Merging upstream version 1.75.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 193 insertions, 0 deletions

diff --git a/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs b/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
new file mode 100644
index 000000000..6189e5379
--- /dev/null
+++ b/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
@@ -0,0 +1,193 @@
+use rustc_data_structures::captures::Captures;
+use rustc_middle::mir::{
+    self, AggregateKind, FakeReadCause, Rvalue, Statement, StatementKind, Terminator,
+    TerminatorKind,
+};
+use rustc_span::Span;
+
+use crate::coverage::graph::{BasicCoverageBlock, BasicCoverageBlockData, CoverageGraph};
+use crate::coverage::spans::CoverageSpan;
+
+pub(super) fn mir_to_initial_sorted_coverage_spans(
+    mir_body: &mir::Body<'_>,
+    fn_sig_span: Span,
+    body_span: Span,
+    basic_coverage_blocks: &CoverageGraph,
+) -> Vec<CoverageSpan> {
+    let mut initial_spans = Vec::with_capacity(mir_body.basic_blocks.len() * 2);
+    for (bcb, bcb_data) in basic_coverage_blocks.iter_enumerated() {
+        initial_spans.extend(bcb_to_initial_coverage_spans(mir_body, body_span, 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(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(|| 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
+}
+
+// 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<'a, 'tcx>(
+    mir_body: &'a mir::Body<'tcx>,
+    body_span: Span,
+    bcb: BasicCoverageBlock,
+    bcb_data: &'a BasicCoverageBlockData,
+) -> impl Iterator<Item = CoverageSpan> + Captures<'a> + Captures<'tcx> {
+    bcb_data.basic_blocks.iter().flat_map(move |&bb| {
+        let data = &mir_body[bb];
+
+        let statement_spans = data.statements.iter().filter_map(move |statement| {
+            let expn_span = filtered_statement_span(statement)?;
+            let span = function_source_span(expn_span, body_span);
+
+            Some(CoverageSpan::new(span, expn_span, bcb, is_closure(statement)))
+        });
+
+        let terminator_span = Some(data.terminator()).into_iter().filter_map(move |terminator| {
+            let expn_span = filtered_terminator_span(terminator)?;
+            let span = function_source_span(expn_span, body_span);
+
+            Some(CoverageSpan::new(span, expn_span, bcb, false))
+        });
+
+        statement_spans.chain(terminator_span)
+    })
+}
+
+fn is_closure(statement: &Statement<'_>) -> bool {
+    match statement.kind {
+        StatementKind::Assign(box (_, Rvalue::Aggregate(box ref agg_kind, _))) => match agg_kind {
+            AggregateKind::Closure(_, _) | AggregateKind::Coroutine(_, _, _) => true,
+            _ => false,
+        },
+        _ => false,
+    }
+}
+
+/// 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::CoroutineDrop
+        | 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 {
+    use rustc_span::source_map::original_sp;
+
+    let original_span = original_sp(span, body_span).with_ctxt(body_span.ctxt());
+    if body_span.contains(original_span) { original_span } else { body_span }
+}