[cfe-dev] FileManager re-factor

[John Kelley]

I've been looking at how FileManager is used in clang to figure out  
how best to use llvm::sys::PathWithStatus to replace large parts of  
FileEntry and it seems possibly all of DirectoryEntry.

I was hoping that I could get rid of the (per-file) directory stat by  
assuming that if the file existed, so does the directory but then I  
saw that we use the directory device and inode on unix-like systems as  
an index in UniqueDirContainer. Is the stat more expensive then  
hitting an llvm::StringMap to see if we've checked this exact  
directory yet? We seem to use the device/inode combo to account for  
sym-linked directories but we don't seem to try to resolve the  
symlinked directory to it's origin so as to avoid the FS stat on open.  
Is this something that should be implemented instead?

Also, the directory stat can be ifdef'd out for WIN32 as the WIN32  
implementation of UniqueDirContainer doesn't make use of any of the  
stat elements.

I've already ben able to replace the path construction and parsing  
code in FileManager with calls to the appropriate Path member function  
which cleans things up nicely.

Thoughts?

John