Auto merge of #45202 - alexcrichton:fix-inline-always, r=michaelwoerister

rustc: Handle #[inline(always)] at -O0

This commit updates the handling of `#[inline(always)]` functions at -O0 to
ensure that it's always inlined regardless of the number of codegen units used.

Closes #45201

src/test/codegen-units/partitioning/local-inlining-but-not-all.rs

@@ -20,7 +20,7 @@
 mod inline {
 
     //~ TRANS_ITEM fn local_inlining_but_not_all::inline[0]::inlined_function[0] @@ local_inlining_but_not_all-inline[External]
-    #[inline(always)]
+    #[inline]
     pub fn inlined_function()
     {
 

src/test/run-make/inline-always-many-cgu/Makefile

@@ -0,0 +1,8 @@
+-include ../tools.mk
+
+all:
+	$(RUSTC) foo.rs --emit llvm-ir -C codegen-units=2
+	if grep -w call $(TMPDIR)/*.ll; then \
+		echo "found call instruction when one wasn't expected"; \
+		exit 1; \
+	fi

src/test/run-make/inline-always-many-cgu/foo.rs

@@ -0,0 +1,25 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![crate_type = "lib"]
+
+pub mod a {
+    #[inline(always)]
+    pub fn foo() {
+    }
+
+    pub fn bar() {
+    }
+}
+
+#[no_mangle]
+pub fn bar() {
+    a::foo();
+}