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| 1 | +//! Provides the implementation of the `custom_mir` attribute. |
| 2 | +//! |
| 3 | +//! Up until MIR building, this attribute has absolutely no effect. The `mir!` macro is a normal |
| 4 | +//! decl macro that expands like any other, and the code goes through parsing, name resolution and |
| 5 | +//! type checking like all other code. In MIR building we finally detect whether this attribute is |
| 6 | +//! present, and if so we branch off into this module, which implements the attribute by |
| 7 | +//! implementing a custom lowering from THIR to MIR. |
| 8 | +//! |
| 9 | +//! The result of this lowering is returned "normally" from the `mir_built` query, with the only |
| 10 | +//! notable difference being that the `injected` field in the body is set. Various components of the |
| 11 | +//! MIR pipeline, like borrowck and the pass manager will then consult this field (via |
| 12 | +//! `body.should_skip()`) to skip the parts of the MIR pipeline that precede the MIR phase the user |
| 13 | +//! specified. |
| 14 | +//! |
| 15 | +//! This file defines the general framework for the custom parsing. The parsing for all the |
| 16 | +//! "top-level" constructs can be found in the `parse` submodule, while the parsing for statements, |
| 17 | +//! terminators, and everything below can be found in the `parse::instruction` submodule. |
| 18 | +//! |
| 19 | +
|
| 20 | +use rustc_ast::Attribute; |
| 21 | +use rustc_data_structures::fx::FxHashMap; |
| 22 | +use rustc_hir::def_id::DefId; |
| 23 | +use rustc_index::vec::IndexVec; |
| 24 | +use rustc_middle::{ |
| 25 | + mir::*, |
| 26 | + thir::*, |
| 27 | + ty::{Ty, TyCtxt}, |
| 28 | +}; |
| 29 | +use rustc_span::Span; |
| 30 | + |
| 31 | +mod parse; |
| 32 | + |
| 33 | +pub(super) fn build_custom_mir<'tcx>( |
| 34 | + tcx: TyCtxt<'tcx>, |
| 35 | + did: DefId, |
| 36 | + thir: &Thir<'tcx>, |
| 37 | + expr: ExprId, |
| 38 | + params: &IndexVec<ParamId, Param<'tcx>>, |
| 39 | + return_ty: Ty<'tcx>, |
| 40 | + return_ty_span: Span, |
| 41 | + span: Span, |
| 42 | + attr: &Attribute, |
| 43 | +) -> Body<'tcx> { |
| 44 | + let mut body = Body { |
| 45 | + basic_blocks: BasicBlocks::new(IndexVec::new()), |
| 46 | + source: MirSource::item(did), |
| 47 | + phase: MirPhase::Built, |
| 48 | + source_scopes: IndexVec::new(), |
| 49 | + generator: None, |
| 50 | + local_decls: LocalDecls::new(), |
| 51 | + user_type_annotations: IndexVec::new(), |
| 52 | + arg_count: params.len(), |
| 53 | + spread_arg: None, |
| 54 | + var_debug_info: Vec::new(), |
| 55 | + span, |
| 56 | + required_consts: Vec::new(), |
| 57 | + is_polymorphic: false, |
| 58 | + tainted_by_errors: None, |
| 59 | + injection_phase: None, |
| 60 | + pass_count: 1, |
| 61 | + }; |
| 62 | + |
| 63 | + body.local_decls.push(LocalDecl::new(return_ty, return_ty_span)); |
| 64 | + body.basic_blocks_mut().push(BasicBlockData::new(None)); |
| 65 | + body.source_scopes.push(SourceScopeData { |
| 66 | + span, |
| 67 | + parent_scope: None, |
| 68 | + inlined: None, |
| 69 | + inlined_parent_scope: None, |
| 70 | + local_data: ClearCrossCrate::Clear, |
| 71 | + }); |
| 72 | + body.injection_phase = Some(parse_attribute(attr)); |
| 73 | + |
| 74 | + let mut pctxt = ParseCtxt { |
| 75 | + tcx, |
| 76 | + thir, |
| 77 | + source_info: SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE }, |
| 78 | + body: &mut body, |
| 79 | + local_map: FxHashMap::default(), |
| 80 | + block_map: FxHashMap::default(), |
| 81 | + }; |
| 82 | + |
| 83 | + let res = (|| { |
| 84 | + pctxt.parse_args(¶ms)?; |
| 85 | + pctxt.parse_body(expr) |
| 86 | + })(); |
| 87 | + if let Err(err) = res { |
| 88 | + tcx.sess.diagnostic().span_fatal( |
| 89 | + err.span, |
| 90 | + format!("Could not parse {}, found: {:?}", err.expected, err.item_description), |
| 91 | + ) |
| 92 | + } |
| 93 | + |
| 94 | + body |
| 95 | +} |
| 96 | + |
| 97 | +fn parse_attribute(attr: &Attribute) -> MirPhase { |
| 98 | + let meta_items = attr.meta_item_list().unwrap(); |
| 99 | + let mut dialect: Option<String> = None; |
| 100 | + let mut phase: Option<String> = None; |
| 101 | + |
| 102 | + for nested in meta_items { |
| 103 | + let name = nested.name_or_empty(); |
| 104 | + let value = nested.value_str().unwrap().as_str().to_string(); |
| 105 | + match name.as_str() { |
| 106 | + "dialect" => { |
| 107 | + assert!(dialect.is_none()); |
| 108 | + dialect = Some(value); |
| 109 | + } |
| 110 | + "phase" => { |
| 111 | + assert!(phase.is_none()); |
| 112 | + phase = Some(value); |
| 113 | + } |
| 114 | + other => { |
| 115 | + panic!("Unexpected key {}", other); |
| 116 | + } |
| 117 | + } |
| 118 | + } |
| 119 | + |
| 120 | + let Some(dialect) = dialect else { |
| 121 | + assert!(phase.is_none()); |
| 122 | + return MirPhase::Built; |
| 123 | + }; |
| 124 | + |
| 125 | + MirPhase::parse(dialect, phase) |
| 126 | +} |
| 127 | + |
| 128 | +struct ParseCtxt<'tcx, 'body> { |
| 129 | + tcx: TyCtxt<'tcx>, |
| 130 | + thir: &'body Thir<'tcx>, |
| 131 | + source_info: SourceInfo, |
| 132 | + |
| 133 | + body: &'body mut Body<'tcx>, |
| 134 | + local_map: FxHashMap<LocalVarId, Local>, |
| 135 | + block_map: FxHashMap<LocalVarId, BasicBlock>, |
| 136 | +} |
| 137 | + |
| 138 | +struct ParseError { |
| 139 | + span: Span, |
| 140 | + item_description: String, |
| 141 | + expected: String, |
| 142 | +} |
| 143 | + |
| 144 | +impl<'tcx, 'body> ParseCtxt<'tcx, 'body> { |
| 145 | + fn expr_error(&self, expr: ExprId, expected: &'static str) -> ParseError { |
| 146 | + let expr = &self.thir[expr]; |
| 147 | + ParseError { |
| 148 | + span: expr.span, |
| 149 | + item_description: format!("{:?}", expr.kind), |
| 150 | + expected: expected.to_string(), |
| 151 | + } |
| 152 | + } |
| 153 | +} |
| 154 | + |
| 155 | +type PResult<T> = Result<T, ParseError>; |
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