[lld] check cache before real_path in loadDylib (llvm#140791)

Author: rmaz

lld/MachO/DriverUtils.cpp

@@ -227,19 +227,31 @@ static DenseMap<CachedHashStringRef, DylibFile *> loadedDylibs;
 
 DylibFile *macho::loadDylib(MemoryBufferRef mbref, DylibFile *umbrella,
                             bool isBundleLoader, bool explicitlyLinked) {
-  // Frameworks can be found from different symlink paths, so resolve
-  // symlinks before looking up in the dylib cache.
-  SmallString<128> realPath;
-  std::error_code err = fs::real_path(mbref.getBufferIdentifier(), realPath);
-  CachedHashStringRef path(!err ? uniqueSaver().save(StringRef(realPath))
-                                : mbref.getBufferIdentifier());
+  CachedHashStringRef path(mbref.getBufferIdentifier());
   DylibFile *&file = loadedDylibs[path];
   if (file) {
     if (explicitlyLinked)
       file->setExplicitlyLinked();
     return file;
   }
 
+  // Frameworks can be found from different symlink paths, so resolve
+  // symlinks and look up in the dylib cache.
+  DylibFile *&realfile = file;
+  SmallString<128> realPath;
+  std::error_code err = fs::real_path(mbref.getBufferIdentifier(), realPath);
+  if (!err) {
+    CachedHashStringRef resolvedPath(uniqueSaver().save(StringRef(realPath)));
+    realfile = loadedDylibs[resolvedPath];
+    if (realfile) {
+      if (explicitlyLinked)
+        realfile->setExplicitlyLinked();
+
+      file = realfile;
+      return realfile;
+    }
+  }
+
   DylibFile *newFile;
   file_magic magic = identify_magic(mbref.getBuffer());
   if (magic == file_magic::tapi_file) {
@@ -251,6 +263,7 @@ DylibFile *macho::loadDylib(MemoryBufferRef mbref, DylibFile *umbrella,
     }
     file =
         make<DylibFile>(**result, umbrella, isBundleLoader, explicitlyLinked);
+    realfile = file;
 
     // parseReexports() can recursively call loadDylib(). That's fine since
     // we wrote the DylibFile we just loaded to the loadDylib cache via the
@@ -266,6 +279,7 @@ DylibFile *macho::loadDylib(MemoryBufferRef mbref, DylibFile *umbrella,
            magic == file_magic::macho_executable ||
            magic == file_magic::macho_bundle);
     file = make<DylibFile>(mbref, umbrella, isBundleLoader, explicitlyLinked);
+    realfile = file;
 
     // parseLoadCommands() can also recursively call loadDylib(). See comment
     // in previous block for why this means we must copy `file` here.