[libc] Export GPU extensions to `libc` for external use

[jhuber6]

Summary

The GPU port of the LLVM C library needs to export a few extensions to
the interface such that users can interface with it. This patch adds the
necessary logic to define a GPU extension. Currently, this only exports
a rpc_reset_client function. This allows us to use the server in
D147054 to set up the RPC interface outside of libc.

Depends on https://reviews.llvm.org/D147054

[jhuber6]

@sivachandra This isn't exporting the function rpc_reset_client in the header. Where does that need to be added?

[sivachandra]

libc/config/gpu/entrypoints.txt

84

The CMake machinery will look for an entrypoint named reset but more importantly, libc-hdrgen will also look for a function named reset in a spec. Since you do not have a function with name reset, I would have expected libc-hdrgen to error out somewhere. To solve your problem, rename the entrypoint target to match the function name.

libc/src/gpu/CMakeLists.txt

2

We have to match the target name with the entrypoint name.

[jhuber6]

Change entrypoint to rpc_reset. Still doesn't seem to be appearing in the output function lists.

[jhuber6]

Exports the function now. Trying ot get it to provide the Opcodes with the enum handling, but it's not showing up.

[sivachandra]

In D152283#4401585, @jhuber6 wrote:

Exports the function now. Trying ot get it to provide the Opcodes with the enum handling, but it's not showing up.

I suppose you want to add something like:

enum rpc_opcode {
  ...
};

If yes, you will have to add a type header like any of these: https://github.com/llvm/llvm-project/tree/main/libc/include/llvm-libc-types

[sivachandra]

libc/spec/gpu_ext.td

19

This is good if you want to add type less enumerations. You will also have to add the list in api.td like this: https://github.com/llvm/llvm-project/blob/main/libc/config/linux/api.td#L149.

[jhuber6]

Add enumerations for the opcodes and switch over to using the generated header / types file.

[sivachandra]

OK for the file structuring.

libc/include/llvm-libc-types/rpc_opcodes_t.h

12 ↗

(On Diff #529264)

This would be C++ - is that OK?

[jhuber6]

libc/include/llvm-libc-types/rpc_opcodes_t.h

12 ↗

(On Diff #529264)

I thought that this was legal C, https://godbolt.org/z/aonTa87Me.

[sivachandra]

libc/include/llvm-libc-types/rpc_opcodes_t.h

12 ↗

(On Diff #529264)

I thought that this was legal C, https://godbolt.org/z/aonTa87Me.

Using gcc and passing -std=c99 -pedantic shows you this warning:

warning: ISO C does not support specifying 'enum' underlying types before C2X [-Wpedantic]x86-64 gcc (trunk) #1

So, may be OK because it does go through fine with c23. But, we want LLVM's libc to be C11 compliant. Up to you for the GPU side though.

[jhuber6]

libc/include/llvm-libc-types/rpc_opcodes_t.h

12 ↗

(On Diff #529264)

I see, well the size is relevant so we could probably do one of those OPCODE_LAST = 0xFFFF things instead.

libc/config/gpu/api.td

 include "config/public_api.td"
 
 include "spec/stdc.td"
+include "spec/gpu_ext.td"
 
 def StringAPI : PublicAPI<"string.h"> {
   let Types = ["size_t"];
 }
 
 def StdlibAPI : PublicAPI<"stdlib.h"> {
   let Types = [
     "size_t",

libc/config/gpu/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.errno.errno
 
     # stdio.h entrypoints
     libc.src.stdio.puts
     libc.src.stdio.fputs
     libc.src.stdio.stdin
     libc.src.stdio.stdout
     libc.src.stdio.stderr
+
+    # gpu/rpc.h entrypoints
+    libc.src.gpu.reset
 )
 
 set(TARGET_LLVMLIBC_ENTRYPOINTS
   ${TARGET_LIBC_ENTRYPOINTS}
 )
 

libc/config/gpu/headers.txt

 set(TARGET_PUBLIC_HEADERS
     libc.include.ctype
     libc.include.string
     libc.include.fenv
     libc.include.errno
     libc.include.stdlib
     libc.include.stdio
+
+    # Header for RPC extensions
+    libc.include.gpu_rpc
 )

libc/include/CMakeLists.txt

add_gen_header(
   DEPENDS
     .llvm_libc_common_h
     .llvm-libc-macros.wchar_macros
     .llvm-libc-types.size_t
     .llvm-libc-types.wint_t
     .llvm-libc-types.wchar_t
 )
 
+if(LIBC_TARGET_ARCHITECTURE_IS_GPU)
+file(MAKE_DIRECTORY "gpu")
+
+add_gen_header(
+  gpu_rpc
+  DEF_FILE gpu/rpc.h.def
+  GEN_HDR gpu/rpc.h
+  DEPENDS
+    .llvm_libc_common_h
+)
+endif()
+
 if(NOT LLVM_LIBC_FULL_BUILD)
   # We don't install headers in non-fullbuild mode.
   return()
 endif()
 
 function(get_all_install_header_targets out_var)
   set(all_deps ${ARGN})
   foreach(target IN LISTS ARGN)

libc/include/gpu/rpc.h.def

+//===-- GPO header rpc.h --------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_GPU_RPC_H
+#define LLVM_LIBC_GPU_RPC_H
+
+#include <__llvm-libc-common.h>
+
+%%public_api()
+
+#endif // LLVM_LIBC_GPU_RPC_H

libc/spec/gpu_ext.td

+def GPUExtensions : StandardSpec<"GPUExtensions"> {
+  HeaderSpec RPC = HeaderSpec<
+    "gpu/rpc.h",
+    [], // Macros
+    [], // Types
+    [], // Enumerations
+    [
+        FunctionSpec<
+            "rpc_reset_client",
+            RetValSpec<VoidType>,
+            [ArgSpec<UnsignedIntType>, ArgSpec<VoidPtr>]
+        >,
+    ]
+  >;
+  let Headers = [
+    RPC,
+  ];
+}

libc/src/CMakeLists.txt

if(${LIBC_TARGET_OS} STREQUAL "linux")
   add_subdirectory(fcntl)
   add_subdirectory(pthread)
   add_subdirectory(sched)
   add_subdirectory(sys)
   add_subdirectory(termios)
   add_subdirectory(unistd)
 endif()
 
+if(${LIBC_TARGET_OS} STREQUAL "gpu")
+  add_subdirectory(gpu)
+endif()
+
 if(NOT LLVM_LIBC_FULL_BUILD)
   return()
 endif()
 
 add_subdirectory(assert)
 add_subdirectory(network)
 add_subdirectory(setjmp)
 add_subdirectory(signal)
 add_subdirectory(spawn)
 add_subdirectory(threads)
 add_subdirectory(time)

libc/src/gpu/CMakeLists.txt

+add_entrypoint_object(
+  reset
+  SRCS
+    reset.cpp
+  HDRS
+    reset.h
+  DEPENDS
+    libc.src.__support.RPC.rpc_client
+    libc.src.__support.GPU.utils
+)

libc/src/gpu/reset.h

+//===-- Implementation header for RPC functions -----------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_GPU_RPC_H
+#define LLVM_LIBC_SRC_GPU_RPC_H
+
+namespace __llvm_libc {
+
+void rpc_reset_client(unsigned int num_ports, void *buffer);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_GPU_RPC_H

libc/src/gpu/reset.cpp

+//===---------- GPU implementation of the external RPC functionion --------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/gpu/reset.h"
+
+#include "src/__support/GPU/utils.h"
+#include "src/__support/RPC/rpc_client.h"
+#include "src/__support/common.h"
+
+namespace __llvm_libc {
+
+// This is the external interface to initialize the RPC client with the
+// shared buffer.
+LLVM_LIBC_FUNCTION(void, rpc_reset_client,
+                   (unsigned int num_ports, void *rpc_shared_buffer)) {
+  __llvm_libc::rpc::client.reset(num_ports, __llvm_libc::gpu::get_lane_size(),
+                                 rpc_shared_buffer);
+}
+
+} // namespace __llvm_libc