::MustBeExecutedIterator::count ( const Instruction *  I ) const

inline

Return true if I was encountered by this iterator already.

Definition at line 331 of file MustExecute.h.

References llvm::detail::DenseSetImpl< ValueT, MapTy, ValueInfoT >::count(), llvm::FORWARD, and I.

Referenced by llvm::MustBeExecutedContextExplorer::findInContextOf().

getCurrentInst()

const Instruction * llvm::MustBeExecutedIterator::getCurrentInst ( ) const

inline

Definition at line 328 of file MustExecute.h.

operator!=()

bool llvm::MustBeExecutedIterator::operator!= ( const MustBeExecutedIterator &  Other ) const

inline

Definition at line 321 of file MustExecute.h.

References llvm::Other.

operator*()

const Instruction *& llvm::MustBeExecutedIterator::operator* ( )

inline

}

Return the underlying instruction.

Definition at line 327 of file MustExecute.h.

operator++() [1/2]

MustBeExecutedIterator & llvm::MustBeExecutedIterator::operator++ ( )

inline

Pre- and post-increment operators.

{

Definition at line 303 of file MustExecute.h.

Referenced by operator++().

operator++() [2/2]

MustBeExecutedIterator llvm::MustBeExecutedIterator::operator++ ( int  )

inline

Definition at line 308 of file MustExecute.h.

References operator++().

operator=()

MustBeExecutedIterator & llvm::MustBeExecutedIterator::operator= ( MustBeExecutedIterator &&  Other )

inline

Definition at line 289 of file MustExecute.h.

References llvm::Other, and std::swap().

operator==()

bool llvm::MustBeExecutedIterator::operator== ( const MustBeExecutedIterator &  Other ) const

inline

}

Equality and inequality operators. Note that we ignore the history here. {

Definition at line 317 of file MustExecute.h.

References llvm::Other.

Friends And Related Function Documentation

MustBeExecutedContextExplorer

friend struct MustBeExecutedContextExplorer

friend

Definition at line 372 of file MustExecute.h.

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

• include/llvm/Analysis/MustExecute.h
• lib/Analysis/MustExecute.cpp