use super::place::PlaceRef; use super::{FunctionCx, LocalRef}; use crate::base; use crate::glue; use crate::traits::*; use crate::MemFlags; use rustc_middle::mir; use rustc_middle::mir::interpret::{ConstValue, Pointer, Scalar}; use rustc_middle::ty::layout::{LayoutOf, TyAndLayout}; use rustc_middle::ty::Ty; use rustc_target::abi::{Abi, Align, Size}; use std::fmt; /// The representation of a Rust value. The enum variant is in fact /// uniquely determined by the value's type, but is kept as a /// safety check. #[derive(Copy, Clone, Debug)] pub enum OperandValue { /// A reference to the actual operand. The data is guaranteed /// to be valid for the operand's lifetime. /// The second value, if any, is the extra data (vtable or length) /// which indicates that it refers to an unsized rvalue. Ref(V, Option, Align), /// A single LLVM value. Immediate(V), /// A pair of immediate LLVM values. Used by fat pointers too. Pair(V, V), } /// An `OperandRef` is an "SSA" reference to a Rust value, along with /// its type. /// /// NOTE: unless you know a value's type exactly, you should not /// generate LLVM opcodes acting on it and instead act via methods, /// to avoid nasty edge cases. In particular, using `Builder::store` /// directly is sure to cause problems -- use `OperandRef::store` /// instead. #[derive(Copy, Clone)] pub struct OperandRef<'tcx, V> { // The value. pub val: OperandValue, // The layout of value, based on its Rust type. pub layout: TyAndLayout<'tcx>, } impl fmt::Debug for OperandRef<'_, V> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { write!(f, "OperandRef({:?} @ {:?})", self.val, self.layout) } } impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> { pub fn new_zst>( bx: &mut Bx, layout: TyAndLayout<'tcx>, ) -> OperandRef<'tcx, V> { assert!(layout.is_zst()); OperandRef { val: OperandValue::Immediate(bx.const_undef(bx.immediate_backend_type(layout))), layout, } } pub fn from_const>( bx: &mut Bx, val: ConstValue<'tcx>, ty: Ty<'tcx>, ) -> Self { let layout = bx.layout_of(ty); if layout.is_zst() { return OperandRef::new_zst(bx, layout); } let val = match val { ConstValue::Scalar(x) => { let Abi::Scalar(scalar) = layout.abi else { bug!("from_const: invalid ByVal layout: {:#?}", layout); }; let llval = bx.scalar_to_backend(x, scalar, bx.immediate_backend_type(layout)); OperandValue::Immediate(llval) } ConstValue::ZeroSized => { let llval = bx.zst_to_backend(bx.immediate_backend_type(layout)); OperandValue::Immediate(llval) } ConstValue::Slice { data, start, end } => { let Abi::ScalarPair(a_scalar, _) = layout.abi else { bug!("from_const: invalid ScalarPair layout: {:#?}", layout); }; let a = Scalar::from_pointer( Pointer::new(bx.tcx().create_memory_alloc(data), Size::from_bytes(start)), &bx.tcx(), ); let a_llval = bx.scalar_to_backend( a, a_scalar, bx.scalar_pair_element_backend_type(layout, 0, true), ); let b_llval = bx.const_usize((end - start) as u64); OperandValue::Pair(a_llval, b_llval) } ConstValue::ByRef { alloc, offset } => { return bx.load_operand(bx.from_const_alloc(layout, alloc, offset)); } }; OperandRef { val, layout } } /// Asserts that this operand refers to a scalar and returns /// a reference to its value. pub fn immediate(self) -> V { match self.val { OperandValue::Immediate(s) => s, _ => bug!("not immediate: {:?}", self), } } pub fn deref>(self, cx: &Cx) -> PlaceRef<'tcx, V> { if self.layout.ty.is_box() { bug!("dereferencing {:?} in codegen", self.layout.ty); } let projected_ty = self .layout .ty .builtin_deref(true) .unwrap_or_else(|| bug!("deref of non-pointer {:?}", self)) .ty; let (llptr, llextra) = match self.val { OperandValue::Immediate(llptr) => (llptr, None), OperandValue::Pair(llptr, llextra) => (llptr, Some(llextra)), OperandValue::Ref(..) => bug!("Deref of by-Ref operand {:?}", self), }; let layout = cx.layout_of(projected_ty); PlaceRef { llval: llptr, llextra, layout, align: layout.align.abi } } /// If this operand is a `Pair`, we return an aggregate with the two values. /// For other cases, see `immediate`. pub fn immediate_or_packed_pair>( self, bx: &mut Bx, ) -> V { if let OperandValue::Pair(a, b) = self.val { let llty = bx.cx().backend_type(self.layout); debug!("Operand::immediate_or_packed_pair: packing {:?} into {:?}", self, llty); // Reconstruct the immediate aggregate. let mut llpair = bx.cx().const_undef(llty); let imm_a = bx.from_immediate(a); let imm_b = bx.from_immediate(b); llpair = bx.insert_value(llpair, imm_a, 0); llpair = bx.insert_value(llpair, imm_b, 1); llpair } else { self.immediate() } } /// If the type is a pair, we return a `Pair`, otherwise, an `Immediate`. pub fn from_immediate_or_packed_pair>( bx: &mut Bx, llval: V, layout: TyAndLayout<'tcx>, ) -> Self { let val = if let Abi::ScalarPair(a, b) = layout.abi { debug!("Operand::from_immediate_or_packed_pair: unpacking {:?} @ {:?}", llval, layout); // Deconstruct the immediate aggregate. let a_llval = bx.extract_value(llval, 0); let a_llval = bx.to_immediate_scalar(a_llval, a); let b_llval = bx.extract_value(llval, 1); let b_llval = bx.to_immediate_scalar(b_llval, b); OperandValue::Pair(a_llval, b_llval) } else { OperandValue::Immediate(llval) }; OperandRef { val, layout } } pub fn extract_field>( &self, bx: &mut Bx, i: usize, ) -> Self { let field = self.layout.field(bx.cx(), i); let offset = self.layout.fields.offset(i); 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); } // Newtype of a scalar, scalar pair or vector. (OperandValue::Immediate(_) | OperandValue::Pair(..), _) if field.size == self.layout.size => { assert_eq!(offset.bytes(), 0); self.val } // Extract a scalar component from a pair. (OperandValue::Pair(a_llval, b_llval), Abi::ScalarPair(a, b)) => { if offset.bytes() == 0 { assert_eq!(field.size, a.size(bx.cx())); OperandValue::Immediate(a_llval) } else { assert_eq!(offset, a.size(bx.cx()).align_to(b.align(bx.cx()).abi)); assert_eq!(field.size, b.size(bx.cx())); OperandValue::Immediate(b_llval) } } // `#[repr(simd)]` types are also immediate. (OperandValue::Immediate(llval), Abi::Vector { .. }) => { OperandValue::Immediate(bx.extract_element(llval, bx.cx().const_usize(i as u64))) } _ => bug!("OperandRef::extract_field({:?}): not applicable", self), }; match (&mut val, field.abi) { (OperandValue::Immediate(llval), _) => { // Bools in union fields needs to be truncated. *llval = bx.to_immediate(*llval, field); // HACK(eddyb) have to bitcast pointers until LLVM removes pointee types. *llval = bx.bitcast(*llval, bx.cx().immediate_backend_type(field)); } (OperandValue::Pair(a, b), Abi::ScalarPair(a_abi, b_abi)) => { // Bools in union fields needs to be truncated. *a = bx.to_immediate_scalar(*a, a_abi); *b = bx.to_immediate_scalar(*b, b_abi); // HACK(eddyb) have to bitcast pointers until LLVM removes pointee types. *a = bx.bitcast(*a, bx.cx().scalar_pair_element_backend_type(field, 0, true)); *b = bx.bitcast(*b, bx.cx().scalar_pair_element_backend_type(field, 1, true)); } (OperandValue::Pair(..), _) => bug!(), (OperandValue::Ref(..), _) => bug!(), } OperandRef { val, layout: field } } } impl<'a, 'tcx, V: CodegenObject> OperandValue { pub fn store>( self, bx: &mut Bx, dest: PlaceRef<'tcx, V>, ) { self.store_with_flags(bx, dest, MemFlags::empty()); } pub fn volatile_store>( self, bx: &mut Bx, dest: PlaceRef<'tcx, V>, ) { self.store_with_flags(bx, dest, MemFlags::VOLATILE); } pub fn unaligned_volatile_store>( self, bx: &mut Bx, dest: PlaceRef<'tcx, V>, ) { self.store_with_flags(bx, dest, MemFlags::VOLATILE | MemFlags::UNALIGNED); } pub fn nontemporal_store>( self, bx: &mut Bx, dest: PlaceRef<'tcx, V>, ) { self.store_with_flags(bx, dest, MemFlags::NONTEMPORAL); } fn store_with_flags>( self, bx: &mut Bx, dest: PlaceRef<'tcx, V>, 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::Ref(r, None, source_align) => { if flags.contains(MemFlags::NONTEMPORAL) { // HACK(nox): This is inefficient but there is no nontemporal memcpy. let ty = bx.backend_type(dest.layout); let ptr = bx.pointercast(r, bx.type_ptr_to(ty)); let val = bx.load(ty, ptr, source_align); bx.store_with_flags(val, dest.llval, dest.align, flags); return; } base::memcpy_ty(bx, dest.llval, dest.align, r, source_align, dest.layout, flags) } OperandValue::Ref(_, Some(_), _) => { bug!("cannot directly store unsized values"); } OperandValue::Immediate(s) => { let val = bx.from_immediate(s); bx.store_with_flags(val, dest.llval, dest.align, flags); } OperandValue::Pair(a, b) => { let Abi::ScalarPair(a_scalar, b_scalar) = dest.layout.abi else { bug!("store_with_flags: invalid ScalarPair layout: {:#?}", dest.layout); }; let ty = bx.backend_type(dest.layout); let b_offset = a_scalar.size(bx).align_to(b_scalar.align(bx).abi); let llptr = bx.struct_gep(ty, dest.llval, 0); let val = bx.from_immediate(a); let align = dest.align; bx.store_with_flags(val, llptr, align, flags); let llptr = bx.struct_gep(ty, dest.llval, 1); let val = bx.from_immediate(b); let align = dest.align.restrict_for_offset(b_offset); bx.store_with_flags(val, llptr, align, flags); } } } pub fn store_unsized>( self, bx: &mut Bx, indirect_dest: PlaceRef<'tcx, V>, ) { debug!("OperandRef::store_unsized: operand={:?}, indirect_dest={:?}", self, indirect_dest); let flags = MemFlags::empty(); // `indirect_dest` must have `*mut T` type. We extract `T` out of it. let unsized_ty = indirect_dest .layout .ty .builtin_deref(true) .unwrap_or_else(|| bug!("indirect_dest has non-pointer type: {:?}", indirect_dest)) .ty; let OperandValue::Ref(llptr, Some(llextra), _) = self else { bug!("store_unsized called with a sized value") }; // FIXME: choose an appropriate alignment, or use dynamic align somehow let max_align = Align::from_bits(128).unwrap(); let min_align = Align::from_bits(8).unwrap(); // Allocate an appropriate region on the stack, and copy the value into it let (llsize, _) = glue::size_and_align_of_dst(bx, unsized_ty, Some(llextra)); let lldst = bx.array_alloca(bx.cx().type_i8(), llsize, max_align); bx.memcpy(lldst, max_align, llptr, min_align, llsize, flags); // Store the allocated region and the extra to the indirect place. let indirect_operand = OperandValue::Pair(lldst, llextra); indirect_operand.store(bx, indirect_dest); } } impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { fn maybe_codegen_consume_direct( &mut self, bx: &mut Bx, place_ref: mir::PlaceRef<'tcx>, ) -> Option> { debug!("maybe_codegen_consume_direct(place_ref={:?})", place_ref); match self.locals[place_ref.local] { LocalRef::Operand(Some(mut o)) => { // Moves out of scalar and scalar pair fields are trivial. for elem in place_ref.projection.iter() { match elem { mir::ProjectionElem::Field(ref f, _) => { o = o.extract_field(bx, f.index()); } mir::ProjectionElem::Index(_) | mir::ProjectionElem::ConstantIndex { .. } => { // ZSTs don't require any actual memory access. // FIXME(eddyb) deduplicate this with the identical // 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); } else { return None; } } _ => return None, } } Some(o) } LocalRef::Operand(None) => { bug!("use of {:?} before def", place_ref); } LocalRef::Place(..) | LocalRef::UnsizedPlace(..) => { // watch out for locals that do not have an // alloca; they are handled somewhat differently None } } } pub fn codegen_consume( &mut self, bx: &mut Bx, place_ref: mir::PlaceRef<'tcx>, ) -> OperandRef<'tcx, Bx::Value> { debug!("codegen_consume(place_ref={:?})", place_ref); let ty = self.monomorphized_place_ty(place_ref); let layout = bx.cx().layout_of(ty); // ZSTs don't require any actual memory access. if layout.is_zst() { return OperandRef::new_zst(bx, layout); } if let Some(o) = self.maybe_codegen_consume_direct(bx, place_ref) { return o; } // for most places, to consume them we just load them // out from their home let place = self.codegen_place(bx, place_ref); bx.load_operand(place) } pub fn codegen_operand( &mut self, bx: &mut Bx, operand: &mir::Operand<'tcx>, ) -> OperandRef<'tcx, Bx::Value> { debug!("codegen_operand(operand={:?})", operand); match *operand { mir::Operand::Copy(ref place) | mir::Operand::Move(ref place) => { self.codegen_consume(bx, place.as_ref()) } mir::Operand::Constant(ref constant) => { // This cannot fail because we checked all required_consts in advance. self.eval_mir_constant_to_operand(bx, constant).unwrap_or_else(|_err| { span_bug!(constant.span, "erroneous constant not captured by required_consts") }) } } } }