compiler/rustc_codegen_cranelift/src/constant.rs

   1 //! Handling of `static`s, `const`s and promoted allocations
   2
   3 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
   4 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
   5 use rustc_middle::mir::interpret::{
   6     read_target_uint, AllocId, ConstAllocation, ConstValue, ErrorHandled, GlobalAlloc, Scalar,
   7 };
   8 use rustc_middle::ty::ConstKind;
   9 use rustc_span::DUMMY_SP;
  10
  11 use cranelift_codegen::ir::GlobalValueData;
  12 use cranelift_module::*;
  13
  14 use crate::prelude::*;
  15
  16 pub(crate) struct ConstantCx {
  17     todo: Vec<TodoItem>,
  18     done: FxHashSet<DataId>,
  19     anon_allocs: FxHashMap<AllocId, DataId>,
  20 }
  21
  22 #[derive(Copy, Clone, Debug)]
  23 enum TodoItem {
  24     Alloc(AllocId),
  25     Static(DefId),
  26 }
  27
  28 impl ConstantCx {
  29     pub(crate) fn new() -> Self {
  30         ConstantCx { todo: vec![], done: FxHashSet::default(), anon_allocs: FxHashMap::default() }
  31     }
  32
  33     pub(crate) fn finalize(mut self, tcx: TyCtxt<'_>, module: &mut dyn Module) {
  34         //println!("todo {:?}", self.todo);
  35         define_all_allocs(tcx, module, &mut self);
  36         //println!("done {:?}", self.done);
  37         self.done.clear();
  38     }
  39 }
  40
  41 pub(crate) fn check_constants(fx: &mut FunctionCx<'_, '_, '_>) -> bool {
  42     let mut all_constants_ok = true;
  43     for constant in &fx.mir.required_consts {
  44         let const_ = match fx.monomorphize(constant.literal) {
  45             ConstantKind::Ty(ct) => ct,
  46             ConstantKind::Val(..) => continue,
  47         };
  48         match const_.kind() {
  49             ConstKind::Value(_) => {}
  50             ConstKind::Unevaluated(unevaluated) => {
  51                 if let Err(err) =
  52                     fx.tcx.const_eval_resolve(ParamEnv::reveal_all(), unevaluated, None)
  53                 {
  54                     all_constants_ok = false;
  55                     match err {
  56                         ErrorHandled::Reported(_) | ErrorHandled::Linted => {
  57                             fx.tcx.sess.span_err(constant.span, "erroneous constant encountered");
  58                         }
  59                         ErrorHandled::TooGeneric => {
  60                             span_bug!(
  61                                 constant.span,
  62                                 "codgen encountered polymorphic constant: {:?}",
  63                                 err
  64                             );
  65                         }
  66                     }
  67                 }
  68             }
  69             ConstKind::Param(_)
  70             | ConstKind::Infer(_)
  71             | ConstKind::Bound(_, _)
  72             | ConstKind::Placeholder(_)
  73             | ConstKind::Error(_) => unreachable!("{:?}", const_),
  74         }
  75     }
  76     all_constants_ok
  77 }
  78
  79 pub(crate) fn codegen_static(tcx: TyCtxt<'_>, module: &mut dyn Module, def_id: DefId) {
  80     let mut constants_cx = ConstantCx::new();
  81     constants_cx.todo.push(TodoItem::Static(def_id));
  82     constants_cx.finalize(tcx, module);
  83 }
  84
  85 pub(crate) fn codegen_tls_ref<'tcx>(
  86     fx: &mut FunctionCx<'_, '_, 'tcx>,
  87     def_id: DefId,
  88     layout: TyAndLayout<'tcx>,
  89 ) -> CValue<'tcx> {
  90     let data_id = data_id_for_static(fx.tcx, fx.module, def_id, false);
  91     let local_data_id = fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
  92     if fx.clif_comments.enabled() {
  93         fx.add_comment(local_data_id, format!("tls {:?}", def_id));
  94     }
  95     let tls_ptr = fx.bcx.ins().tls_value(fx.pointer_type, local_data_id);
  96     CValue::by_val(tls_ptr, layout)
  97 }
  98
  99 fn codegen_static_ref<'tcx>(
 100     fx: &mut FunctionCx<'_, '_, 'tcx>,
 101     def_id: DefId,
 102     layout: TyAndLayout<'tcx>,
 103 ) -> CPlace<'tcx> {
 104     let data_id = data_id_for_static(fx.tcx, fx.module, def_id, false);
 105     let local_data_id = fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
 106     if fx.clif_comments.enabled() {
 107         fx.add_comment(local_data_id, format!("{:?}", def_id));
 108     }
 109     let global_ptr = fx.bcx.ins().global_value(fx.pointer_type, local_data_id);
 110     assert!(!layout.is_unsized(), "unsized statics aren't supported");
 111     assert!(
 112         matches!(
 113             fx.bcx.func.global_values[local_data_id],
 114             GlobalValueData::Symbol { tls: false, .. }
 115         ),
 116         "tls static referenced without Rvalue::ThreadLocalRef"
 117     );
 118     CPlace::for_ptr(crate::pointer::Pointer::new(global_ptr), layout)
 119 }
 120
 121 pub(crate) fn codegen_constant<'tcx>(
 122     fx: &mut FunctionCx<'_, '_, 'tcx>,
 123     constant: &Constant<'tcx>,
 124 ) -> CValue<'tcx> {
 125     let const_ = match fx.monomorphize(constant.literal) {
 126         ConstantKind::Ty(ct) => ct,
 127         ConstantKind::Val(val, ty) => return codegen_const_value(fx, val, ty),
 128     };
 129     let const_val = match const_.kind() {
 130         ConstKind::Value(valtree) => fx.tcx.valtree_to_const_val((const_.ty(), valtree)),
 131         ConstKind::Unevaluated(ty::Unevaluated { def, substs, promoted })
 132             if fx.tcx.is_static(def.did) =>
 133         {
 134             assert!(substs.is_empty());
 135             assert!(promoted.is_none());
 136
 137             return codegen_static_ref(fx, def.did, fx.layout_of(const_.ty())).to_cvalue(fx);
 138         }
 139         ConstKind::Unevaluated(unevaluated) => {
 140             match fx.tcx.const_eval_resolve(ParamEnv::reveal_all(), unevaluated, None) {
 141                 Ok(const_val) => const_val,
 142                 Err(_) => {
 143                     span_bug!(constant.span, "erroneous constant not captured by required_consts");
 144                 }
 145             }
 146         }
 147         ConstKind::Param(_)
 148         | ConstKind::Infer(_)
 149         | ConstKind::Bound(_, _)
 150         | ConstKind::Placeholder(_)
 151         | ConstKind::Error(_) => unreachable!("{:?}", const_),
 152     };
 153
 154     codegen_const_value(fx, const_val, const_.ty())
 155 }
 156
 157 pub(crate) fn codegen_const_value<'tcx>(
 158     fx: &mut FunctionCx<'_, '_, 'tcx>,
 159     const_val: ConstValue<'tcx>,
 160     ty: Ty<'tcx>,
 161 ) -> CValue<'tcx> {
 162     let layout = fx.layout_of(ty);
 163     assert!(!layout.is_unsized(), "sized const value");
 164
 165     if layout.is_zst() {
 166         return CValue::by_ref(crate::Pointer::dangling(layout.align.pref), layout);
 167     }
 168
 169     match const_val {
 170         ConstValue::Scalar(x) => match x {
 171             Scalar::Int(int) => {
 172                 if fx.clif_type(layout.ty).is_some() {
 173                     return CValue::const_val(fx, layout, int);
 174                 } else {
 175                     let raw_val = int.to_bits(int.size()).unwrap();
 176                     let val = match int.size().bytes() {
 177                         1 => fx.bcx.ins().iconst(types::I8, raw_val as i64),
 178                         2 => fx.bcx.ins().iconst(types::I16, raw_val as i64),
 179                         4 => fx.bcx.ins().iconst(types::I32, raw_val as i64),
 180                         8 => fx.bcx.ins().iconst(types::I64, raw_val as i64),
 181                         16 => {
 182                             let lsb = fx.bcx.ins().iconst(types::I64, raw_val as u64 as i64);
 183                             let msb =
 184                                 fx.bcx.ins().iconst(types::I64, (raw_val >> 64) as u64 as i64);
 185                             fx.bcx.ins().iconcat(lsb, msb)
 186                         }
 187                         _ => unreachable!(),
 188                     };
 189
 190                     let place = CPlace::new_stack_slot(fx, layout);
 191                     place.to_ptr().store(fx, val, MemFlags::trusted());
 192                     place.to_cvalue(fx)
 193                 }
 194             }
 195             Scalar::Ptr(ptr, _size) => {
 196                 let (alloc_id, offset) = ptr.into_parts(); // we know the `offset` is relative
 197                 let alloc_kind = fx.tcx.get_global_alloc(alloc_id);
 198                 let base_addr = match alloc_kind {
 199                     Some(GlobalAlloc::Memory(alloc)) => {
 200                         let data_id = data_id_for_alloc_id(
 201                             &mut fx.constants_cx,
 202                             fx.module,
 203                             alloc_id,
 204                             alloc.inner().mutability,
 205                         );
 206                         let local_data_id =
 207                             fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
 208                         if fx.clif_comments.enabled() {
 209                             fx.add_comment(local_data_id, format!("{:?}", alloc_id));
 210                         }
 211                         fx.bcx.ins().global_value(fx.pointer_type, local_data_id)
 212                     }
 213                     Some(GlobalAlloc::Function(instance)) => {
 214                         let func_id = crate::abi::import_function(fx.tcx, fx.module, instance);
 215                         let local_func_id =
 216                             fx.module.declare_func_in_func(func_id, &mut fx.bcx.func);
 217                         fx.bcx.ins().func_addr(fx.pointer_type, local_func_id)
 218                     }
 219                     Some(GlobalAlloc::Static(def_id)) => {
 220                         assert!(fx.tcx.is_static(def_id));
 221                         let data_id = data_id_for_static(fx.tcx, fx.module, def_id, false);
 222                         let local_data_id =
 223                             fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
 224                         if fx.clif_comments.enabled() {
 225                             fx.add_comment(local_data_id, format!("{:?}", def_id));
 226                         }
 227                         fx.bcx.ins().global_value(fx.pointer_type, local_data_id)
 228                     }
 229                     None => bug!("missing allocation {:?}", alloc_id),
 230                 };
 231                 let val = if offset.bytes() != 0 {
 232                     fx.bcx.ins().iadd_imm(base_addr, i64::try_from(offset.bytes()).unwrap())
 233                 } else {
 234                     base_addr
 235                 };
 236                 CValue::by_val(val, layout)
 237             }
 238         },
 239         ConstValue::ByRef { alloc, offset } => CValue::by_ref(
 240             pointer_for_allocation(fx, alloc)
 241                 .offset_i64(fx, i64::try_from(offset.bytes()).unwrap()),
 242             layout,
 243         ),
 244         ConstValue::Slice { data, start, end } => {
 245             let ptr = pointer_for_allocation(fx, data)
 246                 .offset_i64(fx, i64::try_from(start).unwrap())
 247                 .get_addr(fx);
 248             let len = fx
 249                 .bcx
 250                 .ins()
 251                 .iconst(fx.pointer_type, i64::try_from(end.checked_sub(start).unwrap()).unwrap());
 252             CValue::by_val_pair(ptr, len, layout)
 253         }
 254     }
 255 }
 256
 257 pub(crate) fn pointer_for_allocation<'tcx>(
 258     fx: &mut FunctionCx<'_, '_, 'tcx>,
 259     alloc: ConstAllocation<'tcx>,
 260 ) -> crate::pointer::Pointer {
 261     let alloc_id = fx.tcx.create_memory_alloc(alloc);
 262     let data_id = data_id_for_alloc_id(
 263         &mut fx.constants_cx,
 264         &mut *fx.module,
 265         alloc_id,
 266         alloc.inner().mutability,
 267     );
 268
 269     let local_data_id = fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
 270     if fx.clif_comments.enabled() {
 271         fx.add_comment(local_data_id, format!("{:?}", alloc_id));
 272     }
 273     let global_ptr = fx.bcx.ins().global_value(fx.pointer_type, local_data_id);
 274     crate::pointer::Pointer::new(global_ptr)
 275 }
 276
 277 pub(crate) fn data_id_for_alloc_id(
 278     cx: &mut ConstantCx,
 279     module: &mut dyn Module,
 280     alloc_id: AllocId,
 281     mutability: rustc_hir::Mutability,
 282 ) -> DataId {
 283     cx.todo.push(TodoItem::Alloc(alloc_id));
 284     *cx.anon_allocs.entry(alloc_id).or_insert_with(|| {
 285         module.declare_anonymous_data(mutability == rustc_hir::Mutability::Mut, false).unwrap()
 286     })
 287 }
 288
 289 fn data_id_for_static(
 290     tcx: TyCtxt<'_>,
 291     module: &mut dyn Module,
 292     def_id: DefId,
 293     definition: bool,
 294 ) -> DataId {
 295     let rlinkage = tcx.codegen_fn_attrs(def_id).linkage;
 296     let linkage = if definition {
 297         crate::linkage::get_static_linkage(tcx, def_id)
 298     } else if rlinkage == Some(rustc_middle::mir::mono::Linkage::ExternalWeak)
 299         || rlinkage == Some(rustc_middle::mir::mono::Linkage::WeakAny)
 300     {
 301         Linkage::Preemptible
 302     } else {
 303         Linkage::Import
 304     };
 305
 306     let instance = Instance::mono(tcx, def_id).polymorphize(tcx);
 307     let symbol_name = tcx.symbol_name(instance).name;
 308     let ty = instance.ty(tcx, ParamEnv::reveal_all());
 309     let is_mutable = if tcx.is_mutable_static(def_id) {
 310         true
 311     } else {
 312         !ty.is_freeze(tcx.at(DUMMY_SP), ParamEnv::reveal_all())
 313     };
 314     let align = tcx.layout_of(ParamEnv::reveal_all().and(ty)).unwrap().align.pref.bytes();
 315
 316     let attrs = tcx.codegen_fn_attrs(def_id);
 317
 318     let data_id = module
 319         .declare_data(
 320             &*symbol_name,
 321             linkage,
 322             is_mutable,
 323             attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL),
 324         )
 325         .unwrap();
 326
 327     if rlinkage.is_some() {
 328         // Comment copied from https://github.com/rust-lang/rust/blob/45060c2a66dfd667f88bd8b94261b28a58d85bd5/src/librustc_codegen_llvm/consts.rs#L141
 329         // Declare an internal global `extern_with_linkage_foo` which
 330         // is initialized with the address of `foo`.  If `foo` is
 331         // discarded during linking (for example, if `foo` has weak
 332         // linkage and there are no definitions), then
 333         // `extern_with_linkage_foo` will instead be initialized to
 334         // zero.
 335
 336         let ref_name = format!("_rust_extern_with_linkage_{}", symbol_name);
 337         let ref_data_id = module.declare_data(&ref_name, Linkage::Local, false, false).unwrap();
 338         let mut data_ctx = DataContext::new();
 339         data_ctx.set_align(align);
 340         let data = module.declare_data_in_data(data_id, &mut data_ctx);
 341         data_ctx.define(std::iter::repeat(0).take(pointer_ty(tcx).bytes() as usize).collect());
 342         data_ctx.write_data_addr(0, data, 0);
 343         match module.define_data(ref_data_id, &data_ctx) {
 344             // Every time the static is referenced there will be another definition of this global,
 345             // so duplicate definitions are expected and allowed.
 346             Err(ModuleError::DuplicateDefinition(_)) => {}
 347             res => res.unwrap(),
 348         }
 349         ref_data_id
 350     } else {
 351         data_id
 352     }
 353 }
 354
 355 fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut ConstantCx) {
 356     while let Some(todo_item) = cx.todo.pop() {
 357         let (data_id, alloc, section_name) = match todo_item {
 358             TodoItem::Alloc(alloc_id) => {
 359                 //println!("alloc_id {}", alloc_id);
 360                 let alloc = match tcx.get_global_alloc(alloc_id).unwrap() {
 361                     GlobalAlloc::Memory(alloc) => alloc,
 362                     GlobalAlloc::Function(_) | GlobalAlloc::Static(_) => unreachable!(),
 363                 };
 364                 let data_id = *cx.anon_allocs.entry(alloc_id).or_insert_with(|| {
 365                     module
 366                         .declare_anonymous_data(
 367                             alloc.inner().mutability == rustc_hir::Mutability::Mut,
 368                             false,
 369                         )
 370                         .unwrap()
 371                 });
 372                 (data_id, alloc, None)
 373             }
 374             TodoItem::Static(def_id) => {
 375                 //println!("static {:?}", def_id);
 376
 377                 let section_name = tcx.codegen_fn_attrs(def_id).link_section;
 378
 379                 let alloc = tcx.eval_static_initializer(def_id).unwrap();
 380
 381                 let data_id = data_id_for_static(tcx, module, def_id, true);
 382                 (data_id, alloc, section_name)
 383             }
 384         };
 385
 386         //("data_id {}", data_id);
 387         if cx.done.contains(&data_id) {
 388             continue;
 389         }
 390
 391         let mut data_ctx = DataContext::new();
 392         let alloc = alloc.inner();
 393         data_ctx.set_align(alloc.align.bytes());
 394
 395         if let Some(section_name) = section_name {
 396             let (segment_name, section_name) = if tcx.sess.target.is_like_osx {
 397                 let section_name = section_name.as_str();
 398                 if let Some(names) = section_name.split_once(',') {
 399                     names
 400                 } else {
 401                     tcx.sess.fatal(&format!(
 402                         "#[link_section = \"{}\"] is not valid for macos target: must be segment and section separated by comma",
 403                         section_name
 404                     ));
 405                 }
 406             } else {
 407                 ("", section_name.as_str())
 408             };
 409             data_ctx.set_segment_section(segment_name, section_name);
 410         }
 411
 412         let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(0..alloc.len()).to_vec();
 413         data_ctx.define(bytes.into_boxed_slice());
 414
 415         for &(offset, alloc_id) in alloc.relocations().iter() {
 416             let addend = {
 417                 let endianness = tcx.data_layout.endian;
 418                 let offset = offset.bytes() as usize;
 419                 let ptr_size = tcx.data_layout.pointer_size;
 420                 let bytes = &alloc.inspect_with_uninit_and_ptr_outside_interpreter(
 421                     offset..offset + ptr_size.bytes() as usize,
 422                 );
 423                 read_target_uint(endianness, bytes).unwrap()
 424             };
 425
 426             let reloc_target_alloc = tcx.get_global_alloc(alloc_id).unwrap();
 427             let data_id = match reloc_target_alloc {
 428                 GlobalAlloc::Function(instance) => {
 429                     assert_eq!(addend, 0);
 430                     let func_id = crate::abi::import_function(tcx, module, instance);
 431                     let local_func_id = module.declare_func_in_data(func_id, &mut data_ctx);
 432                     data_ctx.write_function_addr(offset.bytes() as u32, local_func_id);
 433                     continue;
 434                 }
 435                 GlobalAlloc::Memory(target_alloc) => {
 436                     data_id_for_alloc_id(cx, module, alloc_id, target_alloc.inner().mutability)
 437                 }
 438                 GlobalAlloc::Static(def_id) => {
 439                     if tcx.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::THREAD_LOCAL)
 440                     {
 441                         tcx.sess.fatal(&format!(
 442                             "Allocation {:?} contains reference to TLS value {:?}",
 443                             alloc, def_id
 444                         ));
 445                     }
 446
 447                     // Don't push a `TodoItem::Static` here, as it will cause statics used by
 448                     // multiple crates to be duplicated between them. It isn't necessary anyway,
 449                     // as it will get pushed by `codegen_static` when necessary.
 450                     data_id_for_static(tcx, module, def_id, false)
 451                 }
 452             };
 453
 454             let global_value = module.declare_data_in_data(data_id, &mut data_ctx);
 455             data_ctx.write_data_addr(offset.bytes() as u32, global_value, addend as i64);
 456         }
 457
 458         module.define_data(data_id, &data_ctx).unwrap();
 459         cx.done.insert(data_id);
 460     }
 461
 462     assert!(cx.todo.is_empty(), "{:?}", cx.todo);
 463 }
 464
 465 pub(crate) fn mir_operand_get_const_val<'tcx>(
 466     fx: &FunctionCx<'_, '_, 'tcx>,
 467     operand: &Operand<'tcx>,
 468 ) -> Option<ConstValue<'tcx>> {
 469     match operand {
 470         Operand::Constant(const_) => match const_.literal {
 471             ConstantKind::Ty(const_) => fx
 472                 .monomorphize(const_)
 473                 .eval_for_mir(fx.tcx, ParamEnv::reveal_all())
 474                 .try_to_value(fx.tcx),
 475             ConstantKind::Val(val, _) => Some(val),
 476         },
 477         // FIXME(rust-lang/rust#85105): Casts like `IMM8 as u32` result in the const being stored
 478         // inside a temporary before being passed to the intrinsic requiring the const argument.
 479         // This code tries to find a single constant defining definition of the referenced local.
 480         Operand::Copy(place) | Operand::Move(place) => {
 481             if !place.projection.is_empty() {
 482                 return None;
 483             }
 484             let mut computed_const_val = None;
 485             for bb_data in fx.mir.basic_blocks() {
 486                 for stmt in &bb_data.statements {
 487                     match &stmt.kind {
 488                         StatementKind::Assign(local_and_rvalue) if &local_and_rvalue.0 == place => {
 489                             match &local_and_rvalue.1 {
 490                                 Rvalue::Cast(CastKind::Misc, operand, ty) => {
 491                                     if computed_const_val.is_some() {
 492                                         return None; // local assigned twice
 493                                     }
 494                                     if !matches!(ty.kind(), ty::Uint(_) | ty::Int(_)) {
 495                                         return None;
 496                                     }
 497                                     let const_val = mir_operand_get_const_val(fx, operand)?;
 498                                     if fx.layout_of(*ty).size
 499                                         != const_val.try_to_scalar_int()?.size()
 500                                     {
 501                                         return None;
 502                                     }
 503                                     computed_const_val = Some(const_val);
 504                                 }
 505                                 Rvalue::Use(operand) => {
 506                                     computed_const_val = mir_operand_get_const_val(fx, operand)
 507                                 }
 508                                 _ => return None,
 509                             }
 510                         }
 511                         StatementKind::SetDiscriminant { place: stmt_place, variant_index: _ }
 512                             if &**stmt_place == place =>
 513                         {
 514                             return None;
 515                         }
 516                         StatementKind::CopyNonOverlapping(_) => {
 517                             return None;
 518                         } // conservative handling
 519                         StatementKind::Assign(_)
 520                         | StatementKind::FakeRead(_)
 521                         | StatementKind::SetDiscriminant { .. }
 522                         | StatementKind::Deinit(_)
 523                         | StatementKind::StorageLive(_)
 524                         | StatementKind::StorageDead(_)
 525                         | StatementKind::Retag(_, _)
 526                         | StatementKind::AscribeUserType(_, _)
 527                         | StatementKind::Coverage(_)
 528                         | StatementKind::Nop => {}
 529                     }
 530                 }
 531                 match &bb_data.terminator().kind {
 532                     TerminatorKind::Goto { .. }
 533                     | TerminatorKind::SwitchInt { .. }
 534                     | TerminatorKind::Resume
 535                     | TerminatorKind::Abort
 536                     | TerminatorKind::Return
 537                     | TerminatorKind::Unreachable
 538                     | TerminatorKind::Drop { .. }
 539                     | TerminatorKind::Assert { .. } => {}
 540                     TerminatorKind::DropAndReplace { .. }
 541                     | TerminatorKind::Yield { .. }
 542                     | TerminatorKind::GeneratorDrop
 543                     | TerminatorKind::FalseEdge { .. }
 544                     | TerminatorKind::FalseUnwind { .. } => unreachable!(),
 545                     TerminatorKind::InlineAsm { .. } => return None,
 546                     TerminatorKind::Call { destination, target: Some(_), .. }
 547                         if destination == place =>
 548                     {
 549                         return None;
 550                     }
 551                     TerminatorKind::Call { .. } => {}
 552                 }
 553             }
 554             computed_const_val
 555         }
 556     }
 557 }