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Rollup merge of #130013 - jonathan-conder:await_coverage, r=Zalathar

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coverage: Count await when the Future is immediately ready

Currently `await` is only counted towards coverage if the containing
function is suspended and resumed at least once. This is because it
expands to code which contains a branch on the discriminant of `Poll`.

By treating it like a branching macro (e.g. `assert!`), these
implementation details will be hidden from the coverage results.

I added a test to ensure the fix works in simple cases, but the heuristic of picking only the first await-related covspan might be unreliable. I plan on testing more thoroughly with a real codebase over the next couple of weeks.

closes #98712
This commit is contained in:
Matthias Krüger 2024-09-06 07:33:59 +02:00 committed by GitHub
commit 11d5614a74
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GPG Key ID: B5690EEEBB952194
8 changed files with 161 additions and 64 deletions
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36
compiler/rustc_mir_transform/src/coverage/spans.rs
View File

@ -3,7 +3,7 @@
use rustc_data_structures::captures::Captures;
use rustc_data_structures::fx::FxHashSet;
use rustc_middle::mir;
use rustc_span::Span;
use rustc_span::{DesugaringKind, ExpnKind, MacroKind, Span};
use tracing::{debug, debug_span, instrument};
use crate::coverage::graph::{BasicCoverageBlock, CoverageGraph};
@ -25,7 +25,7 @@ pub(super) fn extract_refined_covspans(
// First, perform the passes that need macro information.
covspans.sort_by(|a, b| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb));
remove_unwanted_macro_spans(&mut covspans);
remove_unwanted_expansion_spans(&mut covspans);
split_visible_macro_spans(&mut covspans);
// We no longer need the extra information in `SpanFromMir`, so convert to `Covspan`.
@ -76,18 +76,24 @@ pub(super) fn extract_refined_covspans(
/// invocation, which is unhelpful. Keeping only the first such span seems to
/// give better mappings, so remove the others.
///
/// Similarly, `await` expands to a branch on the discriminant of `Poll`, which
/// leads to incorrect coverage if the `Future` is immediately ready (#98712).
///
/// (The input spans should be sorted in BCB dominator order, so that the
/// retained "first" span is likely to dominate the others.)
fn remove_unwanted_macro_spans(covspans: &mut Vec<SpanFromMir>) {
let mut seen_macro_spans = FxHashSet::default();
covspans.retain(|covspan| {
// Ignore (retain) non-macro-expansion spans.
if covspan.visible_macro.is_none() {
return true;
}
fn remove_unwanted_expansion_spans(covspans: &mut Vec<SpanFromMir>) {
let mut deduplicated_spans = FxHashSet::default();
// Retain only the first macro-expanded covspan with this span.
seen_macro_spans.insert(covspan.span)
covspans.retain(|covspan| {
match covspan.expn_kind {
// Retain only the first await-related or macro-expanded covspan with this span.
Some(ExpnKind::Desugaring(kind)) if kind == DesugaringKind::Await => {
deduplicated_spans.insert(covspan.span)
}
Some(ExpnKind::Macro(MacroKind::Bang, _)) => deduplicated_spans.insert(covspan.span),
// Ignore (retain) other spans.
_ => true,
}
});
}
@ -99,7 +105,9 @@ fn split_visible_macro_spans(covspans: &mut Vec<SpanFromMir>) {
let mut extra_spans = vec![];
covspans.retain(|covspan| {
let Some(visible_macro) = covspan.visible_macro else { return true };
let Some(ExpnKind::Macro(MacroKind::Bang, visible_macro)) = covspan.expn_kind else {
return true;
};
let split_len = visible_macro.as_str().len() as u32 + 1;
let (before, after) = covspan.span.split_at(split_len);
@ -111,8 +119,8 @@ fn split_visible_macro_spans(covspans: &mut Vec<SpanFromMir>) {
return true;
}
extra_spans.push(SpanFromMir::new(before, covspan.visible_macro, covspan.bcb));
extra_spans.push(SpanFromMir::new(after, covspan.visible_macro, covspan.bcb));
extra_spans.push(SpanFromMir::new(before, covspan.expn_kind.clone(), covspan.bcb));
extra_spans.push(SpanFromMir::new(after, covspan.expn_kind.clone(), covspan.bcb));
false // Discard the original covspan that we just split.
});

22
compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
View File

@ -3,13 +3,13 @@
use rustc_middle::mir::{
self, FakeReadCause, Statement, StatementKind, Terminator, TerminatorKind,
};
use rustc_span::{Span, Symbol};
use rustc_span::{ExpnKind, Span};
use crate::coverage::graph::{
BasicCoverageBlock, BasicCoverageBlockData, CoverageGraph, START_BCB,
};
use crate::coverage::spans::Covspan;
use crate::coverage::unexpand::unexpand_into_body_span_with_visible_macro;
use crate::coverage::unexpand::unexpand_into_body_span_with_expn_kind;
use crate::coverage::ExtractedHirInfo;
pub(crate) struct ExtractedCovspans {
@ -60,7 +60,7 @@ fn bcb_to_initial_coverage_spans<'a, 'tcx>(
let data = &mir_body[bb];
let unexpand = move |expn_span| {
unexpand_into_body_span_with_visible_macro(expn_span, body_span)
unexpand_into_body_span_with_expn_kind(expn_span, body_span)
// Discard any spans that fill the entire body, because they tend
// to represent compiler-inserted code, e.g. implicitly returning `()`.
.filter(|(span, _)| !span.source_equal(body_span))
@ -68,9 +68,9 @@ fn bcb_to_initial_coverage_spans<'a, 'tcx>(
let mut extract_statement_span = |statement| {
let expn_span = filtered_statement_span(statement)?;
let (span, visible_macro) = unexpand(expn_span)?;
let (span, expn_kind) = unexpand(expn_span)?;
initial_covspans.push(SpanFromMir::new(span, visible_macro, bcb));
initial_covspans.push(SpanFromMir::new(span, expn_kind, bcb));
Some(())
};
for statement in data.statements.iter() {
@ -79,9 +79,9 @@ fn bcb_to_initial_coverage_spans<'a, 'tcx>(
let mut extract_terminator_span = |terminator| {
let expn_span = filtered_terminator_span(terminator)?;
let (span, visible_macro) = unexpand(expn_span)?;
let (span, expn_kind) = unexpand(expn_span)?;
initial_covspans.push(SpanFromMir::new(span, visible_macro, bcb));
initial_covspans.push(SpanFromMir::new(span, expn_kind, bcb));
Some(())
};
extract_terminator_span(data.terminator());
@ -214,7 +214,7 @@ pub(crate) struct SpanFromMir {
/// With the exception of `fn_sig_span`, this should always be contained
/// within `body_span`.
pub(crate) span: Span,
pub(crate) visible_macro: Option<Symbol>,
pub(crate) expn_kind: Option<ExpnKind>,
pub(crate) bcb: BasicCoverageBlock,
}
@ -223,12 +223,12 @@ fn for_fn_sig(fn_sig_span: Span) -> Self {
Self::new(fn_sig_span, None, START_BCB)
}
pub(crate) fn new(span: Span, visible_macro: Option<Symbol>, bcb: BasicCoverageBlock) -> Self {
Self { span, visible_macro, bcb }
pub(crate) fn new(span: Span, expn_kind: Option<ExpnKind>, bcb: BasicCoverageBlock) -> Self {
Self { span, expn_kind, bcb }
}
pub(crate) fn into_covspan(self) -> Covspan {
let Self { span, visible_macro: _, bcb } = self;
let Self { span, expn_kind: _, bcb } = self;
Covspan { span, bcb }
}
}

15
compiler/rustc_mir_transform/src/coverage/unexpand.rs
View File

@ -1,4 +1,4 @@
use rustc_span::{ExpnKind, MacroKind, Span, Symbol};
use rustc_span::{ExpnKind, Span};
/// Walks through the expansion ancestors of `original_span` to find a span that
/// is contained in `body_span` and has the same [syntax context] as `body_span`.
@ -13,20 +13,15 @@ pub(crate) fn unexpand_into_body_span(original_span: Span, body_span: Span) -> O
///
/// If the returned span represents a bang-macro invocation (e.g. `foo!(..)`),
/// the returned symbol will be the name of that macro (e.g. `foo`).
pub(crate) fn unexpand_into_body_span_with_visible_macro(
pub(crate) fn unexpand_into_body_span_with_expn_kind(
original_span: Span,
body_span: Span,
) -> Option<(Span, Option<Symbol>)> {
) -> Option<(Span, Option<ExpnKind>)> {
let (span, prev) = unexpand_into_body_span_with_prev(original_span, body_span)?;
let visible_macro = prev
.map(|prev| match prev.ctxt().outer_expn_data().kind {
ExpnKind::Macro(MacroKind::Bang, name) => Some(name),
_ => None,
})
.flatten();
let expn_kind = prev.map(|prev| prev.ctxt().outer_expn_data().kind);
Some((span, visible_macro))
Some((span, expn_kind))
}
/// Walks through the expansion ancestors of `original_span` to find a span that

48
tests/coverage/async.cov-map
View File

@ -92,20 +92,18 @@ Number of file 0 mappings: 1
- Code(Counter(0)) at (prev + 25, 1) to (start + 0, 23)
Function name: async::g::{closure#0} (unused)
Raw bytes (69): 0x[01, 01, 00, 0d, 00, 19, 17, 01, 0c, 00, 02, 09, 00, 0a, 00, 00, 0e, 00, 11, 00, 00, 12, 00, 17, 00, 00, 1b, 00, 1c, 00, 00, 20, 00, 22, 00, 01, 09, 00, 0a, 00, 00, 0e, 00, 11, 00, 00, 12, 00, 17, 00, 00, 1b, 00, 1c, 00, 00, 20, 00, 22, 00, 01, 0e, 00, 10, 00, 02, 01, 00, 02]
Raw bytes (59): 0x[01, 01, 00, 0b, 00, 19, 17, 01, 0c, 00, 02, 09, 00, 0a, 00, 00, 0e, 00, 17, 00, 00, 1b, 00, 1c, 00, 00, 20, 00, 22, 00, 01, 09, 00, 0a, 00, 00, 0e, 00, 17, 00, 00, 1b, 00, 1c, 00, 00, 20, 00, 22, 00, 01, 0e, 00, 10, 00, 02, 01, 00, 02]
Number of files: 1
- file 0 => global file 1
Number of expressions: 0
Number of file 0 mappings: 13
Number of file 0 mappings: 11
- Code(Zero) at (prev + 25, 23) to (start + 1, 12)
- Code(Zero) at (prev + 2, 9) to (start + 0, 10)
- Code(Zero) at (prev + 0, 14) to (start + 0, 17)
- Code(Zero) at (prev + 0, 18) to (start + 0, 23)
- Code(Zero) at (prev + 0, 14) to (start + 0, 23)
- Code(Zero) at (prev + 0, 27) to (start + 0, 28)
- Code(Zero) at (prev + 0, 32) to (start + 0, 34)
- Code(Zero) at (prev + 1, 9) to (start + 0, 10)
- Code(Zero) at (prev + 0, 14) to (start + 0, 17)
- Code(Zero) at (prev + 0, 18) to (start + 0, 23)
- Code(Zero) at (prev + 0, 14) to (start + 0, 23)
- Code(Zero) at (prev + 0, 27) to (start + 0, 28)
- Code(Zero) at (prev + 0, 32) to (start + 0, 34)
- Code(Zero) at (prev + 1, 14) to (start + 0, 16)
@ -120,15 +118,14 @@ Number of file 0 mappings: 1
- Code(Counter(0)) at (prev + 33, 1) to (start + 0, 22)
Function name: async::h::{closure#0} (unused)
Raw bytes (44): 0x[01, 01, 00, 08, 00, 21, 16, 03, 0c, 00, 04, 09, 00, 0a, 00, 00, 0e, 00, 13, 00, 00, 14, 00, 19, 00, 00, 1a, 00, 1b, 00, 00, 20, 00, 22, 00, 01, 0e, 00, 10, 00, 02, 01, 00, 02]
Raw bytes (39): 0x[01, 01, 00, 07, 00, 21, 16, 03, 0c, 00, 04, 09, 00, 0a, 00, 00, 0e, 00, 19, 00, 00, 1a, 00, 1b, 00, 00, 20, 00, 22, 00, 01, 0e, 00, 10, 00, 02, 01, 00, 02]
Number of files: 1
- file 0 => global file 1
Number of expressions: 0
Number of file 0 mappings: 8
Number of file 0 mappings: 7
- Code(Zero) at (prev + 33, 22) to (start + 3, 12)
- Code(Zero) at (prev + 4, 9) to (start + 0, 10)
- Code(Zero) at (prev + 0, 14) to (start + 0, 19)
- Code(Zero) at (prev + 0, 20) to (start + 0, 25)
- Code(Zero) at (prev + 0, 14) to (start + 0, 25)
- Code(Zero) at (prev + 0, 26) to (start + 0, 27)
- Code(Zero) at (prev + 0, 32) to (start + 0, 34)
- Code(Zero) at (prev + 1, 14) to (start + 0, 16)
@ -143,28 +140,25 @@ Number of file 0 mappings: 1
- Code(Counter(0)) at (prev + 42, 1) to (start + 0, 19)
Function name: async::i::{closure#0}
Raw bytes (78): 0x[01, 01, 02, 07, 21, 19, 1d, 0e, 01, 2a, 13, 04, 0c, 0d, 05, 09, 00, 0a, 01, 00, 0e, 00, 12, 05, 00, 13, 00, 18, 09, 00, 1c, 00, 21, 0d, 00, 27, 00, 2a, 15, 00, 2b, 00, 30, 1d, 01, 09, 00, 0a, 11, 00, 0e, 00, 11, 25, 00, 12, 00, 17, 29, 00, 1b, 00, 20, 1d, 00, 24, 00, 26, 21, 01, 0e, 00, 10, 03, 02, 01, 00, 02]
Raw bytes (63): 0x[01, 01, 02, 07, 19, 11, 15, 0b, 01, 2a, 13, 04, 0c, 09, 05, 09, 00, 0a, 01, 00, 0e, 00, 18, 05, 00, 1c, 00, 21, 09, 00, 27, 00, 30, 15, 01, 09, 00, 0a, 0d, 00, 0e, 00, 17, 1d, 00, 1b, 00, 20, 15, 00, 24, 00, 26, 19, 01, 0e, 00, 10, 03, 02, 01, 00, 02]
Number of files: 1
- file 0 => global file 1
Number of expressions: 2
- expression 0 operands: lhs = Expression(1, Add), rhs = Counter(8)
- expression 1 operands: lhs = Counter(6), rhs = Counter(7)
Number of file 0 mappings: 14
- expression 0 operands: lhs = Expression(1, Add), rhs = Counter(6)
- expression 1 operands: lhs = Counter(4), rhs = Counter(5)
Number of file 0 mappings: 11
- Code(Counter(0)) at (prev + 42, 19) to (start + 4, 12)
- Code(Counter(3)) at (prev + 5, 9) to (start + 0, 10)
- Code(Counter(0)) at (prev + 0, 14) to (start + 0, 18)
- Code(Counter(1)) at (prev + 0, 19) to (start + 0, 24)
- Code(Counter(2)) at (prev + 0, 28) to (start + 0, 33)
- Code(Counter(3)) at (prev + 0, 39) to (start + 0, 42)
- Code(Counter(5)) at (prev + 0, 43) to (start + 0, 48)
- Code(Counter(7)) at (prev + 1, 9) to (start + 0, 10)
- Code(Counter(4)) at (prev + 0, 14) to (start + 0, 17)
- Code(Counter(9)) at (prev + 0, 18) to (start + 0, 23)
- Code(Counter(10)) at (prev + 0, 27) to (start + 0, 32)
- Code(Counter(7)) at (prev + 0, 36) to (start + 0, 38)
- Code(Counter(8)) at (prev + 1, 14) to (start + 0, 16)
- Code(Counter(2)) at (prev + 5, 9) to (start + 0, 10)
- Code(Counter(0)) at (prev + 0, 14) to (start + 0, 24)
- Code(Counter(1)) at (prev + 0, 28) to (start + 0, 33)
- Code(Counter(2)) at (prev + 0, 39) to (start + 0, 48)
- Code(Counter(5)) at (prev + 1, 9) to (start + 0, 10)
- Code(Counter(3)) at (prev + 0, 14) to (start + 0, 23)
- Code(Counter(7)) at (prev + 0, 27) to (start + 0, 32)
- Code(Counter(5)) at (prev + 0, 36) to (start + 0, 38)
- Code(Counter(6)) at (prev + 1, 14) to (start + 0, 16)
- Code(Expression(0, Add)) at (prev + 2, 1) to (start + 0, 2)
= ((c6 + c7) + c8)
= ((c4 + c5) + c6)
Function name: async::j
Raw bytes (58): 0x[01, 01, 02, 07, 0d, 05, 09, 0a, 01, 35, 01, 00, 0d, 01, 0b, 0b, 00, 0c, 05, 01, 09, 00, 0a, 01, 00, 0e, 00, 1b, 05, 00, 1f, 00, 27, 09, 01, 09, 00, 0a, 11, 00, 0e, 00, 1a, 09, 00, 1e, 00, 20, 0d, 01, 0e, 00, 10, 03, 02, 01, 00, 02]

4
tests/coverage/async.coverage
View File

@ -45,9 +45,9 @@
LL| 1| // executed asynchronously.
LL| 1| match x {
LL| 1| y if c(x).await == y + 1 => { d().await; }
^0 ^0 ^0 ^0
^0 ^0
LL| 1| y if f().await == y + 1 => (),
^0 ^0 ^0
^0 ^0
LL| 1| _ => (),
LL| | }
LL| 1|}

25
tests/coverage/await_ready.cov-map Normal file
View File

@ -0,0 +1,25 @@
Function name: await_ready::await_ready
Raw bytes (9): 0x[01, 01, 00, 01, 01, 0a, 01, 00, 1e]
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 + 0, 30)
Function name: await_ready::await_ready::{closure#0}
Raw bytes (14): 0x[01, 01, 00, 02, 01, 0a, 1e, 03, 0f, 05, 04, 01, 00, 02]
Number of files: 1
- file 0 => global file 1
Number of expressions: 0
Number of file 0 mappings: 2
- Code(Counter(0)) at (prev + 10, 30) to (start + 3, 15)
- Code(Counter(1)) at (prev + 4, 1) to (start + 0, 2)
Function name: await_ready::main
Raw bytes (9): 0x[01, 01, 00, 01, 01, 10, 01, 03, 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 + 16, 1) to (start + 3, 2)

38
tests/coverage/await_ready.coverage Normal file
View File

@ -0,0 +1,38 @@
LL| |#![feature(coverage_attribute)]
LL| |#![feature(custom_inner_attributes)] // for #![rustfmt::skip]
LL| |#![feature(noop_waker)]
LL| |#![rustfmt::skip]
LL| |//@ edition: 2021
LL| |
LL| |#[coverage(off)]
LL| |async fn ready() -> u8 { 1 }
LL| |
LL| 1|async fn await_ready() -> u8 {
LL| 1| // await should be covered even if the function never yields
LL| 1| ready()
LL| 1| .await
LL| 1|}
LL| |
LL| 1|fn main() {
LL| 1| let mut future = Box::pin(await_ready());
LL| 1| executor::block_on(future.as_mut());
LL| 1|}
LL| |
LL| |mod executor {
LL| | use core::future::Future;
LL| | use core::pin::pin;
LL| | use core::task::{Context, Poll, Waker};
LL| |
LL| | #[coverage(off)]
LL| | pub fn block_on<F: Future>(mut future: F) -> F::Output {
LL| | let mut future = pin!(future);
LL| | let mut context = Context::from_waker(Waker::noop());
LL| |
LL| | loop {
LL| | if let Poll::Ready(val) = future.as_mut().poll(&mut context) {
LL| | break val;
LL| | }
LL| | }
LL| | }
LL| |}

37
tests/coverage/await_ready.rs Normal file
View File

@ -0,0 +1,37 @@
#![feature(coverage_attribute)]
#![feature(custom_inner_attributes)] // for #![rustfmt::skip]
#![feature(noop_waker)]
#![rustfmt::skip]
//@ edition: 2021
#[coverage(off)]
async fn ready() -> u8 { 1 }
async fn await_ready() -> u8 {
// await should be covered even if the function never yields
ready()
.await
}
fn main() {
let mut future = Box::pin(await_ready());
executor::block_on(future.as_mut());
}
mod executor {
use core::future::Future;
use core::pin::pin;
use core::task::{Context, Poll, Waker};
#[coverage(off)]
pub fn block_on<F: Future>(mut future: F) -> F::Output {
let mut future = pin!(future);
let mut context = Context::from_waker(Waker::noop());
loop {
if let Poll::Ready(val) = future.as_mut().poll(&mut context) {
break val;
}
}
}
}