From 8ea2dd0066b21951651400939c32426a4f1a0cd3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Eduardo=20S=C3=A1nchez=20Mu=C3=B1oz?= <eduardosm-dev@e64.io>
Date: Mon, 5 Dec 2022 00:51:33 +0100
Subject: [PATCH] Enable MIR inlinig for `#[inline(always)]` when
 mir-opt-level=1

---
 compiler/rustc_mir_transform/src/inline.rs    | 28 ++++++++++++-------
 .../inlining-from-extern-crate.rs             |  2 ++
 .../partitioning/local-inlining.rs            |  2 ++
 .../partitioning/local-transitive-inlining.rs |  2 ++
 .../incremental/hashes/function_interfaces.rs |  2 ++
 5 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index bf670c5c26a77..cc6c6a23906b4 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -45,15 +45,7 @@ impl<'tcx> MirPass<'tcx> for Inline {
             return enabled;
         }
 
-        match sess.mir_opt_level() {
-            0 | 1 => false,
-            2 => {
-                (sess.opts.optimize == OptLevel::Default
-                    || sess.opts.optimize == OptLevel::Aggressive)
-                    && sess.opts.incremental == None
-            }
-            _ => true,
-        }
+        sess.mir_opt_level() > 0
     }
 
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
@@ -341,7 +333,23 @@ impl<'tcx> Inliner<'tcx> {
     ) -> Result<(), &'static str> {
         match callee_attrs.inline {
             InlineAttr::Never => return Err("never inline hint"),
-            InlineAttr::Always | InlineAttr::Hint => {}
+            InlineAttr::Always => {}
+            InlineAttr::Hint => match self.tcx.sess.mir_opt_level() {
+                0 | 1 => return Err("at mir-opt-level=1, only #[inline(always)] is inlined"),
+                2 if self.tcx.sess.opts.optimize != OptLevel::Default
+                    && self.tcx.sess.opts.optimize != OptLevel::Aggressive =>
+                {
+                    return Err(
+                        "at mir-opt-level=2, only #[inline(always)] is inlined when opt-level<2",
+                    );
+                }
+                2 if self.tcx.sess.opts.incremental != None => {
+                    return Err(
+                        "at mir-opt-level=2, only #[inline(always)] is inlined when incremental compilation is enabled",
+                    );
+                }
+                _ => {}
+            },
             InlineAttr::None => {
                 if self.tcx.sess.mir_opt_level() <= 2 {
                     return Err("at mir-opt-level=2, only #[inline] is inlined");
diff --git a/src/test/codegen-units/partitioning/inlining-from-extern-crate.rs b/src/test/codegen-units/partitioning/inlining-from-extern-crate.rs
index 1cc21632e4818..0eaa60979952e 100644
--- a/src/test/codegen-units/partitioning/inlining-from-extern-crate.rs
+++ b/src/test/codegen-units/partitioning/inlining-from-extern-crate.rs
@@ -4,6 +4,8 @@
 // incremental
 // compile-flags:-Zprint-mono-items=lazy
 // compile-flags:-Zinline-in-all-cgus
+// To keep mir from doing any inlining
+// compile-flags:-Zmir-opt-level=0
 
 #![crate_type="lib"]
 
diff --git a/src/test/codegen-units/partitioning/local-inlining.rs b/src/test/codegen-units/partitioning/local-inlining.rs
index 841a428e9dd2f..b2ef9be25e1f2 100644
--- a/src/test/codegen-units/partitioning/local-inlining.rs
+++ b/src/test/codegen-units/partitioning/local-inlining.rs
@@ -4,6 +4,8 @@
 // incremental
 // compile-flags:-Zprint-mono-items=lazy
 // compile-flags:-Zinline-in-all-cgus
+// To keep mir from doing any inlining
+// compile-flags:-Zmir-opt-level=0
 
 #![allow(dead_code)]
 #![crate_type="lib"]
diff --git a/src/test/codegen-units/partitioning/local-transitive-inlining.rs b/src/test/codegen-units/partitioning/local-transitive-inlining.rs
index 03c37954d1513..9ef48028af6b8 100644
--- a/src/test/codegen-units/partitioning/local-transitive-inlining.rs
+++ b/src/test/codegen-units/partitioning/local-transitive-inlining.rs
@@ -4,6 +4,8 @@
 // incremental
 // compile-flags:-Zprint-mono-items=lazy
 // compile-flags:-Zinline-in-all-cgus
+// To keep mir from doing any inlining
+// compile-flags:-Zmir-opt-level=0
 
 #![allow(dead_code)]
 #![crate_type="rlib"]
diff --git a/src/test/incremental/hashes/function_interfaces.rs b/src/test/incremental/hashes/function_interfaces.rs
index 3ff949fbb3f80..1e08fdb93b3e9 100644
--- a/src/test/incremental/hashes/function_interfaces.rs
+++ b/src/test/incremental/hashes/function_interfaces.rs
@@ -8,6 +8,8 @@
 // build-pass (FIXME(62277): could be check-pass?)
 // revisions: cfail1 cfail2 cfail3 cfail4 cfail5 cfail6
 // compile-flags: -Z query-dep-graph -O
+// To keep mir from doing any inlining
+// compile-flags: -Z mir-opt-level=0
 // [cfail1]compile-flags: -Zincremental-ignore-spans
 // [cfail2]compile-flags: -Zincremental-ignore-spans
 // [cfail3]compile-flags: -Zincremental-ignore-spans