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coverage: llvm-cov expects column numbers to be bytes, not code points

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This commit is contained in:
Zalathar 2023-12-15 14:12:46 +11:00
parent 88f5759ace
commit 6971e9332d
5 changed files with 112 additions and 27 deletions
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74
compiler/rustc_mir_transform/src/coverage/mod.rs
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@ -23,7 +23,7 @@ use rustc_middle::mir::{
use rustc_middle::ty::TyCtxt;
use rustc_span::def_id::LocalDefId;
use rustc_span::source_map::SourceMap;
use rustc_span::{Span, Symbol};
use rustc_span::{BytePos, Pos, RelativeBytePos, Span, Symbol};
/// Inserts `StatementKind::Coverage` statements that either instrument the binary with injected
/// counters, via intrinsic `llvm.instrprof.increment`, and/or inject metadata used during codegen
@ -258,7 +258,16 @@ fn inject_statement(mir_body: &mut mir::Body<'_>, counter_kind: CoverageKind, bb
data.statements.insert(0, statement);
}
/// Convert the Span into its file name, start line and column, and end line and column
/// Convert the Span into its file name, 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_code_region(
source_map: &SourceMap,
file_name: Symbol,
@ -272,20 +281,55 @@ fn make_code_region(
source_map.span_to_diagnostic_string(body_span)
);
let (file, mut start_line, mut start_col, mut end_line, mut end_col) =
source_map.span_to_location_info(span);
if span.hi() == span.lo() {
// Extend an empty span by one character so the region will be counted.
if span.hi() == body_span.hi() {
start_col = start_col.saturating_sub(1);
} else {
end_col = start_col + 1;
}
};
if let Some(file) = file {
start_line = source_map.doctest_offset_line(&file.name, start_line);
end_line = source_map.doctest_offset_line(&file.name, end_line);
let lo = span.lo();
let hi = span.hi();
let file = source_map.lookup_source_file(lo);
if !file.contains(hi) {
debug!(?span, ?file, ?lo, ?hi, "span crosses multiple files; skipping");
return None;
}
// Column numbers need to be in bytes, so we can't use the more convenient
// `SourceMap` methods for looking up file coordinates.
let rpos_and_line_and_byte_column = |pos: BytePos| -> Option<(RelativeBytePos, 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((rpos, line_index + 1, (rpos - line_start).to_usize() + 1))
};
let (lo_rpos, mut start_line, mut start_col) = rpos_and_line_and_byte_column(lo)?;
let (hi_rpos, mut end_line, mut end_col) = rpos_and_line_and_byte_column(hi)?;
// If the span is empty, try to expand it horizontally by one character's
// worth of bytes, so that it is more visible in `llvm-cov` reports.
// We do this after resolving line/column numbers, so that empty spans at the
// end of a line get an extra column instead of wrapping to the next line.
if span.is_empty()
&& body_span.contains(span)
&& let Some(src) = &file.src
{
// Prefer to expand the end position, if it won't go outside the body span.
if hi < body_span.hi() {
let hi_rpos = hi_rpos.to_usize();
let nudge_bytes = src.ceil_char_boundary(hi_rpos + 1) - hi_rpos;
end_col += nudge_bytes;
} else if lo > body_span.lo() {
let lo_rpos = lo_rpos.to_usize();
let nudge_bytes = lo_rpos - src.floor_char_boundary(lo_rpos - 1);
// Subtract the nudge, but don't go below column 1.
start_col = start_col.saturating_sub(nudge_bytes).max(1);
}
// If neither nudge could be applied, stick with the empty span coordinates.
}
// 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);
Some(CodeRegion {
file_name,
start_line: start_line as u32,