[libc] Implement more input functions on the GPU (#66288)

Summary:
This patch implements the `fgets`, `getc`, `fgetc`, and `getchar`
functions on the GPU. Their implementations are straightforward enough.
One thing worth noting is that the implementation of `fgets` will be
extremely slow due to the high latency to read a single char. A faster
solution would be to make a new RPC call to call `fgets` (due to the
special rule that newline or null breaks the stream). But this is left
out because performance isn't the primary concern here.

Author: jhuber6

libc/config/gpu/entrypoints.txt

@@ -86,6 +86,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.errno.errno
 
     # stdio.h entrypoints
+    libc.src.stdio.feof
+    libc.src.stdio.ferror
+    libc.src.stdio.clearerr
     libc.src.stdio.puts
     libc.src.stdio.fopen
     libc.src.stdio.fclose
@@ -95,6 +98,10 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdio.fputc
     libc.src.stdio.putc
     libc.src.stdio.putchar
+    libc.src.stdio.fgets
+    libc.src.stdio.fgetc
+    libc.src.stdio.getc
+    libc.src.stdio.getchar
     libc.src.stdio.stdin
     libc.src.stdio.stdout
     libc.src.stdio.stderr

libc/docs/gpu/support.rst

@@ -126,6 +126,13 @@ stdio.h
 =============  =========  ============
 Function Name  Available  RPC Required
 =============  =========  ============
+feof           |check|    |check|
+ferror         |check|    |check|
+clearerr       |check|    |check|
+fgetc          |check|    |check|
+fgets          |check|    |check|
+getc           |check|    |check|
+getchar        |check|    |check|
 puts           |check|    |check|
 fputs          |check|    |check|
 fputc          |check|    |check|

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

@@ -23,6 +23,9 @@ typedef enum : unsigned short {
   RPC_FREE = 10,
   RPC_HOST_CALL = 11,
   RPC_ABORT = 12,
+  RPC_FEOF = 13,
+  RPC_FERROR = 14,
+  RPC_CLEARERR = 15,
 } rpc_opcode_t;
 
 #endif // __LLVM_LIBC_TYPES_RPC_OPCODE_H__

libc/src/stdio/CMakeLists.txt

@@ -29,169 +29,6 @@ endif()
 add_subdirectory(printf_core)
 add_subdirectory(scanf_core)
 
-add_entrypoint_object(
-  clearerr
-  SRCS
-    clearerr.cpp
-  HDRS
-    clearerr.h
-  DEPENDS
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  clearerr_unlocked
-  SRCS
-    clearerr_unlocked.cpp
-  HDRS
-    clearerr_unlocked.h
-  DEPENDS
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  feof
-  SRCS
-    feof.cpp
-  HDRS
-    feof.h
-  DEPENDS
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  feof_unlocked
-  SRCS
-    feof_unlocked.cpp
-  HDRS
-    feof_unlocked.h
-  DEPENDS
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  ferror
-  SRCS
-    ferror.cpp
-  HDRS
-    ferror.h
-  DEPENDS
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  ferror_unlocked
-  SRCS
-    ferror_unlocked.cpp
-  HDRS
-    ferror_unlocked.h
-  DEPENDS
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  fgetc
-  SRCS
-    fgetc.cpp
-  HDRS
-    fgetc.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  fgetc_unlocked
-  SRCS
-    fgetc_unlocked.cpp
-  HDRS
-    fgetc_unlocked.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  getc
-  SRCS
-    getc.cpp
-  HDRS
-    getc.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  getc_unlocked
-  SRCS
-    getc_unlocked.cpp
-  HDRS
-    getc_unlocked.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  getchar
-  SRCS
-    getchar.cpp
-  HDRS
-    getchar.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  getchar_unlocked
-  SRCS
-    getc_unlocked.cpp
-  HDRS
-    getc_unlocked.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  fgets
-  SRCS
-    fgets.cpp
-  HDRS
-    fgets.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
 add_entrypoint_object(
   fflush
   SRCS
@@ -470,6 +307,9 @@ add_entrypoint_object(
 )
 
 # These entrypoints have multiple potential implementations.
+add_stdio_entrypoint_object(feof)
+add_stdio_entrypoint_object(ferror)
+add_stdio_entrypoint_object(clearerr)
 add_stdio_entrypoint_object(fopen)
 add_stdio_entrypoint_object(fclose)
 add_stdio_entrypoint_object(fread_unlocked)
@@ -481,6 +321,13 @@ add_stdio_entrypoint_object(fwrite)
 add_stdio_entrypoint_object(fputc)
 add_stdio_entrypoint_object(putc)
 add_stdio_entrypoint_object(putchar)
+add_stdio_entrypoint_object(fgetc)
+add_stdio_entrypoint_object(fgetc_unlocked)
+add_stdio_entrypoint_object(getc)
+add_stdio_entrypoint_object(getc_unlocked)
+add_stdio_entrypoint_object(getchar)
+add_stdio_entrypoint_object(getchar_unlocked)
+add_stdio_entrypoint_object(fgets)
 add_stdio_entrypoint_object(stdin)
 add_stdio_entrypoint_object(stdout)
 add_stdio_entrypoint_object(stderr)