[libc] Implement stdio writing functions for the GPU port (#65809)

Summary:
This patch implements fwrite, putc, putchar, and fputc on the GPU. These
are very straightforward, the main difference for the GPU implementation
is that we are currently ignoring `errno`. This patch also introduces a
minimal smoke test for `putc` that is an exact copy of the `puts` test
except we print the string char by char. This also modifies the `fopen`
test to use `fwrite` to mirror its use of `fread` so that it is tested
as well.

Author: jhuber6

libc/config/gpu/entrypoints.txt

@@ -88,6 +88,10 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdio.fclose
     libc.src.stdio.fread
     libc.src.stdio.fputs
+    libc.src.stdio.fwrite
+    libc.src.stdio.fputc
+    libc.src.stdio.putc
+    libc.src.stdio.putchar
     libc.src.stdio.stdin
     libc.src.stdio.stdout
     libc.src.stdio.stderr

libc/docs/gpu/support.rst

@@ -118,20 +118,24 @@ strtoumax      |check|
 =============  =========  ============
 
 stdio.h
---------
+-------
 
 =============  =========  ============
 Function Name  Available  RPC Required
 =============  =========  ============
 puts           |check|    |check|
 fputs          |check|    |check|
+fputc          |check|    |check|
+fwrite         |check|    |check|
+putc           |check|    |check|
+putchar        |check|    |check|
 fclose         |check|    |check|
 fopen          |check|    |check|
 fread          |check|    |check|
 =============  =========  ============
 
 time.h
---------
+------
 
 =============  =========  ============
 Function Name  Available  RPC Required

libc/src/stdio/CMakeLists.txt

@@ -229,71 +229,6 @@ add_entrypoint_object(
     libc.src.__support.File.platform_file
 )
 
-add_entrypoint_object(
-  fwrite_unlocked
-  SRCS
-    fwrite_unlocked.cpp
-  HDRS
-    fwrite_unlocked.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  fwrite
-  SRCS
-    fwrite.cpp
-  HDRS
-    fwrite.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  fputc
-  SRCS
-    fputc.cpp
-  HDRS
-    fputc.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  putc
-  SRCS
-    putc.cpp
-  HDRS
-    putc.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  putchar
-  SRCS
-    putchar.cpp
-  HDRS
-    putchar.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
@@ -538,6 +473,11 @@ add_stdio_entrypoint_object(fread_unlocked)
 add_stdio_entrypoint_object(fread)
 add_stdio_entrypoint_object(puts)
 add_stdio_entrypoint_object(fputs)
+add_stdio_entrypoint_object(fwrite_unlocked)
+add_stdio_entrypoint_object(fwrite)
+add_stdio_entrypoint_object(fputc)
+add_stdio_entrypoint_object(putc)
+add_stdio_entrypoint_object(putchar)
 add_stdio_entrypoint_object(stdin)
 add_stdio_entrypoint_object(stdout)
 add_stdio_entrypoint_object(stderr)

libc/src/stdio/generic/CMakeLists.txt

@@ -75,6 +75,71 @@ add_entrypoint_object(
     libc.src.__support.File.platform_stdout
 )
 
+add_entrypoint_object(
+  fwrite_unlocked
+  SRCS
+    fwrite_unlocked.cpp
+  HDRS
+    ../fwrite_unlocked.h
+  DEPENDS
+    libc.src.errno.errno
+    libc.include.stdio
+    libc.src.__support.File.file
+    libc.src.__support.File.platform_file
+)
+
+add_entrypoint_object(
+  fwrite
+  SRCS
+    fwrite.cpp
+  HDRS
+    ../fwrite.h
+  DEPENDS
+    libc.src.errno.errno
+    libc.include.stdio
+    libc.src.__support.File.file
+    libc.src.__support.File.platform_file
+)
+
+add_entrypoint_object(
+  fputc
+  SRCS
+    fputc.cpp
+  HDRS
+    ../fputc.h
+  DEPENDS
+    libc.src.errno.errno
+    libc.include.stdio
+    libc.src.__support.File.file
+    libc.src.__support.File.platform_file
+)
+
+add_entrypoint_object(
+  putc
+  SRCS
+    putc.cpp
+  HDRS
+    ../putc.h
+  DEPENDS
+    libc.src.errno.errno
+    libc.include.stdio
+    libc.src.__support.File.file
+    libc.src.__support.File.platform_file
+)
+
+add_entrypoint_object(
+  putchar
+  SRCS
+    putchar.cpp
+  HDRS
+    ../putchar.h
+  DEPENDS
+    libc.src.errno.errno
+    libc.include.stdio
+    libc.src.__support.File.file
+    libc.src.__support.File.platform_file
+)
+
 add_entrypoint_object(
   stdin
   SRCS

libc/src/stdio/fputc.cpp renamed to libc/src/stdio/generic/fputc.cpp

@@ -61,6 +61,50 @@ add_entrypoint_object(
     .gpu_file
 )
 
+add_entrypoint_object(
+  fwrite
+  SRCS
+    fwrite.cpp
+  HDRS
+    ../fwrite.h
+  DEPENDS
+    libc.include.stdio
+    .gpu_file
+)
+
+add_entrypoint_object(
+  fputc
+  SRCS
+    fputc.cpp
+  HDRS
+    ../fputc.h
+  DEPENDS
+    libc.include.stdio
+    .gpu_file
+)
+
+add_entrypoint_object(
+  putc
+  SRCS
+    putc.cpp
+  HDRS
+    ../putc.h
+  DEPENDS
+    libc.include.stdio
+    .gpu_file
+)
+
+add_entrypoint_object(
+  putchar
+  SRCS
+    putchar.cpp
+  HDRS
+    ../putchar.h
+  DEPENDS
+    libc.include.stdio
+    .gpu_file
+)
+
 add_entrypoint_object(
   stdin
   SRCS

libc/src/stdio/fwrite.cpp renamed to libc/src/stdio/generic/fwrite.cpp

@@ -0,0 +1,26 @@
+//===-- GPU implementation of fputc ---------------------------------------===//
+//
+// 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 "file.h"
+#include "src/stdio/fputc.h"
+
+#include <stdio.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, fputc, (int c, ::FILE *stream)) {
+  unsigned char uc = static_cast<unsigned char>(c);
+
+  size_t written = file::write(stream, &uc, 1);
+  if (1 != written)
+    return EOF;
+
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/stdio/fwrite_unlocked.cpp renamed to libc/src/stdio/generic/fwrite_unlocked.cpp

@@ -0,0 +1,26 @@
+//===-- GPU implementation of fwrite --------------------------------------===//
+//
+// 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/fwrite.h"
+#include "file.h"
+
+#include <stdio.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(size_t, fwrite,
+                   (const void *__restrict buffer, size_t size, size_t nmemb,
+                    ::FILE *stream)) {
+  if (size == 0 || nmemb == 0)
+    return 0;
+
+  auto result = file::write(stream, buffer, size * nmemb);
+  return result / size;
+}
+
+} // namespace __llvm_libc

libc/src/stdio/putc.cpp renamed to libc/src/stdio/generic/putc.cpp

@@ -0,0 +1,26 @@
+//===-- GPU implementation of putc ----------------------------------------===//
+//
+// 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/putc.h"
+#include "file.h"
+
+#include <stdio.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, putc, (int c, ::FILE *stream)) {
+  unsigned char uc = static_cast<unsigned char>(c);
+
+  size_t written = file::write(stream, &uc, 1);
+  if (1 != written)
+    return EOF;
+
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/stdio/putchar.cpp renamed to libc/src/stdio/generic/putchar.cpp

@@ -0,0 +1,26 @@
+//===-- GPU implementation of putchar -------------------------------------===//
+//
+// 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 "file.h"
+#include "src/stdio/putchar.h"
+
+#include <stdio.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, putchar, (int c)) {
+  unsigned char uc = static_cast<unsigned char>(c);
+
+  size_t written = file::write(stdout, &uc, 1);
+  if (1 != written)
+    return EOF;
+
+  return 0;
+}
+
+} // namespace __llvm_libc

libc/src/stdio/gpu/CMakeLists.txt

@@ -271,6 +271,20 @@ add_libc_test(
     libc.src.stdio.stderr
 )
 
+add_libc_test(
+  fputc_test
+  HERMETIC_TEST_ONLY # writes to libc's stdout and stderr
+  SUITE
+    libc_stdio_unittests
+  SRCS
+    fputc_test.cpp
+  DEPENDS
+    libc.src.stdio.fputc
+    libc.src.stdio.putchar
+    libc.src.stdio.stdout
+    libc.src.stdio.stderr
+)
+
 add_libc_test(
   fopen_test
   SUITE
@@ -279,7 +293,7 @@ add_libc_test(
     fopen_test.cpp
   DEPENDS
     libc.src.stdio.fread
-    libc.src.stdio.fputs
+    libc.src.stdio.fwrite
     libc.src.stdio.fclose
     libc.src.stdio.fopen
 )