[libc] Factor specifics of packet type out of process

NFC. Simplifies process slightly, gives more options for testing it.

Reviewed By: jhuber6

Differential Revision: https://reviews.llvm.org/D153604

Author: JonChesterfield

libc/src/__support/RPC/rpc.h

@@ -74,7 +74,7 @@ constexpr uint64_t DEFAULT_PORT_COUNT = 64;
 ///   - The client will always start with a 'send' operation.
 ///   - The server will always start with a 'recv' operation.
 ///   - Every 'send' or 'recv' call is mirrored by the other process.
-template <bool Invert, uint32_t lane_size> struct Process {
+template <bool Invert, typename Packet> struct Process {
   LIBC_INLINE Process() = default;
   LIBC_INLINE Process(const Process &) = delete;
   LIBC_INLINE Process &operator=(const Process &) = delete;
@@ -85,7 +85,7 @@ template <bool Invert, uint32_t lane_size> struct Process {
   uint64_t port_count;
   cpp::Atomic<uint32_t> *inbox;
   cpp::Atomic<uint32_t> *outbox;
-  Packet<lane_size> *packet;
+  Packet *packet;
 
   cpp::Atomic<uint32_t> lock[DEFAULT_PORT_COUNT] = {0};
 
@@ -96,8 +96,8 @@ template <bool Invert, uint32_t lane_size> struct Process {
         advance(buffer, inbox_offset(port_count)));
     this->outbox = reinterpret_cast<cpp::Atomic<uint32_t> *>(
         advance(buffer, outbox_offset(port_count)));
-    this->packet = reinterpret_cast<Packet<lane_size> *>(
-        advance(buffer, buffer_offset(port_count)));
+    this->packet =
+        reinterpret_cast<Packet *>(advance(buffer, buffer_offset(port_count)));
   }
 
   /// Returns the beginning of the unified buffer. Intended for initializing the
@@ -221,38 +221,14 @@ template <bool Invert, uint32_t lane_size> struct Process {
     gpu::sync_lane(lane_mask);
   }
 
-  /// Invokes a function accross every active buffer across the total lane size.
-  LIBC_INLINE void invoke_rpc(cpp::function<void(Buffer *)> fn,
-                              Packet<lane_size> &packet) {
-    if constexpr (is_process_gpu()) {
-      fn(&packet.payload.slot[gpu::get_lane_id()]);
-    } else {
-      for (uint32_t i = 0; i < lane_size; i += gpu::get_lane_size())
-        if (packet.header.mask & 1ul << i)
-          fn(&packet.payload.slot[i]);
-    }
-  }
-
-  /// Alternate version that also provides the index of the current lane.
-  LIBC_INLINE void invoke_rpc(cpp::function<void(Buffer *, uint32_t)> fn,
-                              Packet<lane_size> &packet) {
-    if constexpr (is_process_gpu()) {
-      fn(&packet.payload.slot[gpu::get_lane_id()], gpu::get_lane_id());
-    } else {
-      for (uint32_t i = 0; i < lane_size; i += gpu::get_lane_size())
-        if (packet.header.mask & 1ul << i)
-          fn(&packet.payload.slot[i], i);
-    }
-  }
-
   /// Number of bytes to allocate for an inbox or outbox.
   LIBC_INLINE static constexpr uint64_t mailbox_bytes(uint64_t port_count) {
     return port_count * sizeof(cpp::Atomic<uint32_t>);
   }
 
   /// Number of bytes to allocate for the buffer containing the packets.
   LIBC_INLINE static constexpr uint64_t buffer_bytes(uint64_t port_count) {
-    return port_count * sizeof(Packet<lane_size>);
+    return port_count * sizeof(Packet);
   }
 
   /// Offset of the inbox in memory. This is the same as the outbox if inverted.
@@ -267,14 +243,40 @@ template <bool Invert, uint32_t lane_size> struct Process {
 
   /// Offset of the buffer containing the packets after the inbox and outbox.
   LIBC_INLINE static constexpr uint64_t buffer_offset(uint64_t port_count) {
-    return align_up(2 * mailbox_bytes(port_count), alignof(Packet<lane_size>));
+    return align_up(2 * mailbox_bytes(port_count), alignof(Packet));
   }
 };
 
+/// Invokes a function accross every active buffer across the total lane size.
+template <uint32_t lane_size>
+static LIBC_INLINE void invoke_rpc(cpp::function<void(Buffer *)> fn,
+                                   Packet<lane_size> &packet) {
+  if constexpr (is_process_gpu()) {
+    fn(&packet.payload.slot[gpu::get_lane_id()]);
+  } else {
+    for (uint32_t i = 0; i < lane_size; i += gpu::get_lane_size())
+      if (packet.header.mask & 1ul << i)
+        fn(&packet.payload.slot[i]);
+  }
+}
+
+/// Alternate version that also provides the index of the current lane.
+template <uint32_t lane_size>
+static LIBC_INLINE void invoke_rpc(cpp::function<void(Buffer *, uint32_t)> fn,
+                                   Packet<lane_size> &packet) {
+  if constexpr (is_process_gpu()) {
+    fn(&packet.payload.slot[gpu::get_lane_id()], gpu::get_lane_id());
+  } else {
+    for (uint32_t i = 0; i < lane_size; i += gpu::get_lane_size())
+      if (packet.header.mask & 1ul << i)
+        fn(&packet.payload.slot[i], i);
+  }
+}
+
 /// The port provides the interface to communicate between the multiple
 /// processes. A port is conceptually an index into the memory provided by the
 /// underlying process that is guarded by a lock bit.
-template <bool T, uint32_t S> struct Port {
+template <bool T, typename S> struct Port {
   LIBC_INLINE Port(Process<T, S> &process, uint64_t lane_mask, uint64_t index,
                    uint32_t out)
       : process(process), lane_mask(lane_mask), index(index), out(out),
@@ -330,7 +332,7 @@ struct Client {
   LIBC_INLINE Client &operator=(const Client &) = delete;
   LIBC_INLINE ~Client() = default;
 
-  using Port = rpc::Port<false, gpu::LANE_SIZE>;
+  using Port = rpc::Port<false, Packet<gpu::LANE_SIZE>>;
   template <uint16_t opcode> LIBC_INLINE cpp::optional<Port> try_open();
   template <uint16_t opcode> LIBC_INLINE Port open();
 
@@ -339,7 +341,7 @@ struct Client {
   }
 
 private:
-  Process<false, gpu::LANE_SIZE> process;
+  Process<false, Packet<gpu::LANE_SIZE>> process;
 };
 
 /// The RPC server used to respond to the client.
@@ -349,7 +351,7 @@ template <uint32_t lane_size> struct Server {
   LIBC_INLINE Server &operator=(const Server &) = delete;
   LIBC_INLINE ~Server() = default;
 
-  using Port = rpc::Port<true, lane_size>;
+  using Port = rpc::Port<true, Packet<lane_size>>;
   LIBC_INLINE cpp::optional<Port> try_open();
   LIBC_INLINE Port open();
 
@@ -362,15 +364,15 @@ template <uint32_t lane_size> struct Server {
   }
 
   LIBC_INLINE static uint64_t allocation_size(uint64_t port_count) {
-    return Process<true, lane_size>::allocation_size(port_count);
+    return Process<true, Packet<lane_size>>::allocation_size(port_count);
   }
 
 private:
-  Process<true, lane_size> process;
+  Process<true, Packet<lane_size>> process;
 };
 
 /// Applies \p fill to the shared buffer and initiates a send operation.
-template <bool T, uint32_t S>
+template <bool T, typename S>
 template <typename F>
 LIBC_INLINE void Port<T, S>::send(F fill) {
   uint32_t in = owns_buffer ? out ^ T : process.load_inbox(index);
@@ -379,14 +381,14 @@ LIBC_INLINE void Port<T, S>::send(F fill) {
   process.wait_for_ownership(index, out, in);
 
   // Apply the \p fill function to initialize the buffer and release the memory.
-  process.invoke_rpc(fill, process.packet[index]);
+  invoke_rpc(fill, process.packet[index]);
   out = process.invert_outbox(index, out);
   owns_buffer = false;
   receive = false;
 }
 
 /// Applies \p use to the shared buffer and acknowledges the send.
-template <bool T, uint32_t S>
+template <bool T, typename S>
 template <typename U>
 LIBC_INLINE void Port<T, S>::recv(U use) {
   // We only exchange ownership of the buffer during a receive if we are waiting
@@ -402,13 +404,13 @@ LIBC_INLINE void Port<T, S>::recv(U use) {
   process.wait_for_ownership(index, out, in);
 
   // Apply the \p use function to read the memory out of the buffer.
-  process.invoke_rpc(use, process.packet[index]);
+  invoke_rpc(use, process.packet[index]);
   receive = true;
   owns_buffer = true;
 }
 
 /// Combines a send and receive into a single function.
-template <bool T, uint32_t S>
+template <bool T, typename S>
 template <typename F, typename U>
 LIBC_INLINE void Port<T, S>::send_and_recv(F fill, U use) {
   send(fill);
@@ -418,7 +420,7 @@ LIBC_INLINE void Port<T, S>::send_and_recv(F fill, U use) {
 /// Combines a receive and send operation into a single function. The \p work
 /// function modifies the buffer in-place and the send is only used to initiate
 /// the copy back.
-template <bool T, uint32_t S>
+template <bool T, typename S>
 template <typename W>
 LIBC_INLINE void Port<T, S>::recv_and_send(W work) {
   recv(work);
@@ -427,7 +429,7 @@ LIBC_INLINE void Port<T, S>::recv_and_send(W work) {
 
 /// Helper routine to simplify the interface when sending from the GPU using
 /// thread private pointers to the underlying value.
-template <bool T, uint32_t S>
+template <bool T, typename S>
 LIBC_INLINE void Port<T, S>::send_n(const void *src, uint64_t size) {
   static_assert(is_process_gpu(), "Only valid when running on the GPU");
   const void **src_ptr = &src;
@@ -437,7 +439,7 @@ LIBC_INLINE void Port<T, S>::send_n(const void *src, uint64_t size) {
 
 /// Sends an arbitrarily sized data buffer \p src across the shared channel in
 /// multiples of the packet length.
-template <bool T, uint32_t S>
+template <bool T, typename S>
 LIBC_INLINE void Port<T, S>::send_n(const void *const *src, uint64_t *size) {
   uint64_t num_sends = 0;
   send([&](Buffer *buffer, uint32_t id) {
@@ -467,7 +469,7 @@ LIBC_INLINE void Port<T, S>::send_n(const void *const *src, uint64_t *size) {
 /// Receives an arbitrarily sized data buffer across the shared channel in
 /// multiples of the packet length. The \p alloc function is called with the
 /// size of the data so that we can initialize the size of the \p dst buffer.
-template <bool T, uint32_t S>
+template <bool T, typename S>
 template <typename A>
 LIBC_INLINE void Port<T, S>::recv_n(void **dst, uint64_t *size, A &&alloc) {
   uint64_t num_recvs = 0;

libc/test/src/__support/RPC/rpc_smoke_test.cpp

@@ -13,8 +13,12 @@
 namespace {
 enum { lane_size = 8, port_count = 4 };
 
-using ProcAType = __llvm_libc::rpc::Process<false, lane_size>;
-using ProcBType = __llvm_libc::rpc::Process<true, lane_size>;
+struct Packet {
+  uint64_t unused;
+};
+
+using ProcAType = __llvm_libc::rpc::Process<false, Packet>;
+using ProcBType = __llvm_libc::rpc::Process<true, Packet>;
 
 static_assert(ProcAType::inbox_offset(port_count) ==
               ProcBType::outbox_offset(port_count));