From ef24de24a82fe681581cc130f342363c47c0969a Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Fri, 7 Jun 2024 07:48:48 +0200 Subject: Merging upstream version 1.75.0+dfsg1. Signed-off-by: Daniel Baumann --- .../rustc_mir_transform/src/check_alignment.rs | 105 +++++++++++---------- 1 file changed, 54 insertions(+), 51 deletions(-) (limited to 'compiler/rustc_mir_transform/src/check_alignment.rs') diff --git a/compiler/rustc_mir_transform/src/check_alignment.rs b/compiler/rustc_mir_transform/src/check_alignment.rs index 28765af20..42b2f1886 100644 --- a/compiler/rustc_mir_transform/src/check_alignment.rs +++ b/compiler/rustc_mir_transform/src/check_alignment.rs @@ -1,13 +1,12 @@ use crate::MirPass; -use rustc_hir::def_id::DefId; use rustc_hir::lang_items::LangItem; use rustc_index::IndexVec; use rustc_middle::mir::*; use rustc_middle::mir::{ interpret::Scalar, - visit::{PlaceContext, Visitor}, + visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor}, }; -use rustc_middle::ty::{Ty, TyCtxt, TypeAndMut}; +use rustc_middle::ty::{self, ParamEnv, Ty, TyCtxt, TypeAndMut}; use rustc_session::Session; pub struct CheckAlignment; @@ -30,7 +29,12 @@ impl<'tcx> MirPass<'tcx> for CheckAlignment { let basic_blocks = body.basic_blocks.as_mut(); let local_decls = &mut body.local_decls; + let param_env = tcx.param_env_reveal_all_normalized(body.source.def_id()); + // This pass inserts new blocks. Each insertion changes the Location for all + // statements/blocks after. Iterating or visiting the MIR in order would require updating + // our current location after every insertion. By iterating backwards, we dodge this issue: + // The only Locations that an insertion changes have already been handled. for block in (0..basic_blocks.len()).rev() { let block = block.into(); for statement_index in (0..basic_blocks[block].statements.len()).rev() { @@ -38,22 +42,19 @@ impl<'tcx> MirPass<'tcx> for CheckAlignment { let statement = &basic_blocks[block].statements[statement_index]; let source_info = statement.source_info; - let mut finder = PointerFinder { - local_decls, - tcx, - pointers: Vec::new(), - def_id: body.source.def_id(), - }; - for (pointer, pointee_ty) in finder.find_pointers(statement) { - debug!("Inserting alignment check for {:?}", pointer.ty(&*local_decls, tcx).ty); + let mut finder = + PointerFinder { tcx, local_decls, param_env, pointers: Vec::new() }; + finder.visit_statement(statement, location); + for (local, ty) in finder.pointers { + debug!("Inserting alignment check for {:?}", ty); let new_block = split_block(basic_blocks, location); insert_alignment_check( tcx, local_decls, &mut basic_blocks[block], - pointer, - pointee_ty, + local, + ty, source_info, new_block, ); @@ -63,69 +64,71 @@ impl<'tcx> MirPass<'tcx> for CheckAlignment { } } -impl<'tcx, 'a> PointerFinder<'tcx, 'a> { - fn find_pointers(&mut self, statement: &Statement<'tcx>) -> Vec<(Place<'tcx>, Ty<'tcx>)> { - self.pointers.clear(); - self.visit_statement(statement, Location::START); - core::mem::take(&mut self.pointers) - } -} - struct PointerFinder<'tcx, 'a> { - local_decls: &'a mut LocalDecls<'tcx>, tcx: TyCtxt<'tcx>, - def_id: DefId, + local_decls: &'a mut LocalDecls<'tcx>, + param_env: ParamEnv<'tcx>, pointers: Vec<(Place<'tcx>, Ty<'tcx>)>, } impl<'tcx, 'a> Visitor<'tcx> for PointerFinder<'tcx, 'a> { - fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) { - if let Rvalue::AddressOf(..) = rvalue { - // Ignore dereferences inside of an AddressOf - return; + fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) { + // We want to only check reads and writes to Places, so we specifically exclude + // Borrows and AddressOf. + match context { + PlaceContext::MutatingUse( + MutatingUseContext::Store + | MutatingUseContext::AsmOutput + | MutatingUseContext::Call + | MutatingUseContext::Yield + | MutatingUseContext::Drop, + ) => {} + PlaceContext::NonMutatingUse( + NonMutatingUseContext::Copy | NonMutatingUseContext::Move, + ) => {} + _ => { + return; + } } - self.super_rvalue(rvalue, location); - } - fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, _location: Location) { - if let PlaceContext::NonUse(_) = context { - return; - } if !place.is_indirect() { return; } + // Since Deref projections must come first and only once, the pointer for an indirect place + // is the Local that the Place is based on. let pointer = Place::from(place.local); - let pointer_ty = pointer.ty(&*self.local_decls, self.tcx).ty; + let pointer_ty = self.local_decls[place.local].ty; - // We only want to check unsafe pointers + // We only want to check places based on unsafe pointers if !pointer_ty.is_unsafe_ptr() { - trace!("Indirect, but not an unsafe ptr, not checking {:?}", pointer_ty); + trace!("Indirect, but not based on an unsafe ptr, not checking {:?}", place); return; } - let Some(pointee) = pointer_ty.builtin_deref(true) else { - debug!("Indirect but no builtin deref: {:?}", pointer_ty); + let pointee_ty = + pointer_ty.builtin_deref(true).expect("no builtin_deref for an unsafe pointer").ty; + // Ideally we'd support this in the future, but for now we are limited to sized types. + if !pointee_ty.is_sized(self.tcx, self.param_env) { + debug!("Unsafe pointer, but pointee is not known to be sized: {:?}", pointer_ty); return; - }; - let mut pointee_ty = pointee.ty; - if pointee_ty.is_array() || pointee_ty.is_slice() || pointee_ty.is_str() { - pointee_ty = pointee_ty.sequence_element_type(self.tcx); } - if !pointee_ty.is_sized(self.tcx, self.tcx.param_env_reveal_all_normalized(self.def_id)) { - debug!("Unsafe pointer, but unsized: {:?}", pointer_ty); + // Try to detect types we are sure have an alignment of 1 and skip the check + // We don't need to look for str and slices, we already rejected unsized types above + let element_ty = match pointee_ty.kind() { + ty::Array(ty, _) => *ty, + _ => pointee_ty, + }; + if [self.tcx.types.bool, self.tcx.types.i8, self.tcx.types.u8].contains(&element_ty) { + debug!("Trivially aligned place type: {:?}", pointee_ty); return; } - if [self.tcx.types.bool, self.tcx.types.i8, self.tcx.types.u8, self.tcx.types.str_] - .contains(&pointee_ty) - { - debug!("Trivially aligned pointee type: {:?}", pointer_ty); - return; - } + // Ensure that this place is based on an aligned pointer. + self.pointers.push((pointer, pointee_ty)); - self.pointers.push((pointer, pointee_ty)) + self.super_place(place, context, location); } } -- cgit v1.2.3