pto.vsel

pto.vsel is part of the Compare And Select instruction set.

Summary

Per-lane select between two vector operands using an explicit predicate mask.

Mechanism

For each lane i, result[i] = mask[i] ? src0[i] : src1[i]. The operation consumes two same-shaped vector operands and chooses one value per lane according to the explicit predicate mask.

Syntax

PTO Assembly Form

vsel %dst, %src_true, %src_false, %mask : !pto.vreg<NxT>

AS Level 1 (SSA)

%result = pto.vsel %src0, %src1, %mask : !pto.vreg<NxT>, !pto.vreg<NxT>, !pto.mask<G> -> !pto.vreg<NxT>

Inputs

Operand Type Description
%src0 !pto.vreg<NxT> Value selected when the mask bit is 1
%src1 !pto.vreg<NxT> Value selected when the mask bit is 0
%mask !pto.mask<G> Predicate mask that chooses between %src0 and %src1 per lane

Expected Outputs

Result Type Description
%result !pto.vreg<NxT> Selected vector result

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

  • %src0, %src1, and %result MUST have the same vector width N and element type T.
  • The mask width MUST match N.

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 implicit predicate source or a target-specific encoding variant should treat that dependency as target-profile-specific unless the manual states cross-target portability explicitly.

Examples

for (int i = 0; i < N; i++)
    result[i] = mask[i] ? src0[i] : src1[i];
%result = pto.vsel %true_vals, %false_vals, %condition : !pto.vreg<64xf32>, !pto.vreg<64xf32>, !pto.mask<b32> -> !pto.vreg<64xf32>