[SYCL][DOC] Move supported extension docs (#5421)

Move the supported extensions to the "sycl/doc/extensions/supported"
directory, and add a README explaining the content of that directory.
Each extension document has also been renamed to match the name of
its feature-test macro.

Links to these extensions have been removed from the table in
"sycl/doc/extensions/README.md" because we want to avoid the
possibility of that table getting out-of-date with the directory
contents. Instead, users can see the list of supported extensions
by listing the content of the directory.

Author: gmlueck

sycl/ReleaseNotes.md

@@ -29,7 +29,7 @@ Release notes for commit range 4fc5ebe..bd68232
  - Added [documentation](doc/SYCLInstrumentationUsingXPTI.md) of XPTI related
    tracing in SYCL [1308fe7b]
  - Align `SYCL_EXT_ONEAPI_LOCAL_MEMORY` extension
-   [document](doc/extensions/LocalMemory/LocalMemory.asciidoc) with SYCL 2020
+   [document](doc/extensions/supported/SYCL_EXT_ONEAPI_LOCAL_MEMORY.asciidoc) with SYCL 2020
    specification [6ed6565]
 
 ## Improvements
@@ -94,7 +94,7 @@ Release notes for commit range 4fc5ebe..bd68232
  - Optimized Cuda plugin work with small kernels [07189af0]
  - Optimized submission of kernels [441dc3b2][33432df6]
  - Aligned implementation of `SYCL_EXT_ONEAPI_LOCAL_MEMORY` extension
-   [document](doc/extensions/LocalMemory/LocalMemory.asciidoc) with updated
+   [document](doc/extensions/supported/SYCL_EXT_ONEAPI_LOCAL_MEMORY.asciidoc) with updated
    document [b3db5e5]
  - Improved `sycl::accessor` initialization performance on device [a10199d]
  - Added support `sycl::get_kernel_ids` and cache for `sycl::kernel_id` objects
@@ -256,7 +256,7 @@ Release notes for commit range 6a49170027fb..962909fe9e78
  - Added support for AMD GPU devices [ec612228]
  - Implemented SYCL 2020 `sycl::is_device_copyable` type trait [44c1cbcd]
  - Implemented SYCL 2020 USM features [1df6873d]
- - Implemented support for Device UUID from [Intel's Extensions for Device Information](doc/extensions/IntelGPU/IntelGPUDeviceInfo.md) [25aee287]
+ - Implemented support for Device UUID from [Intel's Extensions for Device Information](doc/extensions/supported/SYCL_EXT_INTEL_DEVICE_INFO.md) [25aee287]
  - Implemented SYCL 2020 `sycl::atomic_fence` [dcd59547]
  - Implemented `intel::loop_count_max`, `intel::loop_count_max`,
    `intel::loop_count_avg` attributes that allow to specify number of loop
@@ -269,7 +269,7 @@ Release notes for commit range 6a49170027fb..962909fe9e78
  - Implemented SYCL 2020 interoperability API [e6733e4]
  - Added [group sorting algorithm](doc/extensions/GroupAlgorithms/SYCL_INTEL_group_sort.asciidoc)
    extension specification [edaee9b]
- - Added [initial draft](doc/extensions/LevelZeroBackend/LevelZeroBackend.md)
+ - Added [initial draft](doc/extensions/supported/SYCL_EXT_ONEAPI_BACKEND_LEVEL_ZERO.md)
    for querying of free device memory in LevelZero backend extension [fa428bf]
  - Added [InvokeSIMD](doc/extensions/InvokeSIMD/InvokeSIMD.asciidoc) and
    [Uniform](doc/extensions/Uniform/Uniform.asciidoc) extensions [72e1611]
@@ -355,7 +355,7 @@ Release notes for commit range 6a49170027fb..962909fe9e78
  - Deprecated `sycl::buffer::get_count()`, please use `sycl::buffer::size()`
    instead [baf2ed9d]
  - Implemented `sycl::group_barrier` free function [48363902]
- - Added support of [SYCL_INTEL_enqueue_barrier extension](doc/extensions/EnqueueBarrier/enqueue_barrier.asciidoc) for CUDA backend [2e978482]
+ - Added support of [SYCL_INTEL_enqueue_barrier extension](doc/extensions/supported/SYCL_EXT_ONEAPI_ENQUEUE_BARRIER.asciidoc) for CUDA backend [2e978482]
  - Deprecated `has_extension` method of `sycl::device` and `sycl::platform`
    classes, please use `has` method with aspects APIs instead [51c747da]
  - Deprecated `sycl::*_class` types, please use STL classes instead [51c747da]
@@ -389,7 +389,7 @@ Release notes for commit range 6a49170027fb..962909fe9e78
  - Updated data flow pipes extension to be based on SYCL 2020 [f22f2e0]
  - Updated [ESIMD documentation](doc/extensions/ExplicitSIMD/dpcpp-explicit-simd.md)
    reflecting recent API changes [1e0bd1ed]
- - Updated [devicelib](doc/extensions/C-CXX-StandardLibrary/C-CXX-StandardLibrary.rst)
+ - Updated [devicelib](doc/extensions/supported/C-CXX-StandardLibrary.rst)
    extension document with `scalnbn`, `abs` and `div` (and their variants) as
    supported [febfb5a]
  - Addressed renaming of TBB dll to `tbb12.dll` in the
@@ -512,9 +512,9 @@ Release notes for commit range 2ffafb95f887..6a49170027fb
  - Added an initial AOT implementation of the experimental matrix extension on
    the CPU device to target AMX hardware. Base features are supported [35db973]
  - Added support for
-   [SYCL_INTEL_local_memory extension](doc/extensions/LocalMemory/SYCL_INTEL_local_memory.asciidoc)
+   [SYCL_INTEL_local_memory extension](doc/extensions/supported/SYCL_EXT_ONEAPI_LOCAL_MEMORY.asciidoc)
    [5a66fcb] [9a734f6]
- - Documented [Level Zero backend](doc/extensions/LevelZeroBackend/LevelZeroBackend.md)
+ - Documented [Level Zero backend](doc/extensions/supported/SYCL_EXT_ONEAPI_BACKEND_LEVEL_ZERO.md)
    [8994e6d]
 
 ## Improvements
@@ -807,7 +807,7 @@ Release notes for commit range 5d7e0925..5eebd1e4bfce
    [c70b0477aa8a, cf0d0538d162]
  - Add online compilation API interface [70ac47d23264]
 ### Documentation
- - Proposal for [new device descriptors extension](doc/extensions/IntelGPU/IntelGPUDeviceInfo.md)
+ - Proposal for [new device descriptors extension](doc/extensions/supported/SYCL_EXT_INTEL_DEVICE_INFO.md)
    was added [1ad813ba133e]
  - Added [online compilation extension](doc/extensions/OnlineCompilation/OnlineCompilation.asciidoc)
    specification [e05a19c8d303]
@@ -1188,7 +1188,7 @@ Release notes for commit range 5976ff0..1fc0e4f
   - Added documentation for [`SPV_INTEL_usm_storage_classes`](doc/extensions/SPIRV/SPV_INTEL_usm_storage_classes.asciidoc)
     and [SYCL_INTEL_usm_address_spaces](doc/extensions/USMAddressSpaces/usm_address_spaces.asciidoc) [781fbfc]
   - Fixed SPIR-V format name spelling [6e9bf3b]
-  - Added extension [LocalMemory](doc/extensions/LocalMemory/SYCL_INTEL_local_memory.asciidoc) draft specification [4b5308a]
+  - Added extension [LocalMemory](doc/extensions/supported/SYCL_EXT_ONEAPI_LOCAL_MEMORY.asciidoc) draft specification [4b5308a]
   - Added extension [free functions queries](doc/extensions/FreeFunctionQueries/SYCL_INTEL_free_function_queries.asciidoc) draft specification [8953bfd]
   - Removed documentation for implicit attribute `buffer_location` [71a56e7]
 
@@ -1267,7 +1267,7 @@ Release notes for the commit range 75b3dc2..5976ff0
   - Implemented basic support for the [Explicit SIMD extension](doc/extensions/ExplicitSIMD/dpcpp-explicit-simd.md)
     for low-level GPU performance tuning [84bf234] [32bf607] [a lot of others]
   - Implemented support for the [SYCL_INTEL_usm_address_spaces extension](https://github.com/intel/llvm/pull/1840)
-  - Implemented support for the [Use Pinned Host Memory Property extension](doc/extensions/UsePinnedMemoryProperty/UsePinnedMemoryPropery.adoc) [e5ea144][aee2d6c][396759d]
+  - Implemented support for the [Use Pinned Host Memory Property extension](doc/extensions/supported/SYCL_EXT_ONEAPI_USE_PINNED_HOST_MEMORY_PROPERTY.asciidoc) [e5ea144][aee2d6c][396759d]
   - Implemented aspects feature from the SYCL 2020 provisional Specification
     [89804af]
 
@@ -1348,19 +1348,19 @@ Release notes for the commit range 75b3dc2..5976ff0
     query native handles of SYCL objects and to create SYCL objects by providing
     a native handle: platform, device, queue, program. The feature is described
     in the SYCL 2020 provisional specification [a51c333]
-  - Added support for `sycl::intel::atomic_ref` from [SYCL_INTEL_extended_atomics extension](doc/extensions/ExtendedAtomics/SYCL_INTEL_extended_atomics.asciidoc)
+  - Added support for `sycl::intel::atomic_ref` from [SYCL_INTEL_extended_atomics extension](doc/extensions/supported/SYCL_EXT_ONEAPI_EXTENDED_ATOMICS.asciidoc)
 
 ### Documentation
   - Added [SYCL_INTEL_accessor_properties](doc/extensions/accessor_properties/SYCL_INTEL_accessor_properties.asciidoc) extension specification [58fc414]
   - The documentation for the CUDA BE has been improved [928b815]
   - The [Queue Shortcuts extension](sycl/doc/extensions/QueueShortcuts/QueueShortcuts.adoc)
     document has been updated [defac3c2]
-  - Added [Use Pinned Host Memory Property extension](doc/extensions/UsePinnedMemoryProperty/UsePinnedMemoryPropery.adoc) specification [e5ea144]
-  - Updated the [SYCL_INTEL_extended_atomics extension](doc/extensions/ExtendedAtomics/SYCL_INTEL_extended_atomics.asciidoc)
+  - Added [Use Pinned Host Memory Property extension](doc/extensions/supported/SYCL_EXT_ONEAPI_USE_PINNED_HOST_MEMORY_PROPERTY.asciidoc) specification [e5ea144]
+  - Updated the [SYCL_INTEL_extended_atomics extension](doc/extensions/supported/SYCL_EXT_ONEAPI_EXTENDED_ATOMICS.asciidoc)
     to describe `sycl::intel::atomic_accessor` [4968e7c]
   - The [SYCL_INTEL_sub_group extension](doc/extensions/SubGroup/SYCL_INTEL_sub_group.asciidoc)
     document has been updated [067536e]
-  - Added [FPGA lsu extension](sycl/doc/extensions/IntelFPGA/FPGALsu.md)
+  - Added [FPGA lsu extension](sycl/doc/extensions/supported/SYCL_EXT_INTEL_FPGA_LSU.md)
     document [2c2b5f2]
 
 ## Bug fixes
@@ -1454,7 +1454,7 @@ Release notes for the commit range ba404be..24726df
   - Introduced the Level Zero plugin which enables SYCL working on top of Level0
     API. Interoperability is not supportet yet [d32da99]
   - Implemented [parallel_for simplification extension](doc/extensions/ParallelForSimpification) [13fe9fb]
-  - Implemented [SYCL_INTEL_enqueue_barrier extension](doc/extensions/EnqueueBarrier/enqueue_barrier.asciidoc) [da6bfd0]
+  - Implemented [SYCL_INTEL_enqueue_barrier extension](doc/extensions/supported/SYCL_EXT_ONEAPI_ENQUEUE_BARRIER.asciidoc) [da6bfd0]
   - Implemented [SYCL_INTEL_accessor_simplification extension](https://github.com/intel/llvm/pull/1498) [1f76efc]
   - Implemented OpenCL interoperability API following [SYCL Generalization proposal](https://github.com/KhronosGroup/SYCL-Shared/blob/master/proposals/sycl_generalization.md) [bae0639]
 
@@ -1681,7 +1681,7 @@ Release notes for the commit range ba404be..67d3d9e
     [reduction extension proposal](doc/extensions/Reduction/Reduction.md)
     [f695479]
   - Published [parallel_for simplification extension](doc/extensions/ParallelForSimpification/SYCL_INTEL_parallel_for_simplification.asciidoc) [856a777]
-  - Added memory scope to [ExtendedAtomics extension](doc/extensions/ExtendedAtomics/SYCL_INTEL_extended_atomics.asciidoc) [f8e11e0]
+  - Added memory scope to [ExtendedAtomics extension](doc/extensions/supported/SYCL_EXT_ONEAPI_EXTENDED_ATOMICS.asciidoc) [f8e11e0]
   - Published [math array extension](doc/extensions/MathArray/SYCL_INTEL_math_array.asciidoc) [36c5041]
   - Added more comments that describe Scheduler design [ad441a0]
   - Published [extension mechanism proposal](doc/extensions/ExtensionMechanism/SYCL_INTEL_extension_api.asciidoc) [cf65794]
@@ -1819,7 +1819,7 @@ Release notes for the commit range e8f1f29..ba404be
     [29d9cc2]
   - More details have been added about the `-fintelfpga` option in the
     [Compiler User Manual](doc/SYCLCompilerUserManual.md) [4b03ddb]
-  - Added [SYCL_INTEL_enqueue_barrier extension document](doc/extensions/EnqueueBarrier/enqueue_barrier.asciidoc)
+  - Added [SYCL_INTEL_enqueue_barrier extension document](doc/extensions/supported/SYCL_EXT_ONEAPI_ENQUEUE_BARRIER.asciidoc)
     [6cfd2cb]
   - Added [standard layout relaxation extension](doc/extensions/RelaxStdLayout/SYCL_INTEL_relax_standard_layout.asciidoc)
     [ce53521]
@@ -1983,7 +1983,7 @@ Release notes for commit e8f1f29
     [proposal](doc/extensions/OrderedQueue/OrderedQueue_v2.adoc) [9fa878f]
   - Added device code split options documentation to the
     [user's manual](doc/UsersManual.md) [1355aa6]
-  - Added documentation for [ExtendedAtomics extension](doc/extensions/ExtendedAtomics/SYCL_INTEL_extended_atomics.asciidoc) [4445462]
+  - Added documentation for [ExtendedAtomics extension](doc/extensions/supported/SYCL_EXT_ONEAPI_EXTENDED_ATOMICS.asciidoc) [4445462]
   - Removed old Ordered Queue proposal and make a note of deprecation [e8f1f29]
 
 ## Bug fixes
@@ -2095,7 +2095,7 @@ Release notes for commit 78d80a1cc628af76f09c53673ada906a3d2f0131
 
 ### Documentation
   - Added support for generation of SYCL documentation with Doxygen [de418d6]
-  - [Design document](doc/extensions/C-CXX-StandardLibrary/C-CXX-StandardLibrary.rst)
+  - [Design document](doc/extensions/supported/C-CXX-StandardLibrary.rst)
     which describes design of C/C++ standard library support has been added
 
 ## Bug fixes
@@ -2216,9 +2216,9 @@ Release notes for commit e0a62df4e20eaf4bdff5c7dd46cbde566fbaee90
     to use proper names of AOT related options [b3ee6a2]
   - Added [unnamed lambda extension](doc/extensions/UnnamedKernelLambda/SYCL_INTEL_unnamed_kernel_lambda.asciidoc)
     draft [47c4c71]
-  - Added [kernel restrict all extension](doc/extensions/KernelRestrictAll/SYCL_INTEL_kernel_restrict_all.asciidoc)
+  - Added [kernel restrict all extension](doc/extensions/supported/SYCL_EXT_INTEL_KERNEL_ARGS_RESTRICT.asciidoc)
     draft [47c4c71]
-  - Added initial draft of [data flow pipes extension](doc/extensions/DataFlowPipes/data_flow_pipes.asciidoc)
+  - Added initial draft of [data flow pipes extension](doc/extensions/supported/SYCL_EXT_INTEL_DATAFLOW_PIPES.asciidoc)
     proposal [ee2b482]
   - [USM doc](doc/extensions/USM/USM.adoc) was updated with new version of
     allocation functions [0c32410]
@@ -2508,8 +2508,8 @@ Release notes for commit d4efd2ae3a708fc995e61b7da9c7419dac900372
   See [SYCL ENV VARIABLES](doc/SYCLEnvironmentVariables.md) for information how
   to enable it. [c615566]
 - Added support for
-  [`cl::sycl::intel::fpga_reg`](doc/extensions/IntelFPGA/FPGAReg.md) and
-  [`cl::sycl::intel::fpga_selector`](doc/extensions/IntelFPGA/FPGASelector.md)
+  [`cl::sycl::intel::fpga_reg`](doc/extensions/supported/SYCL_EXT_INTEL_FPGA_REG.md) and
+  [`cl::sycl::intel::fpga_selector`](doc/extensions/supported/SYCL_EXT_INTEL_FPGA_DEVICE_SELECTOR.md)
   extensions. [e438d2b]
 
 ## Improvements

sycl/doc/CompileTimeProperties.md

@@ -148,7 +148,7 @@ kernel arguments.  For example, the [SYCL\_ONEAPI\_accessor\_properties][6]
 extension could be redesigned to use compile-time properties.  Such a redesign
 might look like:
 
-[6]: <https://github.com/intel/llvm/blob/sycl/sycl/doc/extensions/accessor_properties/SYCL_ONEAPI_accessor_properties.asciidoc>
+[6]: <extensions/supported/SYCL_EXT_ONEAPI_ACCESSOR_PROPERTIES.asciidoc>
 
 ```
 namespace sycl {

sycl/doc/EnvironmentVariables.md

@@ -20,7 +20,7 @@ compiler and runtime.
 | `SYCL_CACHE_THRESHOLD` | Positive integer | Cache eviction threshold in days (default value is 7 for 1 week). Set to 0 for disabling time-based cache eviction. |
 | `SYCL_CACHE_MIN_DEVICE_IMAGE_SIZE` | Positive integer | Minimum size of device code image in bytes which is reasonable to cache on disk because disk access operation may take more time than do JIT compilation for it. Default value is 0 to cache all images. |
 | `SYCL_CACHE_MAX_DEVICE_IMAGE_SIZE` | Positive integer | Maximum size of device image in bytes which is cached. Too big kernels may overload disk too fast. Default value is 1 GB. |
-| `SYCL_ENABLE_DEFAULT_CONTEXTS` | '1' or '0' | Enable ('1') or disable ('0') creation of default platform contexts in SYCL runtime. The default context for each platform contains all devices in the platform. Refer to [Platform Default Contexts](extensions/PlatformContext/PlatformContext.adoc) extension to learn more. Enabled by default on Linux and disabled on Windows. |
+| `SYCL_ENABLE_DEFAULT_CONTEXTS` | '1' or '0' | Enable ('1') or disable ('0') creation of default platform contexts in SYCL runtime. The default context for each platform contains all devices in the platform. Refer to [Platform Default Contexts](extensions/supported/SYCL_EXT_ONEAPI_DEFAULT_CONTEXT.asciidoc) extension to learn more. Enabled by default on Linux and disabled on Windows. |
 | `SYCL_USM_HOSTPTR_IMPORT` | Integer | Enable by specifying non-zero value. Buffers created with a host pointer will result in host data promotion to USM, improving data transfer performance. To use this feature, also set SYCL_HOST_UNIFIED_MEMORY=1. |
 
 `(*) Note: Any means this environment variable is effective when set to any non-null value.`

sycl/doc/GetStartedGuide.md

@@ -705,7 +705,7 @@ SYCL_BE=PI_CUDA ./simple-sycl-app-cuda.exe
 
 **NOTE**: DPC++/SYCL developers can specify SYCL device for execution using
 device selectors (e.g. `cl::sycl::cpu_selector`, `cl::sycl::gpu_selector`,
-[Intel FPGA selector(s)](extensions/IntelFPGA/FPGASelector.md)) as
+[Intel FPGA selector(s)](extensions/supported/SYCL_EXT_INTEL_FPGA_DEVICE_SELECTOR.md)) as
 explained in following section [Code the program for a specific
 GPU](#code-the-program-for-a-specific-gpu).
 

sycl/doc/MultiTileCardWithLevelZero.md

@@ -24,7 +24,7 @@ One is using environment variable SYCL_DEVICE_FILTER described in [EnvironmentVa
 $ SYCL_DEVICE_FILTER=level_zero sycl-ls
 [level_zero:0] GPU : Intel(R) Level-Zero 1.1 [1.1.19792]
 ```
-Another way is to use similar SYCL API described in [FilterSelector.md](https://github.com/intel/llvm/blob/sycl/sycl/doc/extensions/FilterSelector/FilterSelector.adoc)
+Another way is to use similar SYCL API described in [SYCL\_EXT\_ONEAPI\_FILTER\_SELECTOR](extensions/supported/SYCL_EXT_ONEAPI_FILTER_SELECTOR.asciidoc)
 E.g. `filter_selector("level_zero")` will only see Level-Zero operated devices.
 
 If there are multiple GPUs in a system then they will be seen as multiple different root-devices.

sycl/doc/extensions/C-CXX-StandardLibrary/DeviceLibExtensions.rst

@@ -48,7 +48,7 @@ Invoking `__devicelib_assert_read` after a kernel doesn't imply the kernel has
 assertion failed.
 
 See also: assert_extension_.
-.. _assert_extension: ../Assert/SYCL_ONEAPI_ASSERT.asciidoc)
+.. _assert_extension: ../supported/SYCL_EXT_ONEAPI_ASSERT.asciidoc)
 
 cl_intel_devicelib_math
 ==========================

sycl/doc/extensions/DiscardQueueEvents/SYCL_EXT_ONEAPI_DISCARD_QUEUE_EVENTS.asciidoc

@@ -168,7 +168,7 @@ enum class event_command_status : int {
 This non-normative section describes the conditions when the DPC++ implementation provides an optimization benefit* for the `discard_events` property.
 
  - The queue must be constructed with the `in_order` property.
- - A kernel submitted to the queue must not use the https://github.com/intel/llvm/blob/sycl/sycl/doc/extensions/Assert/SYCL_ONEAPI_ASSERT.asciidoc[fallback assert feature].
+ - A kernel submitted to the queue must not use the link:../supported/SYCL_EXT_ONEAPI_ASSERT.asciidoc[fallback assert feature].
  - A queue operation submitted to the queue must not use streams or buffer / image accessors. However, local accessors do not inhibit optimization.
  - Any queue operations using Level Zero backend temporarily work without optimization.
 

sycl/doc/extensions/ExplicitSIMD/README.md

@@ -81,7 +81,7 @@ program behavior if violated.
 
 ##### Features not supported with ESIMD extension:
 - Ahead-of-time compilation
-- The [C and C++ Standard libraries support](https://github.com/intel/llvm/blob/sycl/sycl/doc/extensions/C-CXX-StandardLibrary/C-CXX-StandardLibrary.rst)
+- The [C and C++ Standard libraries support](../supported/C-CXX-StandardLibrary.rst)
 - The [Device library extensions](https://github.com/intel/llvm/blob/sycl/sycl/doc/extensions/C-CXX-StandardLibrary/DeviceLibExtensions.rst)
 - Host device (in some cases)
 

sycl/doc/extensions/ExtendedAtomics/README.md

@@ -567,7 +567,7 @@ for (int i = 0; i < msize; i++)
 
 
 ### Memory scope
-The current experimental API uses `joint_` semantics to define the memory scope of the matrix. The long term solution is to use the proposed https://github.com/intel/llvm/blob/sycl/sycl/doc/extensions/LocalMemory/SYCL_INTEL_local_memory.asciidoc[`group_local_memory` extension] to allocate the matrix in local memory associated with a SYCL group as shown in the example below.
+The current experimental API uses `joint_` semantics to define the memory scope of the matrix. The long term solution is to use the proposed link:../supported/SYCL_EXT_ONEAPI_LOCAL_MEMORY.asciidoc[`group_local_memory` extension] to allocate the matrix in local memory associated with a SYCL group as shown in the example below.
 
 
 ```c++