* [PATCH] Simplify common case of use_future_t that uses std::allocator
@ 2019-10-24 14:52 Jonathan Wakely
0 siblings, 0 replies; only message in thread
From: Jonathan Wakely @ 2019-10-24 14:52 UTC (permalink / raw)
To: libstdc++, gcc-patches
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There is no need to store and pass around the allocator object when it's
an instance of std::allocator. Define a partial specialization of
std::use_future_t and the corresponding completion token so that no
allocator is stored. Overload the completion handler constructor to not
expect an allocator to be stored.
* include/experimental/executor (__use_future_ct, use_future_t):
Define partial specializations for std::allocator.
(__use_future_ch): Overload constructor for completion tokens using
std::allocator.
Tested x86_64-linux, committed to trunk.
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commit ff1859de72d39f46118df4f568ee90d78c6be937
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Thu Oct 24 15:34:17 2019 +0100
Simplify common case of use_future_t that uses std::allocator
There is no need to store and pass around the allocator object when it's
an instance of std::allocator. Define a partial specialization of
std::use_future_t and the corresponding completion token so that no
allocator is stored. Overload the completion handler constructor to not
expect an allocator to be stored.
* include/experimental/executor (__use_future_ct, use_future_t):
Define partial specializations for std::allocator.
(__use_future_ch): Overload constructor for completion tokens using
std::allocator.
diff --git a/libstdc++-v3/include/experimental/executor b/libstdc++-v3/include/experimental/executor
index ef141e92cd3..ed18730951c 100644
--- a/libstdc++-v3/include/experimental/executor
+++ b/libstdc++-v3/include/experimental/executor
@@ -1501,12 +1501,18 @@ inline namespace v1
std::tuple<_Func, _Alloc> _M_t;
};
+ template<typename _Func, typename _Tp>
+ struct __use_future_ct<_Func, std::allocator<_Tp>>
+ {
+ _Func _M_f;
+ };
+
template<typename _ProtoAllocator = allocator<void>>
class use_future_t
{
public:
// use_future_t types:
- typedef _ProtoAllocator allocator_type;
+ using allocator_type = _ProtoAllocator;
// use_future_t members:
constexpr use_future_t() noexcept : _M_alloc() { }
@@ -1514,7 +1520,7 @@ inline namespace v1
explicit
use_future_t(const _ProtoAllocator& __a) noexcept : _M_alloc(__a) { }
- template<class _OtherAllocator>
+ template<typename _OtherAllocator>
use_future_t<_OtherAllocator>
rebind(const _OtherAllocator& __a) const noexcept
{ return use_future_t<_OtherAllocator>(__a); }
@@ -1533,6 +1539,35 @@ inline namespace v1
_ProtoAllocator _M_alloc;
};
+ template<typename _Tp>
+ class use_future_t<std::allocator<_Tp>>
+ {
+ public:
+ // use_future_t types:
+ using allocator_type = std::allocator<_Tp>;
+
+ // use_future_t members:
+ constexpr use_future_t() noexcept = default;
+
+ explicit
+ use_future_t(const allocator_type& __a) noexcept { }
+
+ template<class _Up>
+ use_future_t<std::allocator<_Up>>
+ rebind(const std::allocator<_Up>& __a) const noexcept
+ { return use_future_t<std::allocator<_Up>>(__a); }
+
+ allocator_type get_allocator() const noexcept { return {}; }
+
+ template<typename _Func>
+ auto
+ operator()(_Func&& __f) const
+ {
+ using _Token = __use_future_ct<decay_t<_Func>, allocator_type>;
+ return _Token{std::forward<_Func>(__f)};
+ }
+ };
+
constexpr use_future_t<> use_future = use_future_t<>();
template<typename _Func, typename _Alloc, typename _Res, typename... _Args>
@@ -1552,6 +1587,12 @@ inline namespace v1
_M_promise{ std::get<1>(__token._M_t) }
{ }
+ template<typename _Tp>
+ explicit
+ __use_future_ch(__use_future_ct<_Func, std::allocator<_Tp>>&& __token)
+ : _M_f{ std::move(__token._M_f) }
+ { }
+
void
operator()(_Args&&... __args)
{
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