Optimize tail recursive calls while byte compiling.feature/byte-tail-recursion

* lisp/emacs-lisp/byte-opt.el (byte-optimize-stack-adjustment)
  (byte-optimize-conv-return-goto), (byte-optimize-copy-ops),
  (byte-optimize-called-function), (byte-optimize-lapcode-tail-recursion):
  New functions.

* lisp/emacs-lisp/bytecomp.el: Add variables b-c-current-{defun,
  arglist}.
  (byte-compile-file-form-defmumble), (byte-compile): Set them.
  (byte-compile-out-toplevel): Use byte-optimize-lapcode-tail-recursion.

1 files changed, 21 insertions, 8 deletions

diff --git a/lisp/emacs-lisp/bytecomp.el b/lisp/emacs-lisp/bytecomp.el
index 25513bd0248..efe86404fcf 100644
--- a/lisp/emacs-lisp/bytecomp.el
+++ b/lisp/emacs-lisp/bytecomp.el
@@ -197,6 +197,7 @@ adds `c' to it; otherwise adds `.elc'."
 ;; that doesn't define this function, so this seems to be a reasonable
 ;; thing to do.
 (autoload 'byte-decompile-bytecode "byte-opt")
+(autoload 'byte-optimize-lapcode-tail-recursion "byte-opt")
 
 (defcustom byte-compile-verbose
   (and (not noninteractive) (> baud-rate search-slow-speed))
@@ -1000,6 +1001,8 @@ Each function's symbol gets added to `byte-compile-noruntime-functions'."
 (defvar byte-compile-current-file nil)
 (defvar byte-compile-current-group nil)
 (defvar byte-compile-current-buffer nil)
+(defvar byte-compile-current-defun nil)
+(defvar byte-compile-current-arglist nil)
 
 ;; Log something that isn't a warning.
 (defmacro byte-compile-log (format-string &rest args)
@@ -2538,7 +2541,9 @@ not to take responsibility for the actual compilation of the code."
           ;; Tell the caller that we didn't compile it yet.
           nil)
 
-      (let* ((code (byte-compile-lambda (cons arglist body) t)))
+      (let* ((byte-compile-current-defun name)
+             (byte-compile-current-arglist arglist)
+             (code (byte-compile-lambda (cons arglist body) t)))
         (if this-one
             ;; A definition in b-c-initial-m-e should always take precedence
             ;; during compilation, so don't let it be redefined.  (Bug#8647)
@@ -2668,11 +2673,13 @@ If FORM is a lambda or a macro, byte-compile it as a function."
           (setq fun (byte-compile--reify-function fun)))
         ;; Expand macros.
         (setq fun (byte-compile-preprocess fun))
-        (setq fun (byte-compile-top-level fun nil 'eval))
-        (if macro (push 'macro fun))
-        (if (symbolp form)
-            (fset form fun)
-          fun)))))))
+        (let ((byte-compile-current-defun (and (symbolp form) form))
+              (byte-compile-current-arglist (nth 1 (cadr fun))))
+          (setq fun (byte-compile-top-level fun nil 'eval))
+          (if macro (push 'macro fun))
+          (if (symbolp form)
+              (fset form fun)
+            fun))))))))
 
 (defun byte-compile-sexp (sexp)
   "Compile and return SEXP."
@@ -2923,9 +2930,15 @@ for symbols generated by the byte compiler itself."
                 (caar tmp))))))
   (byte-compile-out 'byte-return 0)
   (setq byte-compile-output (nreverse byte-compile-output))
-  (if (memq byte-optimize '(t byte))
+  (when (memq byte-optimize '(t byte))
+    (setq byte-compile-output
+          (byte-optimize-lapcode byte-compile-output))
+    ;; Do tail recursion optimization after `byte-optimize-lapcode',
+    ;; since the lapcode now contains more than a single `byte-return',
+    ;; allowing us to optimize multiple tail recursive calls
+    (when byte-compile-current-defun
       (setq byte-compile-output
-            (byte-optimize-lapcode byte-compile-output)))
+            (byte-optimize-lapcode-tail-recursion byte-compile-output))))
 
   ;; Decompile trivial functions:
   ;; only constants and variables, or a single funcall except in lambdas.