From acdea6f0600816151724f1e3525a3e41433e2646 Mon Sep 17 00:00:00 2001 From: David Mitchell Date: Sat, 12 Mar 2011 22:01:26 +0000 Subject: [PATCH] [perl #82111] de-pessimise some my @array = ... Due to obscure closure and goto tricks, it's sometimes possible for the array or hash in the LHS of 'my @a = ...' and 'my %h = ...' to be non-empty. At compile-time, these conditions are detected and the assign op is compiled with the OPpASSIGN_COMMON, making the assignment slower. This commit speeds it up again by adding a run-time check to pp_aassign to only do the OPpASSIGN_COMMON code-branch if the LHS isn't an empty array or hash. See also #70171. --- pp_hot.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/pp_hot.c b/pp_hot.c index 852ff80..f8a61cb 100644 --- a/pp_hot.c +++ b/pp_hot.c @@ -989,8 +989,19 @@ PP(pp_aassign) /* If there's a common identifier on both sides we have to take * special care that assigning the identifier on the left doesn't * clobber a value on the right that's used later in the list. + * Don't bother if LHS is just an empty hash or array. */ - if (PL_op->op_private & (OPpASSIGN_COMMON)) { + + if ( (PL_op->op_private & OPpASSIGN_COMMON) + && ( + firstlelem != lastlelem + || ! ((sv = *firstlelem)) + || SvMAGICAL(sv) + || ! (SvTYPE(sv) == SVt_PVAV || SvTYPE(sv) == SVt_PVHV) + || (SvTYPE(sv) == SVt_PVAV && AvFILL((AV*)sv) != -1) + || (SvTYPE(sv) == SVt_PVHV && HvKEYS((HV*)sv) != 0) + ) + ) { EXTEND_MORTAL(lastrelem - firstrelem + 1); for (relem = firstrelem; relem <= lastrelem; relem++) { if ((sv = *relem)) { -- 2.7.4