From: Andrey Alekseenko <al42and@gmail.com>
Date: Fri, 12 Mar 2021 15:46:48 +0000 (+0000)
Subject: Add DeviceAccessor<T,read> ctor from const DeviceBuffer<T>
X-Git-Url: http://biod.pnpi.spb.ru/gitweb/?a=commitdiff_plain;h=84ac233e3d361c6b55f3f8c1e519c6b4ce9a3ba8;p=alexxy%2Fgromacs.git

Add DeviceAccessor<T,read> ctor from const DeviceBuffer<T>

A bit hacky, but better preserves the intent behind declaring
DeviceBuffer const.

Part of preparatory work for #3932.
---

diff --git a/src/gromacs/gpu_utils/devicebuffer_sycl.h b/src/gromacs/gpu_utils/devicebuffer_sycl.h
index ff83c6d27c..187b7cf931 100644
--- a/src/gromacs/gpu_utils/devicebuffer_sycl.h
+++ b/src/gromacs/gpu_utils/devicebuffer_sycl.h
@@ -150,6 +150,18 @@ public:
         gmx::internal::PlaceholderAccessor<T, mode>(getSyclBuffer(buffer))
     {
     }
+    //! Construct read-only Accessor from a const DeviceBuffer (must be initialized)
+    DeviceAccessor(const DeviceBuffer<T>& buffer) :
+        gmx::internal::PlaceholderAccessor<T, mode>(getSyclBuffer(const_cast<DeviceBuffer<T>&>(buffer)))
+    {
+        /* There were some discussions about making it possible to create read-only sycl::accessor
+         * from a const sycl::buffer (https://github.com/KhronosGroup/SYCL-Docs/issues/10), but
+         * it did not make it into the SYCL2020 standard. So, we have to use const_cast above */
+        /* Using static_assert to ensure that only mode::read accessors can be created from a
+         * const DeviceBuffer. static_assert provides better error messages than std::enable_if. */
+        static_assert(mode == cl::sycl::access::mode::read,
+                      "Can not create non-read-only accessor from a const DeviceBuffer");
+    }
 
 private:
     //! Helper function to get sycl:buffer object from DeviceBuffer wrapper, with a sanity check.