[OpenMP] Search for static libraries in offload linker tool

This patch adds support for searching through the linker library paths
to identify static libraries that may contain device code. If device
code is present it will be extracted. This should ideally fully support
static linking with OpenMP offloading.

Depends on D116627

Differential Revision: https://reviews.llvm.org/D116675

diff --git a/clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp b/clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp
index 0072ce7..de51e36 100644 (file)
--- a/clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp
+++ b/clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp
@@ -65,7 +65,9 @@ static cl::list<std::string>
 /// Path of the current binary.
 static std::string LinkerExecutable;
 
+/// Temporary files created by the linker wrapper.
 static SmallVector<std::string, 16> TempFiles;
+
 /// Magic section string that marks the existence of offloading data. The
 /// section string will be formatted as `.llvm.offloading.<triple>.<arch>`.
 #define OFFLOAD_SECTION_MAGIC_STR ".llvm.offloading."
@@ -551,6 +553,44 @@ Expected<std::string> wrapDeviceImage(StringRef ImageFile) {
   return static_cast<std::string>(ObjectFile);
 }
 
+Optional<std::string> findFile(StringRef Dir, const Twine &Name) {
+  SmallString<128> Path;
+  // TODO: Parse `--sysroot` somewhere and use it here.
+  sys::path::append(Path, Dir, Name);
+  if (sys::fs::exists(Path))
+    return static_cast<std::string>(Path);
+  return None;
+}
+
+Optional<std::string> findFromSearchPaths(StringRef Name,
+                                          ArrayRef<StringRef> SearchPaths) {
+  for (StringRef Dir : SearchPaths)
+    if (Optional<std::string> File = findFile(Dir, Name))
+      return File;
+  return None;
+}
+
+Optional<std::string> searchLibraryBaseName(StringRef Name,
+                                            ArrayRef<StringRef> SearchPaths) {
+  for (StringRef Dir : SearchPaths) {
+    if (Optional<std::string> File = findFile(Dir, "lib" + Name + ".a"))
+      return File;
+  }
+  return None;
+}
+
+/// Search for static libraries in the linker's library path given input like
+/// `-lfoo` or `-l:libfoo.a`.
+Optional<std::string> searchLibrary(StringRef Input,
+                                    ArrayRef<StringRef> SearchPaths) {
+  if (!Input.startswith("-l"))
+    return None;
+  StringRef Name = Input.drop_front(2);
+  if (Name.startswith(":"))
+    return findFromSearchPaths(Name.drop_front(), SearchPaths);
+  return searchLibraryBaseName(Name, SearchPaths);
+}
+
 } // namespace
 
 int main(int argc, const char **argv) {
@@ -581,16 +621,26 @@ int main(int argc, const char **argv) {
   for (const std::string &Arg : HostLinkerArgs)
     LinkerArgs.push_back(Arg);
 
+  SmallVector<StringRef, 16> LibraryPaths;
+  for (const StringRef Arg : LinkerArgs)
+    if (Arg.startswith("-L"))
+      LibraryPaths.push_back(Arg.drop_front(2));
+
   // Try to extract device code from the linker input and replace the linker
   // input with a new file that has the device section stripped.
   SmallVector<DeviceFile, 4> DeviceFiles;
   for (std::string &Arg : LinkerArgs) {
-    if (sys::path::extension(Arg) == ".o" ||
-        sys::path::extension(Arg) == ".a") {
+    // Search for static libraries in the library link path.
+    std::string Filename = Arg;
+    if (Optional<std::string> Library = searchLibrary(Arg, LibraryPaths))
+      Filename = *Library;
+
+    if (sys::path::extension(Filename) == ".o" ||
+        sys::path::extension(Filename) == ".a") {
       ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
-          MemoryBuffer::getFileOrSTDIN(Arg);
+          MemoryBuffer::getFileOrSTDIN(Filename);
       if (std::error_code EC = BufferOrErr.getError())
-        return reportError(createFileError(Arg, EC));
+        return reportError(createFileError(Filename, EC));
 
       auto NewFileOrErr =
           extractFromBuffer(std::move(*BufferOrErr), DeviceFiles);