diff options
Diffstat (limited to 'compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs')
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs | 344 |
1 files changed, 153 insertions, 191 deletions
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs index 55f43aa5341..84319b4ba2d 100644 --- a/compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs +++ b/compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs @@ -1,64 +1,78 @@ use crate::coverageinfo::ffi::{Counter, CounterExpression, ExprKind}; use rustc_data_structures::fx::FxIndexSet; -use rustc_index::IndexVec; -use rustc_middle::mir::coverage::{CodeRegion, CounterId, ExpressionId, Op, Operand}; +use rustc_index::bit_set::BitSet; +use rustc_middle::mir::coverage::{ + CodeRegion, CounterId, CovTerm, Expression, ExpressionId, FunctionCoverageInfo, Mapping, Op, +}; use rustc_middle::ty::Instance; -use rustc_middle::ty::TyCtxt; -#[derive(Clone, Debug, PartialEq)] -pub struct Expression { - lhs: Operand, - op: Op, - rhs: Operand, - code_regions: Vec<CodeRegion>, -} - -/// Collects all of the coverage regions associated with (a) injected counters, (b) counter -/// expressions (additions or subtraction), and (c) unreachable regions (always counted as zero), -/// for a given Function. This struct also stores the `function_source_hash`, -/// computed during instrumentation, and forwarded with counters. -/// -/// Note, it may be important to understand LLVM's definitions of `unreachable` regions versus "gap -/// regions" (or "gap areas"). A gap region is a code region within a counted region (either counter -/// or expression), but the line or lines in the gap region are not executable (such as lines with -/// only whitespace or comments). According to LLVM Code Coverage Mapping documentation, "A count -/// for a gap area is only used as the line execution count if there are no other regions on a -/// line." +/// Holds all of the coverage mapping data associated with a function instance, +/// collected during traversal of `Coverage` statements in the function's MIR. #[derive(Debug)] pub struct FunctionCoverage<'tcx> { - instance: Instance<'tcx>, - source_hash: u64, + /// Coverage info that was attached to this function by the instrumentor. + function_coverage_info: &'tcx FunctionCoverageInfo, is_used: bool, - counters: IndexVec<CounterId, Option<Vec<CodeRegion>>>, - expressions: IndexVec<ExpressionId, Option<Expression>>, - unreachable_regions: Vec<CodeRegion>, + + /// Tracks which counters have been seen, so that we can identify mappings + /// to counters that were optimized out, and set them to zero. + counters_seen: BitSet<CounterId>, + /// Contains all expression IDs that have been seen in an `ExpressionUsed` + /// coverage statement, plus all expression IDs that aren't directly used + /// by any mappings (and therefore do not have expression-used statements). + /// After MIR traversal is finished, we can conclude that any IDs missing + /// from this set must have had their statements deleted by MIR opts. + expressions_seen: BitSet<ExpressionId>, } impl<'tcx> FunctionCoverage<'tcx> { /// Creates a new set of coverage data for a used (called) function. - pub fn new(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) -> Self { - Self::create(tcx, instance, true) + pub fn new( + instance: Instance<'tcx>, + function_coverage_info: &'tcx FunctionCoverageInfo, + ) -> Self { + Self::create(instance, function_coverage_info, true) } /// Creates a new set of coverage data for an unused (never called) function. - pub fn unused(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) -> Self { - Self::create(tcx, instance, false) + pub fn unused( + instance: Instance<'tcx>, + function_coverage_info: &'tcx FunctionCoverageInfo, + ) -> Self { + Self::create(instance, function_coverage_info, false) } - fn create(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>, is_used: bool) -> Self { - let coverageinfo = tcx.coverageinfo(instance.def); + fn create( + instance: Instance<'tcx>, + function_coverage_info: &'tcx FunctionCoverageInfo, + is_used: bool, + ) -> Self { + let num_counters = function_coverage_info.num_counters; + let num_expressions = function_coverage_info.expressions.len(); debug!( - "FunctionCoverage::create(instance={:?}) has coverageinfo={:?}. is_used={}", - instance, coverageinfo, is_used + "FunctionCoverage::create(instance={instance:?}) has \ + num_counters={num_counters}, num_expressions={num_expressions}, is_used={is_used}" ); + + // Create a filled set of expression IDs, so that expressions not + // directly used by mappings will be treated as "seen". + // (If they end up being unused, LLVM will delete them for us.) + let mut expressions_seen = BitSet::new_filled(num_expressions); + // For each expression ID that is directly used by one or more mappings, + // mark it as not-yet-seen. This indicates that we expect to see a + // corresponding `ExpressionUsed` statement during MIR traversal. + for Mapping { term, .. } in &function_coverage_info.mappings { + if let &CovTerm::Expression(id) = term { + expressions_seen.remove(id); + } + } + Self { - instance, - source_hash: 0, // will be set with the first `add_counter()` + function_coverage_info, is_used, - counters: IndexVec::from_elem_n(None, coverageinfo.num_counters as usize), - expressions: IndexVec::from_elem_n(None, coverageinfo.num_expressions as usize), - unreachable_regions: Vec::new(), + counters_seen: BitSet::new_empty(num_counters), + expressions_seen, } } @@ -67,135 +81,94 @@ impl<'tcx> FunctionCoverage<'tcx> { self.is_used } - /// Sets the function source hash value. If called multiple times for the same function, all - /// calls should have the same hash value. - pub fn set_function_source_hash(&mut self, source_hash: u64) { - if self.source_hash == 0 { - self.source_hash = source_hash; - } else { - debug_assert_eq!(source_hash, self.source_hash); - } - } - - /// Adds code regions to be counted by an injected counter intrinsic. + /// Marks a counter ID as having been seen in a counter-increment statement. #[instrument(level = "debug", skip(self))] - pub(crate) fn add_counter(&mut self, id: CounterId, code_regions: &[CodeRegion]) { - if code_regions.is_empty() { - return; - } - - let slot = &mut self.counters[id]; - match slot { - None => *slot = Some(code_regions.to_owned()), - // If this counter ID slot has already been filled, it should - // contain identical information. - Some(ref previous_regions) => assert_eq!( - previous_regions, code_regions, - "add_counter: code regions for id changed" - ), - } - } - - /// Adds information about a coverage expression, along with zero or more - /// code regions mapped to that expression. - /// - /// Both counters and "counter expressions" (or simply, "expressions") can be operands in other - /// expressions. These are tracked as separate variants of `Operand`, so there is no ambiguity - /// between operands that are counter IDs and operands that are expression IDs. - #[instrument(level = "debug", skip(self))] - pub(crate) fn add_counter_expression( - &mut self, - expression_id: ExpressionId, - lhs: Operand, - op: Op, - rhs: Operand, - code_regions: &[CodeRegion], - ) { - debug_assert!( - expression_id.as_usize() < self.expressions.len(), - "expression_id {} is out of range for expressions.len() = {} - for {:?}", - expression_id.as_usize(), - self.expressions.len(), - self, - ); - - let expression = Expression { lhs, op, rhs, code_regions: code_regions.to_owned() }; - let slot = &mut self.expressions[expression_id]; - match slot { - None => *slot = Some(expression), - // If this expression ID slot has already been filled, it should - // contain identical information. - Some(ref previous_expression) => assert_eq!( - previous_expression, &expression, - "add_counter_expression: expression for id changed" - ), - } + pub(crate) fn mark_counter_id_seen(&mut self, id: CounterId) { + self.counters_seen.insert(id); } - /// Adds regions that will be marked as "unreachable", with a constant "zero counter". + /// Marks an expression ID as having been seen in an expression-used statement. #[instrument(level = "debug", skip(self))] - pub(crate) fn add_unreachable_regions(&mut self, code_regions: &[CodeRegion]) { - assert!(!code_regions.is_empty(), "unreachable regions always have code regions"); - self.unreachable_regions.extend_from_slice(code_regions); + pub(crate) fn mark_expression_id_seen(&mut self, id: ExpressionId) { + self.expressions_seen.insert(id); } - /// Perform some simplifications to make the final coverage mappings - /// slightly smaller. + /// Identify expressions that will always have a value of zero, and note + /// their IDs in [`ZeroExpressions`]. Mappings that refer to a zero expression + /// can instead become mappings to a constant zero value. /// /// This method mainly exists to preserve the simplifications that were /// already being performed by the Rust-side expression renumbering, so that /// the resulting coverage mappings don't get worse. - pub(crate) fn simplify_expressions(&mut self) { + fn identify_zero_expressions(&self) -> ZeroExpressions { // The set of expressions that either were optimized out entirely, or // have zero as both of their operands, and will therefore always have // a value of zero. Other expressions that refer to these as operands - // can have those operands replaced with `Operand::Zero`. + // can have those operands replaced with `CovTerm::Zero`. let mut zero_expressions = FxIndexSet::default(); - // For each expression, perform simplifications based on lower-numbered - // expressions, and then update the set of always-zero expressions if - // necessary. + // Simplify a copy of each expression based on lower-numbered expressions, + // and then update the set of always-zero expressions if necessary. // (By construction, expressions can only refer to other expressions - // that have lower IDs, so one simplification pass is sufficient.) - for (id, maybe_expression) in self.expressions.iter_enumerated_mut() { - let Some(expression) = maybe_expression else { - // If an expression is missing, it must have been optimized away, + // that have lower IDs, so one pass is sufficient.) + for (id, expression) in self.function_coverage_info.expressions.iter_enumerated() { + if !self.expressions_seen.contains(id) { + // If an expression was not seen, it must have been optimized away, // so any operand that refers to it can be replaced with zero. zero_expressions.insert(id); continue; + } + + // We don't need to simplify the actual expression data in the + // expressions list; we can just simplify a temporary copy and then + // use that to update the set of always-zero expressions. + let Expression { mut lhs, op, mut rhs } = *expression; + + // If an expression has an operand that is also an expression, the + // operand's ID must be strictly lower. This is what lets us find + // all zero expressions in one pass. + let assert_operand_expression_is_lower = |operand_id: ExpressionId| { + assert!( + operand_id < id, + "Operand {operand_id:?} should be less than {id:?} in {expression:?}", + ) }; // If an operand refers to an expression that is always zero, then - // that operand can be replaced with `Operand::Zero`. - let maybe_set_operand_to_zero = |operand: &mut Operand| match &*operand { - Operand::Expression(id) if zero_expressions.contains(id) => { - *operand = Operand::Zero; + // that operand can be replaced with `CovTerm::Zero`. + let maybe_set_operand_to_zero = |operand: &mut CovTerm| match *operand { + CovTerm::Expression(id) => { + assert_operand_expression_is_lower(id); + if zero_expressions.contains(&id) { + *operand = CovTerm::Zero; + } } _ => (), }; - maybe_set_operand_to_zero(&mut expression.lhs); - maybe_set_operand_to_zero(&mut expression.rhs); + maybe_set_operand_to_zero(&mut lhs); + maybe_set_operand_to_zero(&mut rhs); // Coverage counter values cannot be negative, so if an expression // involves subtraction from zero, assume that its RHS must also be zero. // (Do this after simplifications that could set the LHS to zero.) - if let Expression { lhs: Operand::Zero, op: Op::Subtract, .. } = expression { - expression.rhs = Operand::Zero; + if lhs == CovTerm::Zero && op == Op::Subtract { + rhs = CovTerm::Zero; } // After the above simplifications, if both operands are zero, then // we know that this expression is always zero too. - if let Expression { lhs: Operand::Zero, rhs: Operand::Zero, .. } = expression { + if lhs == CovTerm::Zero && rhs == CovTerm::Zero { zero_expressions.insert(id); } } + + ZeroExpressions(zero_expressions) } /// Return the source hash, generated from the HIR node structure, and used to indicate whether /// or not the source code structure changed between different compilations. pub fn source_hash(&self) -> u64 { - self.source_hash + if self.is_used { self.function_coverage_info.function_source_hash } else { 0 } } /// Generate an array of CounterExpressions, and an iterator over all `Counter`s and their @@ -204,91 +177,80 @@ impl<'tcx> FunctionCoverage<'tcx> { pub fn get_expressions_and_counter_regions( &self, ) -> (Vec<CounterExpression>, impl Iterator<Item = (Counter, &CodeRegion)>) { - assert!( - self.source_hash != 0 || !self.is_used, - "No counters provided the source_hash for used function: {:?}", - self.instance - ); + let zero_expressions = self.identify_zero_expressions(); - let counter_expressions = self.counter_expressions(); + let counter_expressions = self.counter_expressions(&zero_expressions); // Expression IDs are indices into `self.expressions`, and on the LLVM // side they will be treated as indices into `counter_expressions`, so // the two vectors should correspond 1:1. - assert_eq!(self.expressions.len(), counter_expressions.len()); + assert_eq!(self.function_coverage_info.expressions.len(), counter_expressions.len()); - let counter_regions = self.counter_regions(); - let expression_regions = self.expression_regions(); - let unreachable_regions = self.unreachable_regions(); + let counter_regions = self.counter_regions(zero_expressions); - let counter_regions = - counter_regions.chain(expression_regions.into_iter().chain(unreachable_regions)); (counter_expressions, counter_regions) } - fn counter_regions(&self) -> impl Iterator<Item = (Counter, &CodeRegion)> { - self.counters - .iter_enumerated() - // Filter out counter IDs that we never saw during MIR traversal. - // This can happen if a counter was optimized out by MIR transforms - // (and replaced with `CoverageKind::Unreachable` instead). - .filter_map(|(id, maybe_code_regions)| Some((id, maybe_code_regions.as_ref()?))) - .flat_map(|(id, code_regions)| { - let counter = Counter::counter_value_reference(id); - code_regions.iter().map(move |region| (counter, region)) - }) - } - /// Convert this function's coverage expression data into a form that can be /// passed through FFI to LLVM. - fn counter_expressions(&self) -> Vec<CounterExpression> { + fn counter_expressions(&self, zero_expressions: &ZeroExpressions) -> Vec<CounterExpression> { // We know that LLVM will optimize out any unused expressions before // producing the final coverage map, so there's no need to do the same // thing on the Rust side unless we're confident we can do much better. // (See `CounterExpressionsMinimizer` in `CoverageMappingWriter.cpp`.) - self.expressions + let counter_from_operand = |operand: CovTerm| match operand { + CovTerm::Expression(id) if zero_expressions.contains(id) => Counter::ZERO, + _ => Counter::from_term(operand), + }; + + self.function_coverage_info + .expressions .iter() - .map(|expression| match expression { - None => { - // This expression ID was allocated, but we never saw the - // actual expression, so it must have been optimized out. - // Replace it with a dummy expression, and let LLVM take - // care of omitting it from the expression list. - CounterExpression::DUMMY - } - &Some(Expression { lhs, op, rhs, .. }) => { - // Convert the operands and operator as normal. - CounterExpression::new( - Counter::from_operand(lhs), - match op { - Op::Add => ExprKind::Add, - Op::Subtract => ExprKind::Subtract, - }, - Counter::from_operand(rhs), - ) - } + .map(|&Expression { lhs, op, rhs }| CounterExpression { + lhs: counter_from_operand(lhs), + kind: match op { + Op::Add => ExprKind::Add, + Op::Subtract => ExprKind::Subtract, + }, + rhs: counter_from_operand(rhs), }) .collect::<Vec<_>>() } - fn expression_regions(&self) -> Vec<(Counter, &CodeRegion)> { - // Find all of the expression IDs that weren't optimized out AND have - // one or more attached code regions, and return the corresponding - // mappings as counter/region pairs. - self.expressions - .iter_enumerated() - .filter_map(|(id, maybe_expression)| { - let code_regions = &maybe_expression.as_ref()?.code_regions; - Some((id, code_regions)) - }) - .flat_map(|(id, code_regions)| { - let counter = Counter::expression(id); - code_regions.iter().map(move |code_region| (counter, code_region)) - }) - .collect::<Vec<_>>() + /// Converts this function's coverage mappings into an intermediate form + /// that will be used by `mapgen` when preparing for FFI. + fn counter_regions( + &self, + zero_expressions: ZeroExpressions, + ) -> impl Iterator<Item = (Counter, &CodeRegion)> { + // Historically, mappings were stored directly in counter/expression + // statements in MIR, and MIR optimizations would sometimes remove them. + // That's mostly no longer true, so now we detect cases where that would + // have happened, and zero out the corresponding mappings here instead. + let counter_for_term = move |term: CovTerm| { + let force_to_zero = match term { + CovTerm::Counter(id) => !self.counters_seen.contains(id), + CovTerm::Expression(id) => zero_expressions.contains(id), + CovTerm::Zero => false, + }; + if force_to_zero { Counter::ZERO } else { Counter::from_term(term) } + }; + + self.function_coverage_info.mappings.iter().map(move |mapping| { + let &Mapping { term, ref code_region } = mapping; + let counter = counter_for_term(term); + (counter, code_region) + }) } +} + +/// Set of expression IDs that are known to always evaluate to zero. +/// Any mapping or expression operand that refers to these expressions can have +/// that reference replaced with a constant zero value. +struct ZeroExpressions(FxIndexSet<ExpressionId>); - fn unreachable_regions(&self) -> impl Iterator<Item = (Counter, &CodeRegion)> { - self.unreachable_regions.iter().map(|region| (Counter::ZERO, region)) +impl ZeroExpressions { + fn contains(&self, id: ExpressionId) -> bool { + self.0.contains(&id) } } |