Branch: refs/heads/blead
Home: https://github.com/Perl/perl5
Commit: 08368a773f179335566e09096be6e015368237d1
https://github.com/Perl/perl5/commit/08368a773f179335566e09096be6e015368237d1
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pod/perlref.pod
Log Message:
-----------
document ref assignment in list context
The 'refaliasing' feature, whereby assigning to a literal reference
causes an aliasing operation (e.g. \$x = \...) didn't document what was
returned if the assignment was done in list context.
This commit adds a basic summary to the docs.
See the thread http://nntp.perl.org/group/perl.perl5.porters/267074
for the discussion.
Commit: 823fcbfd95001ebd591a4b9c0c19b0e126f22d76
https://github.com/Perl/perl5/commit/823fcbfd95001ebd591a4b9c0c19b0e126f22d76
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M t/op/lvref.t
Log Message:
-----------
add list context tests to t/op/lvref.t
Codify the existing behaviour of alias list assignment in list
context, e.g.
.... = ( (\$x, \$y, \(@a)) = (....) );
and
( (\$x, \$y, \(@a)) = (....) ) = ....;
Whether the existing behaviour is sane is up for debate, but if
if we change it, it should be a deliberate choice, not an accidental
change not spotted by the existing tests.
Commit: b98a30fe2d2891321ee60dcd6b44ce6498a1f211
https://github.com/Perl/perl5/commit/b98a30fe2d2891321ee60dcd6b44ce6498a1f211
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M t/op/lvref.t
Log Message:
-----------
add lvalue scalar alias tests to lvref.t
This is a compile-time error:
(\$x = \1) = \2;
However, the following is legal code, but is untested (the 'OPf_MOD'
branch in pp_refassign() is not triggered by the test suite):
f(\$x = \1);
So this commit adds some tests. It assumes that the above code is
equivalent to:
\$x = \1;
f(\$x);
Whether the existing behaviour is sane is up for debate, but if
if we change it, it should be a deliberate choice, not an accidental
change not spotted by the existing tests.
Commit: 313c8957d30780156be85d76909da6b1bfdbce27
https://github.com/Perl/perl5/commit/313c8957d30780156be85d76909da6b1bfdbce27
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M ext/Hash-Util-FieldHash/t/02_function.t
Log Message:
-----------
Hash-Util-FieldHash: fixup test on PERL_RC_STACK
Hash::Util::FieldHash is an implementation of "inside out" objects,
where field values are stored in per-field hashes whose keys are the
numeric addresses of the objects, and whose values represent the value
of that field for a particular object.
The hashes are magic, in that they don't hold a reference to each
object, but automatically delete the relevant entry from the hash when
the object is freed. This is achieved internally with weak references
and a bunch of user magic attached to the hash and the object.
A test in 02_function.t checks that such a link in the magic hash to an
object is removed after the real object is freed. This test looked
something like:
$h{[]} = 123;
is(keys %h, 0);
which relied on the temp anon array being freed almost immediately and
triggering the hash delete. Now it turns out that OP_ANONLIST (and its
later optimisation, OP_EMPTYAVHV) return an SvTEMP RV. In the code
above, this means that [] gets freed at the start of the next statement
(by the freetmps() in pp_nextstate()), and all works as expected.
However, when pp_emptyavhv() is unwrapped in the next commit, on
PERL_RC_STACK builds it will skip mortalising the return result, and
just rely on the ref count from the stack to keep the RV alive as long
as needed. By "needed", this is only while the helem op is being
executed, and the temp array is thus freed at the end of the helem,
rather than at the end of the statement. This triggers the entry in the
hash being auto-deleted earlier, so when the next op, the scalar assign,
executes, it triggers a warning:
Useless assignment to a temporary at t/02_function.t line 121.
After a lot of faffing about trying to work out what was going on, I
concluded that the intent of the test could just as well be done by
creating a real array reference variable and to just undef it directly
after the hash assign.
(I.e. it took some time to convince myself that there wasn't a bug in
pp_emptyavhv, pp_sassign nor FieldHash.xs, and that just the test needed
fixing.)
Commit: 14403447b7488675c7d043c7d7325011727b3e45
https://github.com/Perl/perl5/commit/14403447b7488675c7d043c7d7325011727b3e45
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp.c
M t/op/array.t
Log Message:
-----------
make RC-stack-aware: unwrap pp_emptyavhv()
Remove the temporary wrapper from pp_emptyavhv()
Also fix some tests in array.t, which were expecting a temp empty array
ref to be prematurely freed. With PERL_RC_STACK, it's no longer
prematurely freed.
Commit: a98ee9eadd3d547a367869acc3edfa73006f5615
https://github.com/Perl/perl5/commit/a98ee9eadd3d547a367869acc3edfa73006f5615
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M t/op/array.t
Log Message:
-----------
op/array.t: skip \$#{[]} test under PERL_RC_STACK
PERL_RC_STACK builds fixes a bug whereby the [] was being prematurely
freed. So the test, which was testing that perl didn't crash when
trying to set the length of a freed array, was now trying to set the
size of the array to some large number, and was failing under ASAN.
Commit: 604c0355d21cd2bdfa4adbc4cc6e2014acb8760a
https://github.com/Perl/perl5/commit/604c0355d21cd2bdfa4adbc4cc6e2014acb8760a
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp.c
Log Message:
-----------
make RC-stack-aware: unwrap pp_refassign()
Remove the temporary wrapper from pp_refassign()
Also move a couple of variable declarations into the smallest scope
possible: mg and stash are used only by (and implicitly by)
SvCANEXISTDELETE().
Commit: b5e6ad2a94d4362c397ec8bc0931e744534d7b4b
https://github.com/Perl/perl5/commit/b5e6ad2a94d4362c397ec8bc0931e744534d7b4b
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp.c
Log Message:
-----------
make RC-stack-aware: unwrap pp_undef()
Remove the temporary wrapper from pp_undef()
Commit: eb535a3b7c3f7f88348b1e46fc5ad4b7ac140cb1
https://github.com/Perl/perl5/commit/eb535a3b7c3f7f88348b1e46fc5ad4b7ac140cb1
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp_hot.c
Log Message:
-----------
make RC-stack-aware: unwrap pp_aassign()
Remove the temporary wrapper from pp_aassign()
Note that this is a very basic unwrapping: in particular, pp_aassign()
still heavily uses the temps stack, but now mostly unnecessarily. The
next few commits will start optimising things.
Commit: dba1d971bd26e7a07385b61a52522f8418c4c2bf
https://github.com/Perl/perl5/commit/dba1d971bd26e7a07385b61a52522f8418c4c2bf
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp_hot.c
Log Message:
-----------
pp_aassign: optimise AV branch under PERL_RC_STACK
The block of code that handles
(..., @a) = (...);
used to temporarily store on the temps stack, pointers to all the RH
elements, in order to avoid things being prematurely freed, such as in
@a = ($a[0], ...). Under PERL_RC_STACK builds this is no longer
necessary, so simplify the code.
All changes are wrapped in '#ifdef PERL_RC_STACK' etc.
Aliasing needs special handling. When in list context, we return refs
to SVs, but store the SVs themselves in the AV. In the traditional
approach, the stack keeps the RVs while the temps stack has the SvRV()
values - this makes it easy to block copy the SVs to the array while
leaving the stack untouched. When the temps stack is no longer being
used, we have to manually dereference each RV as we assign values to the
stack. Do this using the slow av_store() loop rather than the optimised
Copy(AvARRAY(),...) branch.
Commit: 39a2e63986dff01f0f22286bbed307a7efddd38f
https://github.com/Perl/perl5/commit/39a2e63986dff01f0f22286bbed307a7efddd38f
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp_hot.c
Log Message:
-----------
pp_aassign: optimise HV branch under PERL_RC_STACK
The block of code that handles
(..., %a) = (...);
used to temporarily store on the temps stack, pointers to all the RH
value elements (and sometimes the keys too), in order to avoid things
being prematurely freed, such as in %h = ($h{a}, ...). Under
PERL_RC_STACK builds this is no longer necessary, so simplify the code.
All changes are wrapped in '#ifdef PERL_RC_STACK' etc.
Commit: 5a8fb493e89e0884ef3f3dab320700c106665871
https://github.com/Perl/perl5/commit/5a8fb493e89e0884ef3f3dab320700c106665871
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp_hot.c
Log Message:
-----------
pp_aassign: optimise SV branch under PERL_RC_STACK
The block of code that handles
($scalar, ...) = (...);
used to handle things specially if $scalar was currently a ref, in case
assigning to $scalar freed the referent which was later used on the RHS.
With a ref-counted stack that is no longer a problem.
All changes are wrapped in '#ifdef PERL_RC_STACK' etc.
Commit: 12e444f71226b83247db089c2c3683cb2c42dfce
https://github.com/Perl/perl5/commit/12e444f71226b83247db089c2c3683cb2c42dfce
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp_hot.c
M t/op/sort.t
Log Message:
-----------
pp_aassign: remove panic check under PERL_RC_STACK
There is some code in S_aassign_copy_common() (helper function for
pp_aassign()) which checks for SvIS_FREED() of the current arg.
The comments imply that the check is there specifically to help a TODO
test in t/op/sort.t not randomly crash. That test does stuff which
triggers a premature free of args on the stack.
This test was later disabled entirely, as whatever panics or crashes
were being triggered weren't being caught by the eval {} it was wrapped
in.
This commit, only on PERL_RC_STACK builds, skips the SvIS_FREED check,
and re-enables the test in sort.t (as a real test, not a TODO).
Commit: 8915a2954e1e7a90f4eb871083e3319f024f676d
https://github.com/Perl/perl5/commit/8915a2954e1e7a90f4eb871083e3319f024f676d
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp_hot.c
Log Message:
-----------
pp_aassign: fix "RC==1" optimisation checks
The code sometimes skips a copying step if the ref count of the SV
is 1. Under PERL_RC_STACK, the ref count can now be 2, with the
optimisation still being valid.
Commit: f11efeed3a5b76aaa7931900446768fc0d194c31
https://github.com/Perl/perl5/commit/f11efeed3a5b76aaa7931900446768fc0d194c31
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M embed.fnc
M embed.h
M inline.h
M pod/perlguts.pod
M proto.h
Log Message:
-----------
add rpp_replace_at_norc() to API
It's like rpp_replace_at(), but it assumes that the SV has already had
its refcount bumped. It replaces ugly code like
SV *nsv = newSVsv(*svp);
#ifdef PERL_RC_STACK
rpp_replace(svp, nsv);
SvREFCNT_dec(nsv);
#else
rpp_replace(svp, sv_2mortal(nsv));
#endif
with a simple
rpp_replace_at_norc(svp, newSvsv(*svp));
On PERL_RC_STACK builds it's more efficient than before as it's not
unnecessarily bumping and then immediately unbumping nsv's refcount.
Commit: 0cf81d166744bf23d9c941a5179b74613b9ab090
https://github.com/Perl/perl5/commit/0cf81d166744bf23d9c941a5179b74613b9ab090
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp.c
M pp_hot.c
Log Message:
-----------
use rpp_replace_at_norc in refassign, aassign
Use the just-added function rpp_replace_at_norc() to simplify some blocks
of code recently added to pp_refassign() and pp_aassign()
Commit: cc49ed3d254ee6016cad82e723241fcebef70d9a
https://github.com/Perl/perl5/commit/cc49ed3d254ee6016cad82e723241fcebef70d9a
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M embed.fnc
M embed.h
M inline.h
M pod/perlguts.pod
M proto.h
Log Message:
-----------
Add some _NN variants of rpp_() functions.
Namely:
rpp_popfree_1_NN()
rpp_popfree_2_NN()
rpp_popfree_to_NN(svp)
rpp_replace_1_1_NN(sv)
rpp_replace_2_1_NN(sv)
rpp_replace_at_NN(sp, sv)
rpp_replace_at_norc_NN(sp, sv)
These are more efficient, as they can skip checking that the existing
pointers on the stack are non-NULL before attempting to decrement their
reference count.
Note that the *args* of the original (non-variant) functions (as opposed
the values on the stack) were already assumed to be non-NULL.
Commit: 4d8fbc55082bc8481f72cb39f5a4ca05c1318b29
https://github.com/Perl/perl5/commit/4d8fbc55082bc8481f72cb39f5a4ca05c1318b29
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp_hot.c
Log Message:
-----------
use rpp_foo_NN() variants in pp_aassign, pp_rv2av
These make the code slightly faster. This commit is kind of a proof of
concept: only pp_aassign (and the related op pp_rv2av) have been updated
to use these new variants for now. Making the rest of code use them will
be done later.
Commit: a2515f4c681acde6541dd7f66757e0b20828a670
https://github.com/Perl/perl5/commit/a2515f4c681acde6541dd7f66757e0b20828a670
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp_hot.c
Log Message:
-----------
pp_aassign: add is_list local variable
It may be slightly more efficient than testing for (gimme == G_LIST)
in hot loops.
Commit: 443b64a02939b4e80b4f676b46c9659efe4f1f9f
https://github.com/Perl/perl5/commit/443b64a02939b4e80b4f676b46c9659efe4f1f9f
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp_hot.c
Log Message:
-----------
pp_aassign: skip copying scalars back to stack
Consider a list assignment where there are scalars on the LHS, such
as:
($x,$y,$z) = ($a,$b,$c);
Except in the rare cases where the list assignment is itself in list
context, such as
@a = ( ($x,$y,$z) = ($a,$b,$c) )
then there is no need to copy $x to the $a stack position, $y to $b and
$z to $c in order to return ($x,$y,$z). Instead leave the stack as-is,
containing ($a,$b,$c,$x,$y,$z), with all six SV pointers on the stack
untouched. When pp_assign() is about to return, it will just pop the 6
elements off the stack.
Less messing with the stack becomes more important on PERL_RC_STACK
builds, because needlessly putting things on and off the stack requires
more ref count manipulation and testing.
Commit: 295ebb578ae1ffef86799b72468419cd3d5d8881
https://github.com/Perl/perl5/commit/295ebb578ae1ffef86799b72468419cd3d5d8881
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp_hot.c
Log Message:
-----------
pp_aassign: optimise: store NULLs in L elem slots
(This commit only affects code within PERL_RC_STACK ifdefs)
In a list assignment such as (L1, L2, ...) = (R1, R2, ...),
pp_assign is called with the stack looking like:
* R1 R2 ... * L1 L2 ...
Previously, all elements on the stack were popped at the end. This
commit changes it so that after each L element is processed, it is freed
and a NULL (or sometimes &PL_sv_undef) is stored at that slot in the
stack. Then at the end, PL_stack_sp can just be set to one slot below the
ex-L1, without having to run a loop popping each element off the stack.
This reduces the number of memory reads and branches, at the cost of
more writes.
(All the R elems will still need to be freed, though).
Commit: 971e9b5a17aced68110b4145d2c49bbf08fc5377
https://github.com/Perl/perl5/commit/971e9b5a17aced68110b4145d2c49bbf08fc5377
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp_hot.c
Log Message:
-----------
pp_aassign: optimise: lelem++ at end of loop
There are a couple of loops along the lines of
while (...) {
SV *lsv = *lelem++;
....
do stuff with lelem[-1]
}
change them to
while (...) {
SV *lsv = *lelem;
....
do stuff with *lelem
lelem++
}
Commit: 2a2c64dd01fc7424aea74c5d352932ea964da2fd
https://github.com/Perl/perl5/commit/2a2c64dd01fc7424aea74c5d352932ea964da2fd
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp_hot.c
Log Message:
-----------
pp_aassign: optimise: just zero array stack elems
In PERL_RC_STACK builds, When passing ownership of a bunch of SVs on the
stack to an array they've just been stored in, just zero out that
section of the stack and shift first_discard downwards, rather than
storing &PL_sv_undef in all the stack slots. This means that at the end,
PL_stack_sp can be reset directly to the base of those elements rather
than decrementing the ref count of &PL_sv_undef N times.
Commit: a2677daf97ded4a33bba5f9ff373c93de730d72a
https://github.com/Perl/perl5/commit/a2677daf97ded4a33bba5f9ff373c93de730d72a
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp_hot.c
Log Message:
-----------
pp_aassign: optimise: just zero hash stack elems
Similar to the previous commit but for hashes rather than arrays,
in PERL_RC_STACK builds, When passing ownership of a bunch of SVs on the
stack to a hash they've just been stored in, just zero out that
section of the stack and shift first_discard downwards, rather than
storing &PL_sv_undef in all the stack slots. This means that at the end,
PL_stack_sp can be reset directly to the base of those elements rather
than decrementing the ref count of &PL_sv_undef N times.
Commit: f54903ed18841195b413582d1b798bb5bc7ddbb9
https://github.com/Perl/perl5/commit/f54903ed18841195b413582d1b798bb5bc7ddbb9
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M pp_hot.c
Log Message:
-----------
pp_aassign: move UID/GID code into separate fn
There is a big chunk of code near the end of pp_aassign() which is
responsible for updating the OS's UIDs and/or GIDs after something like
($<,$>) = ($>,$<);
has been executed. This code is long and has little to with list
assignment generally, so move it out into a separate static function.
This commit makes no changes to that chunk of code apart from
indentation (hopefully).
Commit: efc99d519efd522724a3d41fd5caa591f7e8d2b6
https://github.com/Perl/perl5/commit/efc99d519efd522724a3d41fd5caa591f7e8d2b6
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M inline.h
M sv.h
M t/op/hash.t
Log Message:
-----------
fix Perl_rpp_is_lone() for immortals.
Perl_rpp_is_lone() checks whether an SV is kept alive only by the args
and/or temps stack, and thus can in various circumstances be used
directly rather than copying - such as a return value from a function, or
assigning a value to an array or hash.
However, this assumption fails on immortal SVs like PL_sv_undef. Their
refcount can reach 1 but they should still be copied rather than stolen.
This showed itself as an extremely intermittent failure in
cpan/Test-Harness/t/compat/test-harness-compat.t
It only showed up when both these conditions were met:
- on DEBUGGING builds, because that sets the initial ref count of the
immortals to 1000 rather than I32_MAX, making such problems easier to
reproduce; *and*
- under PERL_RC_STACK, because only on that build do you have SVs
on the args stack (but not temps stack) with RC==1 which are stealable.
Also under the RC build, as an optimisation, &PL_sv_undef is often
pushed on the stack without incrementing its RC. Thus it is more liklely
to reach RC==1.
I don't know why the failure on that test was intermittent, even after
setting PERL_HASH_SEED=0. Perhaps it was timing related. Certainly
anything which made it slower, such as strace, valgrind or ASAN, made
the problem go away or fail only after days rather than minutes.
This commit also decreases the value of SvREFCNT_IMMORTAL on
debugging builds from 1000 to 10 under PERL_RC_STACK, to make such
issues/bugs more likely to be triggered.
Commit: 7fbd97b4e807873b45e6847052d923bab2986229
https://github.com/Perl/perl5/commit/7fbd97b4e807873b45e6847052d923bab2986229
Author: David Mitchell <da...@iabyn.com>
Date: 2023-12-04 (Mon, 04 Dec 2023)
Changed paths:
M embed.fnc
M embed.h
M ext/Hash-Util-FieldHash/t/02_function.t
M inline.h
M pod/perlguts.pod
M pod/perlref.pod
M pp.c
M pp_hot.c
M proto.h
M sv.h
M t/op/array.t
M t/op/hash.t
M t/op/lvref.t
M t/op/sort.t
Log Message:
-----------
[MERGE] unwrap, optimise pp_aassign() and friends
This branch:
- makes pp_aassign() RC-stack-aware
- optimises pp_aassign() on PERL_RC_STACK builds.
- also unwraps pp_emptyavhv() pp_refassign() and pp_undef(), chiefly to
avoid skewing list assignment benchmark results.
- documents and adds tests for ref alias assignment in list context
- adds rpp_replace_at_norc() and several rpp_foo_NN() variants to the API
The main intent of this branch is to unwrap and optimise pp_aassign; all
the other commits came about as side-effects of that work.
The main optimisation work on pp_aassign() consists of: firstly,
skipping all the temps stack juggling that it used to do to avoid
prematurely freeing SVs, in such cases as @a = ($_a[0], ...). With an RC
stack this is no longer necessary. Secondly, trying to avoid
manipulating the stack as much as possible, now that every
rpp_replace_1_1() or similar requires two ref count adjustments, one of
which requires a conditional.
The Porting/bench.pl results on the expr::aassign:: subset of the
benchmarks gave an averages of around 96% on Ir, COND etc compared with
a non-PERL_RC_STACK blead build.
The work in this branch turned out to be a lot harder than I expected,
and took around two calendar months to get fully working.
Compare: https://github.com/Perl/perl5/compare/cf76a266bc68...7fbd97b4e807
