From: Richard Sandiford <richard.sandiford@arm.com>
To: gcc-patches@gcc.gnu.org
Subject: [09/23] Add a cut-down version of std::span (array_slice)
Date: Fri, 13 Nov 2020 08:15:55 +0000 [thread overview]
Message-ID: <mpteekx8yf8.fsf@arm.com> (raw)
In-Reply-To: <mpth7ptad81.fsf@arm.com> (Richard Sandiford's message of "Fri, 13 Nov 2020 08:10:54 +0000")
A later patch wants to be able to pass around subarray views of an
existing array. The standard class to do that is std::span, but it's
a C++20 thing. This patch just adds a cut-down version of it.
The intention is just to provide what's currently needed.
gcc/
* vec.h (array_slice): New class.
---
gcc/vec.h | 120 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 120 insertions(+)
diff --git a/gcc/vec.h b/gcc/vec.h
index f02beddc975..7768de9f518 100644
--- a/gcc/vec.h
+++ b/gcc/vec.h
@@ -2128,6 +2128,126 @@ release_vec_vec (vec<vec<T> > &vec)
vec.release ();
}
+// Provide a subset of the std::span functionality. (We can't use std::span
+// itself because it's a C++20 feature.)
+//
+// In addition, provide an invalid value that is distinct from all valid
+// sequences (including the empty sequence). This can be used to return
+// failure without having to use std::optional.
+//
+// There is no operator bool because it would be ambiguous whether it is
+// testing for a valid value or an empty sequence.
+template<typename T>
+class array_slice
+{
+ template<typename OtherT> friend class array_slice;
+
+public:
+ using value_type = T;
+ using iterator = T *;
+ using const_iterator = const T *;
+
+ array_slice () : m_base (nullptr), m_size (0) {}
+
+ template<typename OtherT>
+ array_slice (array_slice<OtherT> other)
+ : m_base (other.m_base), m_size (other.m_size) {}
+
+ array_slice (iterator base, unsigned int size)
+ : m_base (base), m_size (size) {}
+
+ template<size_t N>
+ array_slice (T (&array)[N]) : m_base (array), m_size (N) {}
+
+ template<typename OtherT>
+ array_slice (const vec<OtherT> &v)
+ : m_base (v.address ()), m_size (v.length ()) {}
+
+ iterator begin () { return m_base; }
+ iterator end () { return m_base + m_size; }
+
+ const_iterator begin () const { return m_base; }
+ const_iterator end () const { return m_base + m_size; }
+
+ value_type &front ();
+ value_type &back ();
+ value_type &operator[] (unsigned int i);
+
+ const value_type &front () const;
+ const value_type &back () const;
+ const value_type &operator[] (unsigned int i) const;
+
+ size_t size () const { return m_size; }
+ size_t size_bytes () const { return m_size * sizeof (T); }
+ bool empty () const { return m_size == 0; }
+
+ // An invalid array_slice that represents a failed operation. This is
+ // distinct from an empty slice, which is a valid result in some contexts.
+ static array_slice invalid () { return { nullptr, ~0U }; }
+
+ // True if the array is valid, false if it is an array like INVALID.
+ bool is_valid () const { return m_base || m_size == 0; }
+
+private:
+ iterator m_base;
+ unsigned int m_size;
+};
+
+template<typename T>
+inline typename array_slice<T>::value_type &
+array_slice<T>::front ()
+{
+ gcc_checking_assert (m_size);
+ return m_base[0];
+}
+
+template<typename T>
+inline const typename array_slice<T>::value_type &
+array_slice<T>::front () const
+{
+ gcc_checking_assert (m_size);
+ return m_base[0];
+}
+
+template<typename T>
+inline typename array_slice<T>::value_type &
+array_slice<T>::back ()
+{
+ gcc_checking_assert (m_size);
+ return m_base[m_size - 1];
+}
+
+template<typename T>
+inline const typename array_slice<T>::value_type &
+array_slice<T>::back () const
+{
+ gcc_checking_assert (m_size);
+ return m_base[m_size - 1];
+}
+
+template<typename T>
+inline typename array_slice<T>::value_type &
+array_slice<T>::operator[] (unsigned int i)
+{
+ gcc_checking_assert (i < m_size);
+ return m_base[i];
+}
+
+template<typename T>
+inline const typename array_slice<T>::value_type &
+array_slice<T>::operator[] (unsigned int i) const
+{
+ gcc_checking_assert (i < m_size);
+ return m_base[i];
+}
+
+template<typename T>
+array_slice<T>
+make_array_slice (T *base, unsigned int size)
+{
+ return array_slice<T> (base, size);
+}
+
#if (GCC_VERSION >= 3000)
# pragma GCC poison m_vec m_vecpfx m_vecdata
#endif
--
2.17.1
next prev parent reply other threads:[~2020-11-13 8:15 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-13 8:10 [00/23] Make fwprop use an on-the-side RTL SSA representation Richard Sandiford
2020-11-13 8:11 ` [01/23] vec: Silence clang warning Richard Sandiford
2020-11-25 19:58 ` Jeff Law
2020-11-13 8:12 ` [02/23] rtlanal: Remove noop_move_p REG_EQUAL condition Richard Sandiford
2020-11-25 20:00 ` Jeff Law
2020-11-13 8:12 ` [03/23] reginfo: Add a global_reg_set Richard Sandiford
2020-11-25 20:01 ` Jeff Law
2020-11-13 8:13 ` [04/23] Move iterator_range to a new iterator-utils.h file Richard Sandiford
2020-11-25 20:02 ` Jeff Law
2020-11-13 8:13 ` [05/23] Add more iterator utilities Richard Sandiford
2020-11-25 20:12 ` Jeff Law
2020-11-13 8:14 ` [06/23] Add an RAII class for managing obstacks Richard Sandiford
2020-11-25 20:15 ` Jeff Law
2020-11-13 8:14 ` [07/23] Add a class that multiplexes two pointer types Richard Sandiford
2020-11-25 20:23 ` Jeff Law
2020-11-26 16:15 ` Richard Sandiford
2020-11-30 1:28 ` Jeff Law
2020-11-25 23:33 ` Martin Sebor
2020-11-26 17:06 ` Richard Sandiford
2020-11-27 18:12 ` Richard Sandiford
2020-11-28 0:17 ` Martin Sebor
2020-12-17 0:17 ` Richard Sandiford
2020-12-17 14:21 ` Tom Tromey
2020-12-17 15:38 ` Richard Sandiford
2020-12-17 15:44 ` Nathan Sidwell
2021-01-04 15:32 ` Jeff Law
2020-11-13 8:15 ` [08/23] Add an alternative splay tree implementation Richard Sandiford
2020-12-02 20:36 ` Jeff Law
2020-12-17 0:29 ` Richard Sandiford
2021-01-04 15:27 ` Jeff Law
2021-01-01 8:25 ` Andreas Schwab
2021-01-04 14:53 ` Richard Sandiford
2021-01-04 15:02 ` Andreas Schwab
2021-01-04 15:42 ` Richard Sandiford
2021-01-05 12:13 ` Richard Biener
2020-11-13 8:15 ` Richard Sandiford [this message]
2020-11-30 19:56 ` [09/23] Add a cut-down version of std::span (array_slice) Jeff Law
2022-08-03 15:13 ` Martin Jambor
2022-08-03 15:31 ` Richard Sandiford
2022-08-10 16:03 ` Martin Jambor
2022-08-11 6:58 ` Richard Biener
2022-08-16 7:59 ` Richard Sandiford
2020-11-13 8:16 ` [10/23] Tweak the way that is_a is implemented Richard Sandiford
2020-12-02 5:15 ` Jeff Law
2020-11-13 8:16 ` [11/23] Split update_cfg_for_uncondjump out of combine Richard Sandiford
2020-11-30 6:14 ` Jeff Law
2020-11-13 8:17 ` [12/23] Export print-rtl.c:print_insn_with_notes Richard Sandiford
2020-11-25 20:24 ` Jeff Law
2020-11-13 8:18 ` [13/23] recog: Split out a register_asm_p function Richard Sandiford
2020-11-25 20:24 ` Jeff Law
2020-11-13 8:18 ` [14/23] simplify-rtx: Put simplify routines into a class Richard Sandiford
2020-11-30 19:54 ` Jeff Law
2020-11-13 8:19 ` [15/23] recog: Add a validate_change_xveclen function Richard Sandiford
2020-11-30 20:03 ` Jeff Law
2020-11-13 8:19 ` [16/23] recog: Add a way of temporarily undoing changes Richard Sandiford
2020-11-25 20:27 ` Jeff Law
2020-12-17 0:22 ` Richard Sandiford
2020-11-13 8:20 ` [17/23] recog: Add a class for propagating into insns Richard Sandiford
2020-12-03 22:32 ` Jeff Law
2020-11-13 8:20 ` [18/23] recog: Add an RAII class for undoing insn changes Richard Sandiford
2020-11-25 20:27 ` Jeff Law
2020-11-13 8:20 ` [19/23] rtlanal: Add some new helper classes Richard Sandiford
2020-12-13 17:30 ` Jeff Law
2020-12-14 16:37 ` Richard Sandiford
2020-12-14 20:02 ` Jeff Law
2020-11-13 8:21 ` [20/23] rtlanal: Add simple_regno_set Richard Sandiford
2020-11-25 20:31 ` Jeff Law
2020-12-17 0:47 ` Richard Sandiford
2021-01-04 15:28 ` Jeff Law
2020-11-13 8:22 ` [21/23] doc: Add documentation for rtl-ssa Richard Sandiford
2020-11-30 6:26 ` Jeff Law
2020-11-13 8:23 ` [PATCH 22/23] Add rtl-ssa Richard Sandiford
2020-12-16 3:31 ` Jeff Law
2020-12-17 0:33 ` Richard Sandiford
2020-12-19 20:01 ` Jeff Law
2020-11-13 8:24 ` [PATCH 23/23] fwprop: Rewrite to use RTL SSA Richard Sandiford
2020-12-16 3:52 ` Jeff Law
2020-12-17 0:34 ` Richard Sandiford
2020-11-25 19:58 ` [00/23] Make fwprop use an on-the-side RTL SSA representation Jeff Law
2020-11-26 16:03 ` Richard Sandiford
2020-11-27 15:56 ` Michael Matz
2020-11-27 16:31 ` Richard Sandiford
2020-11-30 21:13 ` Jeff Law
2020-12-01 0:03 ` Michael Matz
2020-12-01 10:15 ` Richard Sandiford
2020-12-02 0:25 ` Jeff Law
2020-11-30 6:45 ` Jeff Law
2020-11-30 14:12 ` Richard Sandiford
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