update uop_given_valid if a node becomes const (#9604)

* update uop_given_valid if a node becomes const

* cleanup

test/unit/test_simplify_valid_idx.py

@@ -124,6 +124,20 @@ class TestValidIdxSimplification(unittest.TestCase):
       "(((ridx0*2)+(ridx3*-1))+1)",
       "(ridx2<1)")
 
+  def test_valid_becomes_const1(self):
+    # from DSP mobilenetv2
+    ridx0 = Range(0, 30)
+    ridx1 = Range(1, 7)
+    ridx2 = Range(2, 2)
+    alu11 = (ridx1+ridx2)
+    alu15 = ((alu11+1)//7)
+    idx = (alu15*-31)+(((((alu11+218)//224)+ridx0)%30)*1568)
+    valid = (ridx2<1)&(ridx1<6)
+    load = get_gated_load_uop(valid, idx)
+    self.check(load,
+      "(ridx0*1568)",
+      "((ridx2<1)&(ridx1<6))")
+
 class TestImageSimplification(unittest.TestCase):
   def check(self, load, svalid, sidx0, sidx1):
     load = full_graph_rewrite(load.sink()).src[0]

tinygrad/codegen/symbolic.py

@@ -275,17 +275,20 @@ def uop_given_valid(valid:UOp, uop:UOp) -> UOp|None:
 
   # simplify uop given that valid is True
   for expr,v in bounds.items():
+    v0, v1 = (expr.vmin if v[0] is None else v[0], expr.vmax if v[1] is None else v[1])
     # some expr has lower bound > upper bound -> valid is an empty set and we return None
-    if v[0] is not None and v[1] is not None and v[0] > v[1]: return None
-
+    if v0 > v1: return None
+    # whole node became a const
+    if v0 == v1:
+      uop = uop.substitute({expr:expr.const_like(v0)}).simplify()
+      continue
     # every candidate is a set of contrained UOp based on valid, and if every item in a set simplifies the uop into a same output, we rewrite uop
     candidates = []
-    if expr.op is Ops.ADD and v[0] == 1 and all(u.op in GroupOp.Irreducible for u in split_uop(expr, Ops.ADD)):
+    if expr.op is Ops.ADD and v0 == 1 and all(u.op in GroupOp.Irreducible for u in split_uop(expr, Ops.ADD)):
       # if the constraint is a simplex: X0 + X1 + ... > 0, we can check if all Xi > 0 simplify into the same output
       candidates.append([(Xi, UOp.variable("fake", 1, Xi.vmax, Xi.dtype)) for Xi in split_uop(expr, Ops.ADD)])
     # try checking the whole clause
-    if expr in uop.toposort:
-      candidates.append([(expr, UOp.variable("fake", expr.vmin if v[0] is None else v[0], expr.vmax if v[1] is None else v[1], expr.dtype))])
+    if expr in uop.toposort: candidates.append([(expr, UOp.variable("fake", v0, v1, expr.dtype))])
 
     for candidate in candidates:
       # if every branch in candidate gives the same simplified uop, we can rewrite the uop