CP023 Accessor aliases, revision 0.3

In order to reduce the verbosity of programming with SYCL accessors,
this proposal aims to reduce the number of template parameters
to just 2 from the current 5.
It achieves this by slightly revising how to treat read-only data
and adding alias templates based on the access target.

1. Main changes
    * Default accessor template parameters
    * Simplify access modes
    * Alias templates based on access target
    * Extend the handler class
2. Accessor alias templates
    * `constant_buffer_accessor
    * `host_accessor` as a new type
3. Treat `const T` the same as `access::mode::read`
    * Simplifies a lot of code
4. Define implicit conversions for equivalent types
5. Implicit conversions that add `const`
6. Added `property::discard`
7. Overload for `handler::require` that also takes `property::discard`
    * To ignore previous data
8. Default all accessor template parameters
    * Expect the data type
    * Default to an accessor to global buffer with read-write access
    * Assumes accessors can be a placeholder without template parameter
9. Good support for CTAD
    * Deduction tags as compile-time properties
    * Made all accessor constructors variadic templates
10. Discussed some considerations and alternatives
11. Examples of reduced verbosity

Author: ProGTX

README.md

@@ -63,5 +63,5 @@ from this registry in the future.
 | CP020 | [Interop Task](interop_task/interop_task.md) | SYCL 1.2.1 | 16 January 2019 | 16 January 2019 | _Available since CE 1.0.5_ |
 | CP021 | [Default-Constructed Buffers](default-constructed-buffers/default-constructed-buffers.md) | SYCL 1.2.1 | 27 August 2019 | 5 September 2019 | _Draft_ |
 | CP022 | [Host Task with Interop capabilities](host_task/host_task.md) | SYCL 1.2.1 | 16 January 2019 | 20 January 2020 | _Final Draft_ |
-| CP023 | [Accessor aliases](accessor-alias/index.md) | SYCL Next (after 1.2.1) | 22 September 2019 | 31 March 2020 | _Work in Progress_ |
+| CP023 | [Accessor aliases](accessor-alias/index.md) | SYCL Next (after 1.2.1) | 22 September 2019 | 6 April 2020 | _Work in Progress_ |
 | CP026 | [Generalized Error Handling For SYCL](error-handling/sycl-error-handling.md) | SYCL Next | 10 March 2020 | 10 March 2020 | _Under Review_ |

accessor-alias/index.md

@@ -4,13 +4,13 @@
 |-------------|--------|
 | Name | Accessor aliases |
 | Date of Creation | 22 September 2019 |
-| Revision | 0.2 |
-| Latest Update | 31 March 2020 |
+| Revision | 0.3 |
+| Latest Update | 6 April 2020 |
 | Target | SYCL Next (after 1.2.1) |
 | Current Status | _Work in Progress_ |
 | Reply-to | Peter Žužek <peter@codeplay.com> |
 | Original author | Peter Žužek <peter@codeplay.com> |
-| Contributors |  |
+| Contributors | Gordon Brown gordon@codeplay.com |
 
 ## Overview
 
@@ -19,4 +19,4 @@ in order to reduce accessor verbosity.
 
 ## Versions
 
-[Revision 0.2](sycl-2.2/index.md)
+[Revision 0.3](sycl-2.2/index.md)