diff --git a/compiler/rustc_codegen_ssa/src/mir/operand.rs b/compiler/rustc_codegen_ssa/src/mir/operand.rs index ddef4aaee3bab..b37797fef4ce3 100644 --- a/compiler/rustc_codegen_ssa/src/mir/operand.rs +++ b/compiler/rustc_codegen_ssa/src/mir/operand.rs @@ -259,6 +259,31 @@ 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. + /// + /// Supports sized types only. + pub fn poison>( + bx: &mut Bx, + layout: TyAndLayout<'tcx>, + ) -> OperandValue { + assert!(layout.is_sized()); + 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) { + let ibty0 = bx.cx().scalar_pair_element_backend_type(layout, 0, true); + let ibty1 = bx.cx().scalar_pair_element_backend_type(layout, 1, true); + OperandValue::Pair(bx.const_poison(ibty0), bx.const_poison(ibty1)) + } else { + let bty = bx.cx().backend_type(layout); + let ptr_bty = bx.cx().type_ptr_to(bty); + OperandValue::Ref(bx.const_poison(ptr_bty), None, layout.align.abi) + } + } + pub fn store>( self, bx: &mut Bx, diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs index 400512fe4e9ad..6e4c0be12f083 100644 --- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs +++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs @@ -158,17 +158,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { debug_assert!(src.layout.is_sized()); debug_assert!(dst.layout.is_sized()); - if src.layout.size != dst.layout.size - || src.layout.abi.is_uninhabited() - || dst.layout.abi.is_uninhabited() - { - // In all of these cases it's UB to run this transmute, but that's - // known statically so might as well trap for it, rather than just - // making it unreachable. - bx.abort(); - return; - } - if let Some(val) = self.codegen_transmute_operand(bx, src, dst.layout) { val.store(bx, dst); return; @@ -202,8 +191,21 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { operand: OperandRef<'tcx, Bx::Value>, cast: TyAndLayout<'tcx>, ) -> Option> { - // Callers already checked that the layout sizes match - debug_assert_eq!(operand.layout.size, cast.size); + // Check for transmutes that are always UB. + if operand.layout.size != cast.size + || operand.layout.abi.is_uninhabited() + || cast.abi.is_uninhabited() + { + if !operand.layout.abi.is_uninhabited() { + // Since this is known statically and the input could have existed + // without already having hit UB, might as well trap for it. + bx.abort(); + } + + // Because this transmute is UB, return something easy to generate, + // since it's fine that later uses of the value are probably UB. + return Some(OperandValue::poison(bx, cast)); + } let operand_kind = self.value_kind(operand.layout); let cast_kind = self.value_kind(cast); @@ -221,11 +223,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { let OperandValueKind::Immediate(in_scalar) = operand_kind else { bug!("Found {operand_kind:?} for operand {operand:?}"); }; - if let OperandValueKind::Immediate(out_scalar) = cast_kind { + if let OperandValueKind::Immediate(out_scalar) = cast_kind + && in_scalar.size(self.cx) == out_scalar.size(self.cx) + { let cast_bty = bx.backend_type(cast); - Some(OperandValue::Immediate(Self::transmute_immediate( - bx, imm, in_scalar, out_scalar, cast_bty, - ))) + Some(OperandValue::Immediate( + self.transmute_immediate(bx, imm, in_scalar, out_scalar, cast_bty), + )) } else { None } @@ -234,12 +238,15 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { let OperandValueKind::Pair(in_a, in_b) = operand_kind else { bug!("Found {operand_kind:?} for operand {operand:?}"); }; - if let OperandValueKind::Pair(out_a, out_b) = cast_kind { + if let OperandValueKind::Pair(out_a, out_b) = cast_kind + && in_a.size(self.cx) == out_a.size(self.cx) + && in_b.size(self.cx) == out_b.size(self.cx) + { let out_a_ibty = bx.scalar_pair_element_backend_type(cast, 0, false); let out_b_ibty = bx.scalar_pair_element_backend_type(cast, 1, false); Some(OperandValue::Pair( - Self::transmute_immediate(bx, imm_a, in_a, out_a, out_a_ibty), - Self::transmute_immediate(bx, imm_b, in_b, out_b, out_b_ibty), + self.transmute_immediate(bx, imm_a, in_a, out_a, out_a_ibty), + self.transmute_immediate(bx, imm_b, in_b, out_b, out_b_ibty), )) } else { None @@ -254,12 +261,15 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { /// `to_backend_ty` must be the *non*-immediate backend type (so it will be /// `i8`, not `i1`, for `bool`-like types.) fn transmute_immediate( + &self, bx: &mut Bx, mut imm: Bx::Value, from_scalar: abi::Scalar, to_scalar: abi::Scalar, to_backend_ty: Bx::Type, ) -> Bx::Value { + debug_assert_eq!(from_scalar.size(self.cx), to_scalar.size(self.cx)); + use abi::Primitive::*; imm = bx.from_immediate(imm); imm = match (from_scalar.primitive(), to_scalar.primitive()) { @@ -831,14 +841,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { let operand_ty = operand.ty(self.mir, self.cx.tcx()); let cast_layout = self.cx.layout_of(self.monomorphize(cast_ty)); let operand_layout = self.cx.layout_of(self.monomorphize(operand_ty)); - if operand_layout.size != cast_layout.size - || operand_layout.abi.is_uninhabited() - || cast_layout.abi.is_uninhabited() - { - // Send UB cases to the full form so the operand version can - // `bitcast` without worrying about malformed IR. - return false; - } match (self.value_kind(operand_layout), self.value_kind(cast_layout)) { // Can always load from a pointer as needed @@ -847,9 +849,12 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { // Need to generate an `alloc` to get a pointer from an immediate (OperandValueKind::Immediate(..) | OperandValueKind::Pair(..), OperandValueKind::Ref) => false, - // When we have scalar immediates, we can convert them as needed - (OperandValueKind::Immediate(..), OperandValueKind::Immediate(..)) | - (OperandValueKind::Pair(..), OperandValueKind::Pair(..)) => true, + // When we have scalar immediates, we can only convert things + // where the sizes match, to avoid endianness questions. + (OperandValueKind::Immediate(a), OperandValueKind::Immediate(b)) => + a.size(self.cx) == b.size(self.cx), + (OperandValueKind::Pair(a0, a1), OperandValueKind::Pair(b0, b1)) => + a0.size(self.cx) == b0.size(self.cx) && a1.size(self.cx) == b1.size(self.cx), // Send mixings between scalars and pairs through the memory route // FIXME: Maybe this could use insertvalue/extractvalue instead? diff --git a/tests/codegen/intrinsics/transmute.rs b/tests/codegen/intrinsics/transmute.rs index 7ad0e62213cb2..c2295ca9a0c3c 100644 --- a/tests/codegen/intrinsics/transmute.rs +++ b/tests/codegen/intrinsics/transmute.rs @@ -54,6 +54,32 @@ pub unsafe fn check_smaller_size(x: u32) -> u16 { } } +// CHECK-LABEL: @check_smaller_array( +#[no_mangle] +#[custom_mir(dialect = "runtime", phase = "initial")] +pub unsafe fn check_smaller_array(x: [u32; 7]) -> [u32; 3] { + // CHECK: call void @llvm.trap + mir!{ + { + RET = CastTransmute(x); + Return() + } + } +} + +// CHECK-LABEL: @check_bigger_array( +#[no_mangle] +#[custom_mir(dialect = "runtime", phase = "initial")] +pub unsafe fn check_bigger_array(x: [u32; 3]) -> [u32; 7] { + // CHECK: call void @llvm.trap + mir!{ + { + RET = CastTransmute(x); + Return() + } + } +} + // CHECK-LABEL: @check_to_uninhabited( #[no_mangle] #[custom_mir(dialect = "runtime", phase = "initial")] @@ -71,7 +97,7 @@ pub unsafe fn check_to_uninhabited(x: u16) -> BigNever { #[no_mangle] #[custom_mir(dialect = "runtime", phase = "initial")] pub unsafe fn check_from_uninhabited(x: BigNever) -> u16 { - // CHECK: call void @llvm.trap + // CHECK: ret i16 poison mir!{ { RET = CastTransmute(x); @@ -301,3 +327,49 @@ pub unsafe fn check_pair_to_array(x: (i64, u64)) -> [u8; 16] { // CHECK: store i64 %x.1, ptr %{{.+}}, align 1 transmute(x) } + +// CHECK-LABEL: @check_heterogeneous_integer_pair( +#[no_mangle] +pub unsafe fn check_heterogeneous_integer_pair(x: (i32, bool)) -> (bool, u32) { + // CHECK: store i32 %x.0 + // CHECK: %[[WIDER:.+]] = zext i1 %x.1 to i8 + // CHECK: store i8 %[[WIDER]] + + // CHECK: %[[BYTE:.+]] = load i8 + // CHECK: trunc i8 %[[BYTE:.+]] to i1 + // CHECK: load i32 + transmute(x) +} + +// CHECK-LABEL: @check_heterogeneous_float_pair( +#[no_mangle] +pub unsafe fn check_heterogeneous_float_pair(x: (f64, f32)) -> (f32, f64) { + // CHECK: store double %x.0 + // CHECK: store float %x.1 + // CHECK: %[[A:.+]] = load float + // CHECK: %[[B:.+]] = load double + // CHECK: %[[P:.+]] = insertvalue { float, double } poison, float %[[A]], 0 + // CHECK: insertvalue { float, double } %[[P]], double %[[B]], 1 + transmute(x) +} + +// CHECK-LABEL: @check_issue_110005( +#[no_mangle] +pub unsafe fn check_issue_110005(x: (usize, bool)) -> Option> { + // CHECK: store i64 %x.0 + // CHECK: %[[WIDER:.+]] = zext i1 %x.1 to i8 + // CHECK: store i8 %[[WIDER]] + // CHECK: load ptr + // CHECK: load i64 + transmute(x) +} + +// CHECK-LABEL: @check_pair_to_dst_ref( +#[no_mangle] +pub unsafe fn check_pair_to_dst_ref<'a>(x: (usize, usize)) -> &'a [u8] { + // CHECK: %0 = inttoptr i64 %x.0 to ptr + // CHECK: %1 = insertvalue { ptr, i64 } poison, ptr %0, 0 + // CHECK: %2 = insertvalue { ptr, i64 } %1, i64 %x.1, 1 + // CHECK: ret { ptr, i64 } %2 + transmute(x) +}