Auto merge of #65052 - ishitatsuyuki:no-inline-cgu, r=<try>

[perf] Disable inline_in_all_cgus when LTO is enabled

I tried to run lolbench with this flag altered; however lolbench either errored or got stuck, so I end up running only 3 of the benchmarks manually. One showed no changes, another one showed 20% perf improvement somehow, and another showed slight (1%) regression.

So I'm thinking of benchmarking it with perf instead; if we still have ThinLTO on CI then we can measure stage2 compiler performance as a metric of how much it affects generated code.

Author: bors

src/librustc_mir/monomorphize/item.rs

@@ -1,6 +1,6 @@
 use rustc::hir::def_id::LOCAL_CRATE;
 use rustc::mir::mono::MonoItem;
-use rustc::session::config::OptLevel;
+use rustc::session::config::{OptLevel, Lto};
 use rustc::ty::{self, TyCtxt, Instance};
 use rustc::ty::subst::InternalSubsts;
 use rustc::ty::print::obsolete::DefPathBasedNames;
@@ -65,7 +65,7 @@ pub trait MonoItemExt<'tcx>: fmt::Debug {
     fn instantiation_mode(&self, tcx: TyCtxt<'tcx>) -> InstantiationMode {
         let inline_in_all_cgus =
             tcx.sess.opts.debugging_opts.inline_in_all_cgus.unwrap_or_else(|| {
-                tcx.sess.opts.optimize != OptLevel::No
+                tcx.sess.opts.optimize != OptLevel::No && if tcx.sess.lto() == Lto::No
             }) && !tcx.sess.opts.cg.link_dead_code;
 
         match *self.as_mono_item() {