pto.vrec

pto.vrec is part of the Unary Vector Instructions instruction set.

Summary

%result holds the reciprocal per active lane.

Mechanism

pto.vrec computes the lane-wise reciprocal: dst[i] = 1 / src[i]. This is commonly used for implementing division via multiplication. Active inputs containing +0 or -0 follow the target's divide-style exceptional behavior. Inactive lanes leave the destination unchanged.

Syntax

PTO Assembly Form

vrec %result, %input, %mask

AS Level 1 (SSA)

%result = pto.vrec %input, %mask : !pto.vreg<NxT>, !pto.mask<G> -> !pto.vreg<NxT>

Documented A5 types or forms: f16, f32.

Inputs

Operand Type Description
%input !pto.vreg<NxT> Source vector register; read at each active lane i
%mask !pto.mask<G> Predicate mask; lanes where mask bit is 1 (true) are active

Expected Outputs

Result Type Description
%result !pto.vreg<NxT> Lane-wise reciprocal: dst[i] = 1 / src[i] on active lanes; inactive lanes are unmodified

Side Effects

This operation has no architectural side effect beyond producing its SSA results. It does not implicitly reserve buffers, signal events, or establish memory fences unless the form says so.

Constraints

Constraints

Only floating-point element types are legal. Active inputs containing +0 or -0 follow the target's divide-style exceptional behavior.

Exceptions

Exceptions

  • The verifier rejects illegal operand shapes, unsupported element types, and attribute combinations that are not valid for the selected instruction set or target profile.
  • Target-defined numeric exceptional behavior, such as divide-by-zero or out-of-domain inputs, remains subject to the selected backend profile unless this page narrows it further.
  • Any additional illegality stated in the constraints section is also part of the contract.

Target-Profile Restrictions

Target-Profile Restrictions
  • Documented A5 coverage: f16, f32.
  • A5 is the most detailed concrete profile in the current manual; CPU simulation and A2/A3-class targets may support narrower subsets or emulate the behavior while preserving the visible PTO contract.
  • Code that depends on an instruction-set-specific type list, distribution mode, or fused form should treat that dependency as target-profile-specific unless the PTO manual states cross-target portability explicitly.

Examples

for (int i = 0; i < N; i++)
    dst[i] = 1.0f / src[i];