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Auto merge of #84582 - richkadel:issue-84561, r=tmandry

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Vastly improves coverage spans for macros

Fixes: #84561

This resolves problems where macros like `trace!(...)` would show zero coverage if tracing was disabled, and `assert_eq!(...)` would show zero coverage if the assertion did not fail, because only one coverage span was generated, for the branch.

This PR started with an idea that I could just drop branching blocks with same span as expanded macro. (See the fixed issue for more details.)

That did help, but it didn't resolve everything.

I also needed to add a span specifically for the macro name (plus `!`) to ensure the macro gets coverage even if it's internal expansion adds conditional branching blocks that are retained, and would otherwise drop the outer span. Now that outer span is _only_ the `(argument, list)`, which can safely be dropped now), because the macro name has its own span.

While testing, I also noticed the spanview debug output can cause an ICE on a function with no body. The
workaround for this is included in this PR (separate commit).

r? `@tmandry`
cc? `@wesleywiser`
This commit is contained in:
bors
2021-05-01 07:48:24 +00:00
parent 3d67e07472 0312bf5fb9
commit 1c2c6b6700
13 changed files with 861 additions and 68 deletions
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242
compiler/rustc_mir/src/transform/coverage/spans.rs
View File

@@ -11,8 +11,9 @@ use rustc_middle::mir::{
use rustc_middle::ty::TyCtxt;
use rustc_span::source_map::original_sp;
use rustc_span::{BytePos, Span};
use rustc_span::{BytePos, ExpnKind, MacroKind, Span, Symbol};
use std::cell::RefCell;
use std::cmp::Ordering;
#[derive(Debug, Copy, Clone)]
@@ -67,6 +68,8 @@ impl CoverageStatement {
#[derive(Debug, Clone)]
pub(super) struct CoverageSpan {
pub span: Span,
pub expn_span: Span,
pub current_macro_or_none: RefCell<Option<Option<Symbol>>>,
pub bcb: BasicCoverageBlock,
pub coverage_statements: Vec<CoverageStatement>,
pub is_closure: bool,
@@ -74,12 +77,20 @@ pub(super) struct CoverageSpan {
impl CoverageSpan {
pub fn for_fn_sig(fn_sig_span: Span) -> Self {
Self { span: fn_sig_span, bcb: START_BCB, coverage_statements: vec![], is_closure: false }
Self {
span: fn_sig_span,
expn_span: fn_sig_span,
current_macro_or_none: Default::default(),
bcb: START_BCB,
coverage_statements: vec![],
is_closure: false,
}
}
pub fn for_statement(
statement: &Statement<'tcx>,
span: Span,
expn_span: Span,
bcb: BasicCoverageBlock,
bb: BasicBlock,
stmt_index: usize,
@@ -94,15 +105,24 @@ impl CoverageSpan {
Self {
span,
expn_span,
current_macro_or_none: Default::default(),
bcb,
coverage_statements: vec![CoverageStatement::Statement(bb, span, stmt_index)],
is_closure,
}
}
pub fn for_terminator(span: Span, bcb: BasicCoverageBlock, bb: BasicBlock) -> Self {
pub fn for_terminator(
span: Span,
expn_span: Span,
bcb: BasicCoverageBlock,
bb: BasicBlock,
) -> Self {
Self {
span,
expn_span,
current_macro_or_none: Default::default(),
bcb,
coverage_statements: vec![CoverageStatement::Terminator(bb, span)],
is_closure: false,
@@ -158,6 +178,38 @@ impl CoverageSpan {
.collect::<Vec<_>>()
.join("\n")
}
/// If the span is part of a macro, returns the macro name symbol.
pub fn current_macro(&self) -> Option<Symbol> {
self.current_macro_or_none
.borrow_mut()
.get_or_insert_with(|| {
if let ExpnKind::Macro(MacroKind::Bang, current_macro) =
self.expn_span.ctxt().outer_expn_data().kind
{
return Some(current_macro);
}
None
})
.map(|symbol| symbol)
}
/// If the span is part of a macro, and the macro is visible (expands directly to the given
/// body_span), returns the macro name symbol.
pub fn visible_macro(&self, body_span: Span) -> Option<Symbol> {
if let Some(current_macro) = self.current_macro() {
if self.expn_span.parent().unwrap_or_else(|| bug!("macro must have a parent")).ctxt()
== body_span.ctxt()
{
return Some(current_macro);
}
}
None
}
pub fn is_macro_expansion(&self) -> bool {
self.current_macro().is_some()
}
}
/// Converts the initial set of `CoverageSpan`s (one per MIR `Statement` or `Terminator`) into a
@@ -191,16 +243,23 @@ pub struct CoverageSpans<'a, 'tcx> {
/// iteration.
some_curr: Option<CoverageSpan>,
/// The original `span` for `curr`, in case the `curr` span is modified.
/// The original `span` for `curr`, in case `curr.span()` is modified. The `curr_original_span`
/// **must not be mutated** (except when advancing to the next `curr`), even if `curr.span()`
/// is mutated.
curr_original_span: Span,
/// The CoverageSpan from a prior iteration; typically assigned from that iteration's `curr`.
/// If that `curr` was discarded, `prev` retains its value from the previous iteration.
some_prev: Option<CoverageSpan>,
/// Assigned from `curr_original_span` from the previous iteration.
/// Assigned from `curr_original_span` from the previous iteration. The `prev_original_span`
/// **must not be mutated** (except when advancing to the next `prev`), even if `prev.span()`
/// is mutated.
prev_original_span: Span,
/// A copy of the expn_span from the prior iteration.
prev_expn_span: Option<Span>,
/// One or more `CoverageSpan`s with the same `Span` but different `BasicCoverageBlock`s, and
/// no `BasicCoverageBlock` in this list dominates another `BasicCoverageBlock` in the list.
/// If a new `curr` span also fits this criteria (compared to an existing list of
@@ -255,15 +314,13 @@ impl<'a, 'tcx> CoverageSpans<'a, 'tcx> {
curr_original_span: Span::with_root_ctxt(BytePos(0), BytePos(0)),
some_prev: None,
prev_original_span: Span::with_root_ctxt(BytePos(0), BytePos(0)),
prev_expn_span: None,
pending_dups: Vec::new(),
};
let sorted_spans = coverage_spans.mir_to_initial_sorted_coverage_spans();
coverage_spans.sorted_spans_iter = Some(sorted_spans.into_iter());
coverage_spans.some_prev = coverage_spans.sorted_spans_iter.as_mut().unwrap().next();
coverage_spans.prev_original_span =
coverage_spans.some_prev.as_ref().expect("at least one span").span;
coverage_spans.to_refined_spans()
}
@@ -317,10 +374,14 @@ impl<'a, 'tcx> CoverageSpans<'a, 'tcx> {
/// de-duplicated `CoverageSpan`s.
fn to_refined_spans(mut self) -> Vec<CoverageSpan> {
while self.next_coverage_span() {
if self.curr().is_mergeable(self.prev()) {
if self.some_prev.is_none() {
debug!(" initial span");
self.check_invoked_macro_name_span();
} else if self.curr().is_mergeable(self.prev()) {
debug!(" same bcb (and neither is a closure), merge with prev={:?}", self.prev());
let prev = self.take_prev();
self.curr_mut().merge_from(prev);
self.check_invoked_macro_name_span();
// Note that curr.span may now differ from curr_original_span
} else if self.prev_ends_before_curr() {
debug!(
@@ -329,7 +390,8 @@ impl<'a, 'tcx> CoverageSpans<'a, 'tcx> {
self.prev()
);
let prev = self.take_prev();
self.refined_spans.push(prev);
self.push_refined_span(prev);
self.check_invoked_macro_name_span();
} else if self.prev().is_closure {
// drop any equal or overlapping span (`curr`) and keep `prev` to test again in the
// next iter
@@ -342,20 +404,45 @@ impl<'a, 'tcx> CoverageSpans<'a, 'tcx> {
} else if self.curr().is_closure {
self.carve_out_span_for_closure();
} else if self.prev_original_span == self.curr().span {
// Note that this compares the new span to `prev_original_span`, which may not
// be the full `prev.span` (if merged during the previous iteration).
self.hold_pending_dups_unless_dominated();
// Note that this compares the new (`curr`) span to `prev_original_span`.
// In this branch, the actual span byte range of `prev_original_span` is not
// important. What is important is knowing whether the new `curr` span was
// **originally** the same as the original span of `prev()`. The original spans
// reflect their original sort order, and for equal spans, conveys a partial
// ordering based on CFG dominator priority.
if self.prev().is_macro_expansion() && self.curr().is_macro_expansion() {
// Macros that expand to include branching (such as
// `assert_eq!()`, `assert_ne!()`, `info!()`, `debug!()`, or
// `trace!()) typically generate callee spans with identical
// ranges (typically the full span of the macro) for all
// `BasicBlocks`. This makes it impossible to distinguish
// the condition (`if val1 != val2`) from the optional
// branched statements (such as the call to `panic!()` on
// assert failure). In this case it is better (or less
// worse) to drop the optional branch bcbs and keep the
// non-conditional statements, to count when reached.
debug!(
" curr and prev are part of a macro expansion, and curr has the same span \
as prev, but is in a different bcb. Drop curr and keep prev for next iter. \
prev={:?}",
self.prev()
);
self.take_curr();
} else {
self.hold_pending_dups_unless_dominated();
}
} else {
self.cutoff_prev_at_overlapping_curr();
self.check_invoked_macro_name_span();
}
}
debug!(" AT END, adding last prev={:?}", self.prev());
let prev = self.take_prev();
let CoverageSpans { pending_dups, mut refined_spans, .. } = self;
let pending_dups = self.pending_dups.split_off(0);
for dup in pending_dups {
debug!(" ...adding at least one pending dup={:?}", dup);
refined_spans.push(dup);
self.push_refined_span(dup);
}
// Async functions wrap a closure that implements the body to be executed. The enclosing
@@ -365,21 +452,60 @@ impl<'a, 'tcx> CoverageSpans<'a, 'tcx> {
// excluded. The closure's `Return` is the only one that will be counted. This provides
// adequate coverage, and more intuitive counts. (Avoids double-counting the closing brace
// of the function body.)
let body_ends_with_closure = if let Some(last_covspan) = refined_spans.last() {
let body_ends_with_closure = if let Some(last_covspan) = self.refined_spans.last() {
last_covspan.is_closure && last_covspan.span.hi() == self.body_span.hi()
} else {
false
};
if !body_ends_with_closure {
refined_spans.push(prev);
self.push_refined_span(prev);
}
// Remove `CoverageSpan`s derived from closures, originally added to ensure the coverage
// regions for the current function leave room for the closure's own coverage regions
// (injected separately, from the closure's own MIR).
refined_spans.retain(|covspan| !covspan.is_closure);
refined_spans
self.refined_spans.retain(|covspan| !covspan.is_closure);
self.refined_spans
}
fn push_refined_span(&mut self, covspan: CoverageSpan) {
let len = self.refined_spans.len();
if len > 0 {
let last = &mut self.refined_spans[len - 1];
if last.is_mergeable(&covspan) {
debug!(
"merging new refined span with last refined span, last={:?}, covspan={:?}",
last, covspan
);
last.merge_from(covspan);
return;
}
}
self.refined_spans.push(covspan)
}
fn check_invoked_macro_name_span(&mut self) {
if let Some(visible_macro) = self.curr().visible_macro(self.body_span) {
if self.prev_expn_span.map_or(true, |prev_expn_span| {
self.curr().expn_span.ctxt() != prev_expn_span.ctxt()
}) {
let merged_prefix_len = self.curr_original_span.lo() - self.curr().span.lo();
let after_macro_bang =
merged_prefix_len + BytePos(visible_macro.as_str().bytes().count() as u32 + 1);
let mut macro_name_cov = self.curr().clone();
self.curr_mut().span =
self.curr().span.with_lo(self.curr().span.lo() + after_macro_bang);
macro_name_cov.span =
macro_name_cov.span.with_hi(macro_name_cov.span.lo() + after_macro_bang);
debug!(
" and curr starts a new macro expansion, so add a new span just for \
the macro `{}!`, new span={:?}",
visible_macro, macro_name_cov
);
self.push_refined_span(macro_name_cov);
}
}
}
// Generate a set of `CoverageSpan`s from the filtered set of `Statement`s and `Terminator`s of
@@ -401,14 +527,17 @@ impl<'a, 'tcx> CoverageSpans<'a, 'tcx> {
.iter()
.enumerate()
.filter_map(move |(index, statement)| {
filtered_statement_span(statement, self.body_span).map(|span| {
CoverageSpan::for_statement(statement, span, bcb, bb, index)
})
filtered_statement_span(statement, self.body_span).map(
|(span, expn_span)| {
CoverageSpan::for_statement(
statement, span, expn_span, bcb, bb, index,
)
},
)
})
.chain(
filtered_terminator_span(data.terminator(), self.body_span)
.map(|span| CoverageSpan::for_terminator(span, bcb, bb)),
)
.chain(filtered_terminator_span(data.terminator(), self.body_span).map(
|(span, expn_span)| CoverageSpan::for_terminator(span, expn_span, bcb, bb),
))
})
.collect()
}
@@ -461,7 +590,7 @@ impl<'a, 'tcx> CoverageSpans<'a, 'tcx> {
let pending_dups = self.pending_dups.split_off(0);
for dup in pending_dups.into_iter() {
debug!(" ...adding at least one pending={:?}", dup);
self.refined_spans.push(dup);
self.push_refined_span(dup);
}
} else {
self.pending_dups.clear();
@@ -473,12 +602,13 @@ impl<'a, 'tcx> CoverageSpans<'a, 'tcx> {
/// Advance `prev` to `curr` (if any), and `curr` to the next `CoverageSpan` in sorted order.
fn next_coverage_span(&mut self) -> bool {
if let Some(curr) = self.some_curr.take() {
self.prev_expn_span = Some(curr.expn_span);
self.some_prev = Some(curr);
self.prev_original_span = self.curr_original_span;
}
while let Some(curr) = self.sorted_spans_iter.as_mut().unwrap().next() {
debug!("FOR curr={:?}", curr);
if self.prev_starts_after_next(&curr) {
if self.some_prev.is_some() && self.prev_starts_after_next(&curr) {
debug!(
" prev.span starts after curr.span, so curr will be dropped (skipping past \
closure?); prev={:?}",
@@ -535,29 +665,38 @@ impl<'a, 'tcx> CoverageSpans<'a, 'tcx> {
for mut dup in pending_dups.iter().cloned() {
dup.span = dup.span.with_hi(left_cutoff);
debug!(" ...and at least one pre_closure dup={:?}", dup);
self.refined_spans.push(dup);
self.push_refined_span(dup);
}
}
self.refined_spans.push(pre_closure);
self.push_refined_span(pre_closure);
}
if has_post_closure_span {
// Update prev.span to start after the closure (and discard curr)
// Mutate `prev.span()` to start after the closure (and discard curr).
// (**NEVER** update `prev_original_span` because it affects the assumptions
// about how the `CoverageSpan`s are ordered.)
self.prev_mut().span = self.prev().span.with_lo(right_cutoff);
self.prev_original_span = self.prev().span;
debug!(" Mutated prev.span to start after the closure. prev={:?}", self.prev());
for dup in pending_dups.iter_mut() {
debug!(" ...and at least one overlapping dup={:?}", dup);
dup.span = dup.span.with_lo(right_cutoff);
}
self.pending_dups.append(&mut pending_dups);
let closure_covspan = self.take_curr();
self.refined_spans.push(closure_covspan); // since self.prev() was already updated
self.push_refined_span(closure_covspan); // since self.prev() was already updated
} else {
pending_dups.clear();
}
}
/// Called if `curr.span` equals `prev_original_span` (and potentially equal to all
/// `pending_dups` spans, if any); but keep in mind, `prev.span` may start at a `Span.lo()` that
/// is less than (further left of) `prev_original_span.lo()`.
/// `pending_dups` spans, if any). Keep in mind, `prev.span()` may have been changed.
/// If prev.span() was merged into other spans (with matching BCB, for instance),
/// `prev.span.hi()` will be greater than (further right of) `prev_original_span.hi()`.
/// If prev.span() was split off to the right of a closure, prev.span().lo() will be
/// greater than prev_original_span.lo(). The actual span of `prev_original_span` is
/// not as important as knowing that `prev()` **used to have the same span** as `curr(),
/// which means their sort order is still meaningful for determinating the dominator
/// relationship.
///
/// When two `CoverageSpan`s have the same `Span`, dominated spans can be discarded; but if
/// neither `CoverageSpan` dominates the other, both (or possibly more than two) are held,
@@ -640,7 +779,7 @@ impl<'a, 'tcx> CoverageSpans<'a, 'tcx> {
} else {
debug!(" ... adding modified prev={:?}", self.prev());
let prev = self.take_prev();
self.refined_spans.push(prev);
self.push_refined_span(prev);
}
} else {
// with `pending_dups`, `prev` cannot have any statements that don't overlap
@@ -653,10 +792,13 @@ impl<'a, 'tcx> CoverageSpans<'a, 'tcx> {
}
}
/// See `function_source_span()` for a description of the two returned spans.
/// If the MIR `Statement` is not contributive to computing coverage spans,
/// returns `None`.
pub(super) fn filtered_statement_span(
statement: &'a Statement<'tcx>,
body_span: Span,
) -> Option<Span> {
) -> Option<(Span, Span)> {
match statement.kind {
// These statements have spans that are often outside the scope of the executed source code
// for their parent `BasicBlock`.
@@ -698,10 +840,13 @@ pub(super) fn filtered_statement_span(
}
}
/// See `function_source_span()` for a description of the two returned spans.
/// If the MIR `Terminator` is not contributive to computing coverage spans,
/// returns `None`.
pub(super) fn filtered_terminator_span(
terminator: &'a Terminator<'tcx>,
body_span: Span,
) -> Option<Span> {
) -> Option<(Span, Span)> {
match terminator.kind {
// These terminators have spans that don't positively contribute to computing a reasonable
// span of actually executed source code. (For example, SwitchInt terminators extracted from
@@ -741,8 +886,23 @@ pub(super) fn filtered_terminator_span(
}
}
/// Returns two spans from the given span (the span associated with a
/// `Statement` or `Terminator`):
///
/// 1. An extrapolated span (pre-expansion[^1]) corresponding to a range within
/// the function's body source. This span is guaranteed to be contained
/// within, or equal to, the `body_span`. If the extrapolated span is not
/// contained within the `body_span`, the `body_span` is returned.
/// 2. The actual `span` value from the `Statement`, before expansion.
///
/// Only the first span is used when computing coverage code regions. The second
/// span is useful if additional expansion data is needed (such as to look up
/// the macro name for a composed span within that macro).)
///
/// [^1]Expansions result from Rust syntax including macros, syntactic
/// sugar, etc.).
#[inline]
fn function_source_span(span: Span, body_span: Span) -> Span {
let span = original_sp(span, body_span).with_ctxt(body_span.ctxt());
if body_span.contains(span) { span } else { body_span }
fn function_source_span(span: Span, body_span: Span) -> (Span, Span) {
let original_span = original_sp(span, body_span).with_ctxt(body_span.ctxt());
(if body_span.contains(original_span) { original_span } else { body_span }, span)
}

13
compiler/rustc_mir/src/transform/coverage/tests.rs
View File

@@ -1,6 +1,10 @@
//! This crate hosts a selection of "unit tests" for components of the `InstrumentCoverage` MIR
//! pass.
//!
//! ```shell
//! ./x.py test --keep-stage 1 compiler/rustc_mir --test-args '--show-output coverage'
//! ```
//!
//! The tests construct a few "mock" objects, as needed, to support the `InstrumentCoverage`
//! functions and algorithms. Mocked objects include instances of `mir::Body`; including
//! `Terminator`s of various `kind`s, and `Span` objects. Some functions used by or used on
@@ -679,10 +683,15 @@ fn test_make_bcb_counters() {
let mut basic_coverage_blocks = graph::CoverageGraph::from_mir(&mir_body);
let mut coverage_spans = Vec::new();
for (bcb, data) in basic_coverage_blocks.iter_enumerated() {
if let Some(span) =
if let Some((span, expn_span)) =
spans::filtered_terminator_span(data.terminator(&mir_body), body_span)
{
coverage_spans.push(spans::CoverageSpan::for_terminator(span, bcb, data.last_bb()));
coverage_spans.push(spans::CoverageSpan::for_terminator(
span,
expn_span,
bcb,
data.last_bb(),
));
}
}
let mut coverage_counters = counters::CoverageCounters::new(0);

19
compiler/rustc_mir/src/util/spanview.rs
View File

@@ -99,7 +99,11 @@ where
W: Write,
{
let def_id = body.source.def_id();
let body_span = hir_body(tcx, def_id).value.span;
let hir_body = hir_body(tcx, def_id);
if hir_body.is_none() {
return Ok(());
}
let body_span = hir_body.unwrap().value.span;
let mut span_viewables = Vec::new();
for (bb, data) in body.basic_blocks().iter_enumerated() {
match spanview {
@@ -664,19 +668,16 @@ fn fn_span<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> Span {
let hir_id =
tcx.hir().local_def_id_to_hir_id(def_id.as_local().expect("expected DefId is local"));
let fn_decl_span = tcx.hir().span(hir_id);
let body_span = hir_body(tcx, def_id).value.span;
if fn_decl_span.ctxt() == body_span.ctxt() {
fn_decl_span.to(body_span)
if let Some(body_span) = hir_body(tcx, def_id).map(|hir_body| hir_body.value.span) {
if fn_decl_span.ctxt() == body_span.ctxt() { fn_decl_span.to(body_span) } else { body_span }
} else {
// This probably occurs for functions defined via macros
body_span
fn_decl_span
}
}
fn hir_body<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx rustc_hir::Body<'tcx> {
fn hir_body<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> Option<&'tcx rustc_hir::Body<'tcx>> {
let hir_node = tcx.hir().get_if_local(def_id).expect("expected DefId is local");
let fn_body_id = hir::map::associated_body(hir_node).expect("HIR node is a function with body");
tcx.hir().body(fn_body_id)
hir::map::associated_body(hir_node).map(|fn_body_id| tcx.hir().body(fn_body_id))
}
fn escape_html(s: &str) -> String {