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* [gcc(refs/vendors/ARM/heads/arm-perf-staging)] libstdc++: Also disable caching of reverse_view::begin() for common_ranges
@ 2020-07-17 13:29 Tamar Christina
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From: Tamar Christina @ 2020-07-17 13:29 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:77e596cf3c1b7bc11ba946394ed8d62a49157b49
commit 77e596cf3c1b7bc11ba946394ed8d62a49157b49
Author: Patrick Palka <ppalka@redhat.com>
Date: Fri Feb 28 10:47:26 2020 -0500
libstdc++: Also disable caching of reverse_view::begin() for common_ranges
When the underlying range models common_range, then reverse_view::begin() is
already O(1) without caching. So we should disable the cache in this case too.
libstdc++-v3/ChangeLog:
* include/std/ranges (reverse_view::_S_needs_cached_begin): Set to false
whenever the underlying range models common_range.
Diff:
---
libstdc++-v3/ChangeLog | 3 +++
libstdc++-v3/include/std/ranges | 3 ++-
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 89e1f5bf952..0feef87cce6 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,8 @@
2020-02-28 Patrick Palka <ppalka@redhat.com>
+ * include/std/ranges (reverse_view::_S_needs_cached_begin): Set to false
+ whenever the underlying range models common_range.
+
* include/std/ranges (__detail::_CachedPosition): New struct.
(views::filter_view::_S_needs_cached_begin): New member variable.
(views::filter_view::_M_cached_begin): New member variable.
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 2f773130979..19d3da950e7 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -3177,7 +3177,8 @@ namespace views
private:
_Vp _M_base = _Vp();
- static constexpr bool _S_needs_cached_begin = !random_access_range<_Vp>;
+ static constexpr bool _S_needs_cached_begin
+ = !common_range<_Vp> && !random_access_range<_Vp>;
[[no_unique_address]]
__detail::__maybe_empty_t<_S_needs_cached_begin,
__detail::_CachedPosition<_Vp>> _M_cached_begin;
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