[LTO] Don't make unnecessary copies of ImportIDTable (#106998)

Without this patch, {ImportMapTy,SortedImportList}::{begin,end} make
unnecessary copies of ImportIDTable via:

  map_iterator(Imports.begin(), IDs);

The second parameter, IDs, is passed by value, so we make a copy of
MapVector inside ImportIDTable every time we call begin and end.
These begin and end show up as time-consuming functions in the
performance profile.

This patch fixes the problem by passing IDs by reference with
std::cref.

While we are at it, this patch deletes the copy constructor and
assignment operator.  I cannot think of any legitimate need reason to
make a copy of the deduplication table.

0 files changed, 0 insertions, 0 deletions