simplify group_for_reduces in get_index [pr] (#7851)

what was that

tinygrad/codegen/lowerer.py

@@ -3,7 +3,6 @@ from __future__ import annotations
 import functools, itertools, operator
 from dataclasses import dataclass
 from typing import List, Tuple, cast, Optional
-from tinygrad.shape.shapetracker import ShapeTracker
 from tinygrad.dtype import dtypes, PtrDType
 from tinygrad.ops import KernelInfo, UOp, Ops, graph_rewrite, PatternMatcher, UPat, sint, identity_element, sint_to_uop
 from tinygrad.renderer import Renderer
@@ -55,14 +54,11 @@ def get_index(ast:UOp, opts:Renderer) -> IndexContext:
   # NOTE: assumes the shape is <global dims> <local dims> <group_for_reduces> <reduces> <upcasts/unrolls>
   full_shape = ast.full_shape
   first_upcasted = len(full_shape)-ki.upcasted
-  first_output_st: ShapeTracker = ast.src[0].st_arg
   # if there's no reduce, this is first_upcasted. assumes reduces are at the end
   first_reduce = min([first_upcasted]+flatten(x.axis_arg for x in ast.sparents if x.op is Ops.REDUCE_AXIS))
   local_loads = [x for x in ast.parents if x.op is Ops.LOAD and x.src[0].op is Ops.DEFINE_LOCAL]
   # NOTE: sum up the reduced axes looking across all local loads, yields the number of grouped reduces
-  group_for_reduces = sum([any(j!=y for j in x) for x,y in zip(
-    [[l.st_arg.shape[i] for l in local_loads] for i in range(first_reduce,first_upcasted)],
-    first_output_st.shape[first_reduce:first_upcasted])]) if local_loads else 0
+  group_for_reduces = sum([any(l.st_arg.shape[i]!=ast.src[0].st_arg.shape[i] for l in local_loads) for i in range(first_reduce,first_upcasted)])
   global_dims = first_reduce-ki.local_dims
 
   if opts.has_local: