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Rollup merge of rust-lang#116974 - Zalathar:signature-spans, r=oli-obk
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coverage: Fix inconsistent handling of function signature spans

While doing some more cleanup of `spans`, I noticed a strange inconsistency in how function signatures are handled. Normally the function signature span is treated as though it were executable as part of the start of the function, but in some cases the signature span disappears entirely from coverage, for no obvious reason.

This is caused by the fact that spans created by `CoverageSpan::for_fn_sig` don't add the span to their `merged_spans` field (unlike normal statement/terminator spans). In cases where the span-processing code looks at those merged spans, it thinks the signature span is no longer visible and deletes it.

Adding the signature span to `merged_spans` resolves the inconsistency.

(Prior to rust-lang#116409 this wouldn't have been possible, because there was no case in the old `CoverageStatement` enum representing a signature. Now that `merged_spans` is just a list of spans, that's no longer an obstacle.)
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matthiaskrgr committed Oct 20, 2023
2 parents a830394 + 2a191e2 commit a7bbf83
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Showing 9 changed files with 233 additions and 67 deletions.
33 changes: 4 additions & 29 deletions compiler/rustc_mir_transform/src/coverage/spans.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@ use std::cell::OnceCell;

use rustc_data_structures::graph::WithNumNodes;
use rustc_index::IndexVec;
use rustc_middle::mir::{self, AggregateKind, Rvalue, Statement, StatementKind};
use rustc_middle::mir;
use rustc_span::{BytePos, ExpnKind, MacroKind, Span, Symbol, DUMMY_SP};

use super::graph::{BasicCoverageBlock, CoverageGraph, START_BCB};
Expand Down Expand Up @@ -75,29 +75,15 @@ struct CoverageSpan {

impl CoverageSpan {
pub fn for_fn_sig(fn_sig_span: Span) -> Self {
Self {
span: fn_sig_span,
expn_span: fn_sig_span,
current_macro_or_none: Default::default(),
bcb: START_BCB,
merged_spans: vec![],
is_closure: false,
}
Self::new(fn_sig_span, fn_sig_span, START_BCB, false)
}

pub fn for_statement(
statement: &Statement<'_>,
pub(super) fn new(
span: Span,
expn_span: Span,
bcb: BasicCoverageBlock,
is_closure: bool,
) -> Self {
let is_closure = match statement.kind {
StatementKind::Assign(box (_, Rvalue::Aggregate(box ref kind, _))) => {
matches!(kind, AggregateKind::Closure(_, _) | AggregateKind::Generator(_, _, _))
}
_ => false,
};

Self {
span,
expn_span,
Expand All @@ -108,17 +94,6 @@ impl CoverageSpan {
}
}

pub fn for_terminator(span: Span, expn_span: Span, bcb: BasicCoverageBlock) -> Self {
Self {
span,
expn_span,
current_macro_or_none: Default::default(),
bcb,
merged_spans: vec![span],
is_closure: false,
}
}

pub fn merge_from(&mut self, mut other: CoverageSpan) {
debug_assert!(self.is_mergeable(&other));
self.span = self.span.to(other.span);
Expand Down
65 changes: 37 additions & 28 deletions compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
Original file line number Diff line number Diff line change
@@ -1,5 +1,7 @@
use rustc_data_structures::captures::Captures;
use rustc_middle::mir::{
self, FakeReadCause, Statement, StatementKind, Terminator, TerminatorKind,
self, AggregateKind, FakeReadCause, Rvalue, Statement, StatementKind, Terminator,
TerminatorKind,
};
use rustc_span::Span;

Expand All @@ -12,7 +14,7 @@ pub(super) fn mir_to_initial_sorted_coverage_spans(
body_span: Span,
basic_coverage_blocks: &CoverageGraph,
) -> Vec<CoverageSpan> {
let mut initial_spans = Vec::<CoverageSpan>::with_capacity(mir_body.basic_blocks.len() * 2);
let mut initial_spans = Vec::with_capacity(mir_body.basic_blocks.len() * 2);
for (bcb, bcb_data) in basic_coverage_blocks.iter_enumerated() {
initial_spans.extend(bcb_to_initial_coverage_spans(mir_body, body_span, bcb, bcb_data));
}
Expand Down Expand Up @@ -50,34 +52,41 @@ pub(super) fn mir_to_initial_sorted_coverage_spans(
// for each `Statement` and `Terminator`. (Note that subsequent stages of coverage analysis will
// merge some `CoverageSpan`s, at which point a `CoverageSpan` may represent multiple
// `Statement`s and/or `Terminator`s.)
fn bcb_to_initial_coverage_spans(
mir_body: &mir::Body<'_>,
fn bcb_to_initial_coverage_spans<'a, 'tcx>(
mir_body: &'a mir::Body<'tcx>,
body_span: Span,
bcb: BasicCoverageBlock,
bcb_data: &BasicCoverageBlockData,
) -> Vec<CoverageSpan> {
bcb_data
.basic_blocks
.iter()
.flat_map(|&bb| {
let data = &mir_body[bb];
data.statements
.iter()
.filter_map(move |statement| {
filtered_statement_span(statement).map(|span| {
CoverageSpan::for_statement(
statement,
function_source_span(span, body_span),
span,
bcb,
)
})
})
.chain(filtered_terminator_span(data.terminator()).map(|span| {
CoverageSpan::for_terminator(function_source_span(span, body_span), span, bcb)
}))
})
.collect()
bcb_data: &'a BasicCoverageBlockData,
) -> impl Iterator<Item = CoverageSpan> + Captures<'a> + Captures<'tcx> {
bcb_data.basic_blocks.iter().flat_map(move |&bb| {
let data = &mir_body[bb];

let statement_spans = data.statements.iter().filter_map(move |statement| {
let expn_span = filtered_statement_span(statement)?;
let span = function_source_span(expn_span, body_span);

Some(CoverageSpan::new(span, expn_span, bcb, is_closure(statement)))
});

let terminator_span = Some(data.terminator()).into_iter().filter_map(move |terminator| {
let expn_span = filtered_terminator_span(terminator)?;
let span = function_source_span(expn_span, body_span);

Some(CoverageSpan::new(span, expn_span, bcb, false))
});

statement_spans.chain(terminator_span)
})
}

fn is_closure(statement: &Statement<'_>) -> bool {
match statement.kind {
StatementKind::Assign(box (_, Rvalue::Aggregate(box ref agg_kind, _))) => match agg_kind {
AggregateKind::Closure(_, _) | AggregateKind::Generator(_, _, _) => true,
_ => false,
},
_ => false,
}
}

/// If the MIR `Statement` has a span contributive to computing coverage spans,
Expand Down
53 changes: 53 additions & 0 deletions tests/coverage-map/fn_sig_into_try.cov-map
Original file line number Diff line number Diff line change
@@ -0,0 +1,53 @@
Function name: fn_sig_into_try::a
Raw bytes (9): 0x[01, 01, 00, 01, 01, 0a, 01, 04, 02]
Number of files: 1
- file 0 => global file 1
Number of expressions: 0
Number of file 0 mappings: 1
- Code(Counter(0)) at (prev + 10, 1) to (start + 4, 2)

Function name: fn_sig_into_try::b
Raw bytes (28): 0x[01, 01, 02, 01, 05, 05, 02, 04, 01, 10, 01, 02, 0f, 00, 02, 0f, 00, 10, 02, 01, 05, 00, 0c, 07, 01, 01, 00, 02]
Number of files: 1
- file 0 => global file 1
Number of expressions: 2
- expression 0 operands: lhs = Counter(0), rhs = Counter(1)
- expression 1 operands: lhs = Counter(1), rhs = Expression(0, Sub)
Number of file 0 mappings: 4
- Code(Counter(0)) at (prev + 16, 1) to (start + 2, 15)
- Code(Zero) at (prev + 2, 15) to (start + 0, 16)
- Code(Expression(0, Sub)) at (prev + 1, 5) to (start + 0, 12)
= (c0 - c1)
- Code(Expression(1, Add)) at (prev + 1, 1) to (start + 0, 2)
= (c1 + (c0 - c1))

Function name: fn_sig_into_try::c
Raw bytes (28): 0x[01, 01, 02, 01, 05, 05, 02, 04, 01, 16, 01, 02, 17, 00, 02, 17, 00, 18, 02, 01, 05, 00, 0c, 07, 01, 01, 00, 02]
Number of files: 1
- file 0 => global file 1
Number of expressions: 2
- expression 0 operands: lhs = Counter(0), rhs = Counter(1)
- expression 1 operands: lhs = Counter(1), rhs = Expression(0, Sub)
Number of file 0 mappings: 4
- Code(Counter(0)) at (prev + 22, 1) to (start + 2, 23)
- Code(Zero) at (prev + 2, 23) to (start + 0, 24)
- Code(Expression(0, Sub)) at (prev + 1, 5) to (start + 0, 12)
= (c0 - c1)
- Code(Expression(1, Add)) at (prev + 1, 1) to (start + 0, 2)
= (c1 + (c0 - c1))

Function name: fn_sig_into_try::d
Raw bytes (28): 0x[01, 01, 02, 01, 05, 05, 02, 04, 01, 1c, 01, 03, 0f, 00, 03, 0f, 00, 10, 02, 01, 05, 00, 0c, 07, 01, 01, 00, 02]
Number of files: 1
- file 0 => global file 1
Number of expressions: 2
- expression 0 operands: lhs = Counter(0), rhs = Counter(1)
- expression 1 operands: lhs = Counter(1), rhs = Expression(0, Sub)
Number of file 0 mappings: 4
- Code(Counter(0)) at (prev + 28, 1) to (start + 3, 15)
- Code(Zero) at (prev + 3, 15) to (start + 0, 16)
- Code(Expression(0, Sub)) at (prev + 1, 5) to (start + 0, 12)
= (c0 - c1)
- Code(Expression(1, Add)) at (prev + 1, 1) to (start + 0, 2)
= (c1 + (c0 - c1))

41 changes: 41 additions & 0 deletions tests/coverage-map/fn_sig_into_try.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,41 @@
#![feature(coverage_attribute)]
// compile-flags: --edition=2021

// Regression test for inconsistent handling of function signature spans that
// are followed by code using the `?` operator.
//
// For each of these similar functions, the line containing the function
// signature should be handled in the same way.

fn a() -> Option<i32>
{
Some(7i32);
Some(0)
}

fn b() -> Option<i32>
{
Some(7i32)?;
Some(0)
}

fn c() -> Option<i32>
{
let _ = Some(7i32)?;
Some(0)
}

fn d() -> Option<i32>
{
let _: () = ();
Some(7i32)?;
Some(0)
}

#[coverage(off)]
fn main() {
a();
b();
c();
d();
}
14 changes: 8 additions & 6 deletions tests/coverage-map/status-quo/inline-dead.cov-map
Original file line number Diff line number Diff line change
Expand Up @@ -31,13 +31,15 @@ Number of file 0 mappings: 2
- Code(Counter(0)) at (prev + 7, 6) to (start + 2, 2)

Function name: inline_dead::main::{closure#0}
Raw bytes (16): 0x[01, 01, 01, 01, 05, 02, 00, 09, 0d, 00, 0e, 03, 02, 05, 00, 06]
Raw bytes (23): 0x[01, 01, 02, 09, 06, 01, 05, 03, 01, 07, 17, 00, 18, 00, 02, 0d, 00, 0e, 03, 02, 05, 00, 06]
Number of files: 1
- file 0 => global file 1
Number of expressions: 1
- expression 0 operands: lhs = Counter(0), rhs = Counter(1)
Number of file 0 mappings: 2
- Code(Zero) at (prev + 9, 13) to (start + 0, 14)
Number of expressions: 2
- expression 0 operands: lhs = Counter(2), rhs = Expression(1, Sub)
- expression 1 operands: lhs = Counter(0), rhs = Counter(1)
Number of file 0 mappings: 3
- Code(Counter(0)) at (prev + 7, 23) to (start + 0, 24)
- Code(Zero) at (prev + 2, 13) to (start + 0, 14)
- Code(Expression(0, Add)) at (prev + 2, 5) to (start + 0, 6)
= (c0 + c1)
= (c2 + (c0 - c1))

6 changes: 3 additions & 3 deletions tests/coverage-map/status-quo/issue-84561.cov-map
Original file line number Diff line number Diff line change
Expand Up @@ -7,15 +7,15 @@ Number of file 0 mappings: 1
- Code(Counter(0)) at (prev + 4, 10) to (start + 0, 19)

Function name: <issue_84561::Foo as core::fmt::Debug>::fmt
Raw bytes (29): 0x[01, 01, 02, 01, 05, 05, 02, 04, 01, 89, 01, 09, 00, 25, 05, 00, 25, 00, 26, 02, 01, 09, 00, 0f, 07, 01, 05, 00, 06]
Raw bytes (29): 0x[01, 01, 02, 01, 05, 05, 02, 04, 01, 88, 01, 05, 01, 25, 05, 01, 25, 00, 26, 02, 01, 09, 00, 0f, 07, 01, 05, 00, 06]
Number of files: 1
- file 0 => global file 1
Number of expressions: 2
- expression 0 operands: lhs = Counter(0), rhs = Counter(1)
- expression 1 operands: lhs = Counter(1), rhs = Expression(0, Sub)
Number of file 0 mappings: 4
- Code(Counter(0)) at (prev + 137, 9) to (start + 0, 37)
- Code(Counter(1)) at (prev + 0, 37) to (start + 0, 38)
- Code(Counter(0)) at (prev + 136, 5) to (start + 1, 37)
- Code(Counter(1)) at (prev + 1, 37) to (start + 0, 38)
- Code(Expression(0, Sub)) at (prev + 1, 9) to (start + 0, 15)
= (c0 - c1)
- Code(Expression(1, Add)) at (prev + 1, 5) to (start + 0, 6)
Expand Down
45 changes: 45 additions & 0 deletions tests/run-coverage/fn_sig_into_try.coverage
Original file line number Diff line number Diff line change
@@ -0,0 +1,45 @@
LL| |#![feature(coverage_attribute)]
LL| |// compile-flags: --edition=2021
LL| |
LL| |// Regression test for inconsistent handling of function signature spans that
LL| |// are followed by code using the `?` operator.
LL| |//
LL| |// For each of these similar functions, the line containing the function
LL| |// signature should be handled in the same way.
LL| |
LL| 1|fn a() -> Option<i32>
LL| 1|{
LL| 1| Some(7i32);
LL| 1| Some(0)
LL| 1|}
LL| |
LL| 1|fn b() -> Option<i32>
LL| 1|{
LL| 1| Some(7i32)?;
^0
LL| 1| Some(0)
LL| 1|}
LL| |
LL| 1|fn c() -> Option<i32>
LL| 1|{
LL| 1| let _ = Some(7i32)?;
^0
LL| 1| Some(0)
LL| 1|}
LL| |
LL| 1|fn d() -> Option<i32>
LL| 1|{
LL| 1| let _: () = ();
LL| 1| Some(7i32)?;
^0
LL| 1| Some(0)
LL| 1|}
LL| |
LL| |#[coverage(off)]
LL| |fn main() {
LL| | a();
LL| | b();
LL| | c();
LL| | d();
LL| |}

41 changes: 41 additions & 0 deletions tests/run-coverage/fn_sig_into_try.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,41 @@
#![feature(coverage_attribute)]
// compile-flags: --edition=2021

// Regression test for inconsistent handling of function signature spans that
// are followed by code using the `?` operator.
//
// For each of these similar functions, the line containing the function
// signature should be handled in the same way.

fn a() -> Option<i32>
{
Some(7i32);
Some(0)
}

fn b() -> Option<i32>
{
Some(7i32)?;
Some(0)
}

fn c() -> Option<i32>
{
let _ = Some(7i32)?;
Some(0)
}

fn d() -> Option<i32>
{
let _: () = ();
Some(7i32)?;
Some(0)
}

#[coverage(off)]
fn main() {
a();
b();
c();
d();
}
2 changes: 1 addition & 1 deletion tests/run-coverage/issue-84561.coverage
Original file line number Diff line number Diff line change
Expand Up @@ -135,7 +135,7 @@
LL| 0|}
LL| |
LL| |impl std::fmt::Debug for Foo {
LL| | fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
LL| 7| fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
LL| 7| write!(f, "try and succeed")?;
^0
LL| 7| Ok(())
Expand Down

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