With CSSPGO, to maximize the benefit of global top-down context-sensitive inlining, we are experimenting with shifting more inlining from LTO prelink to postlink, from cgscc inlining to sample loader inlining. The change adds switches to turn off prelink/postlink cgscc/sample-loader inlining separately. Note this is different from -fno-inline as the new switches only augment pass pipeline without changing inline attribute on functions.
We saw better performance on some benchmark with prelto inlining turned off, but there're other regressions too. Currently both switches default to on so nothing changes by default, even with CSSPGO. I'm exposing the switches to help further tuning.