1 use rustc_middle::ty::adjustment::PointerCast;
2 use rustc_index::vec::IndexVec;
6 pub(crate) fn trans_fn<'tcx, B: Backend + 'static>(
7 cx: &mut crate::CodegenCx<'tcx, B>,
8 instance: Instance<'tcx>,
13 let mir = tcx.instance_mir(instance.def);
16 let (name, sig) = get_function_name_and_sig(tcx, cx.module.isa().triple(), instance, false);
17 let func_id = cx.module.declare_function(&name, linkage, &sig).unwrap();
19 // Make FunctionBuilder
20 let context = &mut cx.cached_context;
22 context.func.name = ExternalName::user(0, func_id.as_u32());
23 context.func.signature = sig;
24 context.func.collect_debug_info();
25 let mut func_ctx = FunctionBuilderContext::new();
26 let mut bcx = FunctionBuilder::new(&mut context.func, &mut func_ctx);
29 let start_block = bcx.create_block();
30 let block_map: IndexVec<BasicBlock, Block> = (0..mir.basic_blocks().len()).map(|_| bcx.create_block()).collect();
33 let pointer_type = cx.module.target_config().pointer_type();
34 let clif_comments = crate::pretty_clif::CommentWriter::new(tcx, instance);
36 let mut fx = FunctionCx {
38 module: &mut cx.module,
46 local_map: FxHashMap::with_capacity_and_hasher(mir.local_decls.len(), Default::default()),
47 caller_location: None, // set by `codegen_fn_prelude`
48 cold_blocks: EntitySet::new(),
51 constants_cx: &mut cx.constants_cx,
52 vtables: &mut cx.vtables,
53 source_info_set: indexmap::IndexSet::new(),
57 let arg_uninhabited = fx.mir.args_iter().any(|arg| fx.layout_of(fx.monomorphize(&fx.mir.local_decls[arg].ty)).abi.is_uninhabited());
60 fx.bcx.append_block_params_for_function_params(fx.block_map[START_BLOCK]);
61 fx.bcx.switch_to_block(fx.block_map[START_BLOCK]);
62 crate::trap::trap_unreachable(&mut fx, "function has uninhabited argument");
64 tcx.sess.time("codegen clif ir", || {
65 tcx.sess.time("codegen prelude", || crate::abi::codegen_fn_prelude(&mut fx, start_block));
66 codegen_fn_content(&mut fx);
70 // Recover all necessary data from fx, before accessing func will prevent future access to it.
71 let instance = fx.instance;
72 let mut clif_comments = fx.clif_comments;
73 let source_info_set = fx.source_info_set;
74 let local_map = fx.local_map;
75 let cold_blocks = fx.cold_blocks;
77 crate::pretty_clif::write_clif_file(
87 verify_func(tcx, &clif_comments, &context.func);
89 // Perform rust specific optimizations
90 tcx.sess.time("optimize clif ir", || {
91 crate::optimize::optimize_function(tcx, instance, context, &cold_blocks, &mut clif_comments);
94 // If the return block is not reachable, then the SSA builder may have inserted a `iconst.i128`
95 // instruction, which doesn't have an encoding.
96 context.compute_cfg();
97 context.compute_domtree();
98 context.eliminate_unreachable_code(cx.module.isa()).unwrap();
101 let module = &mut cx.module;
104 || module.define_function(
107 &mut cranelift_codegen::binemit::NullTrapSink {},
111 // Write optimized function to file for debugging
112 crate::pretty_clif::write_clif_file(
115 Some(cx.module.isa()),
121 // Define debuginfo for function
122 let isa = cx.module.isa();
123 let debug_context = &mut cx.debug_context;
124 let unwind_context = &mut cx.unwind_context;
125 tcx.sess.time("generate debug info", || {
126 if let Some(debug_context) = debug_context {
127 debug_context.define_function(instance, func_id, &name, isa, context, &source_info_set, local_map);
129 unwind_context.add_function(func_id, &context, isa);
132 // Clear context to make it usable for the next function
136 pub(crate) fn verify_func(tcx: TyCtxt<'_>, writer: &crate::pretty_clif::CommentWriter, func: &Function) {
137 tcx.sess.time("verify clif ir", || {
138 let flags = cranelift_codegen::settings::Flags::new(cranelift_codegen::settings::builder());
139 match cranelift_codegen::verify_function(&func, &flags) {
142 tcx.sess.err(&format!("{:?}", err));
143 let pretty_error = cranelift_codegen::print_errors::pretty_verifier_error(
146 Some(Box::new(writer)),
150 .fatal(&format!("cranelift verify error:\n{}", pretty_error));
156 fn codegen_fn_content(fx: &mut FunctionCx<'_, '_, impl Backend>) {
157 for (bb, bb_data) in fx.mir.basic_blocks().iter_enumerated() {
158 let block = fx.get_block(bb);
159 fx.bcx.switch_to_block(block);
161 if bb_data.is_cleanup {
162 // Unwinding after panicking is not supported
165 // FIXME once unwinding is supported uncomment next lines
166 // // Unwinding is unlikely to happen, so mark cleanup block's as cold.
167 // fx.cold_blocks.insert(block);
171 for stmt in &bb_data.statements {
172 fx.set_debug_loc(stmt.source_info);
173 trans_stmt(fx, block, stmt);
176 #[cfg(debug_assertions)]
178 let mut terminator_head = "\n".to_string();
182 .fmt_head(&mut terminator_head)
184 let inst = fx.bcx.func.layout.last_inst(block).unwrap();
185 fx.add_comment(inst, terminator_head);
188 fx.set_debug_loc(bb_data.terminator().source_info);
190 match &bb_data.terminator().kind {
191 TerminatorKind::Goto { target } => {
192 if let TerminatorKind::Return = fx.mir[*target].terminator().kind {
193 let mut can_immediately_return = true;
194 for stmt in &fx.mir[*target].statements {
195 if let StatementKind::StorageDead(_) = stmt.kind {
197 // FIXME Can sometimes happen, see rust-lang/rust#70531
198 can_immediately_return = false;
203 if can_immediately_return {
204 crate::abi::codegen_return(fx);
209 let block = fx.get_block(*target);
210 fx.bcx.ins().jump(block, &[]);
212 TerminatorKind::Return => {
213 crate::abi::codegen_return(fx);
215 TerminatorKind::Assert {
222 if !fx.tcx.sess.overflow_checks() {
223 if let mir::AssertKind::OverflowNeg(_) = *msg {
224 let target = fx.get_block(*target);
225 fx.bcx.ins().jump(target, &[]);
229 let cond = trans_operand(fx, cond).load_scalar(fx);
231 let target = fx.get_block(*target);
232 let failure = fx.bcx.create_block();
233 fx.cold_blocks.insert(failure);
236 fx.bcx.ins().brz(cond, failure, &[]);
238 fx.bcx.ins().brnz(cond, failure, &[]);
240 fx.bcx.ins().jump(target, &[]);
242 fx.bcx.switch_to_block(failure);
244 let location = fx.get_caller_location(bb_data.terminator().source_info.span).load_scalar(fx);
247 let lang_item = match msg {
248 AssertKind::BoundsCheck { ref len, ref index } => {
249 let len = trans_operand(fx, len).load_scalar(fx);
250 let index = trans_operand(fx, index).load_scalar(fx);
251 args = [index, len, location];
252 rustc_hir::lang_items::PanicBoundsCheckFnLangItem
255 let msg_str = msg.description();
256 let msg_ptr = fx.anonymous_str("assert", msg_str);
257 let msg_len = fx.bcx.ins().iconst(fx.pointer_type, i64::try_from(msg_str.len()).unwrap());
258 args = [msg_ptr, msg_len, location];
259 rustc_hir::lang_items::PanicFnLangItem
263 let def_id = fx.tcx.lang_items().require(lang_item).unwrap_or_else(|s| {
264 fx.tcx.sess.span_fatal(bb_data.terminator().source_info.span, &s)
267 let instance = Instance::mono(fx.tcx, def_id);
268 let symbol_name = fx.tcx.symbol_name(instance).name.as_str();
270 fx.lib_call(&*symbol_name, vec![fx.pointer_type, fx.pointer_type, fx.pointer_type], vec![], &args);
272 crate::trap::trap_unreachable(fx, "panic lang item returned");
275 TerminatorKind::SwitchInt {
281 let discr = trans_operand(fx, discr).load_scalar(fx);
282 let mut switch = ::cranelift_frontend::Switch::new();
283 for (i, value) in values.iter().enumerate() {
284 let block = fx.get_block(targets[i]);
285 switch.set_entry(*value as u64, block);
287 let otherwise_block = fx.get_block(targets[targets.len() - 1]);
288 switch.emit(&mut fx.bcx, discr, otherwise_block);
290 TerminatorKind::Call {
298 fx.tcx.sess.time("codegen call", || crate::abi::codegen_terminator_call(
307 TerminatorKind::InlineAsm {
316 assert_eq!(operands, &[]);
318 Some(destination) => {
319 let destination_block = fx.get_block(destination);
320 fx.bcx.ins().jump(destination_block, &[]);
327 _ => fx.tcx.sess.span_fatal(bb_data.terminator().source_info.span, "Inline assembly is not supported"),
330 TerminatorKind::Resume | TerminatorKind::Abort => {
331 trap_unreachable(fx, "[corruption] Unwinding bb reached.");
333 TerminatorKind::Unreachable => {
334 trap_unreachable(fx, "[corruption] Hit unreachable code.");
336 TerminatorKind::Yield { .. }
337 | TerminatorKind::FalseEdge { .. }
338 | TerminatorKind::FalseUnwind { .. }
339 | TerminatorKind::DropAndReplace { .. }
340 | TerminatorKind::GeneratorDrop => {
341 bug!("shouldn't exist at trans {:?}", bb_data.terminator());
343 TerminatorKind::Drop {
348 let drop_place = trans_place(fx, *place);
349 crate::abi::codegen_drop(fx, bb_data.terminator().source_info.span, drop_place);
351 let target_block = fx.get_block(*target);
352 fx.bcx.ins().jump(target_block, &[]);
357 fx.bcx.seal_all_blocks();
362 fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
363 #[allow(unused_variables)]
365 stmt: &Statement<'tcx>,
367 let _print_guard = crate::PrintOnPanic(|| format!("stmt {:?}", stmt));
369 fx.set_debug_loc(stmt.source_info);
371 #[cfg(false_debug_assertions)]
373 StatementKind::StorageLive(..) | StatementKind::StorageDead(..) => {} // Those are not very useful
375 let inst = fx.bcx.func.layout.last_inst(cur_block).unwrap();
376 fx.add_comment(inst, format!("{:?}", stmt));
381 StatementKind::SetDiscriminant {
385 let place = trans_place(fx, **place);
386 crate::discriminant::codegen_set_discriminant(fx, place, *variant_index);
388 StatementKind::Assign(to_place_and_rval) => {
389 let lval = trans_place(fx, to_place_and_rval.0);
390 let dest_layout = lval.layout();
391 match &to_place_and_rval.1 {
392 Rvalue::Use(operand) => {
393 let val = trans_operand(fx, operand);
394 lval.write_cvalue(fx, val);
396 Rvalue::Ref(_, _, place) | Rvalue::AddressOf(_, place) => {
397 let place = trans_place(fx, *place);
398 place.write_place_ref(fx, lval);
400 Rvalue::ThreadLocalRef(def_id) => {
401 let val = crate::constant::codegen_tls_ref(fx, *def_id, lval.layout());
402 lval.write_cvalue(fx, val);
404 Rvalue::BinaryOp(bin_op, lhs, rhs) => {
405 let lhs = trans_operand(fx, lhs);
406 let rhs = trans_operand(fx, rhs);
408 let res = crate::num::codegen_binop(fx, *bin_op, lhs, rhs);
409 lval.write_cvalue(fx, res);
411 Rvalue::CheckedBinaryOp(bin_op, lhs, rhs) => {
412 let lhs = trans_operand(fx, lhs);
413 let rhs = trans_operand(fx, rhs);
415 let res = if !fx.tcx.sess.overflow_checks() {
417 crate::num::trans_int_binop(fx, *bin_op, lhs, rhs).load_scalar(fx);
418 let is_overflow = fx.bcx.ins().iconst(types::I8, 0);
419 CValue::by_val_pair(val, is_overflow, lval.layout())
421 crate::num::trans_checked_int_binop(fx, *bin_op, lhs, rhs)
424 lval.write_cvalue(fx, res);
426 Rvalue::UnaryOp(un_op, operand) => {
427 let operand = trans_operand(fx, operand);
428 let layout = operand.layout();
429 let val = operand.load_scalar(fx);
430 let res = match un_op {
432 match layout.ty.kind {
434 let res = fx.bcx.ins().icmp_imm(IntCC::Equal, val, 0);
435 CValue::by_val(fx.bcx.ins().bint(types::I8, res), layout)
437 ty::Uint(_) | ty::Int(_) => {
438 CValue::by_val(fx.bcx.ins().bnot(val), layout)
440 _ => unreachable!("un op Not for {:?}", layout.ty),
443 UnOp::Neg => match layout.ty.kind {
444 ty::Int(IntTy::I128) => {
445 // FIXME remove this case once ineg.i128 works
446 let zero = CValue::const_val(fx, layout, 0);
447 crate::num::trans_int_binop(fx, BinOp::Sub, zero, operand)
450 CValue::by_val(fx.bcx.ins().ineg(val), layout)
453 CValue::by_val(fx.bcx.ins().fneg(val), layout)
455 _ => unreachable!("un op Neg for {:?}", layout.ty),
458 lval.write_cvalue(fx, res);
460 Rvalue::Cast(CastKind::Pointer(PointerCast::ReifyFnPointer), operand, to_ty) => {
461 let from_ty = fx.monomorphize(&operand.ty(&fx.mir.local_decls, fx.tcx));
462 let to_layout = fx.layout_of(fx.monomorphize(to_ty));
464 ty::FnDef(def_id, substs) => {
465 let func_ref = fx.get_function_ref(
466 Instance::resolve_for_fn_ptr(fx.tcx, ParamEnv::reveal_all(), def_id, substs)
469 let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
470 lval.write_cvalue(fx, CValue::by_val(func_addr, to_layout));
472 _ => bug!("Trying to ReifyFnPointer on non FnDef {:?}", from_ty),
475 Rvalue::Cast(CastKind::Pointer(PointerCast::UnsafeFnPointer), operand, to_ty)
476 | Rvalue::Cast(CastKind::Pointer(PointerCast::MutToConstPointer), operand, to_ty)
477 | Rvalue::Cast(CastKind::Pointer(PointerCast::ArrayToPointer), operand, to_ty) => {
478 let to_layout = fx.layout_of(fx.monomorphize(to_ty));
479 let operand = trans_operand(fx, operand);
480 lval.write_cvalue(fx, operand.cast_pointer_to(to_layout));
482 Rvalue::Cast(CastKind::Misc, operand, to_ty) => {
483 let operand = trans_operand(fx, operand);
484 let from_ty = operand.layout().ty;
485 let to_ty = fx.monomorphize(to_ty);
488 fx: &FunctionCx<'_, 'tcx, impl Backend>,
491 ty.builtin_deref(true)
496 }| has_ptr_meta(fx.tcx, pointee_ty),
501 if is_fat_ptr(fx, from_ty) {
502 if is_fat_ptr(fx, to_ty) {
503 // fat-ptr -> fat-ptr
504 lval.write_cvalue(fx, operand.cast_pointer_to(dest_layout));
506 // fat-ptr -> thin-ptr
507 let (ptr, _extra) = operand.load_scalar_pair(fx);
508 lval.write_cvalue(fx, CValue::by_val(ptr, dest_layout))
510 } else if let ty::Adt(adt_def, _substs) = from_ty.kind {
511 // enum -> discriminant value
512 assert!(adt_def.is_enum());
514 ty::Uint(_) | ty::Int(_) => {}
515 _ => unreachable!("cast adt {} -> {}", from_ty, to_ty),
518 use rustc_target::abi::{TagEncoding, Int, Variants};
520 match &operand.layout().variants {
521 Variants::Single { index } => {
522 let discr = operand.layout().ty.discriminant_for_variant(fx.tcx, *index).unwrap();
523 let discr = if discr.ty.is_signed() {
524 rustc_middle::mir::interpret::sign_extend(discr.val, fx.layout_of(discr.ty).size)
529 let discr = CValue::const_val(fx, fx.layout_of(to_ty), discr);
530 lval.write_cvalue(fx, discr);
535 tag_encoding: TagEncoding::Direct,
538 let cast_to = fx.clif_type(dest_layout.ty).unwrap();
540 // Read the tag/niche-encoded discriminant from memory.
541 let encoded_discr = operand.value_field(fx, mir::Field::new(*tag_field));
542 let encoded_discr = encoded_discr.load_scalar(fx);
544 // Decode the discriminant (specifically if it's niche-encoded).
545 let signed = match tag.value {
546 Int(_, signed) => signed,
549 let val = clif_intcast(fx, encoded_discr, cast_to, signed);
550 let val = CValue::by_val(val, dest_layout);
551 lval.write_cvalue(fx, val);
553 Variants::Multiple { ..} => unreachable!(),
556 let to_clif_ty = fx.clif_type(to_ty).unwrap();
557 let from = operand.load_scalar(fx);
559 let res = clif_int_or_float_cast(
566 lval.write_cvalue(fx, CValue::by_val(res, dest_layout));
569 Rvalue::Cast(CastKind::Pointer(PointerCast::ClosureFnPointer(_)), operand, _to_ty) => {
570 let operand = trans_operand(fx, operand);
571 match operand.layout().ty.kind {
572 ty::Closure(def_id, substs) => {
573 let instance = Instance::resolve_closure(
577 ty::ClosureKind::FnOnce,
579 let func_ref = fx.get_function_ref(instance);
580 let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
581 lval.write_cvalue(fx, CValue::by_val(func_addr, lval.layout()));
583 _ => bug!("{} cannot be cast to a fn ptr", operand.layout().ty),
586 Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), operand, _to_ty) => {
587 let operand = trans_operand(fx, operand);
588 operand.unsize_value(fx, lval);
590 Rvalue::Discriminant(place) => {
591 let place = trans_place(fx, *place);
592 let value = place.to_cvalue(fx);
594 crate::discriminant::codegen_get_discriminant(fx, value, dest_layout);
595 lval.write_cvalue(fx, discr);
597 Rvalue::Repeat(operand, times) => {
598 let operand = trans_operand(fx, operand);
601 .eval(fx.tcx, ParamEnv::reveal_all())
603 .try_to_bits(fx.tcx.data_layout.pointer_size)
606 let index = fx.bcx.ins().iconst(fx.pointer_type, i as i64);
607 let to = lval.place_index(fx, index);
608 to.write_cvalue(fx, operand);
611 Rvalue::Len(place) => {
612 let place = trans_place(fx, *place);
613 let usize_layout = fx.layout_of(fx.tcx.types.usize);
614 let len = codegen_array_len(fx, place);
615 lval.write_cvalue(fx, CValue::by_val(len, usize_layout));
617 Rvalue::NullaryOp(NullOp::Box, content_ty) => {
618 use rustc_hir::lang_items::ExchangeMallocFnLangItem;
620 let usize_type = fx.clif_type(fx.tcx.types.usize).unwrap();
621 let content_ty = fx.monomorphize(content_ty);
622 let layout = fx.layout_of(content_ty);
623 let llsize = fx.bcx.ins().iconst(usize_type, layout.size.bytes() as i64);
627 .iconst(usize_type, layout.align.abi.bytes() as i64);
628 let box_layout = fx.layout_of(fx.tcx.mk_box(content_ty));
631 let def_id = match fx.tcx.lang_items().require(ExchangeMallocFnLangItem) {
636 .fatal(&format!("allocation of `{}` {}", box_layout.ty, s));
639 let instance = ty::Instance::mono(fx.tcx, def_id);
640 let func_ref = fx.get_function_ref(instance);
641 let call = fx.bcx.ins().call(func_ref, &[llsize, llalign]);
642 let ptr = fx.bcx.inst_results(call)[0];
643 lval.write_cvalue(fx, CValue::by_val(ptr, box_layout));
645 Rvalue::NullaryOp(NullOp::SizeOf, ty) => {
649 .is_sized(fx.tcx.at(stmt.source_info.span), ParamEnv::reveal_all()));
650 let ty_size = fx.layout_of(fx.monomorphize(ty)).size.bytes();
651 let val = CValue::const_val(fx, fx.layout_of(fx.tcx.types.usize), ty_size.into());
652 lval.write_cvalue(fx, val);
654 Rvalue::Aggregate(kind, operands) => match **kind {
655 AggregateKind::Array(_ty) => {
656 for (i, operand) in operands.into_iter().enumerate() {
657 let operand = trans_operand(fx, operand);
658 let index = fx.bcx.ins().iconst(fx.pointer_type, i as i64);
659 let to = lval.place_index(fx, index);
660 to.write_cvalue(fx, operand);
663 _ => unreachable!("shouldn't exist at trans {:?}", to_place_and_rval.1),
667 StatementKind::StorageLive(_)
668 | StatementKind::StorageDead(_)
670 | StatementKind::FakeRead(..)
671 | StatementKind::Retag { .. }
672 | StatementKind::AscribeUserType(..) => {}
674 StatementKind::LlvmInlineAsm(asm) => {
675 use rustc_span::symbol::Symbol;
681 let rustc_hir::LlvmInlineAsmInner {
682 asm: asm_code, // Name
683 outputs, // Vec<Name>
685 clobbers, // Vec<Name>
688 dialect: _, // rustc_ast::ast::AsmDialect
691 match &*asm_code.as_str() {
695 cpuid if cpuid.contains("cpuid") => {
696 crate::trap::trap_unimplemented(
698 "__cpuid_count arch intrinsic is not supported",
702 assert_eq!(inputs, &[Symbol::intern("{ecx}")]);
704 assert_eq!(outputs.len(), 2);
705 for (i, c) in (&["={eax}", "={edx}"]).iter().enumerate() {
706 assert_eq!(&outputs[i].constraint.as_str(), c);
707 assert!(!outputs[i].is_rw);
708 assert!(!outputs[i].is_indirect);
711 assert_eq!(clobbers, &[]);
714 assert!(!alignstack);
716 crate::trap::trap_unimplemented(fx, "_xgetbv arch intrinsic is not supported");
718 // ___chkstk, ___chkstk_ms and __alloca are only used on Windows
719 _ if fx.tcx.symbol_name(fx.instance).name.as_str().starts_with("___chkstk") => {
720 crate::trap::trap_unimplemented(fx, "Stack probes are not supported");
722 _ if fx.tcx.symbol_name(fx.instance).name.as_str() == "__alloca" => {
723 crate::trap::trap_unimplemented(fx, "Alloca is not supported");
725 // Used in sys::windows::abort_internal
727 crate::trap::trap_unimplemented(fx, "Windows abort");
729 _ => fx.tcx.sess.span_fatal(stmt.source_info.span, "Inline assembly is not supported"),
735 fn codegen_array_len<'tcx>(
736 fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
739 match place.layout().ty.kind {
740 ty::Array(_elem_ty, len) => {
741 let len = fx.monomorphize(&len)
742 .eval(fx.tcx, ParamEnv::reveal_all())
743 .eval_usize(fx.tcx, ParamEnv::reveal_all()) as i64;
744 fx.bcx.ins().iconst(fx.pointer_type, len)
746 ty::Slice(_elem_ty) => place
747 .to_ptr_maybe_unsized()
749 .expect("Length metadata for slice place"),
750 _ => bug!("Rvalue::Len({:?})", place),
754 pub(crate) fn trans_place<'tcx>(
755 fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
758 let mut cplace = fx.get_local_place(place.local);
760 for elem in place.projection {
762 PlaceElem::Deref => {
763 cplace = cplace.place_deref(fx);
765 PlaceElem::Field(field, _ty) => {
766 cplace = cplace.place_field(fx, field);
768 PlaceElem::Index(local) => {
769 let index = fx.get_local_place(local).to_cvalue(fx).load_scalar(fx);
770 cplace = cplace.place_index(fx, index);
772 PlaceElem::ConstantIndex {
777 let index = if !from_end {
778 fx.bcx.ins().iconst(fx.pointer_type, offset as i64)
780 let len = codegen_array_len(fx, cplace);
781 fx.bcx.ins().iadd_imm(len, -(offset as i64))
783 cplace = cplace.place_index(fx, index);
785 PlaceElem::Subslice { from, to, from_end } => {
786 // These indices are generated by slice patterns.
787 // slice[from:-to] in Python terms.
789 match cplace.layout().ty.kind {
790 ty::Array(elem_ty, _len) => {
791 assert!(!from_end, "array subslices are never `from_end`");
792 let elem_layout = fx.layout_of(elem_ty);
793 let ptr = cplace.to_ptr();
794 cplace = CPlace::for_ptr(
795 ptr.offset_i64(fx, elem_layout.size.bytes() as i64 * from as i64),
796 fx.layout_of(fx.tcx.mk_array(elem_ty, to as u64 - from as u64)),
799 ty::Slice(elem_ty) => {
800 assert!(from_end, "slice subslices should be `from_end`");
801 let elem_layout = fx.layout_of(elem_ty);
802 let (ptr, len) = cplace.to_ptr_maybe_unsized();
803 let len = len.unwrap();
804 cplace = CPlace::for_ptr_with_extra(
805 ptr.offset_i64(fx, elem_layout.size.bytes() as i64 * from as i64),
806 fx.bcx.ins().iadd_imm(len, -(from as i64 + to as i64)),
813 PlaceElem::Downcast(_adt_def, variant) => {
814 cplace = cplace.downcast_variant(fx, variant);
822 pub(crate) fn trans_operand<'tcx>(
823 fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
824 operand: &Operand<'tcx>,
827 Operand::Move(place) | Operand::Copy(place) => {
828 let cplace = trans_place(fx, *place);
831 Operand::Constant(const_) => crate::constant::trans_constant(fx, const_),