Auto merge of #68965 - eddyb:mir-inline-scope, r=nagisa,oli-obk

 rustc_mir: track inlined callees in SourceScopeData.

We now record which MIR scopes are the roots of *other* (inlined) functions's scope trees, which allows us to generate the correct debuginfo in codegen, similar to what LLVM inlining generates.
This PR makes the `ui` test `backtrace-debuginfo` pass, if the MIR inliner is turned on by default.

Also, `#[track_caller]` is now correct in the face of MIR inlining (cc `@anp).`

Fixes #76997.

r? `@rust-lang/wg-mir-opt`

1 files changed, 17 insertions, 0 deletions

diff --git a/src/test/codegen/inline-debuginfo.rs b/src/test/codegen/inline-debuginfo.rs
new file mode 100644
index 00000000000..1546dfa10a3
--- /dev/null
+++ b/src/test/codegen/inline-debuginfo.rs
@@ -0,0 +1,17 @@
+#![crate_type="rlib"]
+// compile-flags: -Copt-level=3 -g
+// ignore-tidy-linelength
+
+#[no_mangle]
+#[inline(always)]
+pub extern "C" fn callee(x: u32) -> u32 {
+    x + 4
+}
+
+// CHECK-LABEL: caller
+// CHECK: call void @llvm.dbg.value(metadata i32 %y, metadata !{{.*}}, metadata !DIExpression(DW_OP_constu, 3, DW_OP_minus, DW_OP_stack_value)), !dbg [[A:!.*]]
+// CHECK: [[A]] = !DILocation(line: {{.*}}, scope: {{.*}}, inlinedAt: {{.*}})
+#[no_mangle]
+pub extern "C" fn caller(y: u32) -> u32 {
+    callee(y - 3)
+}