[ThinLTO] Option to control path of distributed backend files

Summary:
Add support to control where files for a distributed backend (the
individual index files and optional imports files) are created.

This is invoked with a new thinlto-prefix-replace option in the gold
plugin and llvm-lto. If specified, expects a string of the form
"oldprefix:newprefix", and instead of generating these files in the
same directory path as the corresponding bitcode file, will use a path
formed by replacing the bitcode file's path prefix matching oldprefix
with newprefix.

Also add a new replace_path_prefix helper to Path.h in libSupport.

Depends on D19636.

Reviewers: joker.eph

Subscribers: llvm-commits, joker.eph

Differential Revision: http://reviews.llvm.org/D19644

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@269771 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 0 deletions

diff --git a/include/llvm/Support/Path.h b/include/llvm/Support/Path.h
index f8031036c3e..853f0997571 100644
--- a/include/llvm/Support/Path.h
+++ b/include/llvm/Support/Path.h
@@ -142,6 +142,23 @@ void remove_filename(SmallVectorImpl<char> &path);
 ///                  prepended.
 void replace_extension(SmallVectorImpl<char> &path, const Twine &extension);
 
+/// @brief Replace matching path prefix with another path.
+///
+/// @code
+///   /foo, /old, /new => /foo
+///   /old/foo, /old, /new => /new/foo
+///   /foo, <empty>, /new => /new/foo
+///   /old/foo, /old, <empty> => /foo
+/// @endcode
+///
+/// @param Path If \a Path starts with \a OldPrefix modify to instead
+///        start with \a NewPrefix.
+/// @param OldPrefix The path prefix to strip from \a Path.
+/// @param NewPrefix The path prefix to replace \a NewPrefix with.
+void replace_path_prefix(SmallVectorImpl<char> &Path,
+                         const StringRef &OldPrefix,
+                         const StringRef &NewPrefix);
+
 /// @brief Append to path.
 ///
 /// @code