pto.vshrs

pto.vshrs is part of the Vector-Scalar Instructions instruction set.

Summary

Lane-wise right shift by a broadcast scalar amount.

Mechanism

For each active lane i, dst[i] = src[i] >> scalar. The scalar shift count is applied uniformly to every active lane. Inactive lanes do not participate in the operation.

Syntax

PTO Assembly Form

vshrs %dst, %src, %shift, %mask : !pto.vreg<NxT>, T

AS Level 1 (SSA)

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

Inputs

Operand Type Description
%input !pto.vreg<NxT> Source vector register
%scalar T Uniform shift amount broadcast to every active lane
%mask !pto.mask<G> Predicate mask; only lanes with mask bit 1 participate

Expected Outputs

Result Type Description
%result !pto.vreg<NxT> Lane-wise right-shift result on the active 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

  • Shift forms are defined for integer element types only.
  • The exact sign-extension behavior follows the selected element type and target profile.
  • %input and %result MUST have the same vector width N and element type T.

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
  • Integer element types only.
  • 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.

Examples

for (int i = 0; i < N; i++)
    if (mask[i])
        dst[i] = src[i] >> scalar;
%result = pto.vshrs %values, %shift, %mask : !pto.vreg<64xi32>, i32, !pto.mask<b32> -> !pto.vreg<64xi32>