Better optimise my/local @a = split()

There are currently two optimisations for when the results of a split
are assigned to an array.

For the first,

    @array = split(...);

the aassign and padav/rv2av are optimised away, and pp_split() directly
assigns to the array attached to the split op (via op_pmtargetoff or
op_pmtargetgv).

For the second,

    my @array    = split(...);
    local @array = split(...);
    @{$expr}     = split(...);

The aassign is optimised away, but the padav/rv2av is kept as an additional
arg to split. pp_split itself then uses the first arg popped off the stack
as the array (This was introduced by FC with v5.21.4-409-gef7999f).

This commit moves these two:

    my @array    = split(...);
    local @array = split(...);

from the second case to the first case, by simply setting OPpLVAL_INTRO
on the OP_SPLIT, and making pp_split() do SAVECLEARSV() or save_ary()
as appropriate.

This makes my @a = split(...) a few percent faster.

1 files changed, 2 insertions, 2 deletions

diff --git a/regen/op_private b/regen/op_private
index e511ce145b..d459d479e4 100644
--- a/regen/op_private
+++ b/regen/op_private
@@ -300,7 +300,7 @@ for (qw(nextstate dbstate)) {
 #   my $x
 
 addbits($_, 7 => qw(OPpLVAL_INTRO LVINTRO))
-    for qw(gvsv rv2sv rv2hv rv2gv rv2av aelem helem aslice
+    for qw(gvsv rv2sv rv2hv rv2gv rv2av aelem helem aslice split
            hslice delete padsv padav padhv enteriter entersub padrange
            pushmark cond_expr refassign lvref lvrefslice lvavref multideref),
            'list', # this gets set in my_attrs() for some reason
@@ -732,11 +732,11 @@ addbits('coreargs',
 
 
 addbits('split',
-    7 => qw(OPpSPLIT_IMPLIM IMPLIM), # implicit limit
     # @a = split() has been replaced with  split() where split itself
     # does the array assign
     4 => qw(OPpSPLIT_ASSIGN ASSIGN), 
     3 => qw(OPpSPLIT_LEX LEX),  # the OPpSPLIT_ASSIGN is a lexical array
+    2 => qw(OPpSPLIT_IMPLIM IMPLIM), # implicit limit
 );