From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 14:02:58 +0200 Subject: Adding upstream version 1.64.0+dfsg1. Signed-off-by: Daniel Baumann --- compiler/rustc_const_eval/src/interpret/step.rs | 320 ++++++++++++++++++++++++ 1 file changed, 320 insertions(+) create mode 100644 compiler/rustc_const_eval/src/interpret/step.rs (limited to 'compiler/rustc_const_eval/src/interpret/step.rs') diff --git a/compiler/rustc_const_eval/src/interpret/step.rs b/compiler/rustc_const_eval/src/interpret/step.rs new file mode 100644 index 000000000..fea158a9f --- /dev/null +++ b/compiler/rustc_const_eval/src/interpret/step.rs @@ -0,0 +1,320 @@ +//! This module contains the `InterpCx` methods for executing a single step of the interpreter. +//! +//! The main entry point is the `step` method. + +use rustc_middle::mir; +use rustc_middle::mir::interpret::{InterpResult, Scalar}; +use rustc_middle::ty::layout::LayoutOf; + +use super::{InterpCx, Machine}; + +/// Classify whether an operator is "left-homogeneous", i.e., the LHS has the +/// same type as the result. +#[inline] +fn binop_left_homogeneous(op: mir::BinOp) -> bool { + use rustc_middle::mir::BinOp::*; + match op { + Add | Sub | Mul | Div | Rem | BitXor | BitAnd | BitOr | Offset | Shl | Shr => true, + Eq | Ne | Lt | Le | Gt | Ge => false, + } +} +/// Classify whether an operator is "right-homogeneous", i.e., the RHS has the +/// same type as the LHS. +#[inline] +fn binop_right_homogeneous(op: mir::BinOp) -> bool { + use rustc_middle::mir::BinOp::*; + match op { + Add | Sub | Mul | Div | Rem | BitXor | BitAnd | BitOr | Eq | Ne | Lt | Le | Gt | Ge => true, + Offset | Shl | Shr => false, + } +} + +impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { + pub fn run(&mut self) -> InterpResult<'tcx> { + while self.step()? {} + Ok(()) + } + + /// Returns `true` as long as there are more things to do. + /// + /// This is used by [priroda](https://github.com/oli-obk/priroda) + /// + /// This is marked `#inline(always)` to work around adversarial codegen when `opt-level = 3` + #[inline(always)] + pub fn step(&mut self) -> InterpResult<'tcx, bool> { + if self.stack().is_empty() { + return Ok(false); + } + + let Ok(loc) = self.frame().loc else { + // We are unwinding and this fn has no cleanup code. + // Just go on unwinding. + trace!("unwinding: skipping frame"); + self.pop_stack_frame(/* unwinding */ true)?; + return Ok(true); + }; + let basic_block = &self.body().basic_blocks()[loc.block]; + + if let Some(stmt) = basic_block.statements.get(loc.statement_index) { + let old_frames = self.frame_idx(); + self.statement(stmt)?; + // Make sure we are not updating `statement_index` of the wrong frame. + assert_eq!(old_frames, self.frame_idx()); + // Advance the program counter. + self.frame_mut().loc.as_mut().unwrap().statement_index += 1; + return Ok(true); + } + + M::before_terminator(self)?; + + let terminator = basic_block.terminator(); + self.terminator(terminator)?; + Ok(true) + } + + /// Runs the interpretation logic for the given `mir::Statement` at the current frame and + /// statement counter. + /// + /// This does NOT move the statement counter forward, the caller has to do that! + pub fn statement(&mut self, stmt: &mir::Statement<'tcx>) -> InterpResult<'tcx> { + info!("{:?}", stmt); + + use rustc_middle::mir::StatementKind::*; + + match &stmt.kind { + Assign(box (place, rvalue)) => self.eval_rvalue_into_place(rvalue, *place)?, + + SetDiscriminant { place, variant_index } => { + let dest = self.eval_place(**place)?; + self.write_discriminant(*variant_index, &dest)?; + } + + Deinit(place) => { + let dest = self.eval_place(**place)?; + self.write_uninit(&dest)?; + } + + // Mark locals as alive + StorageLive(local) => { + self.storage_live(*local)?; + } + + // Mark locals as dead + StorageDead(local) => { + self.storage_dead(*local)?; + } + + // No dynamic semantics attached to `FakeRead`; MIR + // interpreter is solely intended for borrowck'ed code. + FakeRead(..) => {} + + // Stacked Borrows. + Retag(kind, place) => { + let dest = self.eval_place(**place)?; + M::retag(self, *kind, &dest)?; + } + + // Call CopyNonOverlapping + CopyNonOverlapping(box rustc_middle::mir::CopyNonOverlapping { src, dst, count }) => { + let src = self.eval_operand(src, None)?; + let dst = self.eval_operand(dst, None)?; + let count = self.eval_operand(count, None)?; + self.copy_intrinsic(&src, &dst, &count, /* nonoverlapping */ true)?; + } + + // Statements we do not track. + AscribeUserType(..) => {} + + // Currently, Miri discards Coverage statements. Coverage statements are only injected + // via an optional compile time MIR pass and have no side effects. Since Coverage + // statements don't exist at the source level, it is safe for Miri to ignore them, even + // for undefined behavior (UB) checks. + // + // A coverage counter inside a const expression (for example, a counter injected in a + // const function) is discarded when the const is evaluated at compile time. Whether + // this should change, and/or how to implement a const eval counter, is a subject of the + // following issue: + // + // FIXME(#73156): Handle source code coverage in const eval + Coverage(..) => {} + + // Defined to do nothing. These are added by optimization passes, to avoid changing the + // size of MIR constantly. + Nop => {} + } + + Ok(()) + } + + /// Evaluate an assignment statement. + /// + /// There is no separate `eval_rvalue` function. Instead, the code for handling each rvalue + /// type writes its results directly into the memory specified by the place. + pub fn eval_rvalue_into_place( + &mut self, + rvalue: &mir::Rvalue<'tcx>, + place: mir::Place<'tcx>, + ) -> InterpResult<'tcx> { + let dest = self.eval_place(place)?; + // FIXME: ensure some kind of non-aliasing between LHS and RHS? + // Also see https://github.com/rust-lang/rust/issues/68364. + + use rustc_middle::mir::Rvalue::*; + match *rvalue { + ThreadLocalRef(did) => { + let ptr = M::thread_local_static_base_pointer(self, did)?; + self.write_pointer(ptr, &dest)?; + } + + Use(ref operand) => { + // Avoid recomputing the layout + let op = self.eval_operand(operand, Some(dest.layout))?; + self.copy_op(&op, &dest, /*allow_transmute*/ false)?; + } + + CopyForDeref(ref place) => { + let op = self.eval_place_to_op(*place, Some(dest.layout))?; + self.copy_op(&op, &dest, /* allow_transmute*/ false)?; + } + + BinaryOp(bin_op, box (ref left, ref right)) => { + let layout = binop_left_homogeneous(bin_op).then_some(dest.layout); + let left = self.read_immediate(&self.eval_operand(left, layout)?)?; + let layout = binop_right_homogeneous(bin_op).then_some(left.layout); + let right = self.read_immediate(&self.eval_operand(right, layout)?)?; + self.binop_ignore_overflow(bin_op, &left, &right, &dest)?; + } + + CheckedBinaryOp(bin_op, box (ref left, ref right)) => { + // Due to the extra boolean in the result, we can never reuse the `dest.layout`. + let left = self.read_immediate(&self.eval_operand(left, None)?)?; + let layout = binop_right_homogeneous(bin_op).then_some(left.layout); + let right = self.read_immediate(&self.eval_operand(right, layout)?)?; + self.binop_with_overflow( + bin_op, /*force_overflow_checks*/ false, &left, &right, &dest, + )?; + } + + UnaryOp(un_op, ref operand) => { + // The operand always has the same type as the result. + let val = self.read_immediate(&self.eval_operand(operand, Some(dest.layout))?)?; + let val = self.unary_op(un_op, &val)?; + assert_eq!(val.layout, dest.layout, "layout mismatch for result of {:?}", un_op); + self.write_immediate(*val, &dest)?; + } + + Aggregate(box ref kind, ref operands) => { + assert!(matches!(kind, mir::AggregateKind::Array(..))); + + for (field_index, operand) in operands.iter().enumerate() { + let op = self.eval_operand(operand, None)?; + let field_dest = self.place_field(&dest, field_index)?; + self.copy_op(&op, &field_dest, /*allow_transmute*/ false)?; + } + } + + Repeat(ref operand, _) => { + let src = self.eval_operand(operand, None)?; + assert!(!src.layout.is_unsized()); + let dest = self.force_allocation(&dest)?; + let length = dest.len(self)?; + + if length == 0 { + // Nothing to copy... but let's still make sure that `dest` as a place is valid. + self.get_place_alloc_mut(&dest)?; + } else { + // Write the src to the first element. + let first = self.mplace_field(&dest, 0)?; + self.copy_op(&src, &first.into(), /*allow_transmute*/ false)?; + + // This is performance-sensitive code for big static/const arrays! So we + // avoid writing each operand individually and instead just make many copies + // of the first element. + let elem_size = first.layout.size; + let first_ptr = first.ptr; + let rest_ptr = first_ptr.offset(elem_size, self)?; + // For the alignment of `rest_ptr`, we crucially do *not* use `first.align` as + // that place might be more aligned than its type mandates (a `u8` array could + // be 4-aligned if it sits at the right spot in a struct). Instead we use + // `first.layout.align`, i.e., the alignment given by the type. + self.mem_copy_repeatedly( + first_ptr, + first.align, + rest_ptr, + first.layout.align.abi, + elem_size, + length - 1, + /*nonoverlapping:*/ true, + )?; + } + } + + Len(place) => { + let src = self.eval_place(place)?; + let mplace = self.force_allocation(&src)?; + let len = mplace.len(self)?; + self.write_scalar(Scalar::from_machine_usize(len, self), &dest)?; + } + + AddressOf(_, place) | Ref(_, _, place) => { + let src = self.eval_place(place)?; + let place = self.force_allocation(&src)?; + self.write_immediate(place.to_ref(self), &dest)?; + } + + NullaryOp(null_op, ty) => { + let ty = self.subst_from_current_frame_and_normalize_erasing_regions(ty)?; + let layout = self.layout_of(ty)?; + if layout.is_unsized() { + // FIXME: This should be a span_bug (#80742) + self.tcx.sess.delay_span_bug( + self.frame().current_span(), + &format!("Nullary MIR operator called for unsized type {}", ty), + ); + throw_inval!(SizeOfUnsizedType(ty)); + } + let val = match null_op { + mir::NullOp::SizeOf => layout.size.bytes(), + mir::NullOp::AlignOf => layout.align.abi.bytes(), + }; + self.write_scalar(Scalar::from_machine_usize(val, self), &dest)?; + } + + ShallowInitBox(ref operand, _) => { + let src = self.eval_operand(operand, None)?; + let v = self.read_immediate(&src)?; + self.write_immediate(*v, &dest)?; + } + + Cast(cast_kind, ref operand, cast_ty) => { + let src = self.eval_operand(operand, None)?; + let cast_ty = + self.subst_from_current_frame_and_normalize_erasing_regions(cast_ty)?; + self.cast(&src, cast_kind, cast_ty, &dest)?; + } + + Discriminant(place) => { + let op = self.eval_place_to_op(place, None)?; + let discr_val = self.read_discriminant(&op)?.0; + self.write_scalar(discr_val, &dest)?; + } + } + + trace!("{:?}", self.dump_place(*dest)); + + Ok(()) + } + + /// Evaluate the given terminator. Will also adjust the stack frame and statement position accordingly. + fn terminator(&mut self, terminator: &mir::Terminator<'tcx>) -> InterpResult<'tcx> { + info!("{:?}", terminator.kind); + + self.eval_terminator(terminator)?; + if !self.stack().is_empty() { + if let Ok(loc) = self.frame().loc { + info!("// executing {:?}", loc.block); + } + } + Ok(()) + } +} -- cgit v1.2.3