compiler/rustc_middle/src/mir/patch.rs

   1 use rustc_index::vec::{Idx, IndexVec};
   2 use rustc_middle::mir::*;
   3 use rustc_middle::ty::Ty;
   4 use rustc_span::Span;
   5
   6 /// This struct represents a patch to MIR, which can add
   7 /// new statements and basic blocks and patch over block
   8 /// terminators.
   9 pub struct MirPatch<'tcx> {
  10     patch_map: IndexVec<BasicBlock, Option<TerminatorKind<'tcx>>>,
  11     new_blocks: Vec<BasicBlockData<'tcx>>,
  12     new_statements: Vec<(Location, StatementKind<'tcx>)>,
  13     new_locals: Vec<LocalDecl<'tcx>>,
  14     resume_block: Option<BasicBlock>,
  15     body_span: Span,
  16     next_local: usize,
  17 }
  18
  19 impl<'tcx> MirPatch<'tcx> {
  20     pub fn new(body: &Body<'tcx>) -> Self {
  21         let mut result = MirPatch {
  22             patch_map: IndexVec::from_elem(None, &body.basic_blocks),
  23             new_blocks: vec![],
  24             new_statements: vec![],
  25             new_locals: vec![],
  26             next_local: body.local_decls.len(),
  27             resume_block: None,
  28             body_span: body.span,
  29         };
  30
  31         // Check if we already have a resume block
  32         for (bb, block) in body.basic_blocks.iter_enumerated() {
  33             if let TerminatorKind::Resume = block.terminator().kind && block.statements.is_empty() {
  34                 result.resume_block = Some(bb);
  35                 break;
  36             }
  37         }
  38
  39         result
  40     }
  41
  42     pub fn resume_block(&mut self) -> BasicBlock {
  43         if let Some(bb) = self.resume_block {
  44             return bb;
  45         }
  46
  47         let bb = self.new_block(BasicBlockData {
  48             statements: vec![],
  49             terminator: Some(Terminator {
  50                 source_info: SourceInfo::outermost(self.body_span),
  51                 kind: TerminatorKind::Resume,
  52             }),
  53             is_cleanup: true,
  54         });
  55         self.resume_block = Some(bb);
  56         bb
  57     }
  58
  59     pub fn is_patched(&self, bb: BasicBlock) -> bool {
  60         self.patch_map[bb].is_some()
  61     }
  62
  63     pub fn terminator_loc(&self, body: &Body<'tcx>, bb: BasicBlock) -> Location {
  64         let offset = match bb.index().checked_sub(body.basic_blocks.len()) {
  65             Some(index) => self.new_blocks[index].statements.len(),
  66             None => body[bb].statements.len(),
  67         };
  68         Location { block: bb, statement_index: offset }
  69     }
  70
  71     pub fn new_internal_with_info(
  72         &mut self,
  73         ty: Ty<'tcx>,
  74         span: Span,
  75         local_info: Option<Box<LocalInfo<'tcx>>>,
  76     ) -> Local {
  77         let index = self.next_local;
  78         self.next_local += 1;
  79         let mut new_decl = LocalDecl::new(ty, span).internal();
  80         new_decl.local_info = local_info;
  81         self.new_locals.push(new_decl);
  82         Local::new(index as usize)
  83     }
  84
  85     pub fn new_temp(&mut self, ty: Ty<'tcx>, span: Span) -> Local {
  86         let index = self.next_local;
  87         self.next_local += 1;
  88         self.new_locals.push(LocalDecl::new(ty, span));
  89         Local::new(index as usize)
  90     }
  91
  92     pub fn new_internal(&mut self, ty: Ty<'tcx>, span: Span) -> Local {
  93         let index = self.next_local;
  94         self.next_local += 1;
  95         self.new_locals.push(LocalDecl::new(ty, span).internal());
  96         Local::new(index as usize)
  97     }
  98
  99     pub fn new_block(&mut self, data: BasicBlockData<'tcx>) -> BasicBlock {
 100         let block = BasicBlock::new(self.patch_map.len());
 101         debug!("MirPatch: new_block: {:?}: {:?}", block, data);
 102         self.new_blocks.push(data);
 103         self.patch_map.push(None);
 104         block
 105     }
 106
 107     pub fn patch_terminator(&mut self, block: BasicBlock, new: TerminatorKind<'tcx>) {
 108         assert!(self.patch_map[block].is_none());
 109         debug!("MirPatch: patch_terminator({:?}, {:?})", block, new);
 110         self.patch_map[block] = Some(new);
 111     }
 112
 113     pub fn add_statement(&mut self, loc: Location, stmt: StatementKind<'tcx>) {
 114         debug!("MirPatch: add_statement({:?}, {:?})", loc, stmt);
 115         self.new_statements.push((loc, stmt));
 116     }
 117
 118     pub fn add_assign(&mut self, loc: Location, place: Place<'tcx>, rv: Rvalue<'tcx>) {
 119         self.add_statement(loc, StatementKind::Assign(Box::new((place, rv))));
 120     }
 121
 122     pub fn apply(self, body: &mut Body<'tcx>) {
 123         debug!(
 124             "MirPatch: {:?} new temps, starting from index {}: {:?}",
 125             self.new_locals.len(),
 126             body.local_decls.len(),
 127             self.new_locals
 128         );
 129         debug!(
 130             "MirPatch: {} new blocks, starting from index {}",
 131             self.new_blocks.len(),
 132             body.basic_blocks.len()
 133         );
 134         let bbs = if self.patch_map.is_empty() && self.new_blocks.is_empty() {
 135             body.basic_blocks.as_mut_preserves_cfg()
 136         } else {
 137             body.basic_blocks.as_mut()
 138         };
 139         bbs.extend(self.new_blocks);
 140         body.local_decls.extend(self.new_locals);
 141         for (src, patch) in self.patch_map.into_iter_enumerated() {
 142             if let Some(patch) = patch {
 143                 debug!("MirPatch: patching block {:?}", src);
 144                 bbs[src].terminator_mut().kind = patch;
 145             }
 146         }
 147
 148         let mut new_statements = self.new_statements;
 149         new_statements.sort_by_key(|s| s.0);
 150
 151         let mut delta = 0;
 152         let mut last_bb = START_BLOCK;
 153         for (mut loc, stmt) in new_statements {
 154             if loc.block != last_bb {
 155                 delta = 0;
 156                 last_bb = loc.block;
 157             }
 158             debug!("MirPatch: adding statement {:?} at loc {:?}+{}", stmt, loc, delta);
 159             loc.statement_index += delta;
 160             let source_info = Self::source_info_for_index(&body[loc.block], loc);
 161             body[loc.block]
 162                 .statements
 163                 .insert(loc.statement_index, Statement { source_info, kind: stmt });
 164             delta += 1;
 165         }
 166     }
 167
 168     pub fn source_info_for_index(data: &BasicBlockData<'_>, loc: Location) -> SourceInfo {
 169         match data.statements.get(loc.statement_index) {
 170             Some(stmt) => stmt.source_info,
 171             None => data.terminator().source_info,
 172         }
 173     }
 174
 175     pub fn source_info_for_location(&self, body: &Body<'tcx>, loc: Location) -> SourceInfo {
 176         let data = match loc.block.index().checked_sub(body.basic_blocks.len()) {
 177             Some(new) => &self.new_blocks[new],
 178             None => &body[loc.block],
 179         };
 180         Self::source_info_for_index(data, loc)
 181     }
 182 }