From d1d9092e3c99343e03abc650e91082b5c9f538b9 Mon Sep 17 00:00:00 2001
From: Wesley Wiser <wesleywiser@microsoft.com>
Date: Thu, 30 Sep 2021 22:03:49 -0400
Subject: [PATCH] Test enabling MIR inliner

---
 compiler/rustc_mir_transform/src/inline.rs | 33 +++++++++++++++-------
 src/test/ui/polymorphization/generators.rs |  2 +-
 2 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index 4f45ae0d050..c99c3b2f1c2 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -9,6 +9,7 @@ use rustc_middle::mir::visit::*;
 use rustc_middle::mir::*;
 use rustc_middle::ty::subst::Subst;
 use rustc_middle::ty::{self, ConstKind, Instance, InstanceDef, ParamEnv, Ty, TyCtxt};
+use rustc_session::config::OptLevel;
 use rustc_span::{hygiene::ExpnKind, ExpnData, LocalExpnId, Span};
 use rustc_target::spec::abi::Abi;
 
@@ -43,7 +44,15 @@ impl<'tcx> MirPass<'tcx> for Inline {
             return enabled;
         }
 
-        sess.opts.mir_opt_level() >= 3
+        match sess.mir_opt_level() {
+            0 | 1 => false,
+            2 => {
+                (sess.opts.optimize == OptLevel::Default
+                    || sess.opts.optimize == OptLevel::Aggressive)
+                    && sess.opts.incremental == None
+            }
+            _ => true,
+        }
     }
 
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
@@ -321,8 +330,14 @@ impl<'tcx> Inliner<'tcx> {
         callsite: &CallSite<'tcx>,
         callee_attrs: &CodegenFnAttrs,
     ) -> Result<(), &'static str> {
-        if let InlineAttr::Never = callee_attrs.inline {
-            return Err("never inline hint");
+        match callee_attrs.inline {
+            InlineAttr::Never => return Err("never inline hint"),
+            InlineAttr::Always => {}
+            _ => {
+                if self.tcx.sess.mir_opt_level() <= 2 {
+                    return Err("at mir-opt-level=2, only #[inline(always)] is inlined");
+                }
+            }
         }
 
         // Only inline local functions if they would be eligible for cross-crate
@@ -505,14 +520,12 @@ impl<'tcx> Inliner<'tcx> {
         if let InlineAttr::Always = callee_attrs.inline {
             debug!("INLINING {:?} because inline(always) [cost={}]", callsite, cost);
             Ok(())
+        } else if cost <= threshold {
+            debug!("INLINING {:?} [cost={} <= threshold={}]", callsite, cost, threshold);
+            Ok(())
         } else {
-            if cost <= threshold {
-                debug!("INLINING {:?} [cost={} <= threshold={}]", callsite, cost, threshold);
-                Ok(())
-            } else {
-                debug!("NOT inlining {:?} [cost={} > threshold={}]", callsite, cost, threshold);
-                Err("cost above threshold")
-            }
+            debug!("NOT inlining {:?} [cost={} > threshold={}]", callsite, cost, threshold);
+            Err("cost above threshold")
         }
     }
 
diff --git a/src/test/ui/polymorphization/generators.rs b/src/test/ui/polymorphization/generators.rs
index 68ea4a026d7..779bac0ace2 100644
--- a/src/test/ui/polymorphization/generators.rs
+++ b/src/test/ui/polymorphization/generators.rs
@@ -1,5 +1,5 @@
 // build-fail
-// compile-flags:-Zpolymorphize=on
+// compile-flags:-Zpolymorphize=on -Zinline-mir=off
 #![feature(generic_const_exprs, generators, generator_trait, rustc_attrs)]
 //~^ WARN the feature `generic_const_exprs` is incomplete