C: Added -fno-walkall for -O3 to skip 2nd and more unused sub passes

Skip the new (1.43) recursive package walker steps, not to include
too many new packages.

-fwalkall has an improved package detection, which stores all subs of
all dependent packages, which results in much bigger compile sizes.
This was introduced to catch previously uncompiled packages for computed
methods or undetected run-time dependencies.

Changes

@@ -5,17 +5,18 @@
 
 1.43	2012-11-xx rurban
 	Improved package detection: methods, functions, require, new and bless.
-	Bigger compile sizes. Store all subs of dependent packages.
-	5.16 support
+	Bigger compile sizes with -O0,-O1,-O2: Store all subs of dependent packages.
+	Added 5.16 support
 
 	* C: issue95 and t/perldoc.t: parent @File::Spec::ISA was not saved.
 	Detect typed lexicals objects to reliably find method packages.
 	Sanified package_pv default a bit when a method padsv was not
 	  found. Check for method_named as last argument of methods.
 	Added check_entersub, check_bless, check_require - bless and new caching of
 	  packages for methods
-	Recursively store all package subs in 2nd pass, not only the needed, to be able to
-          call computed methods.
+	Recursively store all directly unused package subs and packages in a new 2nd pass,
+          not only the needed, to be able to call computed methods. Disable with -fno-walkall.
+        Delete packages which appear to be nowhere used automatically with -fdelete-pkg or -O2.
 	try_isa(): Desperate method finding attempt by trying all seen packages, which
 	  slows down the compiler a lot. Added internal ISA Caching.
 	Special case Carp calling threads and B methods.

lib/B/C.pm

@@ -322,7 +322,7 @@ our ($curcv, $module, $init_name, %savINC, $mainfile);
 our ($use_av_undef_speedup, $use_svpop_speedup) = (1, 1);
 our ($pv_copy_on_grow, $optimize_ppaddr, $optimize_warn_sv, $use_perl_script_name,
     $save_data_fh, $save_sig, $optimize_cop, $av_init, $av_init2, $ro_inc, $destruct,
-    $fold, $warnings, $const_strings, $stash, $can_delete_pkg);
+    $fold, $warnings, $const_strings, $stash, $can_delete_pkg, $walkall);
 our $verbose = 0;
 our %option_map = (
     'cog'             => \$B::C::pv_copy_on_grow,
@@ -332,8 +332,9 @@ our %option_map = (
     'warn-sv'         => \$B::C::optimize_warn_sv,
     'av-init'         => \$B::C::av_init,
     'av-init2'        => \$B::C::av_init2,
-    'delete-pkg'      => \$B::C::can_delete_pkg,
     'ro-inc'          => \$B::C::ro_inc,
+    'delete-pkg'      => \$B::C::can_delete_pkg,
+    'walkall'         => \$B::C::walkall,
     'stash'           => \$B::C::stash,    # disable with -fno-stash
     'destruct'        => \$B::C::destruct, # disable with -fno-destruct
     'fold'            => \$B::C::fold,     # disable with -fno-fold
@@ -5739,7 +5740,7 @@ sub save_unused_subs {
   }
   my $main = $module ? $module."::" : "main::";
 
-  # Better strategy for compile-time added and required packages:
+  # -fwalkall: Better strategy for compile-time added and required packages.
   # loop savecv and check pkg cache for new pkgs.
   # if so loop again with those new pkgs only, until the list of new pkgs is empty
   my (@init_unused, @unused);
@@ -5761,6 +5762,9 @@ sub save_unused_subs {
     if ($verbose) {
       warn sprintf("old unused: %d, new: %d\n", scalar @init_unused, scalar @unused);
     }
+    if (!$B::C::walkall) {
+      @unused = @init_unused = ();
+    }
   } while @unused > @init_unused;
 
   if ( $sav_debug{unused} ) {
@@ -6140,13 +6144,14 @@ sub compile {
   $B::C::stash    = 1;
   $B::C::save_sig = 1;
   $B::C::stash    = 0;
+  $B::C::walkall  = 1;
   $B::C::fold     = 1 if $] >= 5.013009; # always include utf8::Cased tables
   $B::C::warnings = 1 if $] >= 5.013005; # always include Carp warnings categories and B
   my %optimization_map = (
     0 => [qw()],                # special case
     1 => [qw(-fcog -fppaddr -fwarn-sv -fav-init2)], # falls back to -fav-init
     2 => [qw(-fro-inc -fsave-data -fdelete-pkg)],
-    3 => [qw(-fno-destruct -fconst-strings -fno-fold -fno-warnings)],
+    3 => [qw(-fno-destruct -fconst-strings -fno-fold -fno-warnings -fno-walkall)],
     4 => [qw(-fcop)],
   );
   mark_skip qw(B::C B::C::Flags B::CC B::Asmdata B::FAKEOP O B::C::Section
@@ -6391,16 +6396,17 @@ Force end of options
 
 Force all subs from Package to be compiled.
 
-This allows programs to use eval "foo()" even when sub foo is never
-seen to be used at compile time. The down side is that any subs which
-really are never used also have code generated. This option is
-necessary, for example, if you have a signal handler foo which you
-initialise with C<$SIG{BAR} = "foo">.  A better fix, though, is just
-to change it to C<$SIG{BAR} = \&foo>. You can have multiple B<-u>
-options. The compiler tries to figure out which packages may possibly
-have subs in which need compiling but the current version doesn't do
-it very well. In particular, it is confused by nested packages (i.e.
-of the form C<A::B>) where package C<A> does not contain any subs.
+This allows programs to use eval "Package::foo()" even when sub foo is never
+seen to be used at compile time. The down side is that any subs which really
+are never used also have code generated. This option is necessary, for
+example, if you have a signal handler foo which you initialise with
+C<$SIG{BAR} = "Package::foo">.  A better fix, though, is just to change it to
+C<$SIG{BAR} = \&Package::foo>. You can have multiple B<-u> options.
+
+The compiler tries to figure out which packages may possibly have subs in
+which need compiling but the current version doesn't do it very well. In
+particular, it is confused by nested packages (i.e.  of the form C<A::B>)
+where package C<A> does not contain any subs.
 
 =item B<-U>I<Package> "unuse" skip Package
 
@@ -6560,10 +6566,13 @@ Enabled with C<-O2>.
 
 Delete packages which appear to be nowhere used automatically.  This creates
 smaller executables but might miss run-time called methods.  Note that you can
-always use -u to add automatically deleted packages.
+always use C<-u> to add automatically deleted packages.
+
+Without C<-fdelete-pkg> - i.e. with C<-O0> and C<-O1> - only packages which
+are defined by the compiler and its dependencies itself and are apparently
+unused are deleted.
 
-Without -fdelete-pkg - i.e. with -O0,-O1 - only packages which are defined by
-the compiler and its dependencies itself and are apparently unused are deleted.
+See also C<-fno-walkall>.
 
 Enabled with C<-O2>.
 
@@ -6622,6 +6631,20 @@ startup-time.
 
 C<-fno-stash> is the default.
 
+=item B<-fno-walkall>
+
+Skip the new (1.43) recursive package walker steps, not to include
+too many new packages.
+
+-fwalkall has an improved package detection, which stores all subs of
+all dependent packages, which results in much bigger compile sizes.
+This was introduced to catch previously uncompiled packages for computed
+methods or undetected run-time dependencies.
+
+See also C<-fdelete-pkg>.
+
+Enabled with C<-O3>.
+
 =item B<-fuse-script-name>
 
 Use the script name instead of the program name as C<$0>.
@@ -6634,7 +6657,8 @@ DO NOT USE YET!
 
 Omit COP info (nextstate without labels, unneeded NULL ops,
 files, linenumbers) for ~10% faster execution and less space,
-but warnings and errors will have no file and line infos.
+but warnings and errors will have no file and line infos, and
+might even segfault.
 
 It will most likely not work yet. I<(was -fbypass-nullops in earlier
 compilers)>