From e747d6b317ed5919894dac6601e00e573224eb97 Mon Sep 17 00:00:00 2001
From: Santiago Pastorino <spastorino@gmail.com>
Date: Fri, 18 Sep 2020 13:57:08 -0300
Subject: [PATCH] Do not make local copy of inline(always) fns in debug mode

---
 compiler/rustc_middle/src/mir/mono.rs                | 12 +++++++-----
 .../inline-always-many-cgu/Makefile                  |  7 ++++++-
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/compiler/rustc_middle/src/mir/mono.rs b/compiler/rustc_middle/src/mir/mono.rs
index 79e2c5aac2385..5ae6d109981e6 100644
--- a/compiler/rustc_middle/src/mir/mono.rs
+++ b/compiler/rustc_middle/src/mir/mono.rs
@@ -107,12 +107,14 @@ impl<'tcx> MonoItem<'tcx> {
                 }
 
                 // Finally, if this is `#[inline(always)]` we're sure to respect
-                // that with an inline copy per CGU, but otherwise we'll be
-                // creating one copy of this `#[inline]` function which may
-                // conflict with upstream crates as it could be an exported
-                // symbol.
+                // that (unless in OptLevel::No) with an inline copy per CGU,
+                // but otherwise we'll be creating one copy of this `#[inline]`
+                // function which may conflict with upstream crates as it could
+                // be an exported symbol.
                 match tcx.codegen_fn_attrs(instance.def_id()).inline {
-                    InlineAttr::Always => InstantiationMode::LocalCopy,
+                    InlineAttr::Always if tcx.sess.opts.optimize != OptLevel::No => {
+                        InstantiationMode::LocalCopy
+                    }
                     _ => InstantiationMode::GloballyShared { may_conflict: true },
                 }
             }
diff --git a/src/test/run-make-fulldeps/inline-always-many-cgu/Makefile b/src/test/run-make-fulldeps/inline-always-many-cgu/Makefile
index 0cab955f6442b..d12a23fbbf013 100644
--- a/src/test/run-make-fulldeps/inline-always-many-cgu/Makefile
+++ b/src/test/run-make-fulldeps/inline-always-many-cgu/Makefile
@@ -1,7 +1,12 @@
 -include ../tools.mk
 
 all:
-	$(RUSTC) foo.rs --emit llvm-ir -C codegen-units=2
+	$(RUSTC) foo.rs --emit llvm-ir -C codegen-units=2 -C opt-level=0
+	if ![cat $(TMPDIR)/*.ll | $(CGREP) -e '\bcall\b']; then \
+		echo "not found call instruction when one was expected"; \
+		exit 1; \
+	fi
+	$(RUSTC) foo.rs --emit llvm-ir -C codegen-units=2 -C opt-level=1
 	if cat $(TMPDIR)/*.ll | $(CGREP) -e '\bcall\b'; then \
 		echo "found call instruction when one wasn't expected"; \
 		exit 1; \