[clang] [llvm] [LTO] Reduce memory usage for import lists (PR #106772)

[Nikita Popov via cfe-commits]

nikic wrote:

It looks like this causes a compile-time regression. The clang thin link time increases by 1% (https://llvm-compile-time-tracker.com/compare_clang.php?from=9ccf82543d509bb5a0f5d0551fc4d6c1913b9a9b&to=5c0d61e318a77434487fcec8361d8110fb06e59d&stat=instructions%3Au). There is no regression for thin link on CTMark, so the regression here probably scales with the number of modules involved in the link, so is likely even larger for larger applications.

https://github.com/llvm/llvm-project/pull/106772