pto.vsubs

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

Summary

Lane-wise subtract of a broadcast scalar from a vector register.

Mechanism

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

Syntax

PTO Assembly Form

vsubs %dst, %src, %scalar, %mask : !pto.vreg<NxT>, T

AS Level 1 (SSA)

%result = pto.vsubs %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 Scalar operand subtracted from 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 difference 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

  • %input and %result MUST have the same vector width N and element type T.
  • The mask width MUST match N.
  • Signedness and overflow behavior follow the selected element type and target profile.

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 and floating-point forms are both possible; exact legality is target-profile-specific.
  • 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.vsubs %values, %delta, %mask : !pto.vreg<64xf32>, f32, !pto.mask<b32> -> !pto.vreg<64xf32>