Introduce new bytecodes for efficient catch/condition-case in lexbind.

* lisp/emacs-lisp/byte-opt.el (byte-optimize-form-code-walker):
Optimize under `condition-case' and `catch' if
byte-compile--use-old-handlers is nil.
(disassemble-offset): Handle new bytecodes.

* lisp/emacs-lisp/bytecomp.el (byte-pushcatch, byte-pushconditioncase)
(byte-pophandler): New byte codes.
(byte-goto-ops): Adjust accordingly.
(byte-compile--use-old-handlers): New var.
(byte-compile-catch): Use new byte codes depending on
byte-compile--use-old-handlers.
(byte-compile-condition-case--old): Rename from
byte-compile-condition-case.
(byte-compile-condition-case--new): New function.
(byte-compile-condition-case): New function that dispatches depending
on byte-compile--use-old-handlers.
(byte-compile-unwind-protect): Pass a function to byte-unwind-protect
when we can.

* lisp/emacs-lisp/cconv.el (cconv-convert, cconv-analyse-form): Adjust for
the new compilation scheme using the new byte-codes.

* src/alloc.c (Fgarbage_collect): Merge scans of handlerlist and catchlist,
and make them unconditional now that they're heap-allocated.

* src/bytecode.c (BYTE_CODES): Add Bpushcatch, Bpushconditioncase
and Bpophandler.
(bcall0): New function.
(exec_byte_code): Add corresponding cases.  Improve error message when
encountering an invalid byte-code.  Let Bunwind_protect accept
a function (rather than a list of expressions) as argument.

* src/eval.c (catchlist): Remove (merge with handlerlist).
(handlerlist, lisp_eval_depth): Not static any more.
(internal_catch, internal_condition_case, internal_condition_case_1)
(internal_condition_case_2, internal_condition_case_n):
Use PUSH_HANDLER.
(unwind_to_catch, Fthrow, Fsignal): Adjust to merged
handlerlist/catchlist.
(internal_lisp_condition_case): Use PUSH_HANDLER.  Adjust to new
handlerlist which can only handle a single condition-case handler at
a time.
(find_handler_clause): Simplify since we only a single branch here
any more.

* src/lisp.h (struct handler): Merge struct handler and struct catchtag.
(PUSH_HANDLER): New macro.
(catchlist): Remove.
(handlerlist): Always declare.

lisp/emacs-lisp/cconv.el

@@ -79,8 +79,7 @@
 ;;   command-history).
 ;; - canonize code in macro-expand so we don't have to handle (let (var) body)
 ;;   and other oddities.
-;; - new byte codes for unwind-protect, catch, and condition-case so that
-;;   closures aren't needed at all.
+;; - new byte codes for unwind-protect so that closures aren't needed at all.
 ;; - a reference to a var that is known statically to always hold a constant
 ;;   should be turned into a byte-constant rather than a byte-stack-ref.
 ;;   Hmm... right, that's called constant propagation and could be done here,
@@ -421,18 +420,42 @@ places where they originally did not directly appear."
                        forms)))
 
 					;condition-case
-    (`(condition-case ,var ,protected-form . ,handlers)
+    ((and `(condition-case ,var ,protected-form . ,handlers)
+          (guard byte-compile--use-old-handlers))
      (let ((newform (cconv--convert-function
                      () (list protected-form) env form)))
        `(condition-case :fun-body ,newform
-	  ,@(mapcar (lambda (handler)
+          ,@(mapcar (lambda (handler)
                       (list (car handler)
                             (cconv--convert-function
                              (list (or var cconv--dummy-var))
                              (cdr handler) env form)))
                     handlers))))
 
-    (`(,(and head (or `catch `unwind-protect)) ,form . ,body)
+                                        ; condition-case with new byte-codes.
+    (`(condition-case ,var ,protected-form . ,handlers)
+     `(condition-case ,var
+          ,(cconv-convert protected-form env extend)
+        ,@(let* ((cm (and var (member (cons (list var) form)
+                                      cconv-captured+mutated)))
+                 (newenv
+                  (cond (cm (cons `(,var . (car-save ,var)) env))
+                        ((assq var env) (cons `(,var) env))
+                        (t env))))
+            (mapcar
+             (lambda (handler)
+               `(,(car handler)
+                 ,@(let ((body
+                          (mapcar (lambda (form)
+                                    (cconv-convert form newenv extend))
+                                  (cdr handler))))
+                     (if (not cm) body
+                       `((let ((,var (list ,var))) ,@body))))))
+             handlers))))
+
+    (`(,(and head (or (and `catch (guard byte-compile--use-old-handlers))
+                      `unwind-protect))
+       ,form . ,body)
      `(,head ,(cconv-convert form env extend)
         :fun-body ,(cconv--convert-function () body env form)))
 
@@ -491,7 +514,7 @@ places where they originally did not directly appear."
 
     (`(,func . ,forms)
      ;; First element is function or whatever function-like forms are: or, and,
-     ;; if, progn, prog1, prog2, while, until
+     ;; if, catch, progn, prog1, prog2, while, until
      `(,func . ,(mapcar (lambda (form)
                           (cconv-convert form env extend))
                         forms)))
@@ -646,16 +669,32 @@ and updates the data stored in ENV."
     (`(quote . ,_) nil)                 ; quote form
     (`(function . ,_) nil)              ; same as quote
 
-    (`(condition-case ,var ,protected-form . ,handlers)
+    ((and `(condition-case ,var ,protected-form . ,handlers)
+          (guard byte-compile--use-old-handlers))
      ;; FIXME: The bytecode for condition-case forces us to wrap the
-     ;; form and handlers in closures (for handlers, it's understandable
-     ;; but not for the protected form).
+     ;; form and handlers in closures.
      (cconv--analyse-function () (list protected-form) env form)
      (dolist (handler handlers)
-       (cconv--analyse-function (if var (list var)) (cdr handler) env form)))
+       (cconv--analyse-function (if var (list var)) (cdr handler)
+                                env form)))
 
-    ;; FIXME: The bytecode for catch forces us to wrap the body.
-    (`(,(or `catch `unwind-protect) ,form . ,body)
+    (`(condition-case ,var ,protected-form . ,handlers)
+     (cconv-analyse-form protected-form env)
+     (when (and var (symbolp var) (byte-compile-not-lexical-var-p var))
+       (byte-compile-log-warning
+        (format "Lexical variable shadows the dynamic variable %S" var)))
+     (let* ((varstruct (list var nil nil nil nil)))
+       (if var (push varstruct env))
+       (dolist (handler handlers)
+         (dolist (form (cdr handler))
+           (cconv-analyse-form form env)))
+       (if var (cconv--analyse-use (cons (list var) (cdr varstruct))
+                                   form "variable"))))
+
+    ;; FIXME: The bytecode for unwind-protect forces us to wrap the unwind.
+    (`(,(or (and `catch (guard byte-compile--use-old-handlers))
+            `unwind-protect)
+       ,form . ,body)
      (cconv-analyse-form form env)
      (cconv--analyse-function () body env form))