move xpow to sym instead of late_rewrite (tinygrad#8968)

does not need to be in late_rewrite and can be simplified further

Author: chenyuxyz

tinygrad/codegen/rewriter.py

@@ -123,7 +123,6 @@ def simplify_valid_load(buf:UOp, start_idx:UOp, valid:UOp) -> UOp|None:
 def get_late_rewrite_patterns(ops, force_transcendental=False):
   pat: list[tuple[UPat, Callable]] = [(UPat(op, dtype=TRANSCENDENTAL_SUPPORTED_DTYPES, src=(UPat.var("d"),)), f) for op,f in \
            ((Ops.EXP2, xexp2), (Ops.LOG2, xlog2), (Ops.SIN, xsin)) if op not in ops or force_transcendental]
-  pat.append((UPat(Ops.POW, name="p"), lambda p: xpow(*p.src)))
   # rewrite MOD to AND (which should always be supported, but not for generic in tests): x % (2**y) -> x & (2**y-1)
   if Ops.AND in ops:
     pat += [(UPat.var("x", dtypes.ints)%UPat.cvar("c"), lambda x,c: x & (c.arg-1) if c.arg in powers_of_two else None)]
@@ -297,6 +296,8 @@ def reduce_collapse(acc:UOp, ret:UOp, alu:UOp):
   # ** where **
   # push cast to branches
   (UPat.var("s").where(UPat.var("a"), UPat.var("b")).cast().named("cast"), lambda s,a,b,cast: s.where(a.cast(cast.dtype), b.cast(cast.dtype))),
+  # ** pow **
+  ((UPat(Ops.POW, name="p"), lambda p: xpow(*p.src))),
   # ** load/store folding **
   (UPat.store(UPat(Ops.INDEX, name="index"), UPat.load(UPat(Ops.INDEX, name="index"))), lambda index: UOp(Ops.NOOP)),
   (UPat.store(UPat(Ops.INDEX, name="index"), UPat.var("gate").where(UPat.var("alt"), UPat.load(UPat(Ops.INDEX, name="index")))),