tinygrad/tinygrad/schedule/rangeify.py

from dataclasses import dataclass, field, replace
from typing import cast
import itertools
from tinygrad.dtype import dtypes, AddrSpace, Invalid, to_dtype, strong_dtype
from tinygrad.uop.ops import PatternMatcher, UPat, Ops, UOp, resolve, GroupOp, KernelInfo, ParamArg, shape_to_shape_arg
from tinygrad.uop.ops import graph_rewrite, sint, AxisType, BottomUpGate, rewrite_group, identity_element
from tinygrad.uop.symbolic import symbolic
from tinygrad.uop.movement import mop_cleanup
from tinygrad.helpers import prod, getenv, dedup, all_int, DEBUG, SPLIT_REDUCEOP, DEBUG_RANGEIFY, VIZ, MAX_KERNEL_BUFFERS, SPEC
from tinygrad.helpers import PCONTIG, FLOAT16, OPENPILOT_HACKS, argsort, partition, get_single_element
from tinygrad.codegen.simplify import pm_flatten_range, pm_reduce_simplify
from tinygrad.codegen.opt import Opt
from tinygrad.schedule.indexing import run_rangeify, BufferizeOpts, apply_movement_op
from tinygrad.schedule.multi import multi_pm
from tinygrad.schedule.allreduce import create_allreduce_function

# creation can recurse a lot
import sys
sys.setrecursionlimit(10000)

def found_after(ctx:dict[UOp, UOp], after:UOp, src:UOp):
  if (x:=src).op is Ops.CAST and x.dtype == dtypes.half and FLOAT16: x, after = x.src[0], after.cast(dtypes.float)
  while True:
    if x.op is Ops.PERMUTE: x, after = x.src[0], after.permute(argsort(x.marg))
    elif x.op is Ops.RESHAPE: x, after = x.src[0], after.reshape(x.src[0].shape)
    elif x.op is Ops.WHERE and x.src[2].base.is_invalid and x.src[1].op is Ops.PAD:
      x, after = x.src[1].src[0], after.shrink(tuple((o, s+o) for (o,_),s in zip(x.src[1].marg, x.src[1].src[0].shape)))
    else: break
  ctx[x] = after

# *** fold moved AFTERs (hack for openpilot) ***
pm_fold_moved_after = PatternMatcher([
  (UPat(Ops.AFTER, src=(UPat(), UPat(Ops.STORE, src=(UPat(), UPat((*GroupOp.Movement,Ops.CAST,Ops.WHERE), name="src")))), name="after"), found_after),
  # replace ALU sources with AFTER versions found above
  (UPat(GroupOp.ALU, name="alu"), lambda ctx,alu: alu.replace(src=new_src) if (new_src:=tuple(ctx.get(s, s) for s in alu.src)) != alu.src else None),
])

# movement op on INDEX as a PatternMatcher
def _mop_index(r:UOp, idx:UOp):
  idxs = idx.src[1:]
  if len(idxs) == len(r.shape):
    return r.src[0].index(*apply_movement_op(r.op, r.src[0].shape, r.marg, idxs), arg=idx.arg)
  if r.op is Ops.RESHAPE:
    src_prefix = len(r.src[0].shape) - len(r.shape[len(idxs):])
    if src_prefix >= 0 and r.src[0].shape[src_prefix:] == r.shape[len(idxs):]:
      if src_prefix == 0: return r.src[0] if r.src[0].dtype == idx.dtype else None
      ret = r.src[0].index(*apply_movement_op(r.op, r.src[0].shape[:src_prefix], r.shape[:len(idxs)], idxs), arg=idx.arg)
      return ret if ret.shape == idx.shape else None

pm_mops = PatternMatcher([
  # handle movement ops on INDEX
  (UPat(GroupOp.Movement, name="r").f(Ops.INDEX, allow_any_len=True, name="idx"), _mop_index),
  # move movement ops and INDEX after AFTER
  (UPat(GroupOp.Movement|{Ops.INDEX}, name="r").after(name="a", allow_any_len=True),
   lambda r,a: UOp(r.op, src=(a.replace(src=(r.src[0],)+a.src[1:]),)+r.src[1:], arg=r.arg)),
  (UPat(GroupOp.Movement, name="r").end(name="a", allow_any_len=True), lambda r,a: a.replace(src=(r.src[0],)+a.src[1:])),
])

# *****************
# 0. do some cleanup rewrites, mostly copied from the old stuff

def fix_store_hazard(target:UOp, src:UOp):
  if (base:=target.base) not in src.toposort(enter_calls=False): return None
  # PERMUTE and FLIP reorder indices, SHRINK can have overlapping regions when dest is also shrunk
  unsafe = {Ops.PERMUTE, Ops.FLIP} | ({Ops.SHRINK} if target.op_in_backward_slice_with_self(Ops.SHRINK) else set())
  reaches_base: dict[UOp, bool] = {}
  for s in src.toposort(gate=lambda s: s.op is not Ops.CONTIGUOUS):
    reaches_base[s] = s is base or any(reaches_base.get(c) for c in s.src)
    if reaches_base[s] and s.op in unsafe and not (s is target and s.op is Ops.SHRINK): return target.store(src.contiguous())

def split_reduceop(reduce:UOp, x:UOp):
  if prod(reduce.shape) == 0: return None
  if not SPLIT_REDUCEOP or not all_int(x.shape) or (prod(x.shape)//prod(reduce.shape))<getenv("REDUCEOP_SPLIT_THRESHOLD", 32768): return None
  # if there are few globals, make some reduces into globals by splitting into two kernels
  # cap output buffer to 2**22: heuristic number of global outputs to achieve max occupancy with enough locals+upcasts for gemm
  #   ~2**10 should be enough if GROUP is used
  # 256 split maximum should be "negligible reduce" for low prod(reduce.shape), 8 split minimum.
  # split is moved to the end to provide maximum locality for the second phase reduce.

  # get expanded by rangeifying the UOp x
  indexed = x.index(*[UOp.range(s, i) if resolve(s>1) else 0 for i,s in enumerate(x.shape)])
  range_nums = [y.arg[0] for y in indexed.substitute({x.base:UOp(Ops.NOOP)}, extra_pm=pm_mops).ranges]
  is_expanded = [i not in range_nums for i in range(len(x.shape))]

  if not (split_candidates:=[(i,d) for i in range(reduce.arg[1])
                             for d in range(min(256,2**getenv("REDUCEOP_SPLIT_SIZE",22)//prod(reduce.shape)),8-1,-1)
                             if x.shape[i]%d==0 and not is_expanded[i]]): return None
  dim_to_split, divisor = split_candidates[0]
  splitted_shape = x.shape[:dim_to_split]+(divisor,)+(x.shape[dim_to_split]//divisor,)+x.shape[dim_to_split+1:]
  splitted = x.reshape(splitted_shape).permute(tuple([d for d in range(len(splitted_shape)) if d!=dim_to_split]+[dim_to_split]))
  if DEBUG >= 3: print(f"split {divisor}: {x.shape} -> {splitted.shape} -> {reduce.shape}")
  # reduce original axes, then split
  return splitted._rop(reduce.arg[0], tuple(range(reduce.arg[1]))).contiguous()._rop(reduce.arg[0], (len(reduce.shape),)).reshape(reduce.shape)

pm_gather_params = PatternMatcher([ (UPat(Ops.PARAM, name="p"), lambda ctx, p: ctx.append(p) if p.arg.slot >= 0 else None), ])
def resolve_function(c:UOp, allow_param_mismatch=True) -> UOp|None:
  if c.arg.precompile: return None
  params: list[UOp] = []
  graph_rewrite(c.src[0], pm_gather_params, bottom_up=True, ctx=params, name="gather params")
  params = sorted(params, key=lambda x: x.arg.slot)
  args = c.src[1:]

  # NOTE: this isn't really needed. it's okay if there's unused args in the function
  if not allow_param_mismatch:
    if [x.arg.slot for x in params] != list(range(len(params))): raise RuntimeError(f"params not in order: {[x.arg.slot for x in params]}")
    if len(params) != len(args): raise TypeError(f"expected {len(params)} args, got {len(args)}")

  dict_map = {x:args[x.arg.slot] for x in params}
  for i, (p, a) in enumerate(dict_map.items()):
    if p.axis != a.axis: raise TypeError(f"arg {i} axis mismatch: expected {p.axis}, got {a.axis}")
    if p.max_shape != a.max_shape: raise TypeError(f"arg {i} shape mismatch: expected {p.shape}, got {a.shape}")
    if p.dtype != a.dtype: raise TypeError(f"arg {i} dtype mismatch: expected {p.dtype}, got {a.dtype}")
  return c.src[0].substitute(dict_map, walk=True)

# shape-changing bitcast
def expand_bitcast(bc:UOp) -> UOp|None:
  x = bc.src[0]
  if (ns:=bc.dtype.itemsize) == (os:=x.dtype.itemsize) or (isinstance(x.device, str) and x.device.startswith(("DISK", "TINYFS"))): return None
  new_uint, tmp = to_dtype(f"uint{8*ns}"), x.bitcast(to_dtype(f"uint{8*os}"))
  if ns > os:
    tmp = tmp.reshape(x.shape[:-1] + (x.shape[-1]//(rate := ns//os), rate))
    parts = [tmp.shrink((None,)*(len(tmp.shape)-1) + ((i, i+1),)).cast(new_uint)<<8*i*os for i in range(rate)]
    return parts[0].usum(*parts[1:]).squeeze(-1).bitcast(bc.dtype)
  parts = [tmp>>8*i*ns for i in range(os//ns)]
  return parts[0].stack(*parts[1:], dim=-1).flatten(-2).cast(new_uint).bitcast(bc.dtype)

earliest_rewrites = mop_cleanup+PatternMatcher([
  # resolve FUNCTION calls (inline the body)
  (UPat(Ops.FUNCTION, name="c"), resolve_function),

  # resolve TUPLE+GETTUPLE
  (UPat(Ops.GETTUPLE, src=(UPat(Ops.TUPLE, name="t"),), name="g"), lambda g,t: t.src[g.arg]),

  # resolve allreduce (must be bottom up)
  (UPat(Ops.ALLREDUCE, src=(UPat.var("buf"),), name="red"), create_allreduce_function),

  # split_reduceop
  (UPat(Ops.REDUCE, name="reduce", src=(UPat.var("x"),)), split_reduceop),

  # remove DETACH/CONTIGUOUS_BACKWARD (TODO: this is copied in allocations)
  (UPat((Ops.DETACH, Ops.CONTIGUOUS_BACKWARD), name="x"), lambda x: x.src[0]),

  # SINK only ever references the base
  (UPat(Ops.SINK, name="x"), lambda x: x.replace(src=tuple(y.unsharded_base for y in x.src))),

  # ** copy rules **

  # COPY transfers a contiguous range, so materialize a source that's resized (shrink/pad/expand) or reordered (permute/flip)
  (UPat(Ops.COPY, src=(UPat(GroupOp.Movement, name="r"),), name="c"),
   lambda c,r: c.replace(src=(r.contiguous(),)) if resolve(r.numel() != r.base.numel(), False) or r.contiguous_view_offset() is None else None),

  # copy to same device is a no-op
  (UPat(Ops.COPY, src=(UPat.var("x"),), name="copy"), lambda x,copy: x if x.device == copy.device else None),

  # copy on reshape is reshape on copy
  (UPat(Ops.COPY, src=(UPat(Ops.RESHAPE, name="shp"),), name="cpy"), lambda shp,cpy: shp.src[0].copy_to_device(cpy.device).reshape(shp.shape)),

  # reshaping on STORE can be a NOOP
  (UPat(Ops.STORE, src=(UPat(Ops.RESHAPE, src=(UPat.var("dst",),), allow_any_len=True),
                        UPat(Ops.RESHAPE, src=(UPat.var("src",),), allow_any_len=True))),
   lambda dst,src: dst.store(src) if dst.shape == src.shape else None),

  # ** store rules **

  # fix store hazard (dest is in used in src) by adding contiguous: TestAssign.test_post_flipped_assignment
  (UPat(Ops.STORE, src=(UPat(name="target"), UPat(name="src"))), fix_store_hazard),

  # remove two STOREs that store the same thing to the same place: TestSchedule.test_dedup_assign
  (UPat.var("buf").after(UPat.var("buf").store(UPat.var("src")), name="a1").after(UPat.var("a1").store(UPat.var("src"))), lambda buf,src,a1:a1),

  # store a buffer's own current contents back into itself: TestAssign.test_nested_after_contiguous_store_no_init
  (UPat.var("buf").after(UPat.var("buf").store(UPat.var("buf").after(UPat.var("buf").store(UPat.var("src")), name="a1"))), lambda buf,src,a1:a1),

  # move bitcast from store dest to source: TestAssign.test_assign_bitcast
  (UPat(Ops.STORE, src=(UPat(Ops.BITCAST, src=(UPat(name="target"),)), UPat(name="src"))),
   lambda target, src: target.store(src.bitcast(target.dtype))),

  (UPat(Ops.BITCAST, name="bc"), expand_bitcast),

  # ** size 0 **

  # reduce of size 0 is the identity element
  (UPat(Ops.REDUCE, name="reduce", src=(UPat.var("x"),)),
   lambda reduce,x: reduce.const_like(identity_element(reduce.arg[0], reduce.dtype)) if 0 in x.shape and 0 not in reduce.shape else None),
  # handle size 0
  (UPat(GroupOp.All-{Ops.SINK}, name="x"), lambda x: x.const_like(0).rtag(x.tag) if x._shape is not None and 0 in x.shape else None),
])

# *****************
# 3.5 cleanups

ALWAYS_RUN_OPS = {Ops.CONTIGUOUS, Ops.NOOP}

# you don't know in the first pass if axes are going to die, this happens if there's an EXPAND to the left
def cleanup_dead_axes(b:UOp):
  if not b.arg.removable: return None
  # don't optimize ALWAYS_RUN_OPS or AFTER (AFTER is a buffer identity — ranges define consumer access, not computation)
  if b.src[0].op in ALWAYS_RUN_OPS or b.src[0].op is Ops.AFTER: return None

  new_rng = []
  hit = False
  reshape: list[sint] = []
  for s,rng in zip(b.shape, b.src[1:]):
    # skip for symbolic. TODO: fix this
    if rng.op is Ops.RANGE and rng.src[0].op is not Ops.CONST: return None
    # CONSTs are already dead axes
    if rng.op is Ops.CONST or (rng.op is Ops.RANGE and rng not in b.src[0].ranges):
      reshape.append(1)
      hit = True
    else:
      reshape.append(s)
      new_rng.append(rng)
  if hit:
    return b.replace(src=b.src[0:1]+tuple(new_rng)).reshape(tuple(reshape)).expand(b.shape)

def gate_substitute(ctx, b:UOp) -> None:
  if not any(r in b.ranges for r in ctx.keys()): raise BottomUpGate()
pm_gate_substitute = PatternMatcher([(UPat(GroupOp.All, name="b"), gate_substitute)], compiled=False)
# if a buffer is being stored just for permutes or something, remove it
# we want to reexpress the indexes of idx2 in terms of the implied b1
def remove_bufferize(src:UOp, buf:UOp, idx:UOp):
  # see if we can't do it, should this ever hit?
  assert len(buf.src) == len(idx.src), f"index on wrong bufferize, {len(buf.src)} != {len(idx.src)}"
  assert all(x.op in {Ops.RANGE, Ops.CONST} for x in buf.src[1:])

  # if it's user contiguous, we never remove it
  if src.op in ALWAYS_RUN_OPS or not buf.arg.removable: return None

  # *** here is where we compute the cost ***
  # if we return None, the bufferize is kept

  accessed_buffers: list[UOp] = []
  indexes: list[UOp] = []
  reduces: list[UOp] = []
  def red_gate(x:UOp):
    if x.op is Ops.AFTER:
      accessed_buffers.append(x.buf_uop)
      return False
    if (x.op is Ops.STAGE and x.arg.addrspace == AddrSpace.GLOBAL) or x.op is Ops.MSTACK:
      accessed_buffers.append(x)
      return False
    if x.op is Ops.STORE:
      # don't look inside stores, this doesn't count toward buffer accesses
      return False
    if x.op is Ops.PARAM:
      accessed_buffers.append(x)
    if x.op is Ops.INDEX:
      indexes.append(x)
    if x.op is Ops.REDUCE: reduces.append(x)
    return True
  src.toposort(gate=red_gate)
  del red_gate
  accessed_buffers = dedup(accessed_buffers)

  # if this is generated from multiple buffers, don't remove this buffer
  if len(accessed_buffers) > 3 and not (PCONTIG > 2): return None

  # if any reduces access a buffer, don't remove this buffer
  buffer_in_reduce = False
  def buf_gate(x:UOp):
    nonlocal buffer_in_reduce
    if x.op in {Ops.PARAM, Ops.STAGE, Ops.AFTER}: buffer_in_reduce = True
    return not buffer_in_reduce
  UOp.sink(*[x.src[0] for x in reduces]).toposort(gate=buf_gate)
  del buf_gate
  if buffer_in_reduce:
    if PCONTIG > 2:
      out_in_ratio = (prod(buf.shape)+1) / (sum([x.numel() for x in accessed_buffers])+1)
      if out_in_ratio < 10: return None
      # here we have to check the indexes, we might do a partial contig here
      local_indexes = [x for x in indexes if x.src[0].op is Ops.STAGE and x.src[0].arg.addrspace == AddrSpace.LOCAL]
      exclude_ranges = UOp.group(*[UOp.group(*x.src[1:]) for x in local_indexes]).ranges
      subs = [(k,v) for k,v in zip(buf.src[1:], idx.src[1:]) if k.op is not Ops.CONST]
      # if it's bufferized or a reduce, it's pcontig
      is_pcontig, is_subs = partition(subs, lambda x: x[0] in exclude_ranges or any([r.arg[-1] == AxisType.REDUCE for r in x[1].ranges]))
      if not len(is_subs):
        return None
      if len(is_pcontig):
        ret = src.substitute(dict(is_subs), extra_pm=pm_gate_substitute)
        return ret.bufferize(*[x[0] for x in is_pcontig], arg=BufferizeOpts(None, AddrSpace.LOCAL)).index(*[x[1] for x in is_pcontig])
    else:
      return None

  # if it makes it here, the bufferize is removed
  # this is the ranges replaced
  # NOTE: if buf src is a const, we don't replace it. if idx is Invalid (dead load), don't replace it either
  replaced = {k:v for k,v in zip(buf.src[1:], idx.src[1:]) if k.op is not Ops.CONST and not (v.op is Ops.CONST and v.val is Invalid)}
  return src.substitute(replaced, extra_pm=pm_gate_substitute)

def remove_noop_bufferize(idx,b2):
  if idx.src[1:] != b2.src[1:]: return None
  return idx.src[0].shrink(tuple((0, s) for s in b2.shape)) if b2.shape else idx.src[0]

def after_all_invalid(after:UOp):
  buf = after.src[0].buf_uop
  # check all ranges are used (no expand), and same size (no pad and shrink)
  return all(s.op is Ops.END and (st:=s.src[0]).op is Ops.STORE and st.src[1].base.is_invalid and st.src[0].buf_uop is buf
    and all(r in st.src[0].ranges for r in s.ended_ranges)
    and resolve(cast(UOp, prod(r.src[0] for r in s.ended_ranges)).eq(buf.numel()), False) for s in after.src[1:])

pm_const_buffer_folding = pm_mops+PatternMatcher([
  (UPat(Ops.STAGE, name="b"), cleanup_dead_axes),
  # remove noop buffers. if we look at the next index we can remove even more of these
  (UPat(Ops.INDEX, name="idx").f(Ops.STAGE, allow_any_len=True, name="b2"), remove_noop_bufferize),
  (UPat(Ops.INDEX, src=(UPat(Ops.STAGE),), allow_any_len=True, name="idx").f(Ops.NOOP).f(Ops.STAGE, allow_any_len=True, name="b2"),
   remove_noop_bufferize),
  # no buffers for const (ranges don't matter for const - it's the same value everywhere)
  (UPat(Ops.CONST, name='c').f(Ops.STAGE, allow_any_len=True, name="b"), lambda c,b: b.const_like(c.val)),
  # indexing a const is a const
  (UPat(Ops.INDEX, src=(UPat(Ops.CONST, name="c"),),), lambda c: c),
  # indexing an after with all fully invalid stores is invalid
  (UPat(Ops.INDEX, src=(UPat(Ops.AFTER, name="after"),), allow_any_len=True, name="idx"),
   lambda idx,after: idx.const_like(Invalid) if after_all_invalid(after) else None),
  # hack if a noop turned to a const
  (UPat(Ops.NOOP, src=(UPat.cvar("c"),)), lambda c: c),
  # a deviceless MSTACK src is the same value on every device, so indexing the stack is just indexing that value
  (UPat(Ops.MSTACK, src=(UPat.var("s"),), allow_any_len=True).f(Ops.INDEX, allow_any_len=True, name="idx"),
   lambda s,idx: idx.replace(src=(s,)+idx.src[1:]) if s.device is None else None),
])

pm_remove_bufferize = PatternMatcher([
  # remove reindexing with cost function
  (UPat.var("src").f(Ops.STAGE, allow_any_len=True, name="buf").f(Ops.INDEX, allow_any_len=True, name="idx"), remove_bufferize),
  # STORE to self is NOOP
  (UPat.var("x").store(UPat.var("x")), lambda x: UOp(Ops.NOOP)),
  # END on NOOP is NOOP
  (UPat(Ops.END, src=(UPat(Ops.NOOP, name="x"),), allow_any_len=True), lambda x: x),
])

def strip_zero_offset_shrink(x:UOp) -> UOp:
  return x.src[0] if x.op is Ops.SHRINK and all(resolve(start == 0, False) for start,_ in x.marg) else x

def no_indexing_calls(u:UOp):
  new_srcs = []
  for x in u.src:
    if x.op is Ops.INDEX:
      # sometimes if call srcs have children the call will get an INDEX. we remove it here.
      # TODO: we should add safety checks here for contiguous
      new_srcs.append(x.src[0])
    elif x.op is Ops.SHRINK:
      # SHRINK with offset 0 is fine
      new_srcs.append(strip_zero_offset_shrink(x))
    elif x.op is Ops.MSTACK:
      new_srcs.append(x.replace(src=tuple(strip_zero_offset_shrink(s) for s in x.src)))
    else:
      # everything else we pass through
      new_srcs.append(x)
  return u.replace(src=tuple(new_srcs))

pm_no_indexing_calls = PatternMatcher([
  (UPat(Ops.CALL, name="u"), no_indexing_calls),
])

DEVICE_MAX_BUFS = {"METAL": 31, "WEBGPU": 8, "CPU": 31} # TODO: get from device?
@dataclass
class LimitBufsContext:
  buf_cache: dict[UOp, frozenset[UOp]] = field(default_factory=dict)
  range_idx: itertools.count = field(default_factory=itertools.count)

def _limit_bufs(ctx:LimitBufsContext, root:UOp):
  if (device:=root.device) is None: return None # no device, index related calculations
  device = device if isinstance(device, str) else device[0].split(":")[0]
  if not (MAX_BUFS:=MAX_KERNEL_BUFFERS.value or DEVICE_MAX_BUFS.get(device, 0)): return None

  def visitor(u:UOp) -> frozenset[UOp]:
    if u.op in {Ops.STAGE, Ops.AFTER, Ops.PARAM, Ops.MSELECT, Ops.MSTACK}: return frozenset((u,))
    if len(u.src) == 1: return ctx.buf_cache[u.src[0]]
    return frozenset().union(*[ctx.buf_cache[s] for s in u.src])
  bufs = root.topovisit(visitor, ctx.buf_cache)

  if len(bufs) > MAX_BUFS - 1: # NOTE: this -1 is for the output buffer
    srcs = []
    for s in root.src:
      if s.op in GroupOp.Elementwise and s.device is not None:
        # Insert bufferize: all AxisType.REDUCE before bufferize are AxisType.WEAK, the DEVICE range stays a launched axis
        orig_ranges = s.ranges
        end_ranges = [x.replace(arg=(next(ctx.range_idx), AxisType.WEAK)) if x.op is Ops.RANGE and x.arg[-1] is not AxisType.DEVICE else x
                      for x in s.ranges]
        s = s.substitute(dict(zip(orig_ranges, end_ranges))).bufferize(*end_ranges, arg=BufferizeOpts(device=s.device)).index(*orig_ranges)
      srcs.append(s)
    return root.replace(src=tuple(srcs))
pm_limit_bufs = PatternMatcher([(UPat(set.union(GroupOp.Binary, GroupOp.Ternary), name="root"), _limit_bufs)])

# *****************
# 4. put in buffers for bufferize
# TODO: should BUFFERIZE look a lot more like STORE
# BUFFERIZE has device in arg
# BUFFERIZE doesn't have indexing, that's implied by the ranges it closes
# BUFFERIZE returns the BUFFER ready for INDEXing (doing this will make splitting a lot easier)
# NOTE: this has been fixed up a bit

def bufferize_to_store(ctx:itertools.count, x:UOp, idx:UOp, allow_locals=True):
  size = prod(x.shape)
  dtype = strong_dtype(x.dtype)  # a BUFFER is never weak: store at the concrete dtype, the .cast(x.dtype) on the result keeps readers unchanged
  rngs = sorted(idx.ranges, key=lambda x: x.arg)
  assert size > 0 and isinstance(size, int), f"no zero sized or symbolic sized buffers {size}"

  # AFTER: add END to the existing STORE, return buffer with kernel dependency
  if (after:=x.src[0]).op is Ops.AFTER:
    buf = after.src[0].buf_uop.base
    if not (stores := [s for s in after.src[1:] if s.op is Ops.STORE and s.src[0].op is Ops.INDEX]): return buf
    # BUFFERIZE(INDEX(...)); store through the underlying global index instead.
    ended_stores = []
    for store in stores:
      store_target = store.src[0]
      if store_target.src[0].op is Ops.STAGE and store_target.src[0].src[0].op is Ops.INDEX:
        store_target = store_target.src[0].src[0]
      if store.src[1] is store_target: continue  # skip self-assign
      end_rngs = sorted(dedup(tuple(store_target.ranges) + tuple(rngs)), key=lambda x: x.arg)
      ended_stores.append(store_target.store(store.src[1]).end(*end_rngs))
    return buf.after(*ended_stores)

  # NOTE: the local BUFFER needs to be disambiguated here
  if x.arg.addrspace == AddrSpace.GLOBAL:
    buf = UOp(Ops.BUFFER, src=(shape_to_shape_arg((size,)),), arg=ParamArg(next(ctx), dtype, device=x.arg.device, addrspace=AddrSpace.GLOBAL))
    do_store = buf.index(idx).store(x.src[0].cast(dtype)).end(*rngs)
    return buf.after(do_store).cast(x.dtype)

  if allow_locals:
    # handle locals
    buf = UOp.placeholder((size,), dtype, next(ctx), AddrSpace.LOCAL)
    do_store = buf.index(idx).store(x.src[0].cast(dtype)).end(*rngs)
    return buf.after(do_store).cast(x.dtype)

# collapse any BUFFERIZE to single input BUFFERIZE
def flatten_bufferize(x:UOp):
  if len(x.src) == 2: return None
  ret = x.replace(src=(x.src[0], get_single_element(apply_movement_op(Ops.RESHAPE, (prod(x.shape),), x.shape, x.src[1:]))))
  rngs = x.src[1:]
  ret = ret.reshape(x.shape)
  if any(r.op is Ops.RANGE and r.src[0].op is not Ops.CONST for r in rngs):
    sym_shape = tuple([r.src[0] if r.op is not Ops.CONST else 1 for r in rngs])
    ret = ret.shrink(tuple([(0,x) for x in sym_shape]))
  return ret
pm_flatten_bufferize = PatternMatcher([(UPat(Ops.STAGE, name="x"), flatten_bufferize)])

def is_noop_after_dep(x:UOp) -> bool:
  return (x.op is Ops.NOOP and len(x.src) == 0) or (x.op is Ops.END and is_noop_after_dep(x.src[0]))

def remove_noop_afters(x:UOp) -> UOp|None:
  src = (x.src[0],) + tuple(s for s in x.src[1:] if not is_noop_after_dep(s))
  if len(src) != len(x.src): return src[0] if len(src) == 1 else x.replace(src=src)
  return None

pm_add_buffers = pm_mops+pm_flatten_bufferize+PatternMatcher([
  (UPat(Ops.STAGE, src=(UPat(), UPat(name="idx")), name="x"), lambda ctx,x,idx: bufferize_to_store(ctx, x, idx, allow_locals=False)),

  # INDEX of a buffer through the weak cast added above: index the buffer directly and cast the loaded value instead.
  # this must run in the same rewrite that adds the cast, or the expander expands the whole casted buffer into one big VECTORIZE
  (UPat(Ops.INDEX, src=(UPat(Ops.CAST, dtype=dtypes.weaks, src=(UPat.var("buf"),)),), allow_any_len=True, name="u"),
   lambda u,buf: u.replace(dtype=None, src=(buf,)+u.src[1:]).cast(u.dtype)),

  # move RESHAPEs through MSELECT/MSTACK
  (UPat((Ops.MSELECT, Ops.MSTACK), src=UPat(Ops.RESHAPE), name="m"),
   lambda m: m.replace(src=tuple([x.src[0].base for x in m.src])).reshape(m.shape)),

  # remove any RESHAPEs on KERNEL
  (UPat(Ops.CALL, name="k"), lambda k: k.replace(src=tuple(x.src[0] if x.op is Ops.RESHAPE else x for x in k.src))),

  # remove invalid writes
  (UPat(Ops.STORE, src=(UPat(), UPat(Ops.CONTIGUOUS, src=(UPat(Ops.CONST, arg=Invalid),)))), lambda: UOp(Ops.NOOP)),
  (UPat(Ops.STORE, src=(UPat(), UPat(Ops.CONST, arg=Invalid))), lambda: UOp(Ops.NOOP)),
  (UPat(Ops.AFTER, name="x"), remove_noop_afters),
])

# *****************
# 5. split into kernels

@dataclass
class LocalAddBufferContext:
  dg:int = 0
  map:dict = field(default_factory=dict)
  range:int = 0
  opts:tuple|None = None

def debuf(ctx:LocalAddBufferContext, buf:UOp):
  # Variables (ALU buffers with a value range) are scalar symbolic values, not real buffers: they become ALU params with no slot
  if buf.is_variable: return buf.replace(op=Ops.PARAM)
  param = UOp(Ops.PARAM, src=(UOp.const(prod(buf.max_shape)),),
              arg=ParamArg(ctx.dg, buf.dtype, addrspace=buf.addrspace, device=buf.device))
  ret = param.reshape(buf.max_shape)
  # if the buffer has symbolic shape, shrink the max-sized view to the actual shape
  if buf.max_shape != buf.shape: ret = ret.shrink(tuple((0, s) for s in buf.shape))
  if buf not in ctx.map: ctx.map[buf] = buf
  ctx.dg += 1
  return ret

def handle_after(ctx:LocalAddBufferContext, after:UOp):
  if after.addrspace == AddrSpace.LOCAL: return None
  buf = after.buf_uop
  # NOTE: this is bottom up, so we only add it once
  if buf not in ctx.map: ctx.map[buf] = after
  return buf

def renumber_range(ctx:LocalAddBufferContext, r:UOp):
  if r.tag != (): return None
  ret = r.replace(arg=(ctx.range,)+r.arg[1:], tag=None)
  ctx.range += 1
  return ret

def find_bufs(x:UOp):
  idxs = [s for s in x.toposort(gate=lambda x: x.op is not Ops.AFTER) if s.op is Ops.INDEX]
  read_from: dict[UOp, Ops] = {}
  if any((buf:=idx.buf_uop).op in {Ops.BUFFER, Ops.PARAM} and read_from.setdefault(buf, op:=idx.src[0].op) is not op for idx in idxs):
    raise RuntimeError(f"cycle detected while indexing {buf}")

to_define_global = PatternMatcher([
  (UPat(Ops.STORE, name="x"), find_bufs),
  (UPat((Ops.BUFFER, Ops.MSTACK, Ops.MSELECT), name="buf"), debuf),
  (UPat(Ops.PARAM, name="v"), lambda v:
   v.replace(arg=replace(v.arg, slot=-1)) if v.arg.name is not None and v.arg.vmin_vmax is not None and v.arg.slot != -1 else None),

  # this renumbers the params
  (UPat(Ops.PARAM, name="buf"), lambda ctx, buf:
   None if buf.tag != () or buf.arg.name is not None or buf._shape is None else debuf(ctx, buf)),

  # ALU params are scalar symbolic values, not buffers.
  (UPat(Ops.INDEX, src=(UPat(Ops.PARAM, name="v"),)), lambda v: v if v.addrspace == AddrSpace.ALU else None),

  # bound Variables are stores into Variable buffers: strip the store, the buffer becomes an ALU param via debuf
  (UPat(Ops.AFTER, name="b"), lambda b: b.src[0] if b.is_bound_var else None),
  (UPat(Ops.AFTER, name="after"), handle_after),

  # remove device from local BUFFERIZE
  (UPat(Ops.STAGE, name="b"), lambda b: b.replace(arg=replace(b.arg, device=None))),

  # renumber the ranges starting with 0 so that kernel deduping works
  (UPat(Ops.RANGE, name="r"), renumber_range),
])

def get_contiguous(ctx:LocalAddBufferContext, x:UOp):
  if isinstance(x.arg, tuple) and all(isinstance(y, Opt) for y in x.arg): ctx.opts = x.arg
  return x.src[0]

rangeify_codegen = PatternMatcher([
  (UPat(Ops.CONTIGUOUS, name="x"), get_contiguous),

  # no NOOP in the kernel graph
  # TODO: this can be moved into codegen?
  (UPat(Ops.NOOP, name="x"), lambda x: x.src[0] if len(x.src) else None),
])

pm_add_param_range_tags = PatternMatcher([
  (UPat((Ops.PARAM, Ops.RANGE), name="x"), lambda x: x.rtag(())),
])

def split_store(x:UOp) -> UOp|None:
  # if we have any open ranges here, we don't split. open DEVICE ranges are fine, they are bound per device at launch
  if any(r.arg[-1] is not AxisType.DEVICE for r in x.ranges): return None
  # the store of a bound Variable is an input value, not a kernel
  st = x.src[0] if x.op is Ops.END else x
  if st.op is Ops.STORE and st.src[0].is_variable: return None

  # local kernel rewrite
  lctx = LocalAddBufferContext()
  ret = graph_rewrite(x, to_define_global+pm_flatten_range+rangeify_codegen, ctx=lctx, name="kernel split", bottom_up=True)

  # create the Kernel. NOTE: buffers can be on different devices here now, they are compiled to SDMA copies later by schedule
  return ret.sink(arg=KernelInfo(opts_to_apply=lctx.opts)).call(*lctx.map.values())

split_kernels = PatternMatcher([
  (UPat((Ops.STORE, Ops.END), name="x"), split_store),
])

def convert_copy_to_store(ctx, copy:UOp, existing_buf:UOp|None=None):
  input_src = copy.src[0]
  if not input_src.has_buffer_identity(after_ok=True): input_src = input_src.contiguous()
  input_src = input_src.flatten()
  if existing_buf is not None:
    # if the existing buffer is not a full buffer, we can't use it
    if not existing_buf.has_buffer_identity(after_ok=True): return None
    # if there's already a buffer, we just use it
    return existing_buf.flatten().store(input_src)
  # create the output buffer
  buf = UOp(Ops.BUFFER, src=(shape_to_shape_arg(input_src.max_shape),), arg=ParamArg(next(ctx), copy.dtype, device=copy.device))
  # reshape back to input
  return buf.after(buf.store(input_src)).reshape(copy.shape)

pm_copy_to_store = PatternMatcher([
  (UPat(name="existing_buf").store(UPat(Ops.COPY, name="copy")), convert_copy_to_store),
  (UPat(Ops.COPY, name="copy"), convert_copy_to_store),
])

@rewrite_group(new_ctx=False)
def get_kernel_graph(sink:UOp) -> UOp:
  # prepare for rangeify
  tsink = graph_rewrite(sink, multi_pm, name="multi_pm")
  if OPENPILOT_HACKS: tsink = graph_rewrite(tsink, pm_fold_moved_after, ctx={}, name="fold moved afters")
  tsink = graph_rewrite(tsink, pm_mops+earliest_rewrites, bottom_up=True, name="earliest rewrites")
  tsink = graph_rewrite(tsink, pm_copy_to_store, ctx=itertools.count(0), bottom_up=True, name="convert copy to store")

  # convert movement ops to ranges
  tsink = run_rangeify(tsink, bool(DEBUG_RANGEIFY))

  # cleanups for speed and runability
  tsink = graph_rewrite(tsink,
                        symbolic+pm_reduce_simplify+pm_const_buffer_folding+pm_remove_bufferize,
                        name="symbolic+reduce_collapse+debuf")
  next_range = max((x.arg[0] for x in tsink.toposort() if x.op is Ops.RANGE), default=-1) + 1
  tsink = graph_rewrite(tsink, pm_limit_bufs, ctx=LimitBufsContext(range_idx=itertools.count(next_range)), name="limit buffers")
  if VIZ: graph_rewrite(tsink, PatternMatcher([]), name="View Rangeify")

  # bufferize -> store
  slots = [x.arg.slot for x in tsink.toposort() if x.op is Ops.BUFFER and isinstance(x.arg, ParamArg) and x.addrspace is AddrSpace.GLOBAL]
  paramarg_start: int = max([-1]+slots) + 1
  tsink = graph_rewrite(tsink, pm_add_buffers+pm_add_param_range_tags, ctx=itertools.count(paramarg_start), bottom_up=True, name="stage to store")
  tsink = graph_rewrite(tsink, split_kernels, bottom_up=True, name="split kernels")
  tsink = graph_rewrite(tsink, pm_no_indexing_calls, name="remove indexing from call args")

  if VIZ: graph_rewrite(tsink, PatternMatcher([]), name="View Kernel Graph")
  if SPEC:
    # validate the kernel graph
    from tinygrad.uop.spec import type_verify, spec_kernel_graph
    type_verify(tsink, spec_kernel_graph, enter_calls=False)
  return tsink