112 lines
3.4 KiB
Diff
112 lines
3.4 KiB
Diff
From 0fe04e1dc741a43190e79a985fb0cec0493ebfe9 Mon Sep 17 00:00:00 2001
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From: David Mitchell <davem@iabyn.com>
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Date: Wed, 29 Aug 2018 14:32:24 +0100
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Subject: [PATCH] multiconcat: mutator not seen in (lex = ...) .= ...
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RT #133441
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TL;DR:
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(($lex = expr1.expr2) .= expr3) was being misinterpreted as
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(expr1 . expr2 . expr3) when the ($lex = expr1) subtree had had the
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assign op optimised away by the OPpTARGET_MY optimisation.
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Full details.
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S_maybe_multiconcat() looks for suitable chains of OP_CONCAT to convert
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into a single OP_MULTICONCAT.
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Part of the code needs to distinguish between (expr . expr) and
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(expr .= expr). This didn't used to be easy, as both are just OP_CONCAT
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ops, but with the OPf_STACKED set on the second one. But...
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perl also used to optimise ($a . $b . $c) into ($a . $b) .= $c, to
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reuse the padtmp returned by the $a.$b concat. This meant that an
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OP_CONCAT could have the OPf_STACKED flag on even when it was a '.'
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rather than a '.='.
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I disambiguated these cases by seeing whether the top op in the LHS
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expression had the OPf_MOD flag set too - if so, it implies '.='.
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This fails in the specific case where the LHS expression is a
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sub-expression which is assigned to a lexical variable, e.g.
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($lex = $a+$b) .= $c.
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Initially the top node in the LHS expression above is OP_SASSIGN, with
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OPf_MOD set due to the enclosing '.='. Then the OPpTARGET_MY
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optimisation kicks in, and the ($lex = $a + $b) part of the optree is
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converted from
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sassign sKPRMS
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add[t4] sK
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padsv[a$] s
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padsv[$b] s
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padsv[$lex] s
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to
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add[$lex] sK/TARGMY
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padsv[a$] s
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padsv[$b] s
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which is all fine and dandy, except that the top node of that optree no
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longer has the OPf_MOD flag set, which trips up S_maybe_multiconcat into
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no longer spotting that the outer concat is a '.=' rather than a '.'.
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Whether the OPpTARGET_MY optimising code should copy the OPf_MOD from
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the being-removed sassign op to its successor is an issue I won't
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address here. But in the meantime, the good news is that for 5.28.0
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I added the OPpCONCAT_NESTED private flag, which is set whenever
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($a . $b . $c) is optimised into ($a . $b) .= $c. This means that it's
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no longer necessary to inspect the OPf_MOD flag of the first child to
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disambiguate the two cases. So the fix is trivial.
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Signed-off-by: Petr Písař <ppisar@redhat.com>
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---
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op.c | 1 -
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t/opbasic/concat.t | 10 +++++++++-
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2 files changed, 9 insertions(+), 2 deletions(-)
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diff --git a/op.c b/op.c
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index ddeb484b64..d0dcffbecb 100644
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--- a/op.c
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+++ b/op.c
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@@ -2722,7 +2722,6 @@ S_maybe_multiconcat(pTHX_ OP *o)
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}
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else if ( topop->op_type == OP_CONCAT
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&& (topop->op_flags & OPf_STACKED)
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- && (cUNOPo->op_first->op_flags & OPf_MOD)
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&& (!(topop->op_private & OPpCONCAT_NESTED))
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)
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{
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diff --git a/t/opbasic/concat.t b/t/opbasic/concat.t
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index 9ce9722f5c..4b73b22c1c 100644
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--- a/t/opbasic/concat.t
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+++ b/t/opbasic/concat.t
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@@ -39,7 +39,7 @@ sub is {
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return $ok;
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}
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-print "1..253\n";
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+print "1..254\n";
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($a, $b, $c) = qw(foo bar);
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@@ -853,3 +853,11 @@ package RT132595 {
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my $res = $a.$t.$a.$t;
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::is($res, "b1c1b1c2", "RT #132595");
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}
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+
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+# RT #133441
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+# multiconcat wasn't seeing a mutator as a mutator
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+{
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+ my ($a, $b) = qw(a b);
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+ ($a = 'A'.$b) .= 'c';
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+ is($a, "Abc", "RT #133441");
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+}
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--
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2.14.4
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