[libc] Implement fseek, fflush, and ftell on the GPU (#67160)

Summary: This patch adds the necessary entrypoints to handle the `fseek`, `fflush`, and `ftell` functions. These are all very straightfoward, we simply make RPC calls to the associated function on the other end. Implementing it this way allows us to more or less borrow the state of the stream from the server as we intentionally maintain no internal state on the GPU device. However, this does not implement the `errno` functinality so that must be ignored.
llvm · Sep 26, 2023 · 7ac8e26 · 7ac8e26
1 parent 0b3f9d8
commit 7ac8e26
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Showing 13 changed files with 186 additions and 39 deletions.
diff --git a/libc/config/gpu/entrypoints.txt b/libc/config/gpu/entrypoints.txt
@@ -88,6 +88,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     # stdio.h entrypoints
     libc.src.stdio.feof
     libc.src.stdio.ferror
+    libc.src.stdio.fseek
+    libc.src.stdio.fflush
+    libc.src.stdio.ftell
     libc.src.stdio.clearerr
     libc.src.stdio.puts
     libc.src.stdio.fopen

diff --git a/libc/docs/gpu/support.rst b/libc/docs/gpu/support.rst
@@ -129,6 +129,9 @@ Function Name  Available  RPC Required
 feof           |check|    |check|
 ferror         |check|    |check|
 clearerr       |check|    |check|
+fseek          |check|    |check|
+ftell          |check|    |check|
+fflush         |check|    |check|
 fgetc          |check|    |check|
 fgets          |check|    |check|
 getc           |check|    |check|

diff --git a/libc/include/llvm-libc-types/rpc_opcodes_t.h b/libc/include/llvm-libc-types/rpc_opcodes_t.h
@@ -26,6 +26,9 @@ typedef enum : unsigned short {
   RPC_FEOF = 13,
   RPC_FERROR = 14,
   RPC_CLEARERR = 15,
+  RPC_FSEEK = 16,
+  RPC_FTELL = 17,
+  RPC_FFLUSH = 18,
 } rpc_opcode_t;
 
 #endif // __LLVM_LIBC_TYPES_RPC_OPCODE_H__
diff --git a/libc/src/stdio/CMakeLists.txt b/libc/src/stdio/CMakeLists.txt
@@ -26,19 +26,6 @@ if(NOT LIBC_TARGET_ARCHITECTURE_IS_GPU)
   add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/generic)
 endif()
 
-add_entrypoint_object(
-  fflush
-  SRCS
-    fflush.cpp
-  HDRS
-    fflush.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
 add_entrypoint_object(
   flockfile
   SRCS
@@ -63,19 +50,6 @@ add_entrypoint_object(
     libc.src.__support.File.platform_file
 )
 
-add_entrypoint_object(
-  fseek
-  SRCS
-    fseek.cpp
-  HDRS
-    fseek.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
 add_entrypoint_object(
   ungetc
   SRCS
@@ -302,19 +276,6 @@ add_entrypoint_object(
 add_subdirectory(printf_core)
 add_subdirectory(scanf_core)
 
-add_entrypoint_object(
-  ftell
-  SRCS
-    ftell.cpp
-  HDRS
-    ftell.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
 add_entrypoint_object(
   remove
   ALIAS
@@ -327,6 +288,9 @@ add_stdio_entrypoint_object(feof)
 add_stdio_entrypoint_object(feof_unlocked)
 add_stdio_entrypoint_object(ferror)
 add_stdio_entrypoint_object(ferror_unlocked)
+add_stdio_entrypoint_object(fseek)
+add_stdio_entrypoint_object(ftell)
+add_stdio_entrypoint_object(fflush)
 add_stdio_entrypoint_object(clearerr)
 add_stdio_entrypoint_object(clearerr_unlocked)
 add_stdio_entrypoint_object(fopen)

diff --git a/libc/src/stdio/generic/CMakeLists.txt b/libc/src/stdio/generic/CMakeLists.txt
@@ -70,6 +70,45 @@ add_entrypoint_object(
     libc.src.__support.File.platform_file
 )
 
+add_entrypoint_object(
+  fflush
+  SRCS
+    fflush.cpp
+  HDRS
+    ../fflush.h
+  DEPENDS
+    libc.src.errno.errno
+    libc.include.stdio
+    libc.src.__support.File.file
+    libc.src.__support.File.platform_file
+)
+
+add_entrypoint_object(
+  fseek
+  SRCS
+    fseek.cpp
+  HDRS
+    ../fseek.h
+  DEPENDS
+    libc.src.errno.errno
+    libc.include.stdio
+    libc.src.__support.File.file
+    libc.src.__support.File.platform_file
+)
+
+add_entrypoint_object(
+  ftell
+  SRCS
+    ftell.cpp
+  HDRS
+    ftell.h
+  DEPENDS
+    libc.src.errno.errno
+    libc.include.stdio
+    libc.src.__support.File.file
+    libc.src.__support.File.platform_file
+)
+
 add_entrypoint_object(
   fopen
   SRCS

diff --git a/libc/src/stdio/fflush.cpp → libc/src/stdio/generic/fflush.cpp b/libc/src/stdio/fflush.cpp → libc/src/stdio/generic/fflush.cpp
diff --git a/libc/src/stdio/fseek.cpp → libc/src/stdio/generic/fseek.cpp b/libc/src/stdio/fseek.cpp → libc/src/stdio/generic/fseek.cpp
diff --git a/libc/src/stdio/ftell.cpp → libc/src/stdio/generic/ftell.cpp b/libc/src/stdio/ftell.cpp → libc/src/stdio/generic/ftell.cpp
diff --git a/libc/src/stdio/gpu/CMakeLists.txt b/libc/src/stdio/gpu/CMakeLists.txt
@@ -32,6 +32,39 @@ add_entrypoint_object(
     libc.src.__support.RPC.rpc_client
 )
 
+add_entrypoint_object(
+  fseek
+  SRCS
+    fseek.cpp
+  HDRS
+    ../fseek.h
+  DEPENDS
+    libc.include.stdio
+    .gpu_file
+)
+
+add_entrypoint_object(
+  ftell
+  SRCS
+    ftell.cpp
+  HDRS
+    ../ftell.h
+  DEPENDS
+    libc.include.stdio
+    .gpu_file
+)
+
+add_entrypoint_object(
+  fflush
+  SRCS
+    fflush.cpp
+  HDRS
+    ../fflush.h
+  DEPENDS
+    libc.include.stdio
+    .gpu_file
+)
+
 add_entrypoint_object(
   clearerr
   SRCS

diff --git a/libc/src/stdio/gpu/fflush.cpp b/libc/src/stdio/gpu/fflush.cpp
@@ -0,0 +1,26 @@
+//===-- Implementation of fflush ------------------------------------------===//
+//
+// 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/stdio/fflush.h"
+#include "file.h"
+
+#include <stdio.h>
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(int, fflush, (::FILE * stream)) {
+  int ret;
+  rpc::Client::Port port = rpc::client.open<RPC_FFLUSH>();
+  port.send_and_recv(
+      [=](rpc::Buffer *buffer) { buffer->data[0] = file::from_stream(stream); },
+      [&](rpc::Buffer *buffer) { ret = static_cast<int>(buffer->data[0]); });
+  port.close();
+  return ret;
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdio/gpu/fseek.cpp b/libc/src/stdio/gpu/fseek.cpp
@@ -0,0 +1,30 @@
+//===-- GPU implementation of fseek ---------------------------------------===//
+//
+// 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/stdio/fseek.h"
+#include "file.h"
+
+#include <stdio.h>
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(int, fseek, (::FILE * stream, long offset, int whence)) {
+  int ret;
+  rpc::Client::Port port = rpc::client.open<RPC_FSEEK>();
+  port.send_and_recv(
+      [=](rpc::Buffer *buffer) {
+        buffer->data[0] = file::from_stream(stream);
+        buffer->data[1] = static_cast<uint64_t>(offset);
+        buffer->data[2] = static_cast<uint64_t>(whence);
+      },
+      [&](rpc::Buffer *buffer) { ret = static_cast<int>(buffer->data[0]); });
+  port.close();
+  return ret;
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdio/gpu/ftell.cpp b/libc/src/stdio/gpu/ftell.cpp
@@ -0,0 +1,26 @@
+//===-- GPU implementation of ftell ---------------------------------------===//
+//
+// 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/stdio/ftell.h"
+#include "file.h"
+
+#include <stdio.h>
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(long, ftell, (::FILE * stream)) {
+  long ret;
+  rpc::Client::Port port = rpc::client.open<RPC_FSEEK>();
+  port.send_and_recv(
+      [=](rpc::Buffer *buffer) { buffer->data[0] = file::from_stream(stream); },
+      [&](rpc::Buffer *buffer) { ret = static_cast<long>(buffer->data[0]); });
+  port.close();
+  return ret;
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/utils/gpu/server/rpc_server.cpp b/libc/utils/gpu/server/rpc_server.cpp
@@ -164,6 +164,26 @@ struct Server {
       });
       break;
     }
+    case RPC_FSEEK: {
+      port->recv_and_send([](rpc::Buffer *buffer) {
+        buffer->data[0] = fseek(file::to_stream(buffer->data[0]),
+                                static_cast<long>(buffer->data[1]),
+                                static_cast<int>(buffer->data[2]));
+      });
+      break;
+    }
+    case RPC_FTELL: {
+      port->recv_and_send([](rpc::Buffer *buffer) {
+        buffer->data[0] = ftell(file::to_stream(buffer->data[0]));
+      });
+      break;
+    }
+    case RPC_FFLUSH: {
+      port->recv_and_send([](rpc::Buffer *buffer) {
+        buffer->data[0] = fflush(file::to_stream(buffer->data[0]));
+      });
+      break;
+    }
     case RPC_NOOP: {
       port->recv([](rpc::Buffer *) {});
       break;