pto.vshift

pto.vshift is part of the Data Rearrangement instruction set.

Summary

Single-source shift that inserts zero-fill at the vacated lanes.

Mechanism

pto.vshift is the single-source sibling of pto.vslide. It shifts the source vector by %amt lanes and fills newly uncovered lanes with zero according to the selected element type.

Syntax

PTO Assembly Form

vshift %dst, %src, %amt

AS Level 1 (SSA)

%result = pto.vshift %src, %amt : !pto.vreg<NxT>, i16 -> !pto.vreg<NxT>

Inputs

Operand Type Description
%src !pto.vreg<NxT> Source vector
%amt i16 Shift amount in lanes

Expected Outputs

Result Type Description
%result !pto.vreg<NxT> Shifted vector with zero-filled vacated lanes

Side Effects

This operation has no architectural side effect beyond producing its destination values. It does not implicitly reserve buffers, signal events, or establish memory fences.

Constraints

Constraints

  • %src and %result MUST have the same element type and vector width.
  • The shift amount MUST satisfy the range supported by the selected target profile.
  • Zero-fill versus any alternative fill behavior MUST match the selected form.

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.
  • Any additional illegality stated in the constraints section is also part of the contract.

Target-Profile Restrictions

Target-Profile Restrictions
  • 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 packing, selector, or permutation mode should treat that dependency as target-profile-specific unless the manual states cross-target portability explicitly.

Examples

for (int i = 0; i < N; i++)
    dst[i] = (i >= amt) ? src[i - amt] : 0;