1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use rustc::ty::{self, Ty};
12 use rustc::ty::cast::{CastTy, IntTy};
13 use rustc::ty::layout::{self, LayoutOf, HasTyCtxt};
15 use rustc::middle::lang_items::ExchangeMallocFnLangItem;
16 use rustc_apfloat::{ieee, Float, Status, Round};
17 use std::{u128, i128};
20 use builder::MemFlags;
22 use common::{self, RealPredicate};
23 use rustc_codegen_utils::common::IntPredicate;
25 use type_of::LayoutLlvmExt;
29 use super::{FunctionCx, LocalRef};
30 use super::operand::{OperandRef, OperandValue};
31 use super::place::PlaceRef;
33 impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
34 pub fn codegen_rvalue(
37 dest: PlaceRef<'tcx, Bx::Value>,
38 rvalue: &mir::Rvalue<'tcx>
40 debug!("codegen_rvalue(dest.llval={:?}, rvalue={:?})",
44 mir::Rvalue::Use(ref operand) => {
45 let cg_operand = self.codegen_operand(&bx, operand);
46 // FIXME: consider not copying constants through stack. (fixable by codegenning
47 // constants into OperandValue::Ref, why don’t we do that yet if we don’t?)
48 cg_operand.val.store(&bx, dest);
52 mir::Rvalue::Cast(mir::CastKind::Unsize, ref source, _) => {
53 // The destination necessarily contains a fat pointer, so if
54 // it's a scalar pair, it's a fat pointer or newtype thereof.
55 if dest.layout.is_llvm_scalar_pair() {
56 // into-coerce of a thin pointer to a fat pointer - just
57 // use the operand path.
58 let (bx, temp) = self.codegen_rvalue_operand(bx, rvalue);
59 temp.val.store(&bx, dest);
63 // Unsize of a nontrivial struct. I would prefer for
64 // this to be eliminated by MIR building, but
65 // `CoerceUnsized` can be passed by a where-clause,
66 // so the (generic) MIR may not be able to expand it.
67 let operand = self.codegen_operand(&bx, source);
69 OperandValue::Pair(..) |
70 OperandValue::Immediate(_) => {
71 // unsize from an immediate structure. We don't
72 // really need a temporary alloca here, but
73 // avoiding it would require us to have
74 // `coerce_unsized_into` use extractvalue to
75 // index into the struct, and this case isn't
76 // important enough for it.
77 debug!("codegen_rvalue: creating ugly alloca");
78 let scratch = PlaceRef::alloca(&bx, operand.layout, "__unsize_temp");
79 scratch.storage_live(&bx);
80 operand.val.store(&bx, scratch);
81 base::coerce_unsized_into(&bx, scratch, dest);
82 scratch.storage_dead(&bx);
84 OperandValue::Ref(llref, None, align) => {
85 let source = PlaceRef::new_sized(llref, operand.layout, align);
86 base::coerce_unsized_into(&bx, source, dest);
88 OperandValue::Ref(_, Some(_), _) => {
89 bug!("unsized coercion on an unsized rvalue")
95 mir::Rvalue::Repeat(ref elem, count) => {
96 let cg_elem = self.codegen_operand(&bx, elem);
98 // Do not generate the loop for zero-sized elements or empty arrays.
99 if dest.layout.is_zst() {
103 let start = dest.project_index(&bx, bx.cx().const_usize(0)).llval;
105 if let OperandValue::Immediate(v) = cg_elem.val {
106 let size = bx.cx().const_usize(dest.layout.size.bytes());
108 // Use llvm.memset.p0i8.* to initialize all zero arrays
109 if bx.cx().is_const_integral(v) && bx.cx().const_to_uint(v) == 0 {
110 let fill = bx.cx().const_u8(0);
111 bx.memset(start, fill, size, dest.align, MemFlags::empty());
115 // Use llvm.memset.p0i8.* to initialize byte arrays
116 let v = base::from_immediate(&bx, v);
117 if bx.cx().val_ty(v) == bx.cx().type_i8() {
118 bx.memset(start, v, size, dest.align, MemFlags::empty());
123 let count = bx.cx().const_usize(count);
124 let end = dest.project_index(&bx, count).llval;
126 let header_bx = bx.build_sibling_block("repeat_loop_header");
127 let body_bx = bx.build_sibling_block("repeat_loop_body");
128 let next_bx = bx.build_sibling_block("repeat_loop_next");
130 bx.br(header_bx.llbb());
131 let current = header_bx.phi(bx.cx().val_ty(start), &[start], &[bx.llbb()]);
133 let keep_going = header_bx.icmp(IntPredicate::IntNE, current, end);
134 header_bx.cond_br(keep_going, body_bx.llbb(), next_bx.llbb());
136 cg_elem.val.store(&body_bx,
137 PlaceRef::new_sized(current, cg_elem.layout, dest.align));
139 let next = body_bx.inbounds_gep(current, &[bx.cx().const_usize(1)]);
140 body_bx.br(header_bx.llbb());
141 header_bx.add_incoming_to_phi(current, next, body_bx.llbb());
146 mir::Rvalue::Aggregate(ref kind, ref operands) => {
147 let (dest, active_field_index) = match **kind {
148 mir::AggregateKind::Adt(adt_def, variant_index, _, _, active_field_index) => {
149 dest.codegen_set_discr(&bx, variant_index);
150 if adt_def.is_enum() {
151 (dest.project_downcast(&bx, variant_index), active_field_index)
153 (dest, active_field_index)
158 for (i, operand) in operands.iter().enumerate() {
159 let op = self.codegen_operand(&bx, operand);
160 // Do not generate stores and GEPis for zero-sized fields.
161 if !op.layout.is_zst() {
162 let field_index = active_field_index.unwrap_or(i);
163 op.val.store(&bx, dest.project_field(&bx, field_index));
170 assert!(self.rvalue_creates_operand(rvalue));
171 let (bx, temp) = self.codegen_rvalue_operand(bx, rvalue);
172 temp.val.store(&bx, dest);
178 pub fn codegen_rvalue_unsized(
181 indirect_dest: PlaceRef<'tcx, Bx::Value>,
182 rvalue: &mir::Rvalue<'tcx>,
184 debug!("codegen_rvalue_unsized(indirect_dest.llval={:?}, rvalue={:?})",
185 indirect_dest.llval, rvalue);
188 mir::Rvalue::Use(ref operand) => {
189 let cg_operand = self.codegen_operand(&bx, operand);
190 cg_operand.val.store_unsized(&bx, indirect_dest);
194 _ => bug!("unsized assignment other than Rvalue::Use"),
198 pub fn codegen_rvalue_operand(
201 rvalue: &mir::Rvalue<'tcx>
202 ) -> (Bx, OperandRef<'tcx, Bx::Value>) {
203 assert!(self.rvalue_creates_operand(rvalue), "cannot codegen {:?} to operand", rvalue);
206 mir::Rvalue::Cast(ref kind, ref source, mir_cast_ty) => {
207 let operand = self.codegen_operand(&bx, source);
208 debug!("cast operand is {:?}", operand);
209 let cast = bx.cx().layout_of(self.monomorphize(&mir_cast_ty));
211 let val = match *kind {
212 mir::CastKind::ReifyFnPointer => {
213 match operand.layout.ty.sty {
214 ty::FnDef(def_id, substs) => {
215 if bx.cx().tcx().has_attr(def_id, "rustc_args_required_const") {
216 bug!("reifying a fn ptr that requires \
219 OperandValue::Immediate(
220 callee::resolve_and_get_fn(bx.cx(), def_id, substs))
223 bug!("{} cannot be reified to a fn ptr", operand.layout.ty)
227 mir::CastKind::ClosureFnPointer => {
228 match operand.layout.ty.sty {
229 ty::Closure(def_id, substs) => {
230 let instance = monomorphize::resolve_closure(
231 bx.cx().tcx(), def_id, substs, ty::ClosureKind::FnOnce);
232 OperandValue::Immediate(bx.cx().get_fn(instance))
235 bug!("{} cannot be cast to a fn ptr", operand.layout.ty)
239 mir::CastKind::UnsafeFnPointer => {
240 // this is a no-op at the LLVM level
243 mir::CastKind::Unsize => {
244 assert!(cast.is_llvm_scalar_pair());
246 OperandValue::Pair(lldata, llextra) => {
247 // unsize from a fat pointer - this is a
248 // "trait-object-to-supertrait" coercion, for
250 // &'a fmt::Debug+Send => &'a fmt::Debug,
252 // HACK(eddyb) have to bitcast pointers
253 // until LLVM removes pointee types.
254 let lldata = bx.pointercast(lldata,
255 bx.cx().scalar_pair_element_backend_type(cast, 0, true));
256 OperandValue::Pair(lldata, llextra)
258 OperandValue::Immediate(lldata) => {
260 let (lldata, llextra) = base::unsize_thin_ptr(&bx, lldata,
261 operand.layout.ty, cast.ty);
262 OperandValue::Pair(lldata, llextra)
264 OperandValue::Ref(..) => {
265 bug!("by-ref operand {:?} in codegen_rvalue_operand",
270 mir::CastKind::Misc if operand.layout.is_llvm_scalar_pair() => {
271 if let OperandValue::Pair(data_ptr, meta) = operand.val {
272 if cast.is_llvm_scalar_pair() {
273 let data_cast = bx.pointercast(data_ptr,
274 bx.cx().scalar_pair_element_backend_type(cast, 0, true));
275 OperandValue::Pair(data_cast, meta)
276 } else { // cast to thin-ptr
277 // Cast of fat-ptr to thin-ptr is an extraction of data-ptr and
278 // pointer-cast of that pointer to desired pointer type.
279 let llcast_ty = bx.cx().immediate_backend_type(cast);
280 let llval = bx.pointercast(data_ptr, llcast_ty);
281 OperandValue::Immediate(llval)
284 bug!("Unexpected non-Pair operand")
287 mir::CastKind::Misc => {
288 assert!(cast.is_llvm_immediate());
289 let ll_t_out = bx.cx().immediate_backend_type(cast);
290 if operand.layout.abi.is_uninhabited() {
291 let val = OperandValue::Immediate(bx.cx().const_undef(ll_t_out));
292 return (bx, OperandRef {
297 let r_t_in = CastTy::from_ty(operand.layout.ty)
298 .expect("bad input type for cast");
299 let r_t_out = CastTy::from_ty(cast.ty).expect("bad output type for cast");
300 let ll_t_in = bx.cx().immediate_backend_type(operand.layout);
301 match operand.layout.variants {
302 layout::Variants::Single { index } => {
303 if let Some(def) = operand.layout.ty.ty_adt_def() {
305 .discriminant_for_variant(bx.cx().tcx(), index)
307 let discr = bx.cx().const_uint_big(ll_t_out, discr_val);
308 return (bx, OperandRef {
309 val: OperandValue::Immediate(discr),
314 layout::Variants::Tagged { .. } |
315 layout::Variants::NicheFilling { .. } => {},
317 let llval = operand.immediate();
319 let mut signed = false;
320 if let layout::Abi::Scalar(ref scalar) = operand.layout.abi {
321 if let layout::Int(_, s) = scalar.value {
322 // We use `i1` for bytes that are always `0` or `1`,
323 // e.g. `#[repr(i8)] enum E { A, B }`, but we can't
324 // let LLVM interpret the `i1` as signed, because
325 // then `i1 1` (i.e. E::B) is effectively `i8 -1`.
326 signed = !scalar.is_bool() && s;
328 let er = scalar.valid_range_exclusive(bx.cx());
329 if er.end != er.start &&
330 scalar.valid_range.end() > scalar.valid_range.start() {
331 // We want `table[e as usize]` to not
332 // have bound checks, and this is the most
333 // convenient place to put the `assume`.
335 base::call_assume(&bx, bx.icmp(
336 IntPredicate::IntULE,
338 bx.cx().const_uint_big(ll_t_in, *scalar.valid_range.end())
344 let newval = match (r_t_in, r_t_out) {
345 (CastTy::Int(_), CastTy::Int(_)) => {
346 bx.intcast(llval, ll_t_out, signed)
348 (CastTy::Float, CastTy::Float) => {
349 let srcsz = bx.cx().float_width(ll_t_in);
350 let dstsz = bx.cx().float_width(ll_t_out);
352 bx.fpext(llval, ll_t_out)
353 } else if srcsz > dstsz {
354 bx.fptrunc(llval, ll_t_out)
359 (CastTy::Ptr(_), CastTy::Ptr(_)) |
360 (CastTy::FnPtr, CastTy::Ptr(_)) |
361 (CastTy::RPtr(_), CastTy::Ptr(_)) =>
362 bx.pointercast(llval, ll_t_out),
363 (CastTy::Ptr(_), CastTy::Int(_)) |
364 (CastTy::FnPtr, CastTy::Int(_)) =>
365 bx.ptrtoint(llval, ll_t_out),
366 (CastTy::Int(_), CastTy::Ptr(_)) => {
367 let usize_llval = bx.intcast(llval, bx.cx().type_isize(), signed);
368 bx.inttoptr(usize_llval, ll_t_out)
370 (CastTy::Int(_), CastTy::Float) =>
371 cast_int_to_float(&bx, signed, llval, ll_t_in, ll_t_out),
372 (CastTy::Float, CastTy::Int(IntTy::I)) =>
373 cast_float_to_int(&bx, true, llval, ll_t_in, ll_t_out),
374 (CastTy::Float, CastTy::Int(_)) =>
375 cast_float_to_int(&bx, false, llval, ll_t_in, ll_t_out),
376 _ => bug!("unsupported cast: {:?} to {:?}", operand.layout.ty, cast.ty)
378 OperandValue::Immediate(newval)
387 mir::Rvalue::Ref(_, bk, ref place) => {
388 let cg_place = self.codegen_place(&bx, place);
390 let ty = cg_place.layout.ty;
392 // Note: places are indirect, so storing the `llval` into the
393 // destination effectively creates a reference.
394 let val = if !bx.cx().type_has_metadata(ty) {
395 OperandValue::Immediate(cg_place.llval)
397 OperandValue::Pair(cg_place.llval, cg_place.llextra.unwrap())
401 layout: self.cx.layout_of(self.cx.tcx().mk_ref(
402 self.cx.tcx().types.re_erased,
403 ty::TypeAndMut { ty, mutbl: bk.to_mutbl_lossy() }
408 mir::Rvalue::Len(ref place) => {
409 let size = self.evaluate_array_len(&bx, place);
410 let operand = OperandRef {
411 val: OperandValue::Immediate(size),
412 layout: bx.cx().layout_of(bx.tcx().types.usize),
417 mir::Rvalue::BinaryOp(op, ref lhs, ref rhs) => {
418 let lhs = self.codegen_operand(&bx, lhs);
419 let rhs = self.codegen_operand(&bx, rhs);
420 let llresult = match (lhs.val, rhs.val) {
421 (OperandValue::Pair(lhs_addr, lhs_extra),
422 OperandValue::Pair(rhs_addr, rhs_extra)) => {
423 self.codegen_fat_ptr_binop(&bx, op,
429 (OperandValue::Immediate(lhs_val),
430 OperandValue::Immediate(rhs_val)) => {
431 self.codegen_scalar_binop(&bx, op, lhs_val, rhs_val, lhs.layout.ty)
436 let operand = OperandRef {
437 val: OperandValue::Immediate(llresult),
438 layout: bx.cx().layout_of(
439 op.ty(bx.tcx(), lhs.layout.ty, rhs.layout.ty)),
443 mir::Rvalue::CheckedBinaryOp(op, ref lhs, ref rhs) => {
444 let lhs = self.codegen_operand(&bx, lhs);
445 let rhs = self.codegen_operand(&bx, rhs);
446 let result = self.codegen_scalar_checked_binop(&bx, op,
447 lhs.immediate(), rhs.immediate(),
449 let val_ty = op.ty(bx.tcx(), lhs.layout.ty, rhs.layout.ty);
450 let operand_ty = bx.tcx().intern_tup(&[val_ty, bx.tcx().types.bool]);
451 let operand = OperandRef {
453 layout: bx.cx().layout_of(operand_ty)
459 mir::Rvalue::UnaryOp(op, ref operand) => {
460 let operand = self.codegen_operand(&bx, operand);
461 let lloperand = operand.immediate();
462 let is_float = operand.layout.ty.is_fp();
463 let llval = match op {
464 mir::UnOp::Not => bx.not(lloperand),
465 mir::UnOp::Neg => if is_float {
472 val: OperandValue::Immediate(llval),
473 layout: operand.layout,
477 mir::Rvalue::Discriminant(ref place) => {
478 let discr_ty = rvalue.ty(&*self.mir, bx.tcx());
479 let discr = self.codegen_place(&bx, place)
480 .codegen_get_discr(&bx, discr_ty);
482 val: OperandValue::Immediate(discr),
483 layout: self.cx.layout_of(discr_ty)
487 mir::Rvalue::NullaryOp(mir::NullOp::SizeOf, ty) => {
488 assert!(bx.cx().type_is_sized(ty));
489 let val = bx.cx().const_usize(bx.cx().layout_of(ty).size.bytes());
490 let tcx = self.cx.tcx();
492 val: OperandValue::Immediate(val),
493 layout: self.cx.layout_of(tcx.types.usize),
497 mir::Rvalue::NullaryOp(mir::NullOp::Box, content_ty) => {
498 let content_ty: Ty<'tcx> = self.monomorphize(&content_ty);
499 let (size, align) = bx.cx().layout_of(content_ty).size_and_align();
500 let llsize = bx.cx().const_usize(size.bytes());
501 let llalign = bx.cx().const_usize(align.abi());
502 let box_layout = bx.cx().layout_of(bx.tcx().mk_box(content_ty));
503 let llty_ptr = bx.cx().backend_type(box_layout);
506 let def_id = match bx.tcx().lang_items().require(ExchangeMallocFnLangItem) {
509 bx.cx().sess().fatal(&format!("allocation of `{}` {}", box_layout.ty, s));
512 let instance = ty::Instance::mono(bx.tcx(), def_id);
513 let r = bx.cx().get_fn(instance);
514 let val = bx.pointercast(bx.call(r, &[llsize, llalign], None), llty_ptr);
516 let operand = OperandRef {
517 val: OperandValue::Immediate(val),
522 mir::Rvalue::Use(ref operand) => {
523 let operand = self.codegen_operand(&bx, operand);
526 mir::Rvalue::Repeat(..) |
527 mir::Rvalue::Aggregate(..) => {
528 // According to `rvalue_creates_operand`, only ZST
529 // aggregate rvalues are allowed to be operands.
530 let ty = rvalue.ty(self.mir, self.cx.tcx());
531 (bx, OperandRef::new_zst(self.cx,
532 self.cx.layout_of(self.monomorphize(&ty))))
537 fn evaluate_array_len(
540 place: &mir::Place<'tcx>,
542 // ZST are passed as operands and require special handling
543 // because codegen_place() panics if Local is operand.
544 if let mir::Place::Local(index) = *place {
545 if let LocalRef::Operand(Some(op)) = self.locals[index] {
546 if let ty::Array(_, n) = op.layout.ty.sty {
547 let n = n.unwrap_usize(bx.cx().tcx());
548 return bx.cx().const_usize(n);
552 // use common size calculation for non zero-sized types
553 let cg_value = self.codegen_place(bx, place);
554 return cg_value.len(bx.cx());
557 pub fn codegen_scalar_binop(
565 let is_float = input_ty.is_fp();
566 let is_signed = input_ty.is_signed();
567 let is_unit = input_ty.is_unit();
569 mir::BinOp::Add => if is_float {
574 mir::BinOp::Sub => if is_float {
579 mir::BinOp::Mul => if is_float {
584 mir::BinOp::Div => if is_float {
586 } else if is_signed {
591 mir::BinOp::Rem => if is_float {
593 } else if is_signed {
598 mir::BinOp::BitOr => bx.or(lhs, rhs),
599 mir::BinOp::BitAnd => bx.and(lhs, rhs),
600 mir::BinOp::BitXor => bx.xor(lhs, rhs),
601 mir::BinOp::Offset => bx.inbounds_gep(lhs, &[rhs]),
602 mir::BinOp::Shl => common::build_unchecked_lshift(bx, lhs, rhs),
603 mir::BinOp::Shr => common::build_unchecked_rshift(bx, input_ty, lhs, rhs),
604 mir::BinOp::Ne | mir::BinOp::Lt | mir::BinOp::Gt |
605 mir::BinOp::Eq | mir::BinOp::Le | mir::BinOp::Ge => if is_unit {
606 bx.cx().const_bool(match op {
607 mir::BinOp::Ne | mir::BinOp::Lt | mir::BinOp::Gt => false,
608 mir::BinOp::Eq | mir::BinOp::Le | mir::BinOp::Ge => true,
613 base::bin_op_to_fcmp_predicate(op.to_hir_binop()),
618 base::bin_op_to_icmp_predicate(op.to_hir_binop(), is_signed),
625 pub fn codegen_fat_ptr_binop(
630 lhs_extra: Bx::Value,
632 rhs_extra: Bx::Value,
638 bx.icmp(IntPredicate::IntEQ, lhs_addr, rhs_addr),
639 bx.icmp(IntPredicate::IntEQ, lhs_extra, rhs_extra)
644 bx.icmp(IntPredicate::IntNE, lhs_addr, rhs_addr),
645 bx.icmp(IntPredicate::IntNE, lhs_extra, rhs_extra)
648 mir::BinOp::Le | mir::BinOp::Lt |
649 mir::BinOp::Ge | mir::BinOp::Gt => {
650 // a OP b ~ a.0 STRICT(OP) b.0 | (a.0 == b.0 && a.1 OP a.1)
651 let (op, strict_op) = match op {
652 mir::BinOp::Lt => (IntPredicate::IntULT, IntPredicate::IntULT),
653 mir::BinOp::Le => (IntPredicate::IntULE, IntPredicate::IntULT),
654 mir::BinOp::Gt => (IntPredicate::IntUGT, IntPredicate::IntUGT),
655 mir::BinOp::Ge => (IntPredicate::IntUGE, IntPredicate::IntUGT),
660 bx.icmp(strict_op, lhs_addr, rhs_addr),
662 bx.icmp(IntPredicate::IntEQ, lhs_addr, rhs_addr),
663 bx.icmp(op, lhs_extra, rhs_extra)
668 bug!("unexpected fat ptr binop");
673 pub fn codegen_scalar_checked_binop(
680 ) -> OperandValue<Bx::Value> {
681 // This case can currently arise only from functions marked
682 // with #[rustc_inherit_overflow_checks] and inlined from
683 // another crate (mostly core::num generic/#[inline] fns),
684 // while the current crate doesn't use overflow checks.
685 if !bx.cx().check_overflow() {
686 let val = self.codegen_scalar_binop(bx, op, lhs, rhs, input_ty);
687 return OperandValue::Pair(val, bx.cx().const_bool(false));
690 let (val, of) = match op {
691 // These are checked using intrinsics
692 mir::BinOp::Add | mir::BinOp::Sub | mir::BinOp::Mul => {
694 mir::BinOp::Add => OverflowOp::Add,
695 mir::BinOp::Sub => OverflowOp::Sub,
696 mir::BinOp::Mul => OverflowOp::Mul,
699 let intrinsic = get_overflow_intrinsic(oop, bx, input_ty);
700 let res = bx.call(intrinsic, &[lhs, rhs], None);
702 (bx.extract_value(res, 0),
703 bx.extract_value(res, 1))
705 mir::BinOp::Shl | mir::BinOp::Shr => {
706 let lhs_llty = bx.cx().val_ty(lhs);
707 let rhs_llty = bx.cx().val_ty(rhs);
708 let invert_mask = common::shift_mask_val(bx, lhs_llty, rhs_llty, true);
709 let outer_bits = bx.and(rhs, invert_mask);
711 let of = bx.icmp(IntPredicate::IntNE, outer_bits, bx.cx().const_null(rhs_llty));
712 let val = self.codegen_scalar_binop(bx, op, lhs, rhs, input_ty);
717 bug!("Operator `{:?}` is not a checkable operator", op)
721 OperandValue::Pair(val, of)
725 impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
726 pub fn rvalue_creates_operand(&self, rvalue: &mir::Rvalue<'tcx>) -> bool {
728 mir::Rvalue::Ref(..) |
729 mir::Rvalue::Len(..) |
730 mir::Rvalue::Cast(..) | // (*)
731 mir::Rvalue::BinaryOp(..) |
732 mir::Rvalue::CheckedBinaryOp(..) |
733 mir::Rvalue::UnaryOp(..) |
734 mir::Rvalue::Discriminant(..) |
735 mir::Rvalue::NullaryOp(..) |
736 mir::Rvalue::Use(..) => // (*)
738 mir::Rvalue::Repeat(..) |
739 mir::Rvalue::Aggregate(..) => {
740 let ty = rvalue.ty(self.mir, self.cx.tcx());
741 let ty = self.monomorphize(&ty);
742 self.cx.layout_of(ty).is_zst()
746 // (*) this is only true if the type is suitable
750 #[derive(Copy, Clone)]
755 fn get_overflow_intrinsic<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
760 use syntax::ast::IntTy::*;
761 use syntax::ast::UintTy::*;
762 use rustc::ty::{Int, Uint};
766 let new_sty = match ty.sty {
767 Int(Isize) => Int(tcx.sess.target.isize_ty),
768 Uint(Usize) => Uint(tcx.sess.target.usize_ty),
769 ref t @ Uint(_) | ref t @ Int(_) => t.clone(),
770 _ => panic!("tried to get overflow intrinsic for op applied to non-int type")
773 let name = match oop {
774 OverflowOp::Add => match new_sty {
775 Int(I8) => "llvm.sadd.with.overflow.i8",
776 Int(I16) => "llvm.sadd.with.overflow.i16",
777 Int(I32) => "llvm.sadd.with.overflow.i32",
778 Int(I64) => "llvm.sadd.with.overflow.i64",
779 Int(I128) => "llvm.sadd.with.overflow.i128",
781 Uint(U8) => "llvm.uadd.with.overflow.i8",
782 Uint(U16) => "llvm.uadd.with.overflow.i16",
783 Uint(U32) => "llvm.uadd.with.overflow.i32",
784 Uint(U64) => "llvm.uadd.with.overflow.i64",
785 Uint(U128) => "llvm.uadd.with.overflow.i128",
789 OverflowOp::Sub => match new_sty {
790 Int(I8) => "llvm.ssub.with.overflow.i8",
791 Int(I16) => "llvm.ssub.with.overflow.i16",
792 Int(I32) => "llvm.ssub.with.overflow.i32",
793 Int(I64) => "llvm.ssub.with.overflow.i64",
794 Int(I128) => "llvm.ssub.with.overflow.i128",
796 Uint(U8) => "llvm.usub.with.overflow.i8",
797 Uint(U16) => "llvm.usub.with.overflow.i16",
798 Uint(U32) => "llvm.usub.with.overflow.i32",
799 Uint(U64) => "llvm.usub.with.overflow.i64",
800 Uint(U128) => "llvm.usub.with.overflow.i128",
804 OverflowOp::Mul => match new_sty {
805 Int(I8) => "llvm.smul.with.overflow.i8",
806 Int(I16) => "llvm.smul.with.overflow.i16",
807 Int(I32) => "llvm.smul.with.overflow.i32",
808 Int(I64) => "llvm.smul.with.overflow.i64",
809 Int(I128) => "llvm.smul.with.overflow.i128",
811 Uint(U8) => "llvm.umul.with.overflow.i8",
812 Uint(U16) => "llvm.umul.with.overflow.i16",
813 Uint(U32) => "llvm.umul.with.overflow.i32",
814 Uint(U64) => "llvm.umul.with.overflow.i64",
815 Uint(U128) => "llvm.umul.with.overflow.i128",
821 bx.cx().get_intrinsic(&name)
824 fn cast_int_to_float<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
831 // Most integer types, even i128, fit into [-f32::MAX, f32::MAX] after rounding.
832 // It's only u128 -> f32 that can cause overflows (i.e., should yield infinity).
833 // LLVM's uitofp produces undef in those cases, so we manually check for that case.
834 let is_u128_to_f32 = !signed &&
835 bx.cx().int_width(int_ty) == 128 &&
836 bx.cx().float_width(float_ty) == 32;
838 // All inputs greater or equal to (f32::MAX + 0.5 ULP) are rounded to infinity,
839 // and for everything else LLVM's uitofp works just fine.
840 use rustc_apfloat::ieee::Single;
841 use rustc_apfloat::Float;
842 const MAX_F32_PLUS_HALF_ULP: u128 = ((1 << (Single::PRECISION + 1)) - 1)
843 << (Single::MAX_EXP - Single::PRECISION as i16);
844 let max = bx.cx().const_uint_big(int_ty, MAX_F32_PLUS_HALF_ULP);
845 let overflow = bx.icmp(IntPredicate::IntUGE, x, max);
846 let infinity_bits = bx.cx().const_u32(ieee::Single::INFINITY.to_bits() as u32);
847 let infinity = bx.bitcast(infinity_bits, float_ty);
848 bx.select(overflow, infinity, bx.uitofp(x, float_ty))
851 bx.sitofp(x, float_ty)
853 bx.uitofp(x, float_ty)
858 fn cast_float_to_int<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
865 let fptosui_result = if signed {
871 if !bx.cx().sess().opts.debugging_opts.saturating_float_casts {
872 return fptosui_result;
874 // LLVM's fpto[su]i returns undef when the input x is infinite, NaN, or does not fit into the
875 // destination integer type after rounding towards zero. This `undef` value can cause UB in
876 // safe code (see issue #10184), so we implement a saturating conversion on top of it:
877 // Semantically, the mathematical value of the input is rounded towards zero to the next
878 // mathematical integer, and then the result is clamped into the range of the destination
879 // integer type. Positive and negative infinity are mapped to the maximum and minimum value of
880 // the destination integer type. NaN is mapped to 0.
882 // Define f_min and f_max as the largest and smallest (finite) floats that are exactly equal to
883 // a value representable in int_ty.
884 // They are exactly equal to int_ty::{MIN,MAX} if float_ty has enough significand bits.
885 // Otherwise, int_ty::MAX must be rounded towards zero, as it is one less than a power of two.
886 // int_ty::MIN, however, is either zero or a negative power of two and is thus exactly
887 // representable. Note that this only works if float_ty's exponent range is sufficiently large.
888 // f16 or 256 bit integers would break this property. Right now the smallest float type is f32
889 // with exponents ranging up to 127, which is barely enough for i128::MIN = -2^127.
890 // On the other hand, f_max works even if int_ty::MAX is greater than float_ty::MAX. Because
891 // we're rounding towards zero, we just get float_ty::MAX (which is always an integer).
892 // This already happens today with u128::MAX = 2^128 - 1 > f32::MAX.
893 let int_max = |signed: bool, int_ty: Bx::Type| -> u128 {
894 let shift_amount = 128 - bx.cx().int_width(int_ty);
896 i128::MAX as u128 >> shift_amount
898 u128::MAX >> shift_amount
901 let int_min = |signed: bool, int_ty: Bx::Type| -> i128 {
903 i128::MIN >> (128 - bx.cx().int_width(int_ty))
909 let compute_clamp_bounds_single =
910 |signed: bool, int_ty: Bx::Type| -> (u128, u128) {
911 let rounded_min = ieee::Single::from_i128_r(int_min(signed, int_ty), Round::TowardZero);
912 assert_eq!(rounded_min.status, Status::OK);
913 let rounded_max = ieee::Single::from_u128_r(int_max(signed, int_ty), Round::TowardZero);
914 assert!(rounded_max.value.is_finite());
915 (rounded_min.value.to_bits(), rounded_max.value.to_bits())
917 let compute_clamp_bounds_double =
918 |signed: bool, int_ty: Bx::Type| -> (u128, u128) {
919 let rounded_min = ieee::Double::from_i128_r(int_min(signed, int_ty), Round::TowardZero);
920 assert_eq!(rounded_min.status, Status::OK);
921 let rounded_max = ieee::Double::from_u128_r(int_max(signed, int_ty), Round::TowardZero);
922 assert!(rounded_max.value.is_finite());
923 (rounded_min.value.to_bits(), rounded_max.value.to_bits())
926 let float_bits_to_llval = |bits| {
927 let bits_llval = match bx.cx().float_width(float_ty) {
928 32 => bx.cx().const_u32(bits as u32),
929 64 => bx.cx().const_u64(bits as u64),
930 n => bug!("unsupported float width {}", n),
932 bx.bitcast(bits_llval, float_ty)
934 let (f_min, f_max) = match bx.cx().float_width(float_ty) {
935 32 => compute_clamp_bounds_single(signed, int_ty),
936 64 => compute_clamp_bounds_double(signed, int_ty),
937 n => bug!("unsupported float width {}", n),
939 let f_min = float_bits_to_llval(f_min);
940 let f_max = float_bits_to_llval(f_max);
941 // To implement saturation, we perform the following steps:
943 // 1. Cast x to an integer with fpto[su]i. This may result in undef.
944 // 2. Compare x to f_min and f_max, and use the comparison results to select:
945 // a) int_ty::MIN if x < f_min or x is NaN
946 // b) int_ty::MAX if x > f_max
947 // c) the result of fpto[su]i otherwise
948 // 3. If x is NaN, return 0.0, otherwise return the result of step 2.
950 // This avoids resulting undef because values in range [f_min, f_max] by definition fit into the
951 // destination type. It creates an undef temporary, but *producing* undef is not UB. Our use of
952 // undef does not introduce any non-determinism either.
953 // More importantly, the above procedure correctly implements saturating conversion.
955 // If x is NaN, 0 is returned by definition.
956 // Otherwise, x is finite or infinite and thus can be compared with f_min and f_max.
957 // This yields three cases to consider:
958 // (1) if x in [f_min, f_max], the result of fpto[su]i is returned, which agrees with
959 // saturating conversion for inputs in that range.
960 // (2) if x > f_max, then x is larger than int_ty::MAX. This holds even if f_max is rounded
961 // (i.e., if f_max < int_ty::MAX) because in those cases, nextUp(f_max) is already larger
962 // than int_ty::MAX. Because x is larger than int_ty::MAX, the return value of int_ty::MAX
964 // (3) if x < f_min, then x is smaller than int_ty::MIN. As shown earlier, f_min exactly equals
965 // int_ty::MIN and therefore the return value of int_ty::MIN is correct.
968 // Step 1 was already performed above.
970 // Step 2: We use two comparisons and two selects, with %s1 being the result:
971 // %less_or_nan = fcmp ult %x, %f_min
972 // %greater = fcmp olt %x, %f_max
973 // %s0 = select %less_or_nan, int_ty::MIN, %fptosi_result
974 // %s1 = select %greater, int_ty::MAX, %s0
975 // Note that %less_or_nan uses an *unordered* comparison. This comparison is true if the
976 // operands are not comparable (i.e., if x is NaN). The unordered comparison ensures that s1
977 // becomes int_ty::MIN if x is NaN.
978 // Performance note: Unordered comparison can be lowered to a "flipped" comparison and a
979 // negation, and the negation can be merged into the select. Therefore, it not necessarily any
980 // more expensive than a ordered ("normal") comparison. Whether these optimizations will be
981 // performed is ultimately up to the backend, but at least x86 does perform them.
982 let less_or_nan = bx.fcmp(RealPredicate::RealULT, x, f_min);
983 let greater = bx.fcmp(RealPredicate::RealOGT, x, f_max);
984 let int_max = bx.cx().const_uint_big(int_ty, int_max(signed, int_ty));
985 let int_min = bx.cx().const_uint_big(int_ty, int_min(signed, int_ty) as u128);
986 let s0 = bx.select(less_or_nan, int_min, fptosui_result);
987 let s1 = bx.select(greater, int_max, s0);
989 // Step 3: NaN replacement.
990 // For unsigned types, the above step already yielded int_ty::MIN == 0 if x is NaN.
991 // Therefore we only need to execute this step for signed integer types.
993 // LLVM has no isNaN predicate, so we use (x == x) instead
994 bx.select(bx.fcmp(RealPredicate::RealOEQ, x, x), s1, bx.cx().const_uint(int_ty, 0))