enum SCEV::NoWrapFlags

Description

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.

Declared at: llvm/include/llvm/Analysis/ScalarEvolution.h:130

Enumerators