[libc] Implement (v|f)printf on the GPU (#96369)

Summary:
This patch implements the `printf` family of functions on the GPU using
the new variadic support. This patch adapts the old handling in the
`rpc_fprintf` placeholder, but adds an extra RPC call to get the size of
the buffer to copy. This prevents the GPU from needing to parse the
string. While it's theoretically possible for the pass to know the size
of the struct, it's prohibitively difficult to do while maintaining ABI
compatibility with NVIDIA's varargs.

Depends on https://github.com/llvm/llvm-project/pull/96015.

3 files changed, 91 insertions, 13 deletions

diff --git a/libc/src/stdio/generic/CMakeLists.txt b/libc/src/stdio/generic/CMakeLists.txt
index b0ce8ccc08bd..a86b86a32dce 100644
--- a/libc/src/stdio/generic/CMakeLists.txt
+++ b/libc/src/stdio/generic/CMakeLists.txt
@@ -363,19 +363,6 @@ add_entrypoint_object(
     libc.src.__support.File.platform_file
 )
 
-list(APPEND printf_deps
-      libc.src.__support.arg_list
-      libc.src.stdio.printf_core.vfprintf_internal
-)
-
-if(LLVM_LIBC_FULL_BUILD)
-  list(APPEND printf_deps
-      libc.src.__support.File.file
-      libc.src.__support.File.platform_file
-      libc.src.__support.File.platform_stdout
-  )
-endif()
-
 add_entrypoint_object(
   printf
   SRCS
@@ -397,6 +384,32 @@ add_entrypoint_object(
 )
 
 add_entrypoint_object(
+  fprintf
+  SRCS
+    fprintf.cpp
+  HDRS
+    ../fprintf.h
+  DEPENDS
+    libc.hdr.types.FILE
+    libc.src.__support.arg_list
+    libc.src.stdio.printf_core.vfprintf_internal
+    ${printf_deps}
+)
+
+add_entrypoint_object(
+  vfprintf
+  SRCS
+    vfprintf.cpp
+  HDRS
+    ../vfprintf.h
+  DEPENDS
+    libc.hdr.types.FILE
+    libc.src.__support.arg_list
+    libc.src.stdio.printf_core.vfprintf_internal
+    ${printf_deps}
+)
+
+add_entrypoint_object(
   fgets
   SRCS
     fgets.cpp
diff --git a/libc/src/stdio/generic/fprintf.cpp b/libc/src/stdio/generic/fprintf.cpp
new file mode 100644
index 000000000000..087aeadfc52c
--- /dev/null
+++ b/libc/src/stdio/generic/fprintf.cpp
@@ -0,0 +1,34 @@
+//===-- Implementation of fprintf -------------------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/fprintf.h"
+
+#include "src/__support/File/file.h"
+#include "src/__support/arg_list.h"
+#include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/vfprintf_internal.h"
+
+#include "hdr/types/FILE.h"
+#include <stdarg.h>
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, fprintf,
+                   (::FILE *__restrict stream, const char *__restrict format,
+                    ...)) {
+  va_list vlist;
+  va_start(vlist, format);
+  internal::ArgList args(vlist); // This holder class allows for easier copying
+                                 // and pointer semantics, as well as handling
+                                 // destruction automatically.
+  va_end(vlist);
+  int ret_val = printf_core::vfprintf_internal(stream, format, args);
+  return ret_val;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdio/generic/vfprintf.cpp b/libc/src/stdio/generic/vfprintf.cpp
new file mode 100644
index 000000000000..01f4265f118a
--- /dev/null
+++ b/libc/src/stdio/generic/vfprintf.cpp
@@ -0,0 +1,31 @@
+//===-- Implementation of vfprintf ------------------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/vfprintf.h"
+
+#include "src/__support/File/file.h"
+#include "src/__support/arg_list.h"
+#include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/vfprintf_internal.h"
+
+#include "hdr/types/FILE.h"
+#include <stdarg.h>
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, vfprintf,
+                   (::FILE *__restrict stream, const char *__restrict format,
+                    va_list vlist)) {
+  internal::ArgList args(vlist); // This holder class allows for easier copying
+                                 // and pointer semantics, as well as handling
+                                 // destruction automatically.
+  int ret_val = printf_core::vfprintf_internal(stream, format, args);
+  return ret_val;
+}
+
+} // namespace LIBC_NAMESPACE_DECL