Tune SAFE_FREE

On my platform (Fedora 28 x86-64, AMD Phenom II X4 910e) this sped
up a SAFE_FREE-using microbenchmark (string-distance "abc" "abc")
by about 18%, and shrank the Emacs text size by about 0.1%.
* src/callint.c (Fcall_interactively):
* src/callproc.c (call_process):
* src/doc.c (get_doc_string, Fsnarf_documentation):
* src/editfns.c (Freplace_buffer_contents):
* src/emacs-module.c (funcall_module):
* src/eval.c (Flet):
* src/process.c (Fmake_process):
* src/term.c (tty_menu_show):
* src/xdisp.c (safe__call):
* src/xmenu.c (x_menu_show):
Use SAFE_FREE_UNBIND_TO.
* src/data.c (wrong_choice): No need to call SAFE_FREE here.
* src/lisp.h (USE_SAFE_ALLOCA):
* src/regex.c (REGEX_USE_SAFE_ALLOCA):
Do not declare sa_must_free local; no longer needed.
All uses removed.
(SAFE_FREE): Rewrite in terms of safe_free.
(safe_free): New function, optimized to use xfree.
(SAFE_FREE_UNBIND_TO): New macro.
(safe_free_unbind_to): New function.

1 files changed, 3 insertions, 5 deletions

diff --git a/src/editfns.c b/src/editfns.c
index 7d032a7ca4c..88dfba1f910 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -3198,6 +3198,8 @@ differences between the two buffers.  */)
       return Qnil;
     }
 
+  ptrdiff_t count = SPECPDL_INDEX ();
+
   /* FIXME: It is not documented how to initialize the contents of the
      context structure.  This code cargo-cults from the existing
      caller in src/analyze.c of GNU Diffutils, which appears to
@@ -3231,7 +3233,6 @@ differences between the two buffers.  */)
   eassert (! early_abort);
 
   Fundo_boundary ();
-  ptrdiff_t count = SPECPDL_INDEX ();
   record_unwind_protect_excursion ();
 
   ptrdiff_t i = size_a;
@@ -3279,10 +3280,8 @@ differences between the two buffers.  */)
       --i;
       --j;
     }
-  unbind_to (count, Qnil);
-  SAFE_FREE ();
 
-  return Qnil;
+  return SAFE_FREE_UNBIND_TO (count, Qnil);
 }
 
 static void
@@ -4885,7 +4884,6 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
       if (buf == initial_buffer)
         {
           buf = xmalloc (bufsize);
-          sa_must_free = true;
           buf_save_value_index = SPECPDL_INDEX ();
           record_unwind_protect_ptr (xfree, buf);
           memcpy (buf, initial_buffer, used);