diff --git a/compiler/rustc_codegen_gcc/src/builder.rs b/compiler/rustc_codegen_gcc/src/builder.rs index 869344ce92d7d..f9ea0f004564b 100644 --- a/compiler/rustc_codegen_gcc/src/builder.rs +++ b/compiler/rustc_codegen_gcc/src/builder.rs @@ -758,7 +758,7 @@ impl<'a, 'gcc, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'gcc, 'tcx> { assert_eq!(place.llextra.is_some(), place.layout.is_unsized()); if place.layout.is_zst() { - return OperandRef::new_zst(self, place.layout); + return OperandRef::zero_sized(place.layout); } fn scalar_load_metadata<'a, 'gcc, 'tcx>(bx: &mut Builder<'a, 'gcc, 'tcx>, load: RValue<'gcc>, scalar: &abi::Scalar) { diff --git a/compiler/rustc_codegen_gcc/src/type_of.rs b/compiler/rustc_codegen_gcc/src/type_of.rs index 5df8c1a209db2..30a3fe67b8543 100644 --- a/compiler/rustc_codegen_gcc/src/type_of.rs +++ b/compiler/rustc_codegen_gcc/src/type_of.rs @@ -159,8 +159,7 @@ impl<'tcx> LayoutGccExt<'tcx> for TyAndLayout<'tcx> { fn is_gcc_immediate(&self) -> bool { match self.abi { Abi::Scalar(_) | Abi::Vector { .. } => true, - Abi::ScalarPair(..) => false, - Abi::Uninhabited | Abi::Aggregate { .. } => self.is_zst(), + Abi::ScalarPair(..) | Abi::Uninhabited | Abi::Aggregate { .. } => false, } } diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs index 4d0bcd53d1562..5968e70b1ccce 100644 --- a/compiler/rustc_codegen_llvm/src/builder.rs +++ b/compiler/rustc_codegen_llvm/src/builder.rs @@ -486,7 +486,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> { assert_eq!(place.llextra.is_some(), place.layout.is_unsized()); if place.layout.is_zst() { - return OperandRef::new_zst(self, place.layout); + return OperandRef::zero_sized(place.layout); } #[instrument(level = "trace", skip(bx))] diff --git a/compiler/rustc_codegen_llvm/src/type_of.rs b/compiler/rustc_codegen_llvm/src/type_of.rs index e264ce78f0d67..a493c9c0548e9 100644 --- a/compiler/rustc_codegen_llvm/src/type_of.rs +++ b/compiler/rustc_codegen_llvm/src/type_of.rs @@ -198,8 +198,7 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> { fn is_llvm_immediate(&self) -> bool { match self.abi { Abi::Scalar(_) | Abi::Vector { .. } => true, - Abi::ScalarPair(..) => false, - Abi::Uninhabited | Abi::Aggregate { .. } => self.is_zst(), + Abi::ScalarPair(..) | Abi::Uninhabited | Abi::Aggregate { .. } => false, } } diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs index 15c7847155d2f..242d209b68425 100644 --- a/compiler/rustc_codegen_ssa/src/base.rs +++ b/compiler/rustc_codegen_ssa/src/base.rs @@ -295,7 +295,7 @@ pub fn coerce_unsized_into<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>( let (base, info) = match bx.load_operand(src).val { OperandValue::Pair(base, info) => unsize_ptr(bx, base, src_ty, dst_ty, Some(info)), OperandValue::Immediate(base) => unsize_ptr(bx, base, src_ty, dst_ty, None), - OperandValue::Ref(..) => bug!(), + OperandValue::Ref(..) | OperandValue::ZeroSized => bug!(), }; OperandValue::Pair(base, info).store(bx, dst); } diff --git a/compiler/rustc_codegen_ssa/src/mir/block.rs b/compiler/rustc_codegen_ssa/src/mir/block.rs index 3f0b64b1103d6..e0cb26d3ba866 100644 --- a/compiler/rustc_codegen_ssa/src/mir/block.rs +++ b/compiler/rustc_codegen_ssa/src/mir/block.rs @@ -1,5 +1,5 @@ use super::operand::OperandRef; -use super::operand::OperandValue::{Immediate, Pair, Ref}; +use super::operand::OperandValue::{Immediate, Pair, Ref, ZeroSized}; use super::place::PlaceRef; use super::{CachedLlbb, FunctionCx, LocalRef}; @@ -427,6 +427,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { assert_eq!(align, op.layout.align.abi, "return place is unaligned!"); llval } + ZeroSized => bug!("ZST return value shouldn't be in PassMode::Cast"), }; let ty = bx.cast_backend_type(cast_ty); let addr = bx.pointercast(llslot, bx.type_ptr_to(ty)); @@ -1386,6 +1387,16 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { (llval, align, true) } } + ZeroSized => match arg.mode { + PassMode::Indirect { .. } => { + // Though `extern "Rust"` doesn't pass ZSTs, some ABIs pass + // a pointer for `repr(C)` structs even when empty, so get + // one from an `alloca` (which can be left uninitialized). + let scratch = PlaceRef::alloca(bx, arg.layout); + (scratch.llval, scratch.align, true) + } + _ => bug!("ZST {op:?} wasn't ignored, but was passed with abi {arg:?}"), + }, }; if by_ref && !arg.is_indirect() { diff --git a/compiler/rustc_codegen_ssa/src/mir/debuginfo.rs b/compiler/rustc_codegen_ssa/src/mir/debuginfo.rs index bba2800fb0545..4f79c6a3d823c 100644 --- a/compiler/rustc_codegen_ssa/src/mir/debuginfo.rs +++ b/compiler/rustc_codegen_ssa/src/mir/debuginfo.rs @@ -352,6 +352,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { bx.set_var_name(a, &(name.clone() + ".0")); bx.set_var_name(b, &(name.clone() + ".1")); } + OperandValue::ZeroSized => { + // These never have a value to talk about + } }, LocalRef::PendingOperand => {} } diff --git a/compiler/rustc_codegen_ssa/src/mir/mod.rs b/compiler/rustc_codegen_ssa/src/mir/mod.rs index 51393a5d774dc..6617a343d4091 100644 --- a/compiler/rustc_codegen_ssa/src/mir/mod.rs +++ b/compiler/rustc_codegen_ssa/src/mir/mod.rs @@ -129,16 +129,13 @@ enum LocalRef<'tcx, V> { PendingOperand, } -impl<'a, 'tcx, V: CodegenObject> LocalRef<'tcx, V> { - fn new_operand>( - bx: &mut Bx, - layout: TyAndLayout<'tcx>, - ) -> LocalRef<'tcx, V> { +impl<'tcx, V: CodegenObject> LocalRef<'tcx, V> { + fn new_operand(layout: TyAndLayout<'tcx>) -> LocalRef<'tcx, V> { if layout.is_zst() { // Zero-size temporaries aren't always initialized, which // doesn't matter because they don't contain data, but // we need something in the operand. - LocalRef::Operand(OperandRef::new_zst(bx, layout)) + LocalRef::Operand(OperandRef::zero_sized(layout)) } else { LocalRef::PendingOperand } @@ -249,7 +246,7 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>( } } else { debug!("alloc: {:?} -> operand", local); - LocalRef::new_operand(&mut start_bx, layout) + LocalRef::new_operand(layout) } }; @@ -355,7 +352,7 @@ fn arg_local_refs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>( let local = |op| LocalRef::Operand(op); match arg.mode { PassMode::Ignore => { - return local(OperandRef::new_zst(bx, arg.layout)); + return local(OperandRef::zero_sized(arg.layout)); } PassMode::Direct(_) => { let llarg = bx.get_param(llarg_idx); diff --git a/compiler/rustc_codegen_ssa/src/mir/operand.rs b/compiler/rustc_codegen_ssa/src/mir/operand.rs index 2301c3ef13e21..98f7efd13e48b 100644 --- a/compiler/rustc_codegen_ssa/src/mir/operand.rs +++ b/compiler/rustc_codegen_ssa/src/mir/operand.rs @@ -45,6 +45,14 @@ pub enum OperandValue { /// as returned by [`LayoutTypeMethods::scalar_pair_element_backend_type`] /// with `immediate: true`. Pair(V, V), + /// A value taking no bytes, and which therefore needs no LLVM value at all. + /// + /// If you ever need a `V` to pass to something, get a fresh poison value + /// from [`ConstMethods::const_poison`]. + /// + /// An `OperandValue` *must* be this variant for any type for which + /// `is_zst` on its `Layout` returns `true`. + ZeroSized, } /// An `OperandRef` is an "SSA" reference to a Rust value, along with @@ -71,15 +79,9 @@ impl fmt::Debug for OperandRef<'_, V> { } impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> { - pub fn new_zst>( - bx: &mut Bx, - layout: TyAndLayout<'tcx>, - ) -> OperandRef<'tcx, V> { + pub fn zero_sized(layout: TyAndLayout<'tcx>) -> OperandRef<'tcx, V> { assert!(layout.is_zst()); - OperandRef { - val: OperandValue::Immediate(bx.const_poison(bx.immediate_backend_type(layout))), - layout, - } + OperandRef { val: OperandValue::ZeroSized, layout } } pub fn from_const>( @@ -97,7 +99,7 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> { let llval = bx.scalar_to_backend(x, scalar, bx.immediate_backend_type(layout)); OperandValue::Immediate(llval) } - ConstValue::ZeroSized => return OperandRef::new_zst(bx, layout), + ConstValue::ZeroSized => return OperandRef::zero_sized(layout), ConstValue::Slice { data, start, end } => { let Abi::ScalarPair(a_scalar, _) = layout.abi else { bug!("from_const: invalid ScalarPair layout: {:#?}", layout); @@ -147,6 +149,7 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> { OperandValue::Immediate(llptr) => (llptr, None), OperandValue::Pair(llptr, llextra) => (llptr, Some(llextra)), OperandValue::Ref(..) => bug!("Deref of by-Ref operand {:?}", self), + OperandValue::ZeroSized => bug!("Deref of ZST operand {:?}", self), }; let layout = cx.layout_of(projected_ty); PlaceRef { llval: llptr, llextra, layout, align: layout.align.abi } @@ -204,9 +207,7 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> { let mut val = match (self.val, self.layout.abi) { // If the field is ZST, it has no data. - _ if field.is_zst() => { - return OperandRef::new_zst(bx, field); - } + _ if field.is_zst() => OperandValue::ZeroSized, // Newtype of a scalar, scalar pair or vector. (OperandValue::Immediate(_) | OperandValue::Pair(..), _) @@ -237,6 +238,7 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> { }; match (&mut val, field.abi) { + (OperandValue::ZeroSized, _) => {} ( OperandValue::Immediate(llval), Abi::Scalar(_) | Abi::ScalarPair(..) | Abi::Vector { .. }, @@ -290,8 +292,8 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> { impl<'a, 'tcx, V: CodegenObject> OperandValue { /// Returns an `OperandValue` that's generally UB to use in any way. /// - /// Depending on the `layout`, returns an `Immediate` or `Pair` containing - /// poison value(s), or a `Ref` containing a poison pointer. + /// Depending on the `layout`, returns `ZeroSized` for ZSTs, an `Immediate` or + /// `Pair` containing poison value(s), or a `Ref` containing a poison pointer. /// /// Supports sized types only. pub fn poison>( @@ -299,7 +301,9 @@ impl<'a, 'tcx, V: CodegenObject> OperandValue { layout: TyAndLayout<'tcx>, ) -> OperandValue { assert!(layout.is_sized()); - if bx.cx().is_backend_immediate(layout) { + if layout.is_zst() { + OperandValue::ZeroSized + } else if bx.cx().is_backend_immediate(layout) { let ibty = bx.cx().immediate_backend_type(layout); OperandValue::Immediate(bx.const_poison(ibty)) } else if bx.cx().is_backend_scalar_pair(layout) { @@ -352,12 +356,11 @@ impl<'a, 'tcx, V: CodegenObject> OperandValue { flags: MemFlags, ) { debug!("OperandRef::store: operand={:?}, dest={:?}", self, dest); - // Avoid generating stores of zero-sized values, because the only way to have a zero-sized - // value is through `undef`, and store itself is useless. - if dest.layout.is_zst() { - return; - } match self { + OperandValue::ZeroSized => { + // Avoid generating stores of zero-sized values, because the only way to have a zero-sized + // value is through `undef`/`poison`, and the store itself is useless. + } OperandValue::Ref(r, None, source_align) => { if flags.contains(MemFlags::NONTEMPORAL) { // HACK(nox): This is inefficient but there is no nontemporal memcpy. @@ -458,7 +461,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { // checks in `codegen_consume` and `extract_field`. let elem = o.layout.field(bx.cx(), 0); if elem.is_zst() { - o = OperandRef::new_zst(bx, elem); + o = OperandRef::zero_sized(elem); } else { return None; } @@ -492,7 +495,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { // ZSTs don't require any actual memory access. if layout.is_zst() { - return OperandRef::new_zst(bx, layout); + return OperandRef::zero_sized(layout); } if let Some(o) = self.maybe_codegen_consume_direct(bx, place_ref) { diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs index 6e7065713b817..c67eb4b0e3347 100644 --- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs +++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs @@ -70,6 +70,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { OperandValue::Ref(_, Some(_), _) => { bug!("unsized coercion on an unsized rvalue"); } + OperandValue::ZeroSized => { + bug!("unsized coercion on a ZST rvalue"); + } } } @@ -165,11 +168,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { } match src.val { - OperandValue::Ref(..) => { + OperandValue::Ref(..) | OperandValue::ZeroSized => { span_bug!( self.mir.span, "Operand path should have handled transmute \ - from `Ref` {src:?} to place {dst:?}" + from {src:?} to place {dst:?}" ); } OperandValue::Immediate(..) | OperandValue::Pair(..) => { @@ -220,31 +223,33 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { let fake_place = PlaceRef::new_sized_aligned(cast_ptr, cast, align); Some(bx.load_operand(fake_place).val) } + OperandValue::ZeroSized => { + let OperandValueKind::ZeroSized = operand_kind else { + bug!("Found {operand_kind:?} for operand {operand:?}"); + }; + if let OperandValueKind::ZeroSized = cast_kind { + Some(OperandValue::ZeroSized) + } else { + None + } + } OperandValue::Immediate(imm) => { let OperandValueKind::Immediate(in_scalar) = operand_kind else { bug!("Found {operand_kind:?} for operand {operand:?}"); }; - if let OperandValueKind::Immediate(out_scalar) = cast_kind { - match (in_scalar, out_scalar) { - (ScalarOrZst::Zst, ScalarOrZst::Zst) => { - Some(OperandRef::new_zst(bx, cast).val) - } - (ScalarOrZst::Scalar(in_scalar), ScalarOrZst::Scalar(out_scalar)) - if in_scalar.size(self.cx) == out_scalar.size(self.cx) => - { - let operand_bty = bx.backend_type(operand.layout); - let cast_bty = bx.backend_type(cast); - Some(OperandValue::Immediate(self.transmute_immediate( - bx, - imm, - in_scalar, - operand_bty, - out_scalar, - cast_bty, - ))) - } - _ => None, - } + if let OperandValueKind::Immediate(out_scalar) = cast_kind + && in_scalar.size(self.cx) == out_scalar.size(self.cx) + { + let operand_bty = bx.backend_type(operand.layout); + let cast_bty = bx.backend_type(cast); + Some(OperandValue::Immediate(self.transmute_immediate( + bx, + imm, + in_scalar, + operand_bty, + out_scalar, + cast_bty, + ))) } else { None } @@ -457,6 +462,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { OperandValue::Ref(..) => { bug!("by-ref operand {:?} in `codegen_rvalue_operand`", operand); } + OperandValue::ZeroSized => { + bug!("zero-sized operand {:?} in `codegen_rvalue_operand`", operand); + } }; let (lldata, llextra) = base::unsize_ptr(bx, lldata, operand.layout.ty, cast.ty, llextra); @@ -490,6 +498,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { OperandValue::Ref(_, _, _) => todo!(), OperandValue::Immediate(v) => (v, None), OperandValue::Pair(v, l) => (v, Some(l)), + OperandValue::ZeroSized => bug!("ZST -- which is not PointerLike -- in DynStar"), }; let (lldata, llextra) = base::cast_to_dyn_star(bx, lldata, operand.layout, cast.ty, llextra); @@ -713,7 +722,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { // According to `rvalue_creates_operand`, only ZST // aggregate rvalues are allowed to be operands. let ty = rvalue.ty(self.mir, self.cx.tcx()); - OperandRef::new_zst(bx, self.cx.layout_of(self.monomorphize(ty))) + OperandRef::zero_sized(self.cx.layout_of(self.monomorphize(ty))) } mir::Rvalue::ShallowInitBox(ref operand, content_ty) => { let operand = self.codegen_operand(bx, operand); @@ -931,6 +940,12 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { // Can always load from a pointer as needed (OperandValueKind::Ref, _) => true, + // ZST-to-ZST is the easiest thing ever + (OperandValueKind::ZeroSized, OperandValueKind::ZeroSized) => true, + + // But if only one of them is a ZST the sizes can't match + (OperandValueKind::ZeroSized, _) | (_, OperandValueKind::ZeroSized) => false, + // Need to generate an `alloc` to get a pointer from an immediate (OperandValueKind::Immediate(..) | OperandValueKind::Pair(..), OperandValueKind::Ref) => false, @@ -974,12 +989,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { /// Gets which variant of [`OperandValue`] is expected for a particular type. fn value_kind(&self, layout: TyAndLayout<'tcx>) -> OperandValueKind { - if self.cx.is_backend_immediate(layout) { + if layout.is_zst() { + OperandValueKind::ZeroSized + } else if self.cx.is_backend_immediate(layout) { debug_assert!(!self.cx.is_backend_scalar_pair(layout)); OperandValueKind::Immediate(match layout.abi { - abi::Abi::Scalar(s) => ScalarOrZst::Scalar(s), - abi::Abi::Vector { element, .. } => ScalarOrZst::Scalar(element), - _ if layout.is_zst() => ScalarOrZst::Zst, + abi::Abi::Scalar(s) => s, + abi::Abi::Vector { element, .. } => element, x => span_bug!(self.mir.span, "Couldn't translate {x:?} as backend immediate"), }) } else if self.cx.is_backend_scalar_pair(layout) { @@ -1002,21 +1018,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { #[derive(Debug, Copy, Clone)] enum OperandValueKind { Ref, - Immediate(ScalarOrZst), + Immediate(abi::Scalar), Pair(abi::Scalar, abi::Scalar), -} - -#[derive(Debug, Copy, Clone)] -enum ScalarOrZst { - Zst, - Scalar(abi::Scalar), -} - -impl ScalarOrZst { - pub fn size(self, cx: &impl abi::HasDataLayout) -> abi::Size { - match self { - ScalarOrZst::Zst => abi::Size::ZERO, - ScalarOrZst::Scalar(s) => s.size(cx), - } - } + ZeroSized, } diff --git a/tests/codegen/intrinsics/transmute.rs b/tests/codegen/intrinsics/transmute.rs index 664e697c2a5d2..fe42494000e17 100644 --- a/tests/codegen/intrinsics/transmute.rs +++ b/tests/codegen/intrinsics/transmute.rs @@ -14,10 +14,10 @@ use std::intrinsics::{transmute, transmute_unchecked}; // Some of these need custom MIR to not get removed by MIR optimizations. use std::intrinsics::mir::*; -enum Never {} +pub enum ZstNever {} #[repr(align(2))] -pub struct BigNever(Never, u16, Never); +pub struct BigNever(ZstNever, u16, ZstNever); #[repr(align(8))] pub struct Scalar64(i64); @@ -56,11 +56,13 @@ pub unsafe fn check_bigger_array(x: [u32; 3]) -> [u32; 7] { transmute_unchecked(x) } -// CHECK-LABEL: @check_to_uninhabited( +// CHECK-LABEL: @check_to_empty_array( #[no_mangle] #[custom_mir(dialect = "runtime", phase = "optimized")] -pub unsafe fn check_to_uninhabited(x: u16) -> BigNever { +pub unsafe fn check_to_empty_array(x: [u32; 5]) -> [u32; 0] { + // CHECK-NOT: trap // CHECK: call void @llvm.trap + // CHECK-NOT: trap mir!{ { RET = CastTransmute(x); @@ -69,6 +71,37 @@ pub unsafe fn check_to_uninhabited(x: u16) -> BigNever { } } +// CHECK-LABEL: @check_from_empty_array( +#[no_mangle] +#[custom_mir(dialect = "runtime", phase = "optimized")] +pub unsafe fn check_from_empty_array(x: [u32; 0]) -> [u32; 5] { + // CHECK-NOT: trap + // CHECK: call void @llvm.trap + // CHECK-NOT: trap + mir!{ + { + RET = CastTransmute(x); + Return() + } + } +} + +// CHECK-LABEL: @check_to_uninhabited( +#[no_mangle] +#[custom_mir(dialect = "runtime", phase = "optimized")] +pub unsafe fn check_to_uninhabited(x: u16) { + // CHECK-NOT: trap + // CHECK: call void @llvm.trap + // CHECK-NOT: trap + mir!{ + let temp: BigNever; + { + temp = CastTransmute(x); + Return() + } + } +} + // CHECK-LABEL: @check_from_uninhabited( #[no_mangle] #[custom_mir(dialect = "runtime", phase = "optimized")] @@ -366,6 +399,40 @@ pub unsafe fn check_issue_109992(x: ()) -> [(); 1] { } } +// CHECK-LABEL: @check_unit_to_never( +#[no_mangle] +#[custom_mir(dialect = "runtime", phase = "optimized")] +pub unsafe fn check_unit_to_never(x: ()) { + // This uses custom MIR to avoid MIR optimizations having removed ZST ops. + + // CHECK-NOT: trap + // CHECK: call void @llvm.trap + // CHECK-NOT: trap + mir!{ + let temp: ZstNever; + { + temp = CastTransmute(x); + Return() + } + } +} + +// CHECK-LABEL: @check_unit_from_never( +#[no_mangle] +#[custom_mir(dialect = "runtime", phase = "optimized")] +pub unsafe fn check_unit_from_never(x: ZstNever) -> () { + // This uses custom MIR to avoid MIR optimizations having removed ZST ops. + + // CHECK: start + // CHECK-NEXT: ret void + mir!{ + { + RET = CastTransmute(x); + Return() + } + } +} + // CHECK-LABEL: @check_maybe_uninit_pair(i16 %x.0, i64 %x.1) #[no_mangle] pub unsafe fn check_maybe_uninit_pair(