StarPilot/tinygrad_repo/tinygrad/codegen/simplify.py

import itertools
from typing import Callable
from tinygrad.uop.ops import UOp, PatternMatcher, UPat, Ops, graph_rewrite, _substitute, range_start, AxisType
from tinygrad.uop.symbolic import symbolic
from tinygrad.helpers import partition
from tinygrad.dtype import dtypes

def flatten_range(r:UOp) -> UOp|None:
  off = range_start[r.op]
  rngs = r.src[off:]
  if not len(rngs): return None
  # ranges in the cond should not be ended
  backedge = tuple(x for x in rngs if x.dtype in (dtypes.void, dtypes.bool))
  return r.replace(src=r.src[:off]+tuple(UOp.sink(*[x for x in rngs if x not in backedge]).ranges)+backedge)

pm_flatten_range = PatternMatcher([
  # real ranges only
  (UPat((Ops.REDUCE, Ops.END), name="r"), flatten_range),
])

# index/range arithmetic uses FLOORDIV/FLOORMOD prior to late rewrite
def count_divmod(x:UOp) -> int: return sum(u.op in {Ops.FLOORDIV, Ops.FLOORMOD} for u in x.backward_slice)
def simplify_merge_adjacent(u:UOp) -> UOp|None:
  if not all(r.op is Ops.RANGE for r in u.ended_ranges): return None
  reduce_ranges = [x.ranges for x in u.backward_slice_with_self if x.op is Ops.REDUCE]
  # on END we only want to merge adjacent ranges, on REDUCE we want to try all combinations
  for r0, r1 in (zip(u.ended_ranges, u.ended_ranges[1:]) if u.op is Ops.END else itertools.permutations(u.ended_ranges, 2)):
    # check same type
    if r0.arg[-1] == r1.arg[-1]:
      # check if the ranges to merge are in the same reduces
      if all((r0 in rngs) == (r1 in rngs) for rngs in reduce_ranges):
        s0, s1 = r0.src[0], r1.src[0]
        # do the merge
        new_range = r0.replace(src=(s0*s1,))
        nidx = graph_rewrite(u, _substitute+symbolic+pm_flatten_range, ctx={r0:new_range//s1, r1:new_range%s1},
                             name=f"check_merge_{r0.arg[0]}_{r1.arg[0]}")

        # check if it simplifies. return after one merge so the next rewrite uses the new ranges,
        # rather than continuing with stale pairs from the original ended_ranges.
        if count_divmod(nidx) <= count_divmod(u): return nidx
  return None

def mark_gated(ctx, idx):
  if len(idx.src) > 1 and idx.src[1].op is Ops.WHERE:
    x, cond = idx.src[1].get_idx(), idx.src[1].get_valid()
    # get all ranges r with guards "r < c" for some const c
    guards = {r:c for v in cond.split_uop(Ops.AND) if v.op is Ops.CMPLT and (r:=v.src[0]).op is Ops.RANGE and (c:=v.src[1]).op is Ops.CONST}
  else: x, guards = idx, {}
  # ensure that we choose max(c_i) for all i where r < c_i
  ctx |= {r:c for r,c in guards.items() if (r not in ctx or ctx[r].val < c.val)}
  # but if a range is ever ungated, we cannot shrink it
  ctx |= {r:r.src[0] for r in x.ranges if r not in guards}

pm_simplify_ranges = PatternMatcher([
  (UPat((Ops.END, Ops.REDUCE), name="u"), simplify_merge_adjacent),
  (UPat(Ops.INDEX, name="idx"), mark_gated),
  # reduce ranges can't be shrunk
  (UPat(Ops.REDUCE, name="red"), lambda ctx, red: ctx.update({r:r.src[0] for r in red.src[1:]})),
  (UPat(Ops.SINK, name="x"), lambda ctx, x: do_substitute(ctx, x, lambda r,c: r.replace(src=(c,)))),
])

def mark_range_mod(ctx:dict[UOp, UOp|None], r:UOp, c:UOp) -> None:
  # ranges that aren't looped over can't be split
  if r not in ctx and r.arg[-1] not in {AxisType.WARP, AxisType.DEVICE} \
    and r.src[0].op is Ops.CONST and r.src[0].divides(c.val) is not None: ctx[r] = c

def do_substitute(ctx:dict, x: UOp, sub_fxn:Callable[[UOp, UOp], UOp]) -> UOp|None:
  ret = x.substitute({k:sub_fxn(k,v) for k,v in ctx.items() if v is not None})
  ctx.clear()
  return None if ret is x else ret.simplify()

pm_split_ranges = PatternMatcher([
  (UPat(Ops.RANGE, name="r")%UPat.cvar("c"), mark_range_mod),
  (UPat(Ops.SINK, name="x"), lambda ctx, x: do_substitute(ctx, x,
    lambda k,v: k.replace(src=(k.src[0]//v,), arg=k.arg[0:-1]+(0,k.arg[-1]))*v + k.replace(src=(v,), arg=k.arg[0:-1]+(1,k.arg[-1])))),
])

# **** reduce simplification ****

def no_range(u:UOp) -> bool: return not any(x.op is Ops.RANGE for x in u.backward_slice_with_self)

def reduce_unparented(red:UOp) -> UOp|None:
  if red.arg[0] not in {Ops.ADD, Ops.MAX, Ops.MUL}: return None
  assert all(x.op is Ops.RANGE for x in red.src[1:]), "some reduce srcs aren't ranges"
  reduce_parented, reduce_unparented = partition(red.src[1:], lambda x: x in red.src[0].ranges)
  if len(reduce_unparented) == 0: return None
  ret = red.replace(src=(red.src[0],)+tuple(reduce_parented)) if len(reduce_parented) else red.src[0]
  if red.arg[0] is Ops.ADD:
    for r in reduce_unparented: ret = ret * r.src[0]
  if red.arg[0] is Ops.MUL:
    for r in reduce_unparented: ret = ret ** r.src[0]
  return ret

pm_reduce_unparented = PatternMatcher([
  # remove any ranges from a REDUCE that aren't referenced in the reduce source
  (UPat(Ops.REDUCE, name="red"), reduce_unparented),
])

pm_reduce_collapse = pm_reduce_unparented + PatternMatcher([
  # lift x+y out of reduce on lt
  ((UPat.var("x")+UPat.var("y")).or_casted() < UPat.var("c"), lambda x,y,c: (x < (c-y)) if no_range(y) and no_range(c) else None),
  # lift x*y out of reduce
  ((UPat.var("x")*UPat.var("y")) < UPat.var("c"),
   lambda x,y,c: (x < ((c+y-1) // y)) if no_range(y) and no_range(c) and dtypes.is_int(y.dtype) and y.vmin > 0 else None),
  # sum over r in [0,N) of [lower<=r<upper]*val -> clamp(min(upper,N) - max(lower,0), 0, N) * val
  (UPat.any(
    (UPat(Ops.RANGE, name="r") < UPat.var("upper")).where(UPat.var("val"), 0),
    (UPat(Ops.RANGE, name="r") < UPat.var("lower")).where(0, UPat.var("val")),
    ((UPat.var("r")<UPat.var("lower")).logical_not()&(UPat(Ops.RANGE, name="r")<UPat.var("upper"))).where(UPat.var("val"), 0),
  ).reduce(UPat.var("r"), arg=Ops.ADD), lambda r,val,lower=None,upper=None:
    ((upper.minimum(r.src[0]) if upper is not None else r.src[0]) -
     (lower.maximum(0) if lower is not None else r.const_like(0))).maximum(0).minimum(r.src[0]) * val if no_range(val) else None),
  ((UPat.var("x")+UPat.var("y")).reduce(arg=Ops.ADD, allow_any_len=True, name="r"),
   lambda x,y,r: x.reduce(*r.src[1:], arg=Ops.ADD) + y.reduce(*r.src[1:],arg=Ops.ADD)),
  # AND on WHERE
  ((UPat(Ops.PARAM, name="x") & UPat.var("y")).where(UPat.var("c"), 0).reduce(arg=Ops.ADD, allow_any_len=True, name="r"),
    lambda x,y,c,r: y.where(c, 0).reduce(*r.src[1:], arg=Ops.ADD)*x),
  # MUL casted bool
  ((UPat.var("x") * UPat.var("gate", dtype=dtypes.bool).cast()), lambda x,gate: gate.where(x, 0)),
])+symbolic

pm_reduce_load_collapse = pm_reduce_collapse + PatternMatcher([
  # lift x+y out of reduce on ne
  ((UPat.var("x")+UPat.var("y")).or_casted() != UPat.var("c"), lambda x,y,c: (x != (c.cast(y.dtype)-y)) if no_range(y) and no_range(c) else None),
  # reduce on gated load becomes can substitute the range and remove the reduce
  ((UPat.var("idx")!=(UPat(Ops.RANGE, name="r").or_casted())).where(0, UPat.var("expr")).reduce(UPat.var("r"), arg=Ops.ADD),
   lambda r,idx,expr: (v:=(idx.cast(r.dtype) >= 0) & (idx.cast(r.dtype) < r.src[0])).where(expr.substitute({r:idx.cast(r.dtype).valid(v)}),0)),
])

def reduce_collapse(red:UOp, u:UOp, pm:PatternMatcher=pm_reduce_collapse) -> UOp|None:
  for r in red.src[1:]:
    included = u.toposort(gate=lambda x: r in x.ranges)
    if any(x.op in {Ops.STORE, Ops.REDUCE} for x in included): return None
    replaces: dict[UOp, UOp] = {}
    for u in included:
      for s in u.src:
        if s in included or s in replaces or s.op in {Ops.CONST, Ops.PARAM, Ops.BUFFER}: continue
        replaces[s] = UOp.variable(f'in{len(replaces)}', s.vmin, s.vmax, s.dtype, param=True)
    collapse_fxn = u.substitute(replaces).reduce(r, arg=Ops.ADD)
    sink = graph_rewrite(collapse_fxn, pm, name="reduce_collapse")
    if not no_range(sink): return None
    u = sink.substitute({v:k for k,v in replaces.items()})
  return u

def reduce_load_collapse(red:UOp, u:UOp) -> UOp|None: return reduce_collapse(red, u, pm=pm_reduce_load_collapse)

# remove REDUCE without loads (generic arange opt / indexing).
pm_reduce_simplify = pm_reduce_unparented + PatternMatcher([
  (UPat(Ops.REDUCE, src=(UPat.var("u"),), allow_any_len=True, arg=(Ops.ADD, 0), name="red"), reduce_collapse),
])
# remove REDUCE on load, comes from indexing a tensor with another tensor
def no_load(u:UOp) -> bool: return not any(x.op is Ops.INDEX for x in u.backward_slice_with_self)
pm_load_collapse = PatternMatcher([
  (UPat(Ops.REDUCE, arg=(Ops.ADD, 0), src=(UPat.var("u"), UPat()), name="red"), reduce_load_collapse),
  # we want to make sure we dont do math on a loaded index since that can cause overflow, this undoes the rule in pm_reduce_load_collapse
  ((UPat.var("x", dtypes.weakint)+UPat.var("y"))<UPat.var("c"), lambda x,y,c: x < c-y if no_load(y) and no_load(c) and not no_load(x) else None),
])