master bba48d6 2/3: More robust optimisation of `ignore`

[Mattias Engdegård]

branch: master
commit bba48d6ee5d90f326c70cbe8af19dfe6b00651ba
Author: Mattias Engdegård <mattiase@acm.org>
Commit: Mattias Engdegård <mattiase@acm.org>

    More robust optimisation of `ignore`
    
    Treat `ignore` as any other function during source-level optimisation,
    to avoid having its warning-suppression effects cancelled by repeated
    passes.  Instead, define a custom code generation function.
    
    * lisp/emacs-lisp/byte-opt.el (byte-optimize-form-code-walker):
    Don't treat `ignore' specially here.
    (side-effect-free-fns): Don't mark `ignore` as side-effect-free
    or error-free (although it is), since that would allow the optimiser
    to elide calls.
    * lisp/emacs-lisp/bytecomp.el (ignore, byte-compile-ignore):
    Define and register a code-gen function.
---
 lisp/emacs-lisp/byte-opt.el | 11 +++--------
 lisp/emacs-lisp/bytecomp.el |  6 ++++++
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/lisp/emacs-lisp/byte-opt.el b/lisp/emacs-lisp/byte-opt.el
index 0c30d83..23c5a56 100644
--- a/lisp/emacs-lisp/byte-opt.el
+++ b/lisp/emacs-lisp/byte-opt.el
@@ -562,13 +562,6 @@ Same format as `byte-optimize--lexvars', with shared 
structure and contents.")
          `(catch ,(byte-optimize-form tag nil)
             . ,(byte-optimize-body exps for-effect))))
 
-      (`(ignore . ,exps)
-       ;; Don't treat the args to `ignore' as being
-       ;; computed for effect.  We want to avoid the warnings
-       ;; that might occur if they were treated that way.
-       ;; However, don't actually bother calling `ignore'.
-       `(progn ,@(mapcar #'byte-optimize-form exps) nil))
-
       ;; Needed as long as we run byte-optimize-form after cconv.
       (`(internal-make-closure . ,_)
        ;; Look up free vars and mark them to be kept, so that they
@@ -1419,7 +1412,9 @@ See Info node `(elisp) Integer Basics'."
         fixnump floatp following-char framep
         get-largest-window get-lru-window
         hash-table-p
-        identity ignore integerp integer-or-marker-p interactive-p
+         ;; `ignore' isn't here because we don't want calls to it elided;
+         ;; see `byte-compile-ignore'.
+        identity integerp integer-or-marker-p interactive-p
         invocation-directory invocation-name
         keymapp keywordp
         list listp
diff --git a/lisp/emacs-lisp/bytecomp.el b/lisp/emacs-lisp/bytecomp.el
index 145cdba..8ea591b 100644
--- a/lisp/emacs-lisp/bytecomp.el
+++ b/lisp/emacs-lisp/bytecomp.el
@@ -4207,6 +4207,7 @@ discarding."
 (byte-defop-compiler-1 funcall)
 (byte-defop-compiler-1 let)
 (byte-defop-compiler-1 let* byte-compile-let)
+(byte-defop-compiler-1 ignore)
 
 (defun byte-compile-progn (form)
   (byte-compile-body-do-effect (cdr form)))
@@ -4222,6 +4223,11 @@ discarding."
       (if ,discard 'byte-goto-if-nil 'byte-goto-if-nil-else-pop))
     ,tag))
 
+(defun byte-compile-ignore (form)
+  (dolist (arg (cdr form))
+    (byte-compile-form arg t))
+  (byte-compile-form nil))
+
 ;; Return the list of items in CONDITION-PARAM that match PRED-LIST.
 ;; Only return items that are not in ONLY-IF-NOT-PRESENT.
 (defun byte-compile-find-bound-condition (condition-param