From 4069adf4bbc90d16b603e0308b48499c36b2b637 Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Thu, 12 Mar 2020 08:28:05 +0100 Subject: [PATCH] c++: Tweak reshape_init_array_1 [PR94124] Isn't it wasteful to first copy perhaps a large constructor (recursively) and then truncate it to very few elts (zero in this case)? > We should certainly avoid copying if they're the same. The code above for > only copying the bits that aren't going to be thrown away seems pretty > straightforward, might as well use it even if the savings aren't likely to > be large. Calling vec_safe_truncate with the same number of elts the vector already has is a nop, so IMHO we just should make sure we only unshare if it changed. 2020-03-12 Jakub Jelinek PR c++/94124 * decl.c (reshape_init_array_1): Don't unshare constructor if there aren't any trailing zero elts, otherwise only unshare the first nelts. --- gcc/cp/ChangeLog | 9 ++++++++- gcc/cp/decl.c | 19 +++++++++++++++---- 2 files changed, 23 insertions(+), 5 deletions(-) diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index 8cde300..b94e3bb 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,10 @@ +2020-03-12 Jakub Jelinek + + PR c++/94124 + * decl.c (reshape_init_array_1): Don't unshare constructor if there + aren't any trailing zero elts, otherwise only unshare the first + nelts. + 2020-03-11 Jason Merrill PR c++/93907 @@ -27,7 +34,7 @@ 2020-03-10 Jason Merrill - PR c++/93956 + PR c++/93596 * pt.c (maybe_aggr_guide): Check BRACE_ENCLOSED_INITIALIZER_P. 2020-03-10 Jason Merrill diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c index aa58e5f..d240436 100644 --- a/gcc/cp/decl.c +++ b/gcc/cp/decl.c @@ -6066,10 +6066,21 @@ reshape_init_array_1 (tree elt_type, tree max_index, reshape_iter *d, overload resolution. E.g., initializing a class from {{0}} might be invalid while initializing the same class from {{}} might be valid. */ - if (reuse) - new_init = unshare_constructor (new_init); - - vec_safe_truncate (CONSTRUCTOR_ELTS (new_init), nelts); + if (reuse && nelts < CONSTRUCTOR_NELTS (new_init)) + { + vec *v; + vec_alloc (v, nelts); + for (unsigned int i = 0; i < nelts; i++) + { + constructor_elt elt = *CONSTRUCTOR_ELT (new_init, i); + if (TREE_CODE (elt.value) == CONSTRUCTOR) + elt.value = unshare_constructor (elt.value); + v->quick_push (elt); + } + new_init = build_constructor (TREE_TYPE (new_init), v); + } + else + vec_safe_truncate (CONSTRUCTOR_ELTS (new_init), nelts); } return new_init; -- 2.7.4