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Misc MIR building cleanups #67499

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merged 2 commits into from
Dec 22, 2019
Merged

Misc MIR building cleanups #67499

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4f0dc7b
misc cleanup in match MIR building
Centril Dec 20, 2019
f5a8d1a
simplify MIR building with cfg.goto(...)
Centril Dec 20, 2019
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3 changes: 1 addition & 2 deletions src/librustc_mir/build/block.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -33,8 +33,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
this.ast_block_stmts(destination, block, span, stmts, expr,
safety_mode)
});
this.cfg.terminate(unpack!(block_exit), source_info,
TerminatorKind::Goto { target: exit_block });
this.cfg.goto(unpack!(block_exit), source_info, exit_block);
exit_block.unit()
} else {
this.ast_block_stmts(destination, block, span, stmts, expr,
Expand Down
5 changes: 5 additions & 0 deletions src/librustc_mir/build/cfg.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -85,4 +85,9 @@ impl<'tcx> CFG<'tcx> {
kind,
});
}

/// In the `origin` block, push a `goto -> target` terminator.
pub fn goto(&mut self, origin: BasicBlock, source_info: SourceInfo, target: BasicBlock) {
self.terminate(origin, source_info, TerminatorKind::Goto { target })
}
}
28 changes: 6 additions & 22 deletions src/librustc_mir/build/expr/into.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -140,17 +140,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
},
);

this.cfg.terminate(
true_block,
source_info,
TerminatorKind::Goto { target: join_block },
);
this.cfg.terminate(
false_block,
source_info,
TerminatorKind::Goto { target: join_block },
);

// Link up both branches:
this.cfg.goto(true_block, source_info, join_block);
this.cfg.goto(false_block, source_info, join_block);
join_block.unit()
}
ExprKind::Loop { body } => {
Expand All @@ -167,12 +159,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
let loop_block = this.cfg.start_new_block();
let exit_block = this.cfg.start_new_block();

// start the loop
this.cfg.terminate(
block,
source_info,
TerminatorKind::Goto { target: loop_block },
);
// Start the loop.
this.cfg.goto(block, source_info, loop_block);

this.in_breakable_scope(
Some(loop_block),
Expand All @@ -196,11 +184,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
let tmp = this.get_unit_temp();
// Execute the body, branching back to the test.
let body_block_end = unpack!(this.into(&tmp, body_block, body));
this.cfg.terminate(
body_block_end,
source_info,
TerminatorKind::Goto { target: loop_block },
);
this.cfg.goto(body_block_end, source_info, loop_block);
},
);
exit_block.unit()
Expand Down
77 changes: 26 additions & 51 deletions src/librustc_mir/build/matches/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ mod simplify;
mod test;
mod util;

use itertools::Itertools;
use std::convert::TryFrom;

impl<'a, 'tcx> Builder<'a, 'tcx> {
Expand Down Expand Up @@ -258,11 +259,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
scrutinee_span,
match_scope,
);
this.cfg.terminate(
binding_end,
source_info,
TerminatorKind::Goto { target: arm_block },
);
this.cfg.goto(binding_end, source_info, arm_block);
}
}

Expand All @@ -278,11 +275,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
let end_block = self.cfg.start_new_block();

for arm_block in arm_end_blocks {
self.cfg.terminate(
unpack!(arm_block),
outer_source_info,
TerminatorKind::Goto { target: end_block },
);
self.cfg.goto(unpack!(arm_block), outer_source_info, end_block);
}

self.source_scope = outer_source_info.scope;
Expand Down Expand Up @@ -822,45 +815,34 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
);
let (matched_candidates, unmatched_candidates) = candidates.split_at_mut(fully_matched);

let block: BasicBlock;

if !matched_candidates.is_empty() {
let block: BasicBlock = if !matched_candidates.is_empty() {
let otherwise_block = self.select_matched_candidates(
matched_candidates,
start_block,
fake_borrows,
);

if let Some(last_otherwise_block) = otherwise_block {
block = last_otherwise_block
last_otherwise_block
} else {
// Any remaining candidates are unreachable.
if unmatched_candidates.is_empty() {
return;
}
block = self.cfg.start_new_block();
};
self.cfg.start_new_block()
}
} else {
block = *start_block.get_or_insert_with(|| self.cfg.start_new_block());
}
*start_block.get_or_insert_with(|| self.cfg.start_new_block())
};

// If there are no candidates that still need testing, we're
// done. Since all matches are exhaustive, execution should
// never reach this point.
if unmatched_candidates.is_empty() {
let source_info = self.source_info(span);
if let Some(otherwise) = otherwise_block {
self.cfg.terminate(
block,
source_info,
TerminatorKind::Goto { target: otherwise },
);
} else {
self.cfg.terminate(
block,
source_info,
TerminatorKind::Unreachable,
)
match otherwise_block {
Some(otherwise) => self.cfg.goto(block, source_info, otherwise),
None => self.cfg.terminate(block, source_info, TerminatorKind::Unreachable),
}
return;
}
Expand All @@ -885,7 +867,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
/// ...
///
/// We generate real edges from:
/// * `block` to the prebinding_block of the first pattern,
/// * `start_block` to the `prebinding_block` of the first pattern,
/// * the otherwise block of the first pattern to the second pattern,
/// * the otherwise block of the third pattern to the a block with an
/// Unreachable terminator.
Expand Down Expand Up @@ -948,32 +930,25 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
let first_candidate = &reachable_candidates[0];
let first_prebinding_block = first_candidate.pre_binding_block;

// `goto -> first_prebinding_block` from the `start_block` if there is one.
if let Some(start_block) = *start_block {
let source_info = self.source_info(first_candidate.span);
self.cfg.terminate(
start_block,
source_info,
TerminatorKind::Goto { target: first_prebinding_block },
);
self.cfg.goto(start_block, source_info, first_prebinding_block);
} else {
*start_block = Some(first_prebinding_block);
}

for window in reachable_candidates.windows(2) {
if let [first_candidate, second_candidate] = window {
let source_info = self.source_info(first_candidate.span);
if let Some(otherwise_block) = first_candidate.otherwise_block {
self.false_edges(
otherwise_block,
second_candidate.pre_binding_block,
first_candidate.next_candidate_pre_binding_block,
source_info,
);
} else {
bug!("candidate other than the last has no guard");
}
for (first_candidate, second_candidate) in reachable_candidates.iter().tuple_windows() {
let source_info = self.source_info(first_candidate.span);
if let Some(otherwise_block) = first_candidate.otherwise_block {
self.false_edges(
otherwise_block,
second_candidate.pre_binding_block,
first_candidate.next_candidate_pre_binding_block,
source_info,
);
} else {
bug!("<[_]>::windows returned incorrectly sized window");
bug!("candidate other than the last has no guard");
}
}

Expand All @@ -992,8 +967,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
}
}

let last_candidate = reachable_candidates.last().unwrap();

let last_candidate = reachable_candidates.last().unwrap();
if let Some(otherwise) = last_candidate.otherwise_block {
let source_info = self.source_info(last_candidate.span);
let block = self.cfg.start_new_block();
Expand Down
2 changes: 1 addition & 1 deletion src/librustc_mir/build/matches/test.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
Test {
span: match_pair.pattern.span,
kind: TestKind::Switch {
adt_def: adt_def.clone(),
adt_def,
variants: BitSet::new_empty(adt_def.variants.len()),
},
}
Expand Down
10 changes: 1 addition & 9 deletions src/librustc_mir/build/matches/util.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -109,15 +109,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
},
);
}
_ => {
self.cfg.terminate(
from_block,
source_info,
TerminatorKind::Goto {
target: real_target
}
);
}
_ => self.cfg.goto(from_block, source_info, real_target),
}
}
}
Expand Down
9 changes: 3 additions & 6 deletions src/librustc_mir/build/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -606,14 +606,11 @@ where
let fn_end = span.shrink_to_hi();
let source_info = builder.source_info(fn_end);
let return_block = builder.return_block();
builder.cfg.terminate(block, source_info,
TerminatorKind::Goto { target: return_block });
builder.cfg.terminate(return_block, source_info,
TerminatorKind::Return);
builder.cfg.goto(block, source_info, return_block);
builder.cfg.terminate(return_block, source_info, TerminatorKind::Return);
// Attribute any unreachable codepaths to the function's closing brace
if let Some(unreachable_block) = builder.cached_unreachable_block {
builder.cfg.terminate(unreachable_block, source_info,
TerminatorKind::Unreachable);
builder.cfg.terminate(unreachable_block, source_info, TerminatorKind::Unreachable);
}
return_block.unit()
}));
Expand Down
18 changes: 6 additions & 12 deletions src/librustc_mir/build/scope.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -564,14 +564,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
let source_info = scope.source_info(span);
block = match scope.cached_exits.entry((target, region_scope)) {
Entry::Occupied(e) => {
self.cfg.terminate(block, source_info,
TerminatorKind::Goto { target: *e.get() });
self.cfg.goto(block, source_info, *e.get());
return;
}
Entry::Vacant(v) => {
let b = self.cfg.start_new_block();
self.cfg.terminate(block, source_info,
TerminatorKind::Goto { target: b });
self.cfg.goto(block, source_info, b);
v.insert(b);
b
}
Expand All @@ -596,8 +594,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
scope = next_scope;
}

let source_info = self.scopes.source_info(scope_count, span);
self.cfg.terminate(block, source_info, TerminatorKind::Goto { target });
self.cfg.goto(block, self.scopes.source_info(scope_count, span), target);
}

/// Creates a path that performs all required cleanup for dropping a generator.
Expand All @@ -616,14 +613,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {

while let Some(scope) = scopes.next() {
block = if let Some(b) = scope.cached_generator_drop {
self.cfg.terminate(block, src_info,
TerminatorKind::Goto { target: b });
self.cfg.goto(block, src_info, b);
return Some(result);
} else {
let b = self.cfg.start_new_block();
scope.cached_generator_drop = Some(b);
self.cfg.terminate(block, src_info,
TerminatorKind::Goto { target: b });
self.cfg.goto(block, src_info, b);
b
};

Expand Down Expand Up @@ -1243,8 +1238,7 @@ fn build_diverge_scope<'tcx>(cfg: &mut CFG<'tcx>,
// block for our StorageDead statements.
let block = cfg.start_new_cleanup_block();
let source_info = SourceInfo { span: DUMMY_SP, scope: source_scope };
cfg.terminate(block, source_info,
TerminatorKind::Goto { target: target });
cfg.goto(block, source_info, target);
target = block;
target_built_by_us = true;
}
Expand Down