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Avoid invalidating the CFG in MirPatch.

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As a part of this change, we adjust MirPatch to not needlessly create unnecessary resume blocks.
This commit is contained in:
Jakob Degen 2022-08-02 18:57:54 -07:00
parent e4417cf020
commit efa5eaa5d1
45 changed files with 32 additions and 209 deletions
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65
compiler/rustc_middle/src/mir/patch.rs
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@ -11,7 +11,8 @@ pub struct MirPatch<'tcx> {
new_blocks: Vec<BasicBlockData<'tcx>>,
new_statements: Vec<(Location, StatementKind<'tcx>)>,
new_locals: Vec<LocalDecl<'tcx>>,
resume_block: BasicBlock,
resume_block: Option<BasicBlock>,
body_span: Span,
next_local: usize,
}
@ -23,47 +24,36 @@ impl<'tcx> MirPatch<'tcx> {
new_statements: vec![],
new_locals: vec![],
next_local: body.local_decls.len(),
resume_block: START_BLOCK,
resume_block: None,
body_span: body.span,
};
// make sure the MIR we create has a resume block. It is
// completely legal to convert jumps to the resume block
// to jumps to None, but we occasionally have to add
// instructions just before that.
let mut resume_block = None;
let mut resume_stmt_block = None;
// Check if we already have a resume block
for (bb, block) in body.basic_blocks().iter_enumerated() {
if let TerminatorKind::Resume = block.terminator().kind {
if !block.statements.is_empty() {
assert!(resume_stmt_block.is_none());
resume_stmt_block = Some(bb);
} else {
resume_block = Some(bb);
}
if let TerminatorKind::Resume = block.terminator().kind && block.statements.is_empty() {
result.resume_block = Some(bb);
break;
}
}
let resume_block = resume_block.unwrap_or_else(|| {
result.new_block(BasicBlockData {
statements: vec![],
terminator: Some(Terminator {
source_info: SourceInfo::outermost(body.span),
kind: TerminatorKind::Resume,
}),
is_cleanup: true,
})
});
result.resume_block = resume_block;
if let Some(resume_stmt_block) = resume_stmt_block {
result
.patch_terminator(resume_stmt_block, TerminatorKind::Goto { target: resume_block });
}
result
}
pub fn resume_block(&self) -> BasicBlock {
self.resume_block
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 {
@ -138,12 +128,17 @@ impl<'tcx> MirPatch<'tcx> {
self.new_blocks.len(),
body.basic_blocks().len()
);
body.basic_blocks_mut().extend(self.new_blocks);
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);
body[src].terminator_mut().kind = patch;
bbs[src].terminator_mut().kind = patch;
}
}