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| 1 | +use rustc_abi::BackendRepr; |
| 2 | +use rustc_hir::LangItem; |
| 3 | +use rustc_middle::mir; |
| 4 | +use rustc_middle::mir::visit::{NonMutatingUseContext, PlaceContext, Visitor}; |
| 5 | +use rustc_middle::ty::{Mutability, Ty, TyCtxt}; |
| 6 | +use rustc_span::Span; |
| 7 | +use rustc_span::def_id::LOCAL_CRATE; |
| 8 | +use rustc_target::abi::{Float, Integer, Niche, Primitive, Scalar, Size, WrappingRange}; |
| 9 | +use tracing::instrument; |
| 10 | + |
| 11 | +use super::FunctionCx; |
| 12 | +use crate::mir::OperandValue; |
| 13 | +use crate::mir::place::PlaceValue; |
| 14 | +use crate::traits::*; |
| 15 | +use crate::{base, common}; |
| 16 | + |
| 17 | +pub(super) struct NicheFinder<'s, 'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> { |
| 18 | + pub(super) fx: &'s mut FunctionCx<'a, 'tcx, Bx>, |
| 19 | + pub(super) bx: &'s mut Bx, |
| 20 | + pub(super) places: Vec<(mir::Operand<'tcx>, Niche)>, |
| 21 | +} |
| 22 | + |
| 23 | +impl<'s, 'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> Visitor<'tcx> for NicheFinder<'s, 'a, 'tcx, Bx> { |
| 24 | + fn visit_rvalue(&mut self, rvalue: &mir::Rvalue<'tcx>, location: mir::Location) { |
| 25 | + match rvalue { |
| 26 | + mir::Rvalue::Cast(mir::CastKind::Transmute, op, ty) => { |
| 27 | + let ty = self.fx.monomorphize(*ty); |
| 28 | + if let Some(niche) = self.bx.layout_of(ty).largest_niche { |
| 29 | + self.places.push((op.clone(), niche)); |
| 30 | + } |
| 31 | + } |
| 32 | + _ => self.super_rvalue(rvalue, location), |
| 33 | + } |
| 34 | + } |
| 35 | + |
| 36 | + fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, _location: mir::Location) { |
| 37 | + if let mir::TerminatorKind::Return = terminator.kind { |
| 38 | + let op = mir::Operand::Copy(mir::Place::return_place()); |
| 39 | + let ty = op.ty(self.fx.mir, self.bx.tcx()); |
| 40 | + let ty = self.fx.monomorphize(ty); |
| 41 | + if let Some(niche) = self.bx.layout_of(ty).largest_niche { |
| 42 | + self.places.push((op, niche)); |
| 43 | + } |
| 44 | + } |
| 45 | + } |
| 46 | + |
| 47 | + fn visit_place( |
| 48 | + &mut self, |
| 49 | + place: &mir::Place<'tcx>, |
| 50 | + context: PlaceContext, |
| 51 | + _location: mir::Location, |
| 52 | + ) { |
| 53 | + match context { |
| 54 | + PlaceContext::NonMutatingUse( |
| 55 | + NonMutatingUseContext::Copy | NonMutatingUseContext::Move, |
| 56 | + ) => {} |
| 57 | + _ => { |
| 58 | + return; |
| 59 | + } |
| 60 | + } |
| 61 | + |
| 62 | + let ty = place.ty(self.fx.mir, self.bx.tcx()).ty; |
| 63 | + let ty = self.fx.monomorphize(ty); |
| 64 | + if let Some(niche) = self.bx.layout_of(ty).largest_niche { |
| 65 | + self.places.push((mir::Operand::Copy(*place), niche)); |
| 66 | + }; |
| 67 | + } |
| 68 | +} |
| 69 | + |
| 70 | +impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { |
| 71 | + fn value_in_niche( |
| 72 | + &mut self, |
| 73 | + bx: &mut Bx, |
| 74 | + op: crate::mir::OperandRef<'tcx, Bx::Value>, |
| 75 | + niche: Niche, |
| 76 | + ) -> Option<Bx::Value> { |
| 77 | + let niche_ty = niche.ty(bx.tcx()); |
| 78 | + let niche_layout = bx.layout_of(niche_ty); |
| 79 | + |
| 80 | + let (imm, from_scalar, from_backend_ty) = match op.val { |
| 81 | + OperandValue::Immediate(imm) => { |
| 82 | + let BackendRepr::Scalar(from_scalar) = op.layout.backend_repr else { |
| 83 | + unreachable!() |
| 84 | + }; |
| 85 | + let from_backend_ty = bx.backend_type(op.layout); |
| 86 | + (imm, from_scalar, from_backend_ty) |
| 87 | + } |
| 88 | + OperandValue::Pair(first, second) => { |
| 89 | + let BackendRepr::ScalarPair(first_scalar, second_scalar) = op.layout.backend_repr |
| 90 | + else { |
| 91 | + unreachable!() |
| 92 | + }; |
| 93 | + if niche.offset == Size::ZERO { |
| 94 | + (first, first_scalar, bx.scalar_pair_element_backend_type(op.layout, 0, true)) |
| 95 | + } else { |
| 96 | + // yolo |
| 97 | + (second, second_scalar, bx.scalar_pair_element_backend_type(op.layout, 1, true)) |
| 98 | + } |
| 99 | + } |
| 100 | + OperandValue::ZeroSized => unreachable!(), |
| 101 | + OperandValue::Ref(PlaceValue { llval: ptr, .. }) => { |
| 102 | + // General case: Load the niche primitive via pointer arithmetic. |
| 103 | + let niche_ptr_ty = Ty::new_ptr(bx.tcx(), niche_ty, Mutability::Not); |
| 104 | + let ptr = bx.pointercast(ptr, bx.backend_type(bx.layout_of(niche_ptr_ty))); |
| 105 | + |
| 106 | + let offset = niche.offset.bytes() / niche_layout.size.bytes(); |
| 107 | + let niche_backend_ty = bx.backend_type(bx.layout_of(niche_ty)); |
| 108 | + let ptr = bx.inbounds_gep(niche_backend_ty, ptr, &[bx.const_usize(offset)]); |
| 109 | + let value = bx.load(niche_backend_ty, ptr, rustc_target::abi::Align::ONE); |
| 110 | + return Some(value); |
| 111 | + } |
| 112 | + }; |
| 113 | + |
| 114 | + // Any type whose ABI is a Scalar bool is turned into an i1, so it cannot contain a value |
| 115 | + // outside of its niche. |
| 116 | + if from_scalar.is_bool() { |
| 117 | + return None; |
| 118 | + } |
| 119 | + |
| 120 | + let to_scalar = Scalar::Initialized { |
| 121 | + value: niche.value, |
| 122 | + valid_range: WrappingRange::full(niche.size(bx.tcx())), |
| 123 | + }; |
| 124 | + let to_backend_ty = bx.backend_type(niche_layout); |
| 125 | + if from_backend_ty == to_backend_ty { |
| 126 | + return Some(imm); |
| 127 | + } |
| 128 | + let value = self.transmute_immediate( |
| 129 | + bx, |
| 130 | + imm, |
| 131 | + from_scalar, |
| 132 | + from_backend_ty, |
| 133 | + to_scalar, |
| 134 | + to_backend_ty, |
| 135 | + ); |
| 136 | + Some(value) |
| 137 | + } |
| 138 | + |
| 139 | + #[instrument(level = "debug", skip(self, bx))] |
| 140 | + pub fn codegen_niche_check( |
| 141 | + &mut self, |
| 142 | + bx: &mut Bx, |
| 143 | + mir_op: mir::Operand<'tcx>, |
| 144 | + niche: Niche, |
| 145 | + source_info: mir::SourceInfo, |
| 146 | + ) { |
| 147 | + let tcx = bx.tcx(); |
| 148 | + let op_ty = self.monomorphize(mir_op.ty(self.mir, tcx)); |
| 149 | + if op_ty == tcx.types.bool { |
| 150 | + return; |
| 151 | + } |
| 152 | + |
| 153 | + let op = self.codegen_operand(bx, &mir_op); |
| 154 | + |
| 155 | + let Some(value_in_niche) = self.value_in_niche(bx, op, niche) else { |
| 156 | + return; |
| 157 | + }; |
| 158 | + let size = niche.size(tcx); |
| 159 | + |
| 160 | + let start = niche.scalar(niche.valid_range.start, bx); |
| 161 | + let end = niche.scalar(niche.valid_range.end, bx); |
| 162 | + |
| 163 | + let binop_le = base::bin_op_to_icmp_predicate(mir::BinOp::Le, false); |
| 164 | + let binop_ge = base::bin_op_to_icmp_predicate(mir::BinOp::Ge, false); |
| 165 | + let is_valid = if niche.valid_range.start == 0 { |
| 166 | + bx.icmp(binop_le, value_in_niche, end) |
| 167 | + } else if niche.valid_range.end == (u128::MAX >> 128 - size.bits()) { |
| 168 | + bx.icmp(binop_ge, value_in_niche, start) |
| 169 | + } else { |
| 170 | + // We need to check if the value is within a *wrapping* range. We could do this: |
| 171 | + // (niche >= start) && (niche <= end) |
| 172 | + // But what we're going to actually do is this: |
| 173 | + // max = end - start |
| 174 | + // (niche - start) <= max |
| 175 | + // The latter is much more complicated conceptually, but is actually less operations |
| 176 | + // because we can compute max in codegen. |
| 177 | + let mut max = niche.valid_range.end.wrapping_sub(niche.valid_range.start); |
| 178 | + let size = niche.size(tcx); |
| 179 | + if size.bits() < 128 { |
| 180 | + let mask = (1 << size.bits()) - 1; |
| 181 | + max &= mask; |
| 182 | + } |
| 183 | + let max_adjusted_allowed_value = niche.scalar(max, bx); |
| 184 | + |
| 185 | + let biased = bx.sub(value_in_niche, start); |
| 186 | + bx.icmp(binop_le, biased, max_adjusted_allowed_value) |
| 187 | + }; |
| 188 | + |
| 189 | + // Create destination blocks, branching on is_valid |
| 190 | + let panic = bx.append_sibling_block("panic"); |
| 191 | + let success = bx.append_sibling_block("success"); |
| 192 | + bx.cond_br(is_valid, success, panic); |
| 193 | + |
| 194 | + // Switch to the failure block and codegen a call to the panic intrinsic |
| 195 | + bx.switch_to_block(panic); |
| 196 | + self.set_debug_loc(bx, source_info); |
| 197 | + let location = self.get_caller_location(bx, source_info).immediate(); |
| 198 | + self.codegen_panic( |
| 199 | + bx, |
| 200 | + niche.lang_item(), |
| 201 | + &[value_in_niche, start, end, location], |
| 202 | + source_info.span, |
| 203 | + ); |
| 204 | + |
| 205 | + // Continue codegen in the success block. |
| 206 | + bx.switch_to_block(success); |
| 207 | + self.set_debug_loc(bx, source_info); |
| 208 | + } |
| 209 | + |
| 210 | + #[instrument(level = "debug", skip(self, bx))] |
| 211 | + fn codegen_panic(&mut self, bx: &mut Bx, lang_item: LangItem, args: &[Bx::Value], span: Span) { |
| 212 | + if bx.tcx().is_compiler_builtins(LOCAL_CRATE) { |
| 213 | + bx.abort() |
| 214 | + } else { |
| 215 | + let (fn_abi, fn_ptr, instance) = common::build_langcall(bx, Some(span), lang_item); |
| 216 | + let fn_ty = bx.fn_decl_backend_type(&fn_abi); |
| 217 | + let fn_attrs = if bx.tcx().def_kind(self.instance.def_id()).has_codegen_attrs() { |
| 218 | + Some(bx.tcx().codegen_fn_attrs(self.instance.def_id())) |
| 219 | + } else { |
| 220 | + None |
| 221 | + }; |
| 222 | + bx.call(fn_ty, fn_attrs, Some(&fn_abi), fn_ptr, args, None, Some(instance)); |
| 223 | + } |
| 224 | + bx.unreachable(); |
| 225 | + } |
| 226 | +} |
| 227 | + |
| 228 | +trait NicheExt { |
| 229 | + fn ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx>; |
| 230 | + fn size<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Size; |
| 231 | + fn scalar<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(&self, val: u128, bx: &mut Bx) -> Bx::Value; |
| 232 | + fn lang_item(&self) -> LangItem; |
| 233 | +} |
| 234 | + |
| 235 | +impl NicheExt for Niche { |
| 236 | + fn lang_item(&self) -> LangItem { |
| 237 | + match self.value { |
| 238 | + Primitive::Int(Integer::I8, _) => LangItem::PanicOccupiedNicheU8, |
| 239 | + Primitive::Int(Integer::I16, _) => LangItem::PanicOccupiedNicheU16, |
| 240 | + Primitive::Int(Integer::I32, _) => LangItem::PanicOccupiedNicheU32, |
| 241 | + Primitive::Int(Integer::I64, _) => LangItem::PanicOccupiedNicheU64, |
| 242 | + Primitive::Int(Integer::I128, _) => LangItem::PanicOccupiedNicheU128, |
| 243 | + Primitive::Pointer(_) => LangItem::PanicOccupiedNichePtr, |
| 244 | + Primitive::Float(Float::F16) => LangItem::PanicOccupiedNicheU16, |
| 245 | + Primitive::Float(Float::F32) => LangItem::PanicOccupiedNicheU32, |
| 246 | + Primitive::Float(Float::F64) => LangItem::PanicOccupiedNicheU64, |
| 247 | + Primitive::Float(Float::F128) => LangItem::PanicOccupiedNicheU128, |
| 248 | + } |
| 249 | + } |
| 250 | + |
| 251 | + fn ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> { |
| 252 | + let types = &tcx.types; |
| 253 | + match self.value { |
| 254 | + Primitive::Int(Integer::I8, _) => types.u8, |
| 255 | + Primitive::Int(Integer::I16, _) => types.u16, |
| 256 | + Primitive::Int(Integer::I32, _) => types.u32, |
| 257 | + Primitive::Int(Integer::I64, _) => types.u64, |
| 258 | + Primitive::Int(Integer::I128, _) => types.u128, |
| 259 | + Primitive::Pointer(_) => Ty::new_ptr(tcx, types.unit, Mutability::Not), |
| 260 | + Primitive::Float(Float::F16) => types.u16, |
| 261 | + Primitive::Float(Float::F32) => types.u32, |
| 262 | + Primitive::Float(Float::F64) => types.u64, |
| 263 | + Primitive::Float(Float::F128) => types.u128, |
| 264 | + } |
| 265 | + } |
| 266 | + |
| 267 | + fn size<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Size { |
| 268 | + self.value.size(&tcx) |
| 269 | + } |
| 270 | + |
| 271 | + fn scalar<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(&self, val: u128, bx: &mut Bx) -> Bx::Value { |
| 272 | + use rustc_middle::mir::interpret::{Pointer, Scalar}; |
| 273 | + let tcx = bx.tcx(); |
| 274 | + let niche_ty = self.ty(tcx); |
| 275 | + let value = if niche_ty.is_any_ptr() { |
| 276 | + Scalar::from_maybe_pointer(Pointer::from_addr_invalid(val as u64), &tcx) |
| 277 | + } else { |
| 278 | + Scalar::from_uint(val, self.size(tcx)) |
| 279 | + }; |
| 280 | + let layout = rustc_target::abi::Scalar::Initialized { |
| 281 | + value: self.value, |
| 282 | + valid_range: WrappingRange::full(self.size(tcx)), |
| 283 | + }; |
| 284 | + bx.scalar_to_backend(value, layout, bx.backend_type(bx.layout_of(self.ty(tcx)))) |
| 285 | + } |
| 286 | +} |
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