fixup! codegen: Generate dbg_value for the ref statement

Add a test case for the index projection.

Author: dianqk

compiler/rustc_codegen_ssa/src/mir/statement.rs

@@ -131,7 +131,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     });
                     matches!(local_ref_pass_mode, Some(&PassMode::Indirect {..}) | None) &&
                     // Drop unsupported projections.
-                    // FIXME: Add a test case.
                     place.projection.iter().all(|p| p.can_use_in_debuginfo()) &&
                         // Only pointers can be calculated addresses.
                         bx.type_kind(bx.val_ty(place_ref.val.llval)) == TypeKind::Pointer

tests/codegen-llvm/debuginfo-dse.rs

@@ -103,6 +103,21 @@ pub fn tuple(foo: (i32, &Foo)) -> i32 {
     foo.1.0
 }
 
+#[no_mangle]
+fn index(slice: &[i32; 4], idx: usize) -> i32 {
+    // CHECK-LABEL: define {{.*}} i32 @index
+    // CHECK: bb1:
+    // CHECK-NEXT: #dbg_value(ptr poison, [[VAR_index_from_var:![0-9]+]], !DIExpression()
+    // CODEGEN: bb3:
+    // CHECK-NEXT: #dbg_value(ptr %slice, [[VAR_const_index_from_start:![0-9]+]], !DIExpression()
+    // CHECK-NEXT: #dbg_value(ptr poison, [[VAR_const_index_from_end:![0-9]+]], !DIExpression()
+    let index_from_var = &slice[idx];
+    let [ref const_index_from_start, .., ref const_index_from_end] = slice[..] else {
+        return 0;
+    };
+    slice[0]
+}
+
 // CHECK-DAG: [[VAR_invalid_ref_of_ref_foo]] = !DILocalVariable(name: "invalid_ref_of_ref_foo"
 // OPTIMIZED-DAG: [[VAR_ref_foo]] = !DILocalVariable(name: "ref_foo"
 // CHECK-DAG: [[VAR_ref_v0]] = !DILocalVariable(name: "ref_v0"
@@ -116,5 +131,8 @@ pub fn tuple(foo: (i32, &Foo)) -> i32 {
 // CHECK-DAG: [[VAR_fragment_f]] = !DILocalVariable(name: "fragment_f"
 // CHECK-DAG: [[VAR_tuple_dead]] = !DILocalVariable(name: "tuple_dead"
 // CHECK-DAG: [[VAR_deref_dead]] = !DILocalVariable(name: "deref_dead"
-// CHECK-DAG: [[ARG_dead_first_foo]] = !DILocalVariable(name: "dead_first_foo", arg: 1
+// CHECK-DAG: [[ARG_dead_first_foo]] = !DILocalVariable(name: "dead_first_foo"
 // CHECK-DAG: [[VAR_dead_first_v0]] = !DILocalVariable(name: "dead_first_v0"
+// CHECK-DAG: [[VAR_index_from_var]] = !DILocalVariable(name: "index_from_var"
+// CHECK-DAG: [[VAR_const_index_from_start]] = !DILocalVariable(name: "const_index_from_start"
+// CHECK-DAG: [[VAR_const_index_from_end]] = !DILocalVariable(name: "const_index_from_end"