faster codegen process replay (#4858)

* faster codegen process replay

* use self.copy

* regenerate

* delete copy

* test a real error [run_process_replay]

* revert the error change

test/external/replay_codegen.py

@@ -0,0 +1,29 @@
+# compare kernels created by HEAD against master
+import difflib, pickle
+from tqdm import tqdm
+from tinygrad.codegen.linearizer import Linearizer
+from tinygrad.helpers import colored, db_connection, VERSION
+
+page_size = 100
+conn = db_connection()
+cur = conn.cursor()
+row_count = cur.execute(f"select count(*) from 'process_replay_{VERSION}'").fetchone()[0]
+for offset in tqdm(range(0, row_count, page_size)):
+  cur.execute(f"SELECT val FROM 'process_replay_{VERSION}' LIMIT ? OFFSET ?", (page_size, offset))
+  for row in cur.fetchall():
+    compare_k: Linearizer = pickle.loads(row[0])
+    compare_src = compare_k.opts.render("test", compare_k.uops)
+    k = Linearizer(*compare_k.ast, opts=compare_k.opts)
+    for opt in compare_k.applied_opts: k.apply_opt(opt)
+    good_uops = k.linearize().uops
+    good_src = k.opts.render("test", good_uops)
+    try: assert compare_src == good_src
+    except AssertionError:
+      print("PROCESS REPLAY FAILED")
+      print(compare_k.ast)
+      print(compare_k.applied_opts)
+      diff = list(difflib.unified_diff(good_src.splitlines(), compare_src.splitlines()))
+      for line in diff:
+        print(colored(line, "red" if line.startswith("-") else "green" if line.startswith("+") else None))
+      # TODO: fix nondeterminism in ASTs with Variable 4860
+      #raise e