addCSEnvItem env id expr | exprIsBig expr = env
| otherwise = extendCSEnv env id expr
+ -- We don't try to CSE big expressions, because they are expensive to compare
+ -- (and are unlikely to be the same anyway)
extendCSEnv (CS cs in_scope sub) id expr
= CS (addToUFM_C combine cs hash [(id, expr)]) in_scope sub