mov

mov#

mov copies register bits or assembles/disassembles a native register group. It performs no numeric conversion and cannot change which thread owns a value. Use cvt for conversion and ld / st for memory.

The scalar form ends both tensor operands in (1,). All earlier axes after the execution-group prefix are repeats. A scalar source expression can broadcast, for example to fill a register tile. Vector-group mov forms instead use the group length declared by that PTX form; each input/output word remains an explicit operand slot.

Example: filling and copying separated register slots#

from tvm.script import tirx as T
from tvm.tirx.layout import S, TileLayout

gapped = TileLayout(S[(4, 1) : (2, 1)])


@T.function
def register_move(Out: T.Tensor((4, 1), "uint32")):
    T.device_entry(launch=T.cuda.LaunchConfig(grid=1, block=1))
    a = T.alloc_local((4, 1), "uint32", layout="default")
    b = T.alloc_local((4, 1), "uint32", layout=gapped)
    T.cuda.tile.apply(T.ptx["mov.b32"], a, T.uint32(17))
    T.cuda.tile.apply(T.ptx["mov.b32"], b, a)
    T.cuda.tile.apply(T.ptx["st.global.b32"], Out, b)

The first call emits four moves of the same constant. The second emits four moves to offsets 0, 2, 4, and 6 of b; its gaps require no extra remap buffer. All four output values are 17. Ordinary compiler optimizations may subsequently eliminate redundant moves; the tile expansion itself selects no alternative instruction or ownership map.

pred is an ordinary runtime predicate. For a predicated output that must keep its old value, initialize it and pass preserve_dst=True. A suppressed move is not a zero fill. Destination repeats must not overlap each other.

For packed arithmetic, a bit reinterpretation such as halves.view("uint32") can expose the existing low/high halfword storage without a mov. Use an explicit group mov when assembling separately stored values. Group arity and carrier dtype must agree with the selected native form; the pattern does not guess a packing arrangement.

Implementation: python/tvm/backend/cuda/tile/patterns/register.py.

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