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|
use rustc_index::vec::{Idx, IndexVec};
use rustc_middle::mir::*;
use rustc_middle::ty::Ty;
use rustc_span::Span;
/// This struct represents a patch to MIR, which can add
/// new statements and basic blocks and patch over block
/// terminators.
pub struct MirPatch<'tcx> {
patch_map: IndexVec<BasicBlock, Option<TerminatorKind<'tcx>>>,
new_blocks: Vec<BasicBlockData<'tcx>>,
new_statements: Vec<(Location, StatementKind<'tcx>)>,
new_locals: Vec<LocalDecl<'tcx>>,
resume_block: Option<BasicBlock>,
body_span: Span,
next_local: usize,
}
impl<'tcx> MirPatch<'tcx> {
pub fn new(body: &Body<'tcx>) -> Self {
let mut result = MirPatch {
patch_map: IndexVec::from_elem(None, body.basic_blocks()),
new_blocks: vec![],
new_statements: vec![],
new_locals: vec![],
next_local: body.local_decls.len(),
resume_block: None,
body_span: body.span,
};
// Check if we already have a resume block
for (bb, block) in body.basic_blocks().iter_enumerated() {
if let TerminatorKind::Resume = block.terminator().kind && block.statements.is_empty() {
result.resume_block = Some(bb);
break;
}
}
result
}
pub fn resume_block(&mut self) -> BasicBlock {
if let Some(bb) = self.resume_block {
return bb;
}
let bb = self.new_block(BasicBlockData {
statements: vec![],
terminator: Some(Terminator {
source_info: SourceInfo::outermost(self.body_span),
kind: TerminatorKind::Resume,
}),
is_cleanup: true,
});
self.resume_block = Some(bb);
bb
}
pub fn is_patched(&self, bb: BasicBlock) -> bool {
self.patch_map[bb].is_some()
}
pub fn terminator_loc(&self, body: &Body<'tcx>, bb: BasicBlock) -> Location {
let offset = match bb.index().checked_sub(body.basic_blocks().len()) {
Some(index) => self.new_blocks[index].statements.len(),
None => body[bb].statements.len(),
};
Location { block: bb, statement_index: offset }
}
pub fn new_local_with_info(
&mut self,
ty: Ty<'tcx>,
span: Span,
local_info: Option<Box<LocalInfo<'tcx>>>,
) -> Local {
let index = self.next_local;
self.next_local += 1;
let mut new_decl = LocalDecl::new(ty, span);
new_decl.local_info = local_info;
self.new_locals.push(new_decl);
Local::new(index as usize)
}
pub fn new_temp(&mut self, ty: Ty<'tcx>, span: Span) -> Local {
self.new_local_with_info(ty, span, None)
}
pub fn new_internal(&mut self, ty: Ty<'tcx>, span: Span) -> Local {
let index = self.next_local;
self.next_local += 1;
self.new_locals.push(LocalDecl::new(ty, span).internal());
Local::new(index as usize)
}
pub fn new_block(&mut self, data: BasicBlockData<'tcx>) -> BasicBlock {
let block = BasicBlock::new(self.patch_map.len());
debug!("MirPatch: new_block: {:?}: {:?}", block, data);
self.new_blocks.push(data);
self.patch_map.push(None);
block
}
pub fn patch_terminator(&mut self, block: BasicBlock, new: TerminatorKind<'tcx>) {
assert!(self.patch_map[block].is_none());
debug!("MirPatch: patch_terminator({:?}, {:?})", block, new);
self.patch_map[block] = Some(new);
}
pub fn add_statement(&mut self, loc: Location, stmt: StatementKind<'tcx>) {
debug!("MirPatch: add_statement({:?}, {:?})", loc, stmt);
self.new_statements.push((loc, stmt));
}
pub fn add_assign(&mut self, loc: Location, place: Place<'tcx>, rv: Rvalue<'tcx>) {
self.add_statement(loc, StatementKind::Assign(Box::new((place, rv))));
}
pub fn apply(self, body: &mut Body<'tcx>) {
debug!(
"MirPatch: {:?} new temps, starting from index {}: {:?}",
self.new_locals.len(),
body.local_decls.len(),
self.new_locals
);
debug!(
"MirPatch: {} new blocks, starting from index {}",
self.new_blocks.len(),
body.basic_blocks().len()
);
let bbs = if self.patch_map.is_empty() && self.new_blocks.is_empty() {
body.basic_blocks.as_mut_preserves_cfg()
} else {
body.basic_blocks.as_mut()
};
bbs.extend(self.new_blocks);
body.local_decls.extend(self.new_locals);
for (src, patch) in self.patch_map.into_iter_enumerated() {
if let Some(patch) = patch {
debug!("MirPatch: patching block {:?}", src);
bbs[src].terminator_mut().kind = patch;
}
}
let mut new_statements = self.new_statements;
new_statements.sort_by_key(|s| s.0);
let mut delta = 0;
let mut last_bb = START_BLOCK;
let mut stmts_and_targets: Vec<(Statement<'_>, BasicBlock)> = Vec::new();
for (mut loc, stmt) in new_statements {
if loc.block != last_bb {
delta = 0;
last_bb = loc.block;
}
debug!("MirPatch: adding statement {:?} at loc {:?}+{}", stmt, loc, delta);
loc.statement_index += delta;
let source_info = Self::source_info_for_index(&body[loc.block], loc);
// For mir-opt `Derefer` to work in all cases we need to
// get terminator's targets and apply the statement to all of them.
if loc.statement_index > body[loc.block].statements.len() {
let term = body[loc.block].terminator();
for i in term.successors() {
stmts_and_targets.push((Statement { source_info, kind: stmt.clone() }, i));
}
delta += 1;
continue;
}
body[loc.block]
.statements
.insert(loc.statement_index, Statement { source_info, kind: stmt });
delta += 1;
}
for (stmt, target) in stmts_and_targets.into_iter().rev() {
body[target].statements.insert(0, stmt);
}
}
pub fn source_info_for_index(data: &BasicBlockData<'_>, loc: Location) -> SourceInfo {
match data.statements.get(loc.statement_index) {
Some(stmt) => stmt.source_info,
None => data.terminator().source_info,
}
}
pub fn source_info_for_location(&self, body: &Body<'tcx>, loc: Location) -> SourceInfo {
let data = match loc.block.index().checked_sub(body.basic_blocks().len()) {
Some(new) => &self.new_blocks[new],
None => &body[loc.block],
};
Self::source_info_for_index(data, loc)
}
}
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