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coverage: Separate initial span extraction from span processing #116409

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merged 3 commits into from
Oct 10, 2023
Merged

coverage: Separate initial span extraction from span processing #116409

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972ab88
coverage: Move initial MIR span extraction into a submodule
Zalathar Oct 1, 2023
4b471df
coverage: Disconnect span extraction from `CoverageSpansGenerator`
Zalathar Oct 1, 2023
6c44425
coverage: Remove enum `CoverageStatement`
Zalathar Oct 1, 2023
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coverage: Move initial MIR span extraction into a submodule
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@Zalathar
Zalathar committed Oct 10, 2023
commit 972ab8863d6d3c414a964a8aae66b8ee69883d4f
190 changes: 5 additions & 185 deletions compiler/rustc_mir_transform/src/coverage/spans.rs
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Original file line number Diff line number Diff line change
@@ -1,15 +1,13 @@
use super::graph::{BasicCoverageBlock, BasicCoverageBlockData, CoverageGraph, START_BCB};
use std::cell::OnceCell;

use rustc_data_structures::graph::WithNumNodes;
use rustc_index::IndexVec;
use rustc_middle::mir::{
self, AggregateKind, BasicBlock, FakeReadCause, Rvalue, Statement, StatementKind, Terminator,
TerminatorKind,
};
use rustc_span::source_map::original_sp;
use rustc_middle::mir::{self, AggregateKind, BasicBlock, Rvalue, Statement, StatementKind};
use rustc_span::{BytePos, ExpnKind, MacroKind, Span, Symbol};

use std::cell::OnceCell;
use super::graph::{BasicCoverageBlock, CoverageGraph, START_BCB};

mod from_mir;

pub(super) struct CoverageSpans {
/// Map from BCBs to their list of coverage spans.
Expand Down Expand Up @@ -311,41 +309,6 @@ impl<'a, 'tcx> CoverageSpansGenerator<'a, 'tcx> {
coverage_spans.to_refined_spans()
}

fn mir_to_initial_sorted_coverage_spans(&self) -> Vec<CoverageSpan> {
let mut initial_spans =
Vec::<CoverageSpan>::with_capacity(self.mir_body.basic_blocks.len() * 2);
for (bcb, bcb_data) in self.basic_coverage_blocks.iter_enumerated() {
initial_spans.extend(self.bcb_to_initial_coverage_spans(bcb, bcb_data));
}

if initial_spans.is_empty() {
// This can happen if, for example, the function is unreachable (contains only a
// `BasicBlock`(s) with an `Unreachable` terminator).
return initial_spans;
}

initial_spans.push(CoverageSpan::for_fn_sig(self.fn_sig_span));

initial_spans.sort_by(|a, b| {
// First sort by span start.
Ord::cmp(&a.span.lo(), &b.span.lo())
// If span starts are the same, sort by span end in reverse order.
// This ensures that if spans A and B are adjacent in the list,
// and they overlap but are not equal, then either:
// - Span A extends further left, or
// - Both have the same start and span A extends further right
.then_with(|| Ord::cmp(&a.span.hi(), &b.span.hi()).reverse())
// If both spans are equal, sort the BCBs in dominator order,
// so that dominating BCBs come before other BCBs they dominate.
.then_with(|| self.basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb))
// If two spans are otherwise identical, put closure spans first,
// as this seems to be what the refinement step expects.
.then_with(|| Ord::cmp(&a.is_closure, &b.is_closure).reverse())
});

initial_spans
}

/// Iterate through the sorted `CoverageSpan`s, and return the refined list of merged and
/// de-duplicated `CoverageSpan`s.
fn to_refined_spans(mut self) -> Vec<CoverageSpan> {
Expand Down Expand Up @@ -485,48 +448,6 @@ impl<'a, 'tcx> CoverageSpansGenerator<'a, 'tcx> {
}
}

// Generate a set of `CoverageSpan`s from the filtered set of `Statement`s and `Terminator`s of
// the `BasicBlock`(s) in the given `BasicCoverageBlockData`. One `CoverageSpan` is generated
// 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(
&self,
bcb: BasicCoverageBlock,
bcb_data: &'a BasicCoverageBlockData,
) -> Vec<CoverageSpan> {
bcb_data
.basic_blocks
.iter()
.flat_map(|&bb| {
let data = &self.mir_body[bb];
data.statements
.iter()
.enumerate()
.filter_map(move |(index, statement)| {
filtered_statement_span(statement).map(|span| {
CoverageSpan::for_statement(
statement,
function_source_span(span, self.body_span),
span,
bcb,
bb,
index,
)
})
})
.chain(filtered_terminator_span(data.terminator()).map(|span| {
CoverageSpan::for_terminator(
function_source_span(span, self.body_span),
span,
bcb,
bb,
)
}))
})
.collect()
}

fn curr(&self) -> &CoverageSpan {
self.some_curr
.as_ref()
Expand Down Expand Up @@ -774,104 +695,3 @@ impl<'a, 'tcx> CoverageSpansGenerator<'a, 'tcx> {
self.basic_coverage_blocks.dominates(dom_covspan.bcb, covspan.bcb)
}
}

/// If the MIR `Statement` has a span contributive to computing coverage spans,
/// return it; otherwise return `None`.
fn filtered_statement_span(statement: &Statement<'_>) -> Option<Span> {
match statement.kind {
// These statements have spans that are often outside the scope of the executed source code
// for their parent `BasicBlock`.
StatementKind::StorageLive(_)
| StatementKind::StorageDead(_)
// Coverage should not be encountered, but don't inject coverage coverage
| StatementKind::Coverage(_)
// Ignore `ConstEvalCounter`s
| StatementKind::ConstEvalCounter
// Ignore `Nop`s
| StatementKind::Nop => None,

// FIXME(#78546): MIR InstrumentCoverage - Can the source_info.span for `FakeRead`
// statements be more consistent?
//
// FakeReadCause::ForGuardBinding, in this example:
// match somenum {
// x if x < 1 => { ... }
// }...
// The BasicBlock within the match arm code included one of these statements, but the span
// for it covered the `1` in this source. The actual statements have nothing to do with that
// source span:
// FakeRead(ForGuardBinding, _4);
// where `_4` is:
// _4 = &_1; (at the span for the first `x`)
// and `_1` is the `Place` for `somenum`.
//
// If and when the Issue is resolved, remove this special case match pattern:
StatementKind::FakeRead(box (FakeReadCause::ForGuardBinding, _)) => None,

// Retain spans from all other statements
StatementKind::FakeRead(box (_, _)) // Not including `ForGuardBinding`
| StatementKind::Intrinsic(..)
| StatementKind::Assign(_)
| StatementKind::SetDiscriminant { .. }
| StatementKind::Deinit(..)
| StatementKind::Retag(_, _)
| StatementKind::PlaceMention(..)
| StatementKind::AscribeUserType(_, _) => {
Some(statement.source_info.span)
}
}
}

/// If the MIR `Terminator` has a span contributive to computing coverage spans,
/// return it; otherwise return `None`.
fn filtered_terminator_span(terminator: &Terminator<'_>) -> Option<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
// an `if condition { block }` has a span that includes the executed block, if true,
// but for coverage, the code region executed, up to *and* through the SwitchInt,
// actually stops before the if's block.)
TerminatorKind::Unreachable // Unreachable blocks are not connected to the MIR CFG
| TerminatorKind::Assert { .. }
| TerminatorKind::Drop { .. }
| TerminatorKind::SwitchInt { .. }
// For `FalseEdge`, only the `real` branch is taken, so it is similar to a `Goto`.
| TerminatorKind::FalseEdge { .. }
| TerminatorKind::Goto { .. } => None,

// Call `func` operand can have a more specific span when part of a chain of calls
| TerminatorKind::Call { ref func, .. } => {
let mut span = terminator.source_info.span;
if let mir::Operand::Constant(box constant) = func {
if constant.span.lo() > span.lo() {
span = span.with_lo(constant.span.lo());
}
}
Some(span)
}

// Retain spans from all other terminators
TerminatorKind::UnwindResume
| TerminatorKind::UnwindTerminate(_)
| TerminatorKind::Return
| TerminatorKind::Yield { .. }
| TerminatorKind::GeneratorDrop
| TerminatorKind::FalseUnwind { .. }
| TerminatorKind::InlineAsm { .. } => {
Some(terminator.source_info.span)
}
}
}

/// Returns 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.
///
/// [^1]Expansions result from Rust syntax including macros, syntactic sugar,
/// etc.).
#[inline]
fn function_source_span(span: Span, body_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 }
}
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