[Offload] Implement the remaining initial Offload API (#122106)

Implement the complete initial version of the Offload API, to the extent
that is usable for simple offloading programs. Tested with a basic SYCL
program.

As far as possible, these are simple wrappers over existing
functionality in the plugins.

* Allocating and freeing memory (host, device, shared).
* Creating a program 
* Creating a queue (wrapper over asynchronous stream resource)
* Enqueuing memcpy operations
* Enqueuing kernel executions
* Waiting on (optional) output events from the enqueue operations
* Waiting on a queue to finish

Objects created with the API have reference counting semantics to handle
their lifetime. They are created with an initial reference count of 1,
which can be incremented and decremented with retain and release
functions. They are freed when their reference count reaches 0. Platform
and device objects are not reference counted, as they are expected to
persist as long as the library is in use, and it's not meaningful for
users to create or destroy them.

Tests have been added to `offload.unittests`, including device code for
testing program and kernel related functionality.

The API should still be considered unstable and it's very likely we will
need to change the existing entry points.

1 files changed, 5 insertions, 38 deletions

diff --git a/offload/liboffload/API/Platform.td b/offload/liboffload/API/Platform.td
index 03e70cf96ac9..97c2cc2d0570 100644
--- a/offload/liboffload/API/Platform.td
+++ b/offload/liboffload/API/Platform.td
@@ -9,44 +9,10 @@
 // This file contains Offload API definitions related to the Platform handle
 //
 //===----------------------------------------------------------------------===//
-def : Function {
-  let name = "olGetPlatform";
-  let desc = "Retrieves all available platforms";
-  let details = [
-    "Multiple calls to this function will return identical platforms handles, in the same order.",
-  ];
-  let params = [
-    Param<"uint32_t", "NumEntries",
-      "The number of platforms to be added to Platforms. NumEntries must be "
-      "greater than zero.",
-      PARAM_IN>,
-    RangedParam<"ol_platform_handle_t*", "Platforms", 
-      "Array of handle of platforms. If NumEntries is less than the number of "
-      "platforms available, then olGetPlatform shall only retrieve that "
-      "number of platforms.",
-      PARAM_OUT, Range<"0", "NumEntries">>
-  ];
-  let returns = [
-    Return<"OL_ERRC_INVALID_SIZE", [
-      "`NumEntries == 0`"
-    ]>
-  ];
-}
-
-def : Function {
-  let name = "olGetPlatformCount";
-  let desc = "Retrieves the number of available platforms";
-  let params = [
-    Param<"uint32_t*",
-      "NumPlatforms", "returns the total number of platforms available.",
-      PARAM_OUT>
-  ];
-  let returns = [];
-}
 
 def : Enum {
   let name = "ol_platform_info_t";
-  let desc = "Supported platform info";
+  let desc = "Supported platform info.";
   let is_typed = 1;
   let etors = [
     TaggedEtor<"NAME", "char[]", "The string denoting name of the platform. The size of the info needs to be dynamically queried.">,
@@ -58,17 +24,18 @@ def : Enum {
 
 def : Enum {
   let name = "ol_platform_backend_t";
-  let desc = "Identifies the native backend of the platform";
+  let desc = "Identifies the native backend of the platform.";
   let etors =[
     Etor<"UNKNOWN", "The backend is not recognized">,
     Etor<"CUDA", "The backend is CUDA">,
     Etor<"AMDGPU", "The backend is AMDGPU">,
+    Etor<"HOST", "The backend is the host">,
   ];
 }
 
 def : Function {
   let name = "olGetPlatformInfo";
-  let desc = "Queries the given property of the platform";
+  let desc = "Queries the given property of the platform.";
   let details = [
     "`olGetPlatformInfoSize` can be used to query the storage size "
     "required for the given query."
@@ -96,7 +63,7 @@ def : Function {
 
 def : Function {
   let name = "olGetPlatformInfoSize";
-  let desc = "Returns the storage size of the given platform query";
+  let desc = "Returns the storage size of the given platform query.";
   let details = [];
   let params = [
     Param<"ol_platform_handle_t", "Platform", "handle of the platform", PARAM_IN>,