Stop creating symbols we don't need in `DwarfStringPool`. The consumers
only call `DwarfStringPoolEntryRef::getSymbol()` when DWARF is
relocatable, so this just stops creating the unused symbols when it's
not. This drops memory usage from 851 MB to 845 MB, around 0.7%.
(I'm looking at `llc` memory usage on `verify-uselistorder.lto.opt.bc`;
see r236629 for details.)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238122 91177308-0d34-0410-b5e6-96231b3b80d8
Extract out `DwarfStringPoolEntry` and `DwarfStringPoolRef` from
`DwarfStringPool` so that downstream users can start using
`DwarfStringPool::getEntry()` directly. This will allow users to delay
the decision between emitting a symbol or an offset until later.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238116 91177308-0d34-0410-b5e6-96231b3b80d8