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Defer creating drop trees in MIR lowering until leaving that scope
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@matthewjasper
matthewjasper committed May 9, 2020
1 parent 945d110 commit 6119885
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Showing 8 changed files with 766 additions and 735 deletions.
11 changes: 8 additions & 3 deletions src/librustc_mir/util/graphviz.rs
View file
Expand Up @@ -97,12 +97,17 @@ where
write!(w, r#"<table border="0" cellborder="1" cellspacing="0">"#)?;

// Basic block number at the top.
let (blk, color) = if data.is_cleanup {
(format!("{} (cleanup)", block.index()), "lightblue")
} else {
(format!("{}", block.index()), "gray")
};
write!(
w,
r#"<tr><td {attrs} colspan="{colspan}">{blk}</td></tr>"#,
attrs = r#"bgcolor="gray" align="center""#,
r#"<tr><td bgcolor="{color}" align="center" colspan="{colspan}">{blk}</td></tr>"#,
colspan = num_cols,
blk = block.index()
blk = blk,
color = color
)?;

init(w)?;
Expand Down
18 changes: 10 additions & 8 deletions src/librustc_mir_build/build/block.rs
View file
Expand Up @@ -26,14 +26,16 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
self.in_opt_scope(opt_destruction_scope.map(|de| (de, source_info)), move |this| {
this.in_scope((region_scope, source_info), LintLevel::Inherited, move |this| {
if targeted_by_break {
// This is a `break`-able block
let exit_block = this.cfg.start_new_block();
let block_exit =
this.in_breakable_scope(None, exit_block, destination, |this| {
this.ast_block_stmts(destination, block, span, stmts, expr, safety_mode)
});
this.cfg.goto(unpack!(block_exit), source_info, exit_block);
exit_block.unit()
this.in_breakable_scope(None, destination, span, |this| {
Some(this.ast_block_stmts(
destination,
block,
span,
stmts,
expr,
safety_mode,
))
})
} else {
this.ast_block_stmts(destination, block, span, stmts, expr, safety_mode)
}
Expand Down
24 changes: 11 additions & 13 deletions src/librustc_mir_build/build/expr/into.rs
View file
Expand Up @@ -134,32 +134,30 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
// body, even when the exact code in the body cannot unwind

let loop_block = this.cfg.start_new_block();
let exit_block = this.cfg.start_new_block();

// Start the loop.
this.cfg.goto(block, source_info, loop_block);

this.in_breakable_scope(Some(loop_block), exit_block, destination, move |this| {
this.in_breakable_scope(Some(loop_block), destination, expr_span, move |this| {
// conduct the test, if necessary
let body_block = this.cfg.start_new_block();
let diverge_cleanup = this.diverge_cleanup();
this.cfg.terminate(
loop_block,
source_info,
TerminatorKind::FalseUnwind {
real_target: body_block,
unwind: Some(diverge_cleanup),
},
TerminatorKind::FalseUnwind { real_target: body_block, unwind: None },
);
this.diverge_from(loop_block);

// The “return” value of the loop body must always be an unit. We therefore
// introduce a unit temporary as the destination for the loop body.
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.goto(body_block_end, source_info, loop_block);
});
exit_block.unit()

// Loops are only exited by `break` expressions.
None
})
}
ExprKind::Call { ty, fun, args, from_hir_call } => {
let intrinsic = match ty.kind {
Expand Down Expand Up @@ -201,7 +199,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
.collect();

let success = this.cfg.start_new_block();
let cleanup = this.diverge_cleanup();

this.record_operands_moved(&args);

Expand All @@ -211,7 +208,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
TerminatorKind::Call {
func: fun,
args,
cleanup: Some(cleanup),
cleanup: None,
// FIXME(varkor): replace this with an uninhabitedness-based check.
// This requires getting access to the current module to call
// `tcx.is_ty_uninhabited_from`, which is currently tricky to do.
Expand All @@ -223,6 +220,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
from_hir_call,
},
);
this.diverge_from(block);
success.unit()
}
}
Expand Down Expand Up @@ -358,12 +356,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
let scope = this.local_scope();
let value = unpack!(block = this.as_operand(block, scope, value));
let resume = this.cfg.start_new_block();
let cleanup = this.generator_drop_cleanup();
this.cfg.terminate(
block,
source_info,
TerminatorKind::Yield { value, resume, resume_arg: destination, drop: cleanup },
TerminatorKind::Yield { value, resume, resume_arg: destination, drop: None },
);
this.generator_drop_cleanup(block);
resume.unit()
}

Expand Down
17 changes: 5 additions & 12 deletions src/librustc_mir_build/build/matches/mod.rs
View file
Expand Up @@ -225,8 +225,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
outer_source_info: SourceInfo,
fake_borrow_temps: Vec<(Place<'tcx>, Local)>,
) -> BlockAnd<()> {
let match_scope = self.scopes.topmost();

let arm_end_blocks: Vec<_> = arm_candidates
.into_iter()
.map(|(arm, candidate)| {
Expand All @@ -247,7 +245,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
let arm_block = this.bind_pattern(
outer_source_info,
candidate,
arm.guard.as_ref().map(|g| (g, match_scope)),
arm.guard.as_ref(),
&fake_borrow_temps,
scrutinee_span,
Some(arm.scope),
Expand Down Expand Up @@ -284,7 +282,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
&mut self,
outer_source_info: SourceInfo,
candidate: Candidate<'_, 'tcx>,
guard: Option<(&Guard<'tcx>, region::Scope)>,
guard: Option<&Guard<'tcx>>,
fake_borrow_temps: &Vec<(Place<'tcx>, Local)>,
scrutinee_span: Span,
arm_scope: Option<region::Scope>,
Expand Down Expand Up @@ -1563,7 +1561,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
&mut self,
candidate: Candidate<'pat, 'tcx>,
parent_bindings: &[(Vec<Binding<'tcx>>, Vec<Ascription<'tcx>>)],
guard: Option<(&Guard<'tcx>, region::Scope)>,
guard: Option<&Guard<'tcx>>,
fake_borrows: &Vec<(Place<'tcx>, Local)>,
scrutinee_span: Span,
schedule_drops: bool,
Expand Down Expand Up @@ -1675,7 +1673,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
// the reference that we create for the arm.
// * So we eagerly create the reference for the arm and then take a
// reference to that.
if let Some((guard, region_scope)) = guard {
if let Some(guard) = guard {
let tcx = self.hir.tcx();
let bindings = parent_bindings
.iter()
Expand Down Expand Up @@ -1719,12 +1717,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
unreachable
});
let outside_scope = self.cfg.start_new_block();
self.exit_scope(
source_info.span,
region_scope,
otherwise_post_guard_block,
outside_scope,
);
self.exit_top_scope(otherwise_post_guard_block, outside_scope, source_info);
self.false_edges(
outside_scope,
otherwise_block,
Expand Down
6 changes: 3 additions & 3 deletions src/librustc_mir_build/build/matches/test.rs
View file
Expand Up @@ -423,7 +423,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
let bool_ty = self.hir.bool_ty();
let eq_result = self.temp(bool_ty, source_info.span);
let eq_block = self.cfg.start_new_block();
let cleanup = self.diverge_cleanup();
self.cfg.terminate(
block,
source_info,
Expand All @@ -440,11 +439,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
literal: method,
}),
args: vec![val, expect],
destination: Some((eq_result, eq_block)),
cleanup: Some(cleanup),
destination: Some((eq_result.clone(), eq_block)),
cleanup: None,
from_hir_call: false,
},
);
self.diverge_from(block);

if let [success_block, fail_block] = *make_target_blocks(self) {
// check the result
Expand Down
91 changes: 28 additions & 63 deletions src/librustc_mir_build/build/mod.rs
View file
Expand Up @@ -327,11 +327,6 @@ struct Builder<'a, 'tcx> {

var_debug_info: Vec<VarDebugInfo<'tcx>>,

/// Cached block with the `RESUME` terminator; this is created
/// when first set of cleanups are built.
cached_resume_block: Option<BasicBlock>,
/// Cached block with the `RETURN` terminator.
cached_return_block: Option<BasicBlock>,
/// Cached block with the `UNREACHABLE` terminator.
cached_unreachable_block: Option<BasicBlock>,
}
Expand Down Expand Up @@ -590,50 +585,34 @@ where
region::Scope { id: body.value.hir_id.local_id, data: region::ScopeData::CallSite };
let arg_scope =
region::Scope { id: body.value.hir_id.local_id, data: region::ScopeData::Arguments };
let mut block = START_BLOCK;
let source_info = builder.source_info(span);
let call_site_s = (call_site_scope, source_info);
unpack!(
block = builder.in_scope(call_site_s, LintLevel::Inherited, |builder| {
if should_abort_on_panic(tcx, fn_def_id, abi) {
builder.schedule_abort();
}

let arg_scope_s = (arg_scope, source_info);
// `return_block` is called when we evaluate a `return` expression, so
// we just use `START_BLOCK` here.
unpack!(
block = builder.in_breakable_scope(
None,
START_BLOCK,
Place::return_place(),
|builder| {
builder.in_scope(arg_scope_s, LintLevel::Inherited, |builder| {
builder.args_and_body(
block,
fn_def_id.to_def_id(),
&arguments,
arg_scope,
&body.value,
)
})
},
)
);
// Attribute epilogue to function's closing brace
let fn_end = span.shrink_to_hi();
let source_info = builder.source_info(fn_end);
let return_block = builder.return_block();
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);
}
return_block.unit()
})
);
assert_eq!(block, builder.return_block());
unpack!(builder.in_scope(call_site_s, LintLevel::Inherited, |builder| {
let arg_scope_s = (arg_scope, source_info);
// Attribute epilogue to function's closing brace
let fn_end = span.shrink_to_hi();
let return_block =
unpack!(builder.in_breakable_scope(None, Place::return_place(), fn_end, |builder| {
Some(builder.in_scope(arg_scope_s, LintLevel::Inherited, |builder| {
builder.args_and_body(
START_BLOCK,
fn_def_id.to_def_id(),
&arguments,
arg_scope,
&body.value,
)
}))
}));
let source_info = builder.source_info(fn_end);
builder.cfg.terminate(return_block, source_info, TerminatorKind::Return);
let should_abort = should_abort_on_panic(tcx, fn_def_id, abi);
builder.build_drop_trees(should_abort);
// 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);
}
return_block.unit()
}));

let spread_arg = if abi == Abi::RustCall {
// RustCall pseudo-ABI untuples the last argument.
Expand Down Expand Up @@ -667,8 +646,7 @@ fn construct_const<'a, 'tcx>(
let source_info = builder.source_info(span);
builder.cfg.terminate(block, source_info, TerminatorKind::Return);

// Constants can't `return` so a return block should not be created.
assert_eq!(builder.cached_return_block, None);
builder.build_drop_trees(false);

// Constants may be match expressions in which case an unreachable block may
// be created, so terminate it properly.
Expand Down Expand Up @@ -735,7 +713,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
fn_span: span,
arg_count,
generator_kind,
scopes: Default::default(),
scopes: scope::Scopes::new(),
block_context: BlockContext::new(),
source_scopes: IndexVec::new(),
source_scope: OUTERMOST_SOURCE_SCOPE,
Expand All @@ -748,8 +726,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
var_indices: Default::default(),
unit_temp: None,
var_debug_info: vec![],
cached_resume_block: None,
cached_return_block: None,
cached_unreachable_block: None,
};

Expand Down Expand Up @@ -981,17 +957,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
}
}
}

fn return_block(&mut self) -> BasicBlock {
match self.cached_return_block {
Some(rb) => rb,
None => {
let rb = self.cfg.start_new_block();
self.cached_return_block = Some(rb);
rb
}
}
}
}

///////////////////////////////////////////////////////////////////////////
Expand Down

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