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* [gcc/devel/c++-modules] c++: Tweak reshape_init_array_1 [PR94124]
@ 2020-03-19 12:40 Nathan Sidwell
0 siblings, 0 replies; only message in thread
From: Nathan Sidwell @ 2020-03-19 12:40 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:4069adf4bbc90d16b603e0308b48499c36b2b637
commit 4069adf4bbc90d16b603e0308b48499c36b2b637
Author: Jakub Jelinek <jakub@redhat.com>
Date: Thu Mar 12 08:28:05 2020 +0100
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 <jakub@redhat.com>
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.
Diff:
---
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 8cde3000e8d..b94e3bb8eb2 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2020-03-12 Jakub Jelinek <jakub@redhat.com>
+
+ 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 <jason@redhat.com>
PR c++/93907
@@ -27,7 +34,7 @@
2020-03-10 Jason Merrill <jason@redhat.com>
- PR c++/93956
+ PR c++/93596
* pt.c (maybe_aggr_guide): Check BRACE_ENCLOSED_INITIALIZER_P.
2020-03-10 Jason Merrill <jason@redhat.com>
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index aa58e5f88ae..d240436d84a 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<constructor_elt, va_gc> *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;
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