This class represents an analyzed expression in the program. More...

#include "llvm/Analysis/ScalarEvolution.h"

Inheritance diagram for llvm::SCEV:

Public Types
enum	NoWrapFlags { FlagAnyWrap = 0 , FlagNW = (1 << 0) , FlagNUW = (1 << 1) , FlagNSW = (1 << 2) , NoWrapMask = (1 << 3) - 1 }
	NoWrapFlags are bitfield indices into SubclassData. More...

Public Member Functions
	SCEV (const FoldingSetNodeIDRef ID, SCEVTypes SCEVTy, unsigned short ExpressionSize)
	SCEV (const SCEV &)=delete
SCEV &	operator= (const SCEV &)=delete
SCEVTypes	getSCEVType () const
LLVM_ABI Type *	getType () const
	Return the LLVM type of this SCEV expression.
LLVM_ABI ArrayRef< SCEVUse >	operands () const
	Return operands of this SCEV expression.
LLVM_ABI bool	isZero () const
	Return true if the expression is a constant zero.
LLVM_ABI bool	isOne () const
	Return true if the expression is a constant one.
LLVM_ABI bool	isAllOnesValue () const
	Return true if the expression is a constant all-ones value.
LLVM_ABI bool	isNonConstantNegative () const
	Return true if the specified scev is negated, but not a constant.
unsigned short	getExpressionSize () const
LLVM_ABI void	print (raw_ostream &OS) const
	Print out the internal representation of this scalar to the specified stream.
LLVM_ABI void	dump () const
	This method is used for debugging.
Public Member Functions inherited from llvm::FoldingSetBase::Node
	Node ()=default
void *	getNextInBucket () const
void	SetNextInBucket (void *N)

Protected Attributes
const unsigned short	ExpressionSize
unsigned short	SubclassData = 0
	This field is initialized to zero and may be used in subclasses to store miscellaneous information.

Friends
struct	FoldingSetTrait< SCEV >

Detailed Description

This class represents an analyzed expression in the program.

These are opaque objects that the client is not allowed to do much with directly.

Definition at line 144 of file ScalarEvolution.h.

Member Enumeration Documentation

◆ NoWrapFlags

enum llvm::SCEV::NoWrapFlags

NoWrapFlags are bitfield indices into SubclassData.

Add and Mul expressions may have no-unsigned-wrap <NUW> or no-signed-wrap <NSW> properties, which are derived from the IR operator. NSW is a misnomer that we use to mean no signed overflow or underflow.

AddRec expressions may have a no-self-wraparound <NW> property if, in the integer domain, abs(step) * max-iteration(loop) <= unsigned-max(bitwidth). This means that the recurrence will never reach its start value if the step is non-zero. Computing the same value on each iteration is not considered wrapping, and recurrences with step = 0 are trivially <NW>. <NW> is independent of the sign of step and the value the add recurrence starts with.

Note that NUW and NSW are also valid properties of a recurrence, and either implies NW. For convenience, NW will be set for a recurrence whenever either NUW or NSW are set.

We require that the flag on a SCEV apply to the entire scope in which that SCEV is defined. A SCEV's scope is set of locations dominated by a defining location, which is in turn described by the following rules:

A SCEVUnknown is at the point of definition of the Value.
A SCEVConstant is defined at all points.
A SCEVAddRec is defined starting with the header of the associated loop.
All other SCEVs are defined at the earlest point all operands are defined.

The above rules describe a maximally hoisted form (without regards to potential control dependence). A SCEV is defined anywhere a corresponding instruction could be defined in said maximally hoisted form. Note that SCEVUDivExpr (currently the only expression type which can trap) can be defined per these rules in regions where it would trap at runtime. A SCEV being defined does not require the existence of any instruction within the defined scope.