Space explosion in copy-propagation

[Stas Boukarev]

(defun test (n)
  (compile nil
           `(lambda (x)
              (let ((y x))
                ,@(loop for i below n collect
                        `(setf y
                               (if (car x) 0 1)))
                y))))

conses a lot of SSETs and they can't be collected. At the end of each block it collects the TNs which are not modified, and here that set grows with each block.

[Stas Boukarev (stassats)]

In 570bc3c47e03c922eb7cd0ddcfe4825e119ab698