From e43a00e6759ed81edc488dbfd08406a1e8190011 Mon Sep 17 00:00:00 2001
From: Kornel <kornel@geekhood.net>
Date: Sun, 22 Jun 2025 21:31:22 +0100
Subject: [PATCH 1/2] Test MIR inlined var debug info

---
 tests/mir-opt/inline_var_debug_info_kept.rs | 50 +++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 tests/mir-opt/inline_var_debug_info_kept.rs

diff --git a/tests/mir-opt/inline_var_debug_info_kept.rs b/tests/mir-opt/inline_var_debug_info_kept.rs
new file mode 100644
index 0000000000000..e2f00fc6ee929
--- /dev/null
+++ b/tests/mir-opt/inline_var_debug_info_kept.rs
@@ -0,0 +1,50 @@
+//@ test-mir-pass: Inline
+//@ revisions: PRESERVE FULL NONE LIMITED
+//@ [PRESERVE]compile-flags: -O -C debuginfo=0 -Zinline-mir-preserve-debug
+//@ [FULL]compile-flags: -O -C debuginfo=2
+//@ [NONE]compile-flags: -O -C debuginfo=0
+//@ [LIMITED]compile-flags: -O -C debuginfo=1
+
+#[inline(always)]
+fn inline_fn1(arg1: i32) -> i32 {
+    let local1 = arg1 + 1;
+    let _local2 = 10;
+    arg1 + local1
+}
+
+#[inline(always)]
+fn inline_fn2(binding: i32) -> i32 {
+    {
+        let binding = inline_fn1(binding);
+        binding
+    }
+}
+
+#[inline(never)]
+fn test() -> i32 {
+    // CHECK-LABEL: fn test
+    inline_fn2(1)
+    // CHECK-LABEL: (inlined inline_fn2)
+
+    // PRESERVE: debug binding =>
+    // FULL: debug binding =>
+    // NONE-NOT: debug binding =>
+    // LIMITED-NOT: debug binding =>
+
+    // CHECK-LABEL: (inlined inline_fn1)
+
+    // PRESERVE: debug arg1 =>
+    // FULL: debug arg1 =>
+    // NONE-NOT: debug arg1 =>
+    // LIMITED-NOT: debug arg1 =>
+
+    // PRESERVE: debug local1 =>
+    // FULL: debug local1 =>
+    // NONE-NOT: debug local1 =>
+    // LIMITED-NOT: debug local1 =>
+
+    // PRESERVE: debug _local2 =>
+    // FULL: debug _local2 =>
+    // NONE-NOT: debug _local2 =>
+    // LIMITED-NOT: debug _local2 =>
+}

From b7eaae1d5175b8b7b2d7bbca6c85469f2d546a6f Mon Sep 17 00:00:00 2001
From: Kornel <kornel@geekhood.net>
Date: Sat, 8 Feb 2025 01:33:38 +0000
Subject: [PATCH 2/2] Keep inlined var_debug_info only when full debug info is
 used

---
 compiler/rustc_mir_transform/src/inline.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index f48dba9663a52..9e8d5a6bffc7c 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -987,9 +987,10 @@ fn inline_call<'tcx, I: Inliner<'tcx>>(
         .opts
         .unstable_opts
         .inline_mir_preserve_debug
-        .unwrap_or(tcx.sess.opts.debuginfo != DebugInfo::None)
+        // only "full" promises any variable-level information
+        .unwrap_or(self.opts.debuginfo == DebugInfo::Full)
     {
-        // Note that we need to preserve these in the standard library so that
+        // -Zinline-mir-preserve-debug is enabled when building the standard library, so that
         // people working on rust can build with or without debuginfo while
         // still getting consistent results from the mir-opt tests.
         caller_body.var_debug_info.append(&mut callee_body.var_debug_info);