pto.mte_ub_l1

pto.mte_ub_l1 is part of the DMA Copy instruction set.

Summary

Execute a grouped UB→L1 (CBUF) copy. nburst(...) defines the repeated burst transfer that stages a UB tile into the cube-side L1 (CBUF) buffer.

Mechanism

The MTE engine reads %n_burst blocks of %len_burst * 32 bytes from %ub_src and writes them to %l1_dst. Between bursts, the source advances by (len_burst + src_gap) * 32 bytes and the destination advances by (len_burst + dst_gap) * 32 bytes. src_gap and dst_gap are the inter-burst gap fields (in 32-byte units) that follow each copied block.

pto.mte_ub_l1 is the architecturally-supported fallback for moving a Vector-produced tile back into the cube's L1 staging buffer. The hardware applies the ND→NZ layout conversion required by L1's fractal format; see NZ Fractal Layout (when authored) for details.

Syntax

pto.mte_ub_l1 %ub_src, %l1_dst, %len_burst
  nburst(%n_burst, %src_gap, %dst_gap)
  : !pto.ptr<T, ub>, !pto.ptr<T, l1>, i64, i64, i64, i64

Inputs

Parameter Width Description
%ub_src ptr UB source pointer (!pto.ptr<T, ub>, 32B-aligned)
%l1_dst ptr L1 destination pointer (!pto.ptr<T, l1>, 32B-aligned)
%len_burst 16 bits Burst length in units of 32 bytes
nburst(%n_burst, %src_gap, %dst_gap) 16 bits / 16 bits / 16 bits Required copy burst group: count, source gap, destination gap

Expected Outputs

Result Type Description
None — This form does not return SSA values; it writes data into the L1 destination region.

Side Effects

Reads UB-visible storage and writes L1-visible storage. The MTE pipe is engaged for the duration of the transfer. Downstream cube consumers (e.g., pto.mte_l1_l0a / pto.mte_l1_l0b) must wait on the appropriate pipeline-sync events before reading from L1.

Constraints

Constraints

  • UB source and L1 destination addresses must be 32-byte aligned.
  • %len_burst, %src_gap, and %dst_gap are encoded in units of 32 bytes.

Exceptions

Exceptions

  • The verifier rejects illegal operand shapes and clause groups not valid for the selected target profile.
  • Any additional illegality stated in the constraints section is also part of the contract.

Target-Profile Restrictions

Target-Profile Restrictions
  • The UB↔L1 dedicated data path is an architectural feature of cube-equipped profiles (A2/A3/A5). CPU simulation models the copy contract but does not surface the underlying NZ fractal staging.
  • For 1:2 Cube/Vector cooperation, both AIV0 and AIV1 each issue their own pto.mte_ub_l1 against the same L1 base offset; the cube assembles the two sub-tiles into a single contiguous NZ Mat tile.

Examples

pto.mte_ub_l1 %ub_src, %l1_dst, %len32b
  nburst(%rows, %src_gap, %dst_gap)
  : !pto.ptr<i16, ub>, !pto.ptr<i16, l1>, i64, i64, i64, i64