CachePruning: correct comment about file order. NFC

[chfast]

Summary

Actually the list of cached files is sorted by file size, not by last accessed time. Also remove unused file access time param for a helper function.

[davide]

lgtm.

llvm/trunk/lib/Support/CachePruning.cpp

bool CachePruning::prune() {
   }
 
   bool ShouldComputeSize = (PercentageOfAvailableSpace > 0);
 
   // Keep track of space
   std::set<std::pair<uint64_t, std::string>> FileSizes;
   uint64_t TotalSize = 0;
   // Helper to add a path to the set of files to consider for size-based
-  // pruning, sorted by last accessed time.
+  // pruning, sorted by size.
   auto AddToFileListForSizePruning =
-      [&](StringRef Path, sys::TimeValue FileAccessTime) {
+      [&](StringRef Path) {
         if (!ShouldComputeSize)
           return;
         TotalSize += FileStatus.getSize();
         FileSizes.insert(
             std::make_pair(FileStatus.getSize(), std::string(Path)));
       };
 
   // Walk the entire directory cache, looking for unused files.
for (sys::fs::directory_iterator File(CachePathNative, EC), FileEnd;
     if (FileAge > TimeExpiration) {
       DEBUG(dbgs() << "Remove " << File->path() << " (" << FileAge.seconds()
                    << "s old)\n");
       sys::fs::remove(File->path());
       continue;
     }
 
     // Leave it here for now, but add it to the list of size-based pruning.
-    AddToFileListForSizePruning(File->path(), FileAccessTime);
+    AddToFileListForSizePruning(File->path());
   }
 
   // Prune for size now if needed
   if (ShouldComputeSize) {
     auto ErrOrSpaceInfo = sys::fs::disk_space(Path);
     if (!ErrOrSpaceInfo) {
       report_fatal_error("Can't get available size");
     }