From 76e8a3250c585be5cccb1104d227c88695501d7c Mon Sep 17 00:00:00 2001
From: qazal <77887910+Qazalin@users.noreply.github.com>
Date: Mon, 6 Oct 2025 12:52:33 +0300
Subject: [PATCH] rangeify: late zero folding (#12464)

* rangeify: late zero folding

* early

* not kernels

* none

* multi

* linter

* mstack is sink comment

* more comment
---
 test/test_multitensor.py      |  3 +--
 test/test_schedule.py         |  8 ++++++++
 tinygrad/schedule/rangeify.py | 11 ++++++-----
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/test/test_multitensor.py b/test/test_multitensor.py
index d1c24b0d65..5711018454 100644
--- a/test/test_multitensor.py
+++ b/test/test_multitensor.py
@@ -7,7 +7,7 @@ from tinygrad.nn.state import get_parameters, get_state_dict
 from tinygrad.engine.realize import lower_schedule, BufferCopy, CompiledRunner, run_schedule
 import numpy as np
 from hypothesis import given, strategies as strat, settings
-from test.helpers import REAL_DEV, not_support_multi_device, expect_rangeify_fails
+from test.helpers import REAL_DEV, not_support_multi_device
 
 settings.register_profile("my_profile", max_examples=200, deadline=None, derandomize=getenv("DERANDOMIZE_CI", False))
 settings.load_profile("my_profile")
@@ -201,7 +201,6 @@ class TestMultiTensor(unittest.TestCase):
     fn = f(n)
     np.testing.assert_allclose(fX.numpy(), fn, rtol=1e-6, atol=1e-6)
 
-  @expect_rangeify_fails # TODO: fix
   def test_allreduce_shard_ring_sum(self):
     for axis in (0, 1, None):
       for use_ring in (0, 2):
diff --git a/test/test_schedule.py b/test/test_schedule.py
index 7815bbb2fb..3e7055c6a3 100644
--- a/test/test_schedule.py
+++ b/test/test_schedule.py
@@ -814,6 +814,14 @@ class TestSchedule(unittest.TestCase):
     check_schedule(a, 0)
     self.assertEqual(a.tolist(), [])
 
+  def test_zero_size_children(self):
+    r = Tensor.ones(1,2).contiguous().realize().sum(axis=(1,), keepdim=True)
+    ax = r.reshape(1)*2
+    ay = r.reshape(1).shrink(((1,1),))*2
+    out = ax+ay.pad(((1, 0),))
+    run_schedule(check_schedule(out, 1))
+    self.assertEqual(out.item(), 4.)
+
   def test_reduce_permute_nofuse(self):
     x = Tensor.empty(32, 32, 32)
     y = Tensor.empty(32, 32)
diff --git a/tinygrad/schedule/rangeify.py b/tinygrad/schedule/rangeify.py
index c4cd782b18..2e47656d9a 100644
--- a/tinygrad/schedule/rangeify.py
+++ b/tinygrad/schedule/rangeify.py
@@ -57,6 +57,9 @@ earliest_rewrites = PatternMatcher([
   (UPat(Ops.REDUCE_AXIS, name="reduce", src=(UPat.var("x"),)),
    lambda reduce,x: reduce.const_like(identity_element(reduce.arg[0], reduce.dtype)) if x.size == 0 and reduce.size != 0 else None),
 
+  # handle size 0
+  (UPat(GroupOp.All-{Ops.SINK}, name="x"), lambda x: x.const_like(0).rtag(x.tag) if x.st is not None and x.size == 0 else None),
+
   # remove contiguous on movement ops before a copy on disk
   (UPat(GroupOp.Movement-{Ops.SHRINK, Ops.RESHAPE}, name="x").f(Ops.CONTIGUOUS).f(Ops.COPY, allow_any_len=True, name="copy"),
    lambda x,copy: copy.replace(src=(x,)+copy.src[1:]) if isinstance(x.device, str) and x.device.startswith("DISK") else None),
@@ -133,7 +136,8 @@ def extract_children(ctx:ChildrenContext, x:UOp):
   children_map = x.get_children_map()
   ctx.children = {}
   for k,v in children_map.items():
-    non_sink_children = [u for u in v if u.op is not Ops.SINK]
+    # NOTE: we treat mstack children like sink here
+    non_sink_children = [u for u in v if u.op not in {Ops.SINK, Ops.MSTACK}]
     if len(non_sink_children) <= 1: continue
     # NOTE: this gate shouldn't be here
     if k.op_in_parents(Ops.REDUCE_AXIS) and k.op_in_parents(Ops.BUFFER, Ops.CONTIGUOUS):
@@ -363,9 +367,6 @@ pm_rangeify = pm_mops+PatternMatcher([
   # handle arg on any op with weight. old endrange stuff
   (UPat(Ops.INDEX, src=(UPat(GroupOp.Elementwise.union({Ops.REDUCE_AXIS})),), allow_any_len=True, name="idx"), might_end_axis),
 
-  # handle size 0
-  (UPat(Ops.INDEX, name="x"), lambda x: x.replace(src=(x.const_like(0),)+x.src[1:]) if x.st is not None and x.size == 0 else None),
-
   # handle assign
   (UPat(Ops.INDEX, src=(UPat(Ops.ASSIGN, name="assign"),), allow_any_len=True, name="x"),
     lambda x,assign: assign.replace(src=tuple([s.index(*x.src[1:]) for s in assign.src])+(assign.src[0],)) \
@@ -572,7 +573,7 @@ pm_add_buffers = pm_mops+to_bufferview+PatternMatcher([
 
   # 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] for x in m.src]), tag=None).reshape(m.src[0].arg).rtag(m.tag)),
+   lambda m: m.replace(src=tuple([x.src[0].base for x in m.src]), tag=None).reshape(m.src[0].arg).rtag(m.tag)),
 ])
 
 # *****************