Branch: refs/heads/blead
Home: https://github.com/Perl/perl5
Commit: c949292055f73373ddef8037677075cfe1a78fc2
https://github.com/Perl/perl5/commit/c949292055f73373ddef8037677075cfe1a78fc2
Author: David Mitchell
Date: 2024-01-09 (Tue, 09 Jan 2024)
Changed paths:
M ext/B/t/optree_varinit.t
Log Message:
---
add Concise tests for state var assignment
Add tests for
state $x = 1;
my $y = state $x = 1;
to check what context is allocated to the various ops. At the moment it
is actually wrong in places, and this commit captures that wrongness.
The next commit will fix this, and those diffs to the tests added in this
commit will help make it clear what has changed.
Commit: dbcd7f4a222753b4329ac1def41fc1048fbc438b
https://github.com/Perl/perl5/commit/dbcd7f4a222753b4329ac1def41fc1048fbc438b
Author: David Mitchell
Date: 2024-01-09 (Tue, 09 Jan 2024)
Changed paths:
M ext/B/t/optree_varinit.t
M op.c
Log Message:
---
set context in 'state' expressions
The ops associated with a state variable declaration and initial
assignment weren't getting their context (GIMME) assigned.
Background:
state $x = ...;
gets compiled to something similar to
if (first_time)
$x = ...;
else
$x;
Except that the 'if' is performed by an OP_ONCE logop, which checks and
updates a flag in the pad, and branches to op_next or op_other as
appropriate.
During compilation, the context of the state expression wasn't being
passed on to the children of the OP_ONCE. So the assignment (optimised
into a padsv_store) and the padsv were left as UNKNOWN rather than VOID
or SCALAR as appropriate, as in these two examples:
state $x = 1; # should be void
$y = (state $x = 1); # should be scalar
This commit fixes that. Note that at the moment it makes no practical
difference, since the padsv/padsv_store ops don't currently change
their behaviour based on context, but that might change.
Commit: 547324acdb2344f04378d3c32330b611dc0bd519
https://github.com/Perl/perl5/commit/547324acdb2344f04378d3c32330b611dc0bd519
Author: David Mitchell
Date: 2024-01-09 (Tue, 09 Jan 2024)
Changed paths:
M gv.c
M op.c
M pp.c
Log Message:
---
Give OPpTARGET_MY ops real context
Perl has an optimisation whereby an op which returns the RHS of a scalar
assignment to a lexical, and which would normally store its result in
a PADTMP, instead skips the following PADSV and SASSIGN ops and assigns
to the lexical directly, instead of to the PADTMP. For example in
$lex = $a + $b;
the ops (in execution-order) would be changed from
add[t5] sK/2
gvsv[*lex] s
sassign vKS/2
nextstate(main 2 -e:1) v:{
to
add[$lex:1,2] sK/TARGMY,2
nextstate(main 2 -e:1) v:{
However, note that although that the add op is now essentially called in
void context, it is still marked as being in scalar context. This commit
changes it to be be marked as void, i.e.
add[$lex:1,2] vK/TARGMY,2
The main reason for this is to allow for future optimisations in
functions like pp_add(), which will be able to skip pushing the result
onto the stack in in void context. It just so happens that scalar
assignments to lexical vars are typically in void context.
However, since this is a visible change from the perspective of modules
which examine ops or optrees, I'll leave doing any optimisations until
later, in case this commit needs to be reverted.
The main things this commit had to fix up following the change were:
- still call overload methods in scalar context, even though the op is
now marked as void;
- not issuing "useless use of add in void context" style warnings on
such ops;
- making pp_push and pp_unshift still set TARG in void context
No matter whether the op's context is marked as scalar or as void, some
parts of perl will misunderstand, and will need to be special-cased
(since the op is really both, depending on your perspective). So this
commit changes the burden of the special-casing code to be in the
non-hot code paths, like during complication or when calling out to an
overload method.
Commit: c90e7ed39e5df8d5915422454fb76198801f3563
https://github.com/Perl/perl5/commit/c90e7ed39e5df8d5915422454fb76198801f3563
Author: David Mitchell
Date: 2024-01-09 (Tue, 09 Jan 2024)
Changed paths:
M ext/B/t/optree_varinit.t
M peep.c
M pp_hot.c
M t/perf/opcount.t
Log Message:
---
OP_PADSV_STORE: only in void context
For the optimisation which converts $lex = expr into an OP_PADSV_STORE
op, only optimise if the scalar assign is in VOID context.
This allows us to stop pp_padsv_store() from uselessly pushing the
result onto the stack, only to be immediately popped again by the
following nextstate or unstack op. This becomes more important on
PERL_RC_STACK builds, as each push or pop involves manipulating the SV's
reference count.
I'm working on the a
