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| author | Father Chrysostomos <sprout@cpan.org> | 2018-01-21 21:55:00 -0800 |
|---|---|---|
| committer | Father Chrysostomos <sprout@cpan.org> | 2018-02-18 16:25:42 -0800 |
| commit | 1f1dcfb516e063c29a4b9823ad97b1fc58ffc930 (patch) | |
| tree | 7f3616e6e28e78d9e1549eeca675453b6cbfedf7 /mg_vtable.h | |
| parent | 6de18f4499a45f0d6876f2aca180b8a9f06e9240 (diff) | |
| download | perl-1f1dcfb516e063c29a4b9823ad97b1fc58ffc930.tar.gz | |
‘Nonelems’ for pushing sparse array on the stack
To avoid having to create deferred elements every time a sparse array
is pushed on to the stack, store a magic scalar in the array itself,
which av_exists and refto recognise as not existing.
This means there is only a one-time cost for putting such arrays on
the stack.
It also means that deferred elements that live long enough don’t
start pointing to the wrong array entry if the array gets shifted (or
unshifted/spliced) in the mean time. Instead, the scalar is already
in the array, so it cannot lose its place. This fix only applies
when the array as a whole is pushed on to the stack, but it could be
extended in future commits to apply to other places where we currently
use deferred elements.
Diffstat (limited to 'mg_vtable.h')
| -rw-r--r-- | mg_vtable.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/mg_vtable.h b/mg_vtable.h index c71a988cf7..e4f3f3889d 100644 --- a/mg_vtable.h +++ b/mg_vtable.h @@ -52,6 +52,7 @@ #define PERL_MAGIC_vec 'v' /* vec() lvalue */ #define PERL_MAGIC_utf8 'w' /* Cached UTF-8 information */ #define PERL_MAGIC_substr 'x' /* substr() lvalue */ +#define PERL_MAGIC_nonelem 'Y' /* Array element that does not exist */ #define PERL_MAGIC_defelem 'y' /* Shadow "foreach" iterator variable / smart parameter vivification */ #define PERL_MAGIC_lvref '\\' /* Lvalue reference constructor */ @@ -76,6 +77,7 @@ enum { /* pass one of these to get_vtbl */ want_vtbl_lvref, want_vtbl_mglob, want_vtbl_nkeys, + want_vtbl_nonelem, want_vtbl_ovrld, want_vtbl_pack, want_vtbl_packelem, @@ -112,6 +114,7 @@ EXTCONST char * const PL_magic_vtable_names[magic_vtable_max] = { "lvref", "mglob", "nkeys", + "nonelem", "ovrld", "pack", "packelem", @@ -171,6 +174,7 @@ EXT_MGVTBL PL_magic_vtables[magic_vtable_max] = { { 0, Perl_magic_setlvref, 0, 0, 0, 0, 0, 0 }, { 0, Perl_magic_setmglob, 0, 0, 0, 0, 0, 0 }, { Perl_magic_getnkeys, Perl_magic_setnkeys, 0, 0, 0, 0, 0, 0 }, + { 0, Perl_magic_setnonelem, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, Perl_magic_freeovrld, 0, 0, 0 }, { 0, 0, Perl_magic_sizepack, Perl_magic_wipepack, 0, 0, 0, 0 }, { Perl_magic_getpack, Perl_magic_setpack, 0, Perl_magic_clearpack, 0, 0, 0, 0 }, @@ -216,6 +220,7 @@ EXT_MGVTBL PL_magic_vtables[magic_vtable_max]; #define PL_vtbl_lvref PL_magic_vtables[want_vtbl_lvref] #define PL_vtbl_mglob PL_magic_vtables[want_vtbl_mglob] #define PL_vtbl_nkeys PL_magic_vtables[want_vtbl_nkeys] +#define PL_vtbl_nonelem PL_magic_vtables[want_vtbl_nonelem] #define PL_vtbl_ovrld PL_magic_vtables[want_vtbl_ovrld] #define PL_vtbl_pack PL_magic_vtables[want_vtbl_pack] #define PL_vtbl_packelem PL_magic_vtables[want_vtbl_packelem] |