[llvm] [Offload] Introduce offload-tblgen and initial new API implementation (PR #108413)

[Callum Fare via llvm-commits]

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+def : Macro {
+  let name = "OFFLOAD_APICALL";
+  let desc = "Calling convention for all API functions";
+  let condition = "defined(_WIN32)";
+  let value = "__cdecl";
+  let alt_value = "";
+}
+
+def : Macro {
+  let name = "OFFLOAD_APIEXPORT";
+  let desc = "Microsoft-specific dllexport storage-class attribute";
+  let condition = "defined(_WIN32)";
+  let value = "__declspec(dllexport)";
+  let alt_value = "";
+}
+
+def : Macro {
+  let name = "OFFLOAD_DLLEXPORT";
+  let desc = "Microsoft-specific dllexport storage-class attribute";
+  let condition = "defined(_WIN32)";
+  let value = "__declspec(dllexport)";
+}
+
+def : Macro {
+  let name = "OFFLOAD_DLLEXPORT";
+  let desc = "GCC-specific dllexport storage-class attribute";
+  let condition = "__GNUC__ >= 4";
+  let value = "__attribute__ ((visibility (\"default\")))";
+  let alt_value = "";
+}
+
+def : Typedef {
+  let name = "offload_bool_t";
+  let value = "uint8_t";
+  let desc = "compiler-independent type";
+}
+
+def : Handle {
+  let name = "offload_platform_handle_t";
+  let desc = "Handle of a platform instance";
+}
+
+def : Handle {
+  let name = "offload_device_handle_t";
+  let desc = "Handle of platform's device object";
+}
+
+def : Handle {
+  let name = "offload_context_handle_t";
+  let desc = "Handle of context object";
+}
+
+def : Enum {
+  let name = "offload_result_t";
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callumfare wrote:

Ah ok, yeah that makes more sense, thanks!

Would the table contain one or more errors for the last API call or is the idea that the table can be queried for any previous API call that returned an error? If it's the latter then I'm still a bit unsure about how that would work in terms of lifetime; seems like they would just pile up indefinitely since you can never safely clear them. Maybe that's not a big deal in practice but it makes me a bit worried about long-running programs. That's why we made the equivalent in UR thread-local and mandated checking the error message before making another API call on the same thread, since the implementation can safely clear the existing message(s) when setting a new one.



https://github.com/llvm/llvm-project/pull/108413