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Rollup merge of #134497 - Zalathar:spans, r=jieyouxu

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coverage: Store coverage source regions as `Span` until codegen (take 2)

This is an attempt to re-land #133418:

> Historically, coverage spans were converted into line/column coordinates during the MIR instrumentation pass.

> This PR moves that conversion step into codegen, so that coverage spans spend most of their time stored as Span instead.

> In addition to being conceptually nicer, this also reduces the size of coverage mappings in MIR, because Span is smaller than 4x u32.

That PR was reverted by #133608, because in some circumstances not covered by our test suite we were emitting coverage metadata that was causing `llvm-cov` to exit with an error (#133606).

---

The implementation here is *mostly* the same, but adapted for subsequent changes in the relevant code (e.g. #134163).

I believe that the changes in #134163 should be sufficient to prevent the problem that required the original PR to be reverted. But I haven't been able to reproduce the original breakage in a regression test, and the `llvm-cov` error message is extremely unhelpful, so I can't completely rule out the possibility of this breaking again.

r? jieyouxu (reviewer of the original PR)
This commit is contained in:
Matthias Krüger 2024-12-19 15:26:16 +01:00 • committed by GitHub
commit 57cbd078f2
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GPG key ID: B5690EEEBB952194
21 changed files with 298 additions and 270 deletions
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36
compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs
View file

@ -1,6 +1,4 @@
use rustc_middle::mir::coverage::{CounterId, CovTerm, ExpressionId, SourceRegion};
use crate::coverageinfo::mapgen::LocalFileId;
use rustc_middle::mir::coverage::{CounterId, CovTerm, ExpressionId};
/// Must match the layout of `LLVMRustCounterKind`.
#[derive(Copy, Clone, Debug)]
@ -126,30 +124,16 @@ pub(crate) struct CoverageSpan {
/// Local index into the function's local-to-global file ID table.
/// The value at that index is itself an index into the coverage filename
/// table in the CGU's `__llvm_covmap` section.
file_id: u32,
pub(crate) file_id: u32,
/// 1-based starting line of the source code span.
start_line: u32,
pub(crate) start_line: u32,
/// 1-based starting column of the source code span.
start_col: u32,
pub(crate) start_col: u32,
/// 1-based ending line of the source code span.
end_line: u32,
pub(crate) end_line: u32,
/// 1-based ending column of the source code span. High bit must be unset.
end_col: u32,
}
impl CoverageSpan {
pub(crate) fn from_source_region(
local_file_id: LocalFileId,
code_region: &SourceRegion,
) -> Self {
let file_id = local_file_id.as_u32();
let &SourceRegion { start_line, start_col, end_line, end_col } = code_region;
// Internally, LLVM uses the high bit of `end_col` to distinguish between
// code regions and gap regions, so it can't be used by the column number.
assert!(end_col & (1u32 << 31) == 0, "high bit of `end_col` must be unset: {end_col:#X}");
Self { file_id, start_line, start_col, end_line, end_col }
}
pub(crate) end_col: u32,
}
/// Holds tables of the various region types in one struct.
@ -184,7 +168,7 @@ impl Regions {
#[derive(Clone, Debug)]
#[repr(C)]
pub(crate) struct CodeRegion {
pub(crate) span: CoverageSpan,
pub(crate) cov_span: CoverageSpan,
pub(crate) counter: Counter,
}
@ -192,7 +176,7 @@ pub(crate) struct CodeRegion {
#[derive(Clone, Debug)]
#[repr(C)]
pub(crate) struct BranchRegion {
pub(crate) span: CoverageSpan,
pub(crate) cov_span: CoverageSpan,
pub(crate) true_counter: Counter,
pub(crate) false_counter: Counter,
}
@ -201,7 +185,7 @@ pub(crate) struct BranchRegion {
#[derive(Clone, Debug)]
#[repr(C)]
pub(crate) struct MCDCBranchRegion {
pub(crate) span: CoverageSpan,
pub(crate) cov_span: CoverageSpan,
pub(crate) true_counter: Counter,
pub(crate) false_counter: Counter,
pub(crate) mcdc_branch_params: mcdc::BranchParameters,
@ -211,6 +195,6 @@ pub(crate) struct MCDCBranchRegion {
#[derive(Clone, Debug)]
#[repr(C)]
pub(crate) struct MCDCDecisionRegion {
pub(crate) span: CoverageSpan,
pub(crate) cov_span: CoverageSpan,
pub(crate) mcdc_decision_params: mcdc::DecisionParameters,
}

5
compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs
View file

@ -40,11 +40,10 @@ pub(crate) fn create_pgo_func_name_var<'ll>(
}
}
pub(crate) fn write_filenames_to_buffer<'a>(
filenames: impl IntoIterator<Item = &'a str>,
) -> Vec<u8> {
pub(crate) fn write_filenames_to_buffer(filenames: &[impl AsRef<str>]) -> Vec<u8> {
let (pointers, lengths) = filenames
.into_iter()
.map(AsRef::as_ref)
.map(|s: &str| (s.as_c_char_ptr(), s.len()))
.unzip::<_, _, Vec<_>, Vec<_>>();

58
compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
View file

@ -1,11 +1,11 @@
use std::iter;
use std::sync::Arc;
use itertools::Itertools;
use rustc_abi::Align;
use rustc_codegen_ssa::traits::{
BaseTypeCodegenMethods, ConstCodegenMethods, StaticCodegenMethods,
};
use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_index::IndexVec;
use rustc_middle::mir;
@ -13,7 +13,7 @@ use rustc_middle::ty::{self, TyCtxt};
use rustc_session::RemapFileNameExt;
use rustc_session::config::RemapPathScopeComponents;
use rustc_span::def_id::DefIdSet;
use rustc_span::{Span, Symbol};
use rustc_span::{SourceFile, StableSourceFileId};
use tracing::debug;
use crate::common::CodegenCx;
@ -22,6 +22,7 @@ use crate::coverageinfo::mapgen::covfun::prepare_covfun_record;
use crate::llvm;
mod covfun;
mod spans;
/// Generates and exports the coverage map, which is embedded in special
/// linker sections in the final binary.
@ -131,45 +132,51 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
generate_covmap_record(cx, covmap_version, &filenames_buffer);
}
/// Maps "global" (per-CGU) file ID numbers to their underlying filenames.
/// Maps "global" (per-CGU) file ID numbers to their underlying source files.
struct GlobalFileTable {
/// This "raw" table doesn't include the working dir, so a filename's
/// This "raw" table doesn't include the working dir, so a file's
/// global ID is its index in this set **plus one**.
raw_file_table: FxIndexSet<Symbol>,
raw_file_table: FxIndexMap<StableSourceFileId, Arc<SourceFile>>,
}
impl GlobalFileTable {
fn new() -> Self {
Self { raw_file_table: FxIndexSet::default() }
Self { raw_file_table: FxIndexMap::default() }
}
fn global_file_id_for_file_name(&mut self, file_name: Symbol) -> GlobalFileId {
fn global_file_id_for_file(&mut self, file: &Arc<SourceFile>) -> GlobalFileId {
// Ensure the given file has a table entry, and get its index.
let (raw_id, _) = self.raw_file_table.insert_full(file_name);
let entry = self.raw_file_table.entry(file.stable_id);
let raw_id = entry.index();
entry.or_insert_with(|| Arc::clone(file));
// The raw file table doesn't include an entry for the working dir
// (which has ID 0), so add 1 to get the correct ID.
GlobalFileId::from_usize(raw_id + 1)
}
fn make_filenames_buffer(&self, tcx: TyCtxt<'_>) -> Vec<u8> {
let mut table = Vec::with_capacity(self.raw_file_table.len() + 1);
// LLVM Coverage Mapping Format version 6 (zero-based encoded as 5)
// requires setting the first filename to the compilation directory.
// Since rustc generates coverage maps with relative paths, the
// compilation directory can be combined with the relative paths
// to get absolute paths, if needed.
use rustc_session::RemapFileNameExt;
use rustc_session::config::RemapPathScopeComponents;
let working_dir: &str = &tcx
.sess
.opts
.working_dir
.for_scope(tcx.sess, RemapPathScopeComponents::MACRO)
.to_string_lossy();
table.push(
tcx.sess
.opts
.working_dir
.for_scope(tcx.sess, RemapPathScopeComponents::MACRO)
.to_string_lossy(),
);
// Insert the working dir at index 0, before the other filenames.
let filenames =
iter::once(working_dir).chain(self.raw_file_table.iter().map(Symbol::as_str));
llvm_cov::write_filenames_to_buffer(filenames)
// Add the regular entries after the base directory.
table.extend(self.raw_file_table.values().map(|file| {
file.name.for_scope(tcx.sess, RemapPathScopeComponents::MACRO).to_string_lossy()
}));
llvm_cov::write_filenames_to_buffer(&table)
}
}
@ -182,7 +189,7 @@ rustc_index::newtype_index! {
/// An index into a function's list of global file IDs. That underlying list
/// of local-to-global mappings will be embedded in the function's record in
/// the `__llvm_covfun` linker section.
pub(crate) struct LocalFileId {}
struct LocalFileId {}
}
/// Holds a mapping from "local" (per-function) file IDs to "global" (per-CGU)
@ -208,13 +215,6 @@ impl VirtualFileMapping {
}
}
fn span_file_name(tcx: TyCtxt<'_>, span: Span) -> Symbol {
let source_file = tcx.sess.source_map().lookup_source_file(span.lo());
let name =
source_file.name.for_scope(tcx.sess, RemapPathScopeComponents::MACRO).to_string_lossy();
Symbol::intern(&name)
}
/// Generates the contents of the covmap record for this CGU, which mostly
/// consists of a header and a list of filenames. The record is then stored
/// as a global variable in the `__llvm_covmap` section.

49
compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs
View file

@ -10,16 +10,16 @@ use rustc_abi::Align;
use rustc_codegen_ssa::traits::{
BaseTypeCodegenMethods, ConstCodegenMethods, StaticCodegenMethods,
};
use rustc_middle::bug;
use rustc_middle::mir::coverage::{
CovTerm, CoverageIdsInfo, Expression, FunctionCoverageInfo, Mapping, MappingKind, Op,
};
use rustc_middle::ty::{Instance, TyCtxt};
use rustc_span::Span;
use rustc_target::spec::HasTargetSpec;
use tracing::debug;
use crate::common::CodegenCx;
use crate::coverageinfo::mapgen::{GlobalFileTable, VirtualFileMapping, span_file_name};
use crate::coverageinfo::mapgen::{GlobalFileTable, VirtualFileMapping, spans};
use crate::coverageinfo::{ffi, llvm_cov};
use crate::llvm;
@ -67,12 +67,8 @@ pub(crate) fn prepare_covfun_record<'tcx>(
fill_region_tables(tcx, global_file_table, fn_cov_info, ids_info, &mut covfun);
if covfun.regions.has_no_regions() {
if covfun.is_used {
bug!("a used function should have had coverage mapping data but did not: {covfun:?}");
} else {
debug!(?covfun, "unused function had no coverage mapping data");
return None;
}
debug!(?covfun, "function has no mappings to embed; skipping");
return None;
}
Some(covfun)
@ -121,41 +117,58 @@ fn fill_region_tables<'tcx>(
covfun: &mut CovfunRecord<'tcx>,
) {
// Currently a function's mappings must all be in the same file as its body span.
let file_name = span_file_name(tcx, fn_cov_info.body_span);
let source_map = tcx.sess.source_map();
let source_file = source_map.lookup_source_file(fn_cov_info.body_span.lo());
// Look up the global file ID for that filename.
let global_file_id = global_file_table.global_file_id_for_file_name(file_name);
// Look up the global file ID for that file.
let global_file_id = global_file_table.global_file_id_for_file(&source_file);
// Associate that global file ID with a local file ID for this function.
let local_file_id = covfun.virtual_file_mapping.local_id_for_global(global_file_id);
debug!(" file id: {local_file_id:?} => {global_file_id:?} = '{file_name:?}'");
let ffi::Regions { code_regions, branch_regions, mcdc_branch_regions, mcdc_decision_regions } =
&mut covfun.regions;
let make_cov_span = |span: Span| {
spans::make_coverage_span(local_file_id, source_map, fn_cov_info, &source_file, span)
};
let discard_all = tcx.sess.coverage_discard_all_spans_in_codegen();
// For each counter/region pair in this function+file, convert it to a
// form suitable for FFI.
let is_zero_term = |term| !covfun.is_used || ids_info.is_zero_term(term);
for Mapping { kind, ref source_region } in &fn_cov_info.mappings {
for &Mapping { ref kind, span } in &fn_cov_info.mappings {
// If the mapping refers to counters/expressions that were removed by
// MIR opts, replace those occurrences with zero.
let kind = kind.map_terms(|term| if is_zero_term(term) { CovTerm::Zero } else { term });
let span = ffi::CoverageSpan::from_source_region(local_file_id, source_region);
// Convert the `Span` into coordinates that we can pass to LLVM, or
// discard the span if conversion fails. In rare, cases _all_ of a
// function's spans are discarded, and the rest of coverage codegen
// needs to handle that gracefully to avoid a repeat of #133606.
// We don't have a good test case for triggering that organically, so
// instead we set `-Zcoverage-options=discard-all-spans-in-codegen`
// to force it to occur.
let Some(cov_span) = make_cov_span(span) else { continue };
if discard_all {
continue;
}
match kind {
MappingKind::Code(term) => {
code_regions.push(ffi::CodeRegion { span, counter: ffi::Counter::from_term(term) });
code_regions
.push(ffi::CodeRegion { cov_span, counter: ffi::Counter::from_term(term) });
}
MappingKind::Branch { true_term, false_term } => {
branch_regions.push(ffi::BranchRegion {
span,
cov_span,
true_counter: ffi::Counter::from_term(true_term),
false_counter: ffi::Counter::from_term(false_term),
});
}
MappingKind::MCDCBranch { true_term, false_term, mcdc_params } => {
mcdc_branch_regions.push(ffi::MCDCBranchRegion {
span,
cov_span,
true_counter: ffi::Counter::from_term(true_term),
false_counter: ffi::Counter::from_term(false_term),
mcdc_branch_params: ffi::mcdc::BranchParameters::from(mcdc_params),
@ -163,7 +176,7 @@ fn fill_region_tables<'tcx>(
}
MappingKind::MCDCDecision(mcdc_decision_params) => {
mcdc_decision_regions.push(ffi::MCDCDecisionRegion {
span,
cov_span,
mcdc_decision_params: ffi::mcdc::DecisionParameters::from(mcdc_decision_params),
});
}

126
compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/spans.rs Normal file
View file

@ -0,0 +1,126 @@
use rustc_middle::mir::coverage::FunctionCoverageInfo;
use rustc_span::source_map::SourceMap;
use rustc_span::{BytePos, Pos, SourceFile, Span};
use tracing::debug;
use crate::coverageinfo::ffi;
use crate::coverageinfo::mapgen::LocalFileId;
/// Converts the span into its start line and column, and end line and column.
///
/// Line numbers and column numbers are 1-based. Unlike most column numbers emitted by
/// the compiler, these column numbers are denoted in **bytes**, because that's what
/// LLVM's `llvm-cov` tool expects to see in coverage maps.
///
/// Returns `None` if the conversion failed for some reason. This shouldn't happen,
/// but it's hard to rule out entirely (especially in the presence of complex macros
/// or other expansions), and if it does happen then skipping a span or function is
/// better than an ICE or `llvm-cov` failure that the user might have no way to avoid.
pub(crate) fn make_coverage_span(
file_id: LocalFileId,
source_map: &SourceMap,
fn_cov_info: &FunctionCoverageInfo,
file: &SourceFile,
span: Span,
) -> Option<ffi::CoverageSpan> {
let span = ensure_non_empty_span(source_map, fn_cov_info, span)?;
let lo = span.lo();
let hi = span.hi();
// Column numbers need to be in bytes, so we can't use the more convenient
// `SourceMap` methods for looking up file coordinates.
let line_and_byte_column = |pos: BytePos| -> Option<(usize, usize)> {
let rpos = file.relative_position(pos);
let line_index = file.lookup_line(rpos)?;
let line_start = file.lines()[line_index];
// Line numbers and column numbers are 1-based, so add 1 to each.
Some((line_index + 1, (rpos - line_start).to_usize() + 1))
};
let (mut start_line, start_col) = line_and_byte_column(lo)?;
let (mut end_line, end_col) = line_and_byte_column(hi)?;
// Apply an offset so that code in doctests has correct line numbers.
// FIXME(#79417): Currently we have no way to offset doctest _columns_.
start_line = source_map.doctest_offset_line(&file.name, start_line);
end_line = source_map.doctest_offset_line(&file.name, end_line);
check_coverage_span(ffi::CoverageSpan {
file_id: file_id.as_u32(),
start_line: start_line as u32,
start_col: start_col as u32,
end_line: end_line as u32,
end_col: end_col as u32,
})
}
fn ensure_non_empty_span(
source_map: &SourceMap,
fn_cov_info: &FunctionCoverageInfo,
span: Span,
) -> Option<Span> {
if !span.is_empty() {
return Some(span);
}
let lo = span.lo();
let hi = span.hi();
// The span is empty, so try to expand it to cover an adjacent '{' or '}',
// but only within the bounds of the body span.
let try_next = hi < fn_cov_info.body_span.hi();
let try_prev = fn_cov_info.body_span.lo() < lo;
if !(try_next || try_prev) {
return None;
}
source_map
.span_to_source(span, |src, start, end| try {
// Adjusting span endpoints by `BytePos(1)` is normally a bug,
// but in this case we have specifically checked that the character
// we're skipping over is one of two specific ASCII characters, so
// adjusting by exactly 1 byte is correct.
if try_next && src.as_bytes()[end] == b'{' {
Some(span.with_hi(hi + BytePos(1)))
} else if try_prev && src.as_bytes()[start - 1] == b'}' {
Some(span.with_lo(lo - BytePos(1)))
} else {
None
}
})
.ok()?
}
/// If `llvm-cov` sees a source region that is improperly ordered (end < start),
/// it will immediately exit with a fatal error. To prevent that from happening,
/// discard regions that are improperly ordered, or might be interpreted in a
/// way that makes them improperly ordered.
fn check_coverage_span(cov_span: ffi::CoverageSpan) -> Option<ffi::CoverageSpan> {
let ffi::CoverageSpan { file_id: _, start_line, start_col, end_line, end_col } = cov_span;
// Line/column coordinates are supposed to be 1-based. If we ever emit
// coordinates of 0, `llvm-cov` might misinterpret them.
let all_nonzero = [start_line, start_col, end_line, end_col].into_iter().all(|x| x != 0);
// Coverage mappings use the high bit of `end_col` to indicate that a
// region is actually a "gap" region, so make sure it's unset.
let end_col_has_high_bit_unset = (end_col & (1 << 31)) == 0;
// If a region is improperly ordered (end < start), `llvm-cov` will exit
// with a fatal error, which is inconvenient for users and hard to debug.
let is_ordered = (start_line, start_col) <= (end_line, end_col);
if all_nonzero && end_col_has_high_bit_unset && is_ordered {
Some(cov_span)
} else {
debug!(
?cov_span,
?all_nonzero,
?end_col_has_high_bit_unset,
?is_ordered,
"Skipping source region that would be misinterpreted or rejected by LLVM"
);
// If this happens in a debug build, ICE to make it easier to notice.
debug_assert!(false, "Improper source region: {cov_span:?}");
None
}
}

1
compiler/rustc_codegen_llvm/src/lib.rs
View file

@ -17,6 +17,7 @@
#![feature(iter_intersperse)]
#![feature(let_chains)]
#![feature(rustdoc_internals)]
#![feature(try_blocks)]
#![warn(unreachable_pub)]
// tidy-alphabetical-end

6
compiler/rustc_interface/src/tests.rs
View file

@ -766,7 +766,11 @@ fn test_unstable_options_tracking_hash() {
})
);
tracked!(codegen_backend, Some("abc".to_string()));
tracked!(coverage_options, CoverageOptions { level: CoverageLevel::Mcdc, no_mir_spans: true });
tracked!(coverage_options, CoverageOptions {
level: CoverageLevel::Mcdc,
no_mir_spans: true,
discard_all_spans_in_codegen: true
});
tracked!(crate_attr, vec!["abc".to_string()]);
tracked!(cross_crate_inline_threshold, InliningThreshold::Always);
tracked!(debug_info_for_profiling, true);

18
compiler/rustc_middle/src/mir/coverage.rs
View file

@ -154,22 +154,6 @@ impl Debug for CoverageKind {
}
}
#[derive(Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq, Eq, PartialOrd, Ord)]
#[derive(TypeFoldable, TypeVisitable)]
pub struct SourceRegion {
pub start_line: u32,
pub start_col: u32,
pub end_line: u32,
pub end_col: u32,
}
impl Debug for SourceRegion {
fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
let &Self { start_line, start_col, end_line, end_col } = self;
write!(fmt, "{start_line}:{start_col} - {end_line}:{end_col}")
}
}
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
#[derive(TyEncodable, TyDecodable, TypeFoldable, TypeVisitable)]
pub enum Op {
@ -231,7 +215,7 @@ impl MappingKind {
#[derive(TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable, TypeVisitable)]
pub struct Mapping {
pub kind: MappingKind,
pub source_region: SourceRegion,
pub span: Span,
}
/// Stores per-function coverage information attached to a `mir::Body`,

4
compiler/rustc_middle/src/mir/pretty.rs
View file

@ -603,8 +603,8 @@ fn write_function_coverage_info(
for (id, expression) in expressions.iter_enumerated() {
writeln!(w, "{INDENT}coverage {id:?} => {expression:?};")?;
}
for coverage::Mapping { kind, source_region } in mappings {
writeln!(w, "{INDENT}coverage {kind:?} => {source_region:?};")?;
for coverage::Mapping { kind, span } in mappings {
writeln!(w, "{INDENT}coverage {kind:?} => {span:?};")?;
}
writeln!(w)?;

168
compiler/rustc_mir_transform/src/coverage/mod.rs
View file

@ -13,16 +13,15 @@ use rustc_hir::intravisit::{Visitor, walk_expr};
use rustc_middle::hir::map::Map;
use rustc_middle::hir::nested_filter;
use rustc_middle::mir::coverage::{
CoverageKind, DecisionInfo, FunctionCoverageInfo, Mapping, MappingKind, SourceRegion,
CoverageKind, DecisionInfo, FunctionCoverageInfo, Mapping, MappingKind,
};
use rustc_middle::mir::{
self, BasicBlock, BasicBlockData, SourceInfo, Statement, StatementKind, Terminator,
TerminatorKind,
};
use rustc_middle::ty::TyCtxt;
use rustc_span::Span;
use rustc_span::def_id::LocalDefId;
use rustc_span::source_map::SourceMap;
use rustc_span::{BytePos, Pos, SourceFile, Span};
use tracing::{debug, debug_span, trace};
use crate::coverage::counters::{CoverageCounters, Site};
@ -97,7 +96,7 @@ fn instrument_function_for_coverage<'tcx>(tcx: TyCtxt<'tcx>, mir_body: &mut mir:
let coverage_counters =
CoverageCounters::make_bcb_counters(&basic_coverage_blocks, &bcbs_with_counter_mappings);
let mappings = create_mappings(tcx, &hir_info, &extracted_mappings, &coverage_counters);
let mappings = create_mappings(&extracted_mappings, &coverage_counters);
if mappings.is_empty() {
// No spans could be converted into valid mappings, so skip this function.
debug!("no spans could be converted into valid mappings; skipping");
@ -136,18 +135,12 @@ fn instrument_function_for_coverage<'tcx>(tcx: TyCtxt<'tcx>, mir_body: &mut mir:
///
/// Precondition: All BCBs corresponding to those spans have been given
/// coverage counters.
fn create_mappings<'tcx>(
tcx: TyCtxt<'tcx>,
hir_info: &ExtractedHirInfo,
fn create_mappings(
extracted_mappings: &ExtractedMappings,
coverage_counters: &CoverageCounters,
) -> Vec<Mapping> {
let source_map = tcx.sess.source_map();
let file = source_map.lookup_source_file(hir_info.body_span.lo());
let term_for_bcb =
|bcb| coverage_counters.term_for_bcb(bcb).expect("all BCBs with spans were given counters");
let region_for_span = |span: Span| make_source_region(source_map, hir_info, &file, span);
// Fully destructure the mappings struct to make sure we don't miss any kinds.
let ExtractedMappings {
@ -160,22 +153,20 @@ fn create_mappings<'tcx>(
} = extracted_mappings;
let mut mappings = Vec::new();
mappings.extend(code_mappings.iter().filter_map(
mappings.extend(code_mappings.iter().map(
// Ordinary code mappings are the simplest kind.
|&mappings::CodeMapping { span, bcb }| {
let source_region = region_for_span(span)?;
let kind = MappingKind::Code(term_for_bcb(bcb));
Some(Mapping { kind, source_region })
Mapping { kind, span }
},
));
mappings.extend(branch_pairs.iter().filter_map(
mappings.extend(branch_pairs.iter().map(
|&mappings::BranchPair { span, true_bcb, false_bcb }| {
let true_term = term_for_bcb(true_bcb);
let false_term = term_for_bcb(false_bcb);
let kind = MappingKind::Branch { true_term, false_term };
let source_region = region_for_span(span)?;
Some(Mapping { kind, source_region })
Mapping { kind, span }
},
));
@ -183,7 +174,7 @@ fn create_mappings<'tcx>(
|bcb| coverage_counters.term_for_bcb(bcb).expect("all BCBs with spans were given counters");
// MCDC branch mappings are appended with their decisions in case decisions were ignored.
mappings.extend(mcdc_degraded_branches.iter().filter_map(
mappings.extend(mcdc_degraded_branches.iter().map(
|&mappings::MCDCBranch {
span,
true_bcb,
@ -192,10 +183,9 @@ fn create_mappings<'tcx>(
true_index: _,
false_index: _,
}| {
let source_region = region_for_span(span)?;
let true_term = term_for_bcb(true_bcb);
let false_term = term_for_bcb(false_bcb);
Some(Mapping { kind: MappingKind::Branch { true_term, false_term }, source_region })
Mapping { kind: MappingKind::Branch { true_term, false_term }, span }
},
));
@ -203,7 +193,7 @@ fn create_mappings<'tcx>(
let num_conditions = branches.len() as u16;
let conditions = branches
.into_iter()
.filter_map(
.map(
|&mappings::MCDCBranch {
span,
true_bcb,
@ -212,32 +202,28 @@ fn create_mappings<'tcx>(
true_index: _,
false_index: _,
}| {
let source_region = region_for_span(span)?;
let true_term = term_for_bcb(true_bcb);
let false_term = term_for_bcb(false_bcb);
Some(Mapping {
Mapping {
kind: MappingKind::MCDCBranch {
true_term,
false_term,
mcdc_params: condition_info,
},
source_region,
})
span,
}
},
)
.collect::<Vec<_>>();
if conditions.len() == num_conditions as usize
&& let Some(source_region) = region_for_span(decision.span)
{
if conditions.len() == num_conditions as usize {
// LLVM requires end index for counter mapping regions.
let kind = MappingKind::MCDCDecision(DecisionInfo {
bitmap_idx: (decision.bitmap_idx + decision.num_test_vectors) as u32,
num_conditions,
});
mappings.extend(
std::iter::once(Mapping { kind, source_region }).chain(conditions.into_iter()),
);
let span = decision.span;
mappings.extend(std::iter::once(Mapping { kind, span }).chain(conditions.into_iter()));
} else {
mappings.extend(conditions.into_iter().map(|mapping| {
let MappingKind::MCDCBranch { true_term, false_term, mcdc_params: _ } =
@ -245,10 +231,7 @@ fn create_mappings<'tcx>(
else {
unreachable!("all mappings here are MCDCBranch as shown above");
};
Mapping {
kind: MappingKind::Branch { true_term, false_term },
source_region: mapping.source_region,
}
Mapping { kind: MappingKind::Branch { true_term, false_term }, span: mapping.span }
}))
}
}
@ -391,121 +374,6 @@ fn inject_statement(mir_body: &mut mir::Body<'_>, counter_kind: CoverageKind, bb
data.statements.insert(0, statement);
}
fn ensure_non_empty_span(
source_map: &SourceMap,
hir_info: &ExtractedHirInfo,
span: Span,
) -> Option<Span> {
if !span.is_empty() {
return Some(span);
}
let lo = span.lo();
let hi = span.hi();
// The span is empty, so try to expand it to cover an adjacent '{' or '}',
// but only within the bounds of the body span.
let try_next = hi < hir_info.body_span.hi();
let try_prev = hir_info.body_span.lo() < lo;
if !(try_next || try_prev) {
return None;
}
source_map
.span_to_source(span, |src, start, end| try {
// We're only checking for specific ASCII characters, so we don't
// have to worry about multi-byte code points.
if try_next && src.as_bytes()[end] == b'{' {
Some(span.with_hi(hi + BytePos(1)))
} else if try_prev && src.as_bytes()[start - 1] == b'}' {
Some(span.with_lo(lo - BytePos(1)))
} else {
None
}
})
.ok()?
}
/// Converts the span into its start line and column, and end line and column.
///
/// Line numbers and column numbers are 1-based. Unlike most column numbers emitted by
/// the compiler, these column numbers are denoted in **bytes**, because that's what
/// LLVM's `llvm-cov` tool expects to see in coverage maps.
///
/// Returns `None` if the conversion failed for some reason. This shouldn't happen,
/// but it's hard to rule out entirely (especially in the presence of complex macros
/// or other expansions), and if it does happen then skipping a span or function is
/// better than an ICE or `llvm-cov` failure that the user might have no way to avoid.
fn make_source_region(
source_map: &SourceMap,
hir_info: &ExtractedHirInfo,
file: &SourceFile,
span: Span,
) -> Option<SourceRegion> {
let span = ensure_non_empty_span(source_map, hir_info, span)?;
let lo = span.lo();
let hi = span.hi();
// Column numbers need to be in bytes, so we can't use the more convenient
// `SourceMap` methods for looking up file coordinates.
let line_and_byte_column = |pos: BytePos| -> Option<(usize, usize)> {
let rpos = file.relative_position(pos);
let line_index = file.lookup_line(rpos)?;
let line_start = file.lines()[line_index];
// Line numbers and column numbers are 1-based, so add 1 to each.
Some((line_index + 1, (rpos - line_start).to_usize() + 1))
};
let (mut start_line, start_col) = line_and_byte_column(lo)?;
let (mut end_line, end_col) = line_and_byte_column(hi)?;
// Apply an offset so that code in doctests has correct line numbers.
// FIXME(#79417): Currently we have no way to offset doctest _columns_.
start_line = source_map.doctest_offset_line(&file.name, start_line);
end_line = source_map.doctest_offset_line(&file.name, end_line);
check_source_region(SourceRegion {
start_line: start_line as u32,
start_col: start_col as u32,
end_line: end_line as u32,
end_col: end_col as u32,
})
}
/// If `llvm-cov` sees a source region that is improperly ordered (end < start),
/// it will immediately exit with a fatal error. To prevent that from happening,
/// discard regions that are improperly ordered, or might be interpreted in a
/// way that makes them improperly ordered.
fn check_source_region(source_region: SourceRegion) -> Option<SourceRegion> {
let SourceRegion { start_line, start_col, end_line, end_col } = source_region;
// Line/column coordinates are supposed to be 1-based. If we ever emit
// coordinates of 0, `llvm-cov` might misinterpret them.
let all_nonzero = [start_line, start_col, end_line, end_col].into_iter().all(|x| x != 0);
// Coverage mappings use the high bit of `end_col` to indicate that a
// region is actually a "gap" region, so make sure it's unset.
let end_col_has_high_bit_unset = (end_col & (1 << 31)) == 0;
// If a region is improperly ordered (end < start), `llvm-cov` will exit
// with a fatal error, which is inconvenient for users and hard to debug.
let is_ordered = (start_line, start_col) <= (end_line, end_col);
if all_nonzero && end_col_has_high_bit_unset && is_ordered {
Some(source_region)
} else {
debug!(
?source_region,
?all_nonzero,
?end_col_has_high_bit_unset,
?is_ordered,
"Skipping source region that would be misinterpreted or rejected by LLVM"
);
// If this happens in a debug build, ICE to make it easier to notice.
debug_assert!(false, "Improper source region: {source_region:?}");
None
}
}
/// Function information extracted from HIR by the coverage instrumentor.
#[derive(Debug)]
struct ExtractedHirInfo {

10
compiler/rustc_session/src/config.rs
View file

@ -147,18 +147,24 @@ pub enum InstrumentCoverage {
Yes,
}
/// Individual flag values controlled by `-Z coverage-options`.
/// Individual flag values controlled by `-Zcoverage-options`.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Default)]
pub struct CoverageOptions {
pub level: CoverageLevel,
/// `-Z coverage-options=no-mir-spans`: Don't extract block coverage spans
/// `-Zcoverage-options=no-mir-spans`: Don't extract block coverage spans
/// from MIR statements/terminators, making it easier to inspect/debug
/// branch and MC/DC coverage mappings.
///
/// For internal debugging only. If other code changes would make it hard
/// to keep supporting this flag, remove it.
pub no_mir_spans: bool,
/// `-Zcoverage-options=discard-all-spans-in-codegen`: During codgen,
/// discard all coverage spans as though they were invalid. Needed by
/// regression tests for #133606, because we don't have an easy way to
/// reproduce it from actual source code.
pub discard_all_spans_in_codegen: bool,
}
/// Controls whether branch coverage or MC/DC coverage is enabled.

1
compiler/rustc_session/src/options.rs
View file

@ -1037,6 +1037,7 @@ pub mod parse {
"condition" => slot.level = CoverageLevel::Condition,
"mcdc" => slot.level = CoverageLevel::Mcdc,
"no-mir-spans" => slot.no_mir_spans = true,
"discard-all-spans-in-codegen" => slot.discard_all_spans_in_codegen = true,
_ => return false,
}
}

5
compiler/rustc_session/src/session.rs
View file

@ -352,6 +352,11 @@ impl Session {
self.opts.unstable_opts.coverage_options.no_mir_spans
}
/// True if `-Zcoverage-options=discard-all-spans-in-codegen` was passed.
pub fn coverage_discard_all_spans_in_codegen(&self) -> bool {
self.opts.unstable_opts.coverage_options.discard_all_spans_in_codegen
}
pub fn is_sanitizer_cfi_enabled(&self) -> bool {
self.opts.unstable_opts.sanitizer.contains(SanitizerSet::CFI)
}

6
tests/coverage/auxiliary/discard_all_helper.rs Normal file
View file

@ -0,0 +1,6 @@
//@ edition: 2021
// Force this function to be generated in its home crate, so that it ends up
// with normal coverage metadata.
#[inline(never)]
pub fn external_function() {}

7
tests/coverage/discard-all-issue-133606.coverage Normal file
View file

@ -0,0 +1,7 @@
LL| |//@ edition: 2021
LL| |
LL| |// Force this function to be generated in its home crate, so that it ends up
LL| |// with normal coverage metadata.
LL| |#[inline(never)]
LL| 1|pub fn external_function() {}

24
tests/coverage/discard-all-issue-133606.rs Normal file
View file

@ -0,0 +1,24 @@
//! Regression test for <https://github.com/rust-lang/rust/issues/133606>.
//!
//! In rare cases, all of a function's coverage spans are discarded at a late
//! stage during codegen. When that happens, the subsequent code needs to take
//! special care to avoid emitting coverage metadata that would cause `llvm-cov`
//! to fail with a fatal error.
//!
//! We currently don't know of a concise way to reproduce that scenario with
//! ordinary Rust source code, so instead we set a special testing-only flag to
//! force it to occur.
//@ edition: 2021
//@ compile-flags: -Zcoverage-options=discard-all-spans-in-codegen
// The `llvm-cov` tool will complain if the test binary ends up having no
// coverage metadata at all. To prevent that, we also link to instrumented
// code in an auxiliary crate that doesn't have the special flag set.
//@ aux-build: discard_all_helper.rs
extern crate discard_all_helper;
fn main() {
discard_all_helper::external_function();
}

12
tests/mir-opt/coverage/branch_match_arms.main.InstrumentCoverage.diff
View file

@ -30,12 +30,12 @@
+ coverage ExpressionId(0) => Expression { lhs: Counter(1), op: Add, rhs: Counter(2) };
+ coverage ExpressionId(1) => Expression { lhs: Expression(0), op: Add, rhs: Counter(3) };
+ coverage ExpressionId(2) => Expression { lhs: Counter(0), op: Subtract, rhs: Expression(1) };
+ coverage Code(Counter(0)) => 13:1 - 14:21;
+ coverage Code(Counter(1)) => 15:17 - 15:33;
+ coverage Code(Counter(2)) => 16:17 - 16:33;
+ coverage Code(Counter(3)) => 17:17 - 17:33;
+ coverage Code(Expression(2)) => 18:17 - 18:33;
+ coverage Code(Counter(0)) => 20:1 - 20:2;
+ coverage Code(Counter(0)) => $DIR/branch_match_arms.rs:13:1: 14:21 (#0);
+ coverage Code(Counter(1)) => $DIR/branch_match_arms.rs:15:17: 15:33 (#0);
+ coverage Code(Counter(2)) => $DIR/branch_match_arms.rs:16:17: 16:33 (#0);
+ coverage Code(Counter(3)) => $DIR/branch_match_arms.rs:17:17: 17:33 (#0);
+ coverage Code(Expression(2)) => $DIR/branch_match_arms.rs:18:17: 18:33 (#0);
+ coverage Code(Counter(0)) => $DIR/branch_match_arms.rs:20:2: 20:2 (#0);
+
bb0: {
+ Coverage::CounterIncrement(0);

2
tests/mir-opt/coverage/instrument_coverage.bar.InstrumentCoverage.diff
View file

@ -5,7 +5,7 @@
let mut _0: bool;
+ coverage body span: $DIR/instrument_coverage.rs:19:18: 21:2 (#0)
+ coverage Code(Counter(0)) => 19:1 - 21:2;
+ coverage Code(Counter(0)) => $DIR/instrument_coverage.rs:19:1: 21:2 (#0);
+
bb0: {
+ Coverage::CounterIncrement(0);

10
tests/mir-opt/coverage/instrument_coverage.main.InstrumentCoverage.diff
View file

@ -9,11 +9,11 @@
+ coverage body span: $DIR/instrument_coverage.rs:10:11: 16:2 (#0)
+ coverage ExpressionId(0) => Expression { lhs: Counter(0), op: Add, rhs: Counter(1) };
+ coverage Code(Counter(0)) => 10:1 - 10:11;
+ coverage Code(Expression(0)) => 12:12 - 12:17;
+ coverage Code(Counter(0)) => 13:13 - 13:18;
+ coverage Code(Counter(1)) => 14:9 - 14:10;
+ coverage Code(Counter(0)) => 16:1 - 16:2;
+ coverage Code(Counter(0)) => $DIR/instrument_coverage.rs:10:1: 10:11 (#0);
+ coverage Code(Expression(0)) => $DIR/instrument_coverage.rs:12:12: 12:17 (#0);
+ coverage Code(Counter(0)) => $DIR/instrument_coverage.rs:13:13: 13:18 (#0);
+ coverage Code(Counter(1)) => $DIR/instrument_coverage.rs:14:10: 14:10 (#0);
+ coverage Code(Counter(0)) => $DIR/instrument_coverage.rs:16:2: 16:2 (#0);
+
bb0: {
+ Coverage::CounterIncrement(0);

10
tests/mir-opt/coverage/instrument_coverage_cleanup.main.CleanupPostBorrowck.diff
View file

@ -9,11 +9,11 @@
coverage body span: $DIR/instrument_coverage_cleanup.rs:13:11: 15:2 (#0)
coverage ExpressionId(0) => Expression { lhs: Counter(0), op: Subtract, rhs: Counter(1) };
coverage Code(Counter(0)) => 13:1 - 14:36;
coverage Code(Expression(0)) => 14:37 - 14:39;
coverage Code(Counter(1)) => 14:38 - 14:39;
coverage Code(Counter(0)) => 15:1 - 15:2;
coverage Branch { true_term: Expression(0), false_term: Counter(1) } => 14:8 - 14:36;
coverage Code(Counter(0)) => $DIR/instrument_coverage_cleanup.rs:13:1: 14:36 (#0);
coverage Code(Expression(0)) => $DIR/instrument_coverage_cleanup.rs:14:37: 14:39 (#0);
coverage Code(Counter(1)) => $DIR/instrument_coverage_cleanup.rs:14:39: 14:39 (#0);
coverage Code(Counter(0)) => $DIR/instrument_coverage_cleanup.rs:15:2: 15:2 (#0);
coverage Branch { true_term: Expression(0), false_term: Counter(1) } => $DIR/instrument_coverage_cleanup.rs:14:8: 14:36 (#0);
bb0: {
Coverage::CounterIncrement(0);

10
tests/mir-opt/coverage/instrument_coverage_cleanup.main.InstrumentCoverage.diff
View file

@ -9,11 +9,11 @@
+ coverage body span: $DIR/instrument_coverage_cleanup.rs:13:11: 15:2 (#0)
+ coverage ExpressionId(0) => Expression { lhs: Counter(0), op: Subtract, rhs: Counter(1) };
+ coverage Code(Counter(0)) => 13:1 - 14:36;
+ coverage Code(Expression(0)) => 14:37 - 14:39;
+ coverage Code(Counter(1)) => 14:38 - 14:39;
+ coverage Code(Counter(0)) => 15:1 - 15:2;
+ coverage Branch { true_term: Expression(0), false_term: Counter(1) } => 14:8 - 14:36;
+ coverage Code(Counter(0)) => $DIR/instrument_coverage_cleanup.rs:13:1: 14:36 (#0);
+ coverage Code(Expression(0)) => $DIR/instrument_coverage_cleanup.rs:14:37: 14:39 (#0);
+ coverage Code(Counter(1)) => $DIR/instrument_coverage_cleanup.rs:14:39: 14:39 (#0);
+ coverage Code(Counter(0)) => $DIR/instrument_coverage_cleanup.rs:15:2: 15:2 (#0);
+ coverage Branch { true_term: Expression(0), false_term: Counter(1) } => $DIR/instrument_coverage_cleanup.rs:14:8: 14:36 (#0);
+
bb0: {
+ Coverage::CounterIncrement(0);