Implement sys::fs::copy_file using the macOS copyfile(3) API

to support APFS clones.

This patch adds a Darwin-specific implementation of
llvm::sys::fs::copy_file() that uses the macOS copyfile(3) API to
support APFS copy-on-write clones, which should be faster and much
more space efficient.

https://developer.apple.com/library/archive/documentation/FileManagement/Conceptual/APFS_Guide/ToolsandAPIs/ToolsandAPIs.html

Differential Revision: https://reviews.llvm.org/D60802

This reapplies 358628 with an additional bugfix handling the case
where the destination file already exists. (Caught by the clang testsuite).

llvm-svn: 358716

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Support/Path.cpp b/llvm/lib/Support/Path.cpp
index 902df74a68f..9466591c25e 100644
--- a/llvm/lib/Support/Path.cpp
+++ b/llvm/lib/Support/Path.cpp
@@ -935,6 +935,7 @@ std::error_code create_directories(const Twine &Path, bool IgnoreExisting,
   return create_directory(P, IgnoreExisting, Perms);
 }
 
+#ifndef __APPLE__
 static std::error_code copy_file_internal(int ReadFD, int WriteFD) {
   const size_t BufSize = 4096;
   char *Buf = new char[BufSize];
@@ -988,6 +989,7 @@ std::error_code copy_file(const Twine &From, int ToFD) {
 
   return EC;
 }
+#endif
 
 ErrorOr<MD5::MD5Result> md5_contents(int FD) {
   MD5 Hash;