diff options
Diffstat (limited to 'compiler/rustc_mir_transform/src/coverage/query.rs')
| -rw-r--r-- | compiler/rustc_mir_transform/src/coverage/query.rs | 191 |
1 files changed, 191 insertions, 0 deletions
diff --git a/compiler/rustc_mir_transform/src/coverage/query.rs b/compiler/rustc_mir_transform/src/coverage/query.rs new file mode 100644 index 00000000000..760f16eae6b --- /dev/null +++ b/compiler/rustc_mir_transform/src/coverage/query.rs @@ -0,0 +1,191 @@ +use super::*; + +use rustc_middle::mir::coverage::*; +use rustc_middle::mir::{self, Body, Coverage, CoverageInfo}; +use rustc_middle::ty::query::Providers; +use rustc_middle::ty::{self, TyCtxt}; +use rustc_span::def_id::DefId; + +/// A `query` provider for retrieving coverage information injected into MIR. +pub(crate) fn provide(providers: &mut Providers) { + providers.coverageinfo = |tcx, def_id| coverageinfo(tcx, def_id); + providers.covered_file_name = |tcx, def_id| covered_file_name(tcx, def_id); + providers.covered_code_regions = |tcx, def_id| covered_code_regions(tcx, def_id); +} + +/// The `num_counters` argument to `llvm.instrprof.increment` is the max counter_id + 1, or in +/// other words, the number of counter value references injected into the MIR (plus 1 for the +/// reserved `ZERO` counter, which uses counter ID `0` when included in an expression). Injected +/// counters have a counter ID from `1..num_counters-1`. +/// +/// `num_expressions` is the number of counter expressions added to the MIR body. +/// +/// Both `num_counters` and `num_expressions` are used to initialize new vectors, during backend +/// code generate, to lookup counters and expressions by simple u32 indexes. +/// +/// MIR optimization may split and duplicate some BasicBlock sequences, or optimize out some code +/// including injected counters. (It is OK if some counters are optimized out, but those counters +/// are still included in the total `num_counters` or `num_expressions`.) Simply counting the +/// calls may not work; but computing the number of counters or expressions by adding `1` to the +/// highest ID (for a given instrumented function) is valid. +/// +/// This visitor runs twice, first with `add_missing_operands` set to `false`, to find the maximum +/// counter ID and maximum expression ID based on their enum variant `id` fields; then, as a +/// safeguard, with `add_missing_operands` set to `true`, to find any other counter or expression +/// IDs referenced by expression operands, if not already seen. +/// +/// Ideally, each operand ID in a MIR `CoverageKind::Expression` will have a separate MIR `Coverage` +/// statement for the `Counter` or `Expression` with the referenced ID. but since current or future +/// MIR optimizations can theoretically optimize out segments of a MIR, it may not be possible to +/// guarantee this, so the second pass ensures the `CoverageInfo` counts include all referenced IDs. +struct CoverageVisitor { + info: CoverageInfo, + add_missing_operands: bool, +} + +impl CoverageVisitor { + /// Updates `num_counters` to the maximum encountered zero-based counter_id plus 1. Note the + /// final computed number of counters should be the number of all `CoverageKind::Counter` + /// statements in the MIR *plus one* for the implicit `ZERO` counter. + #[inline(always)] + fn update_num_counters(&mut self, counter_id: u32) { + self.info.num_counters = std::cmp::max(self.info.num_counters, counter_id + 1); + } + + /// Computes an expression index for each expression ID, and updates `num_expressions` to the + /// maximum encountered index plus 1. + #[inline(always)] + fn update_num_expressions(&mut self, expression_id: u32) { + let expression_index = u32::MAX - expression_id; + self.info.num_expressions = std::cmp::max(self.info.num_expressions, expression_index + 1); + } + + fn update_from_expression_operand(&mut self, operand_id: u32) { + if operand_id >= self.info.num_counters { + let operand_as_expression_index = u32::MAX - operand_id; + if operand_as_expression_index >= self.info.num_expressions { + // The operand ID is outside the known range of counter IDs and also outside the + // known range of expression IDs. In either case, the result of a missing operand + // (if and when used in an expression) will be zero, so from a computation + // perspective, it doesn't matter whether it is interepretted as a counter or an + // expression. + // + // However, the `num_counters` and `num_expressions` query results are used to + // allocate arrays when generating the coverage map (during codegen), so choose + // the type that grows either `num_counters` or `num_expressions` the least. + if operand_id - self.info.num_counters + < operand_as_expression_index - self.info.num_expressions + { + self.update_num_counters(operand_id) + } else { + self.update_num_expressions(operand_id) + } + } + } + } + + fn visit_body(&mut self, body: &Body<'_>) { + for bb_data in body.basic_blocks().iter() { + for statement in bb_data.statements.iter() { + if let StatementKind::Coverage(box ref coverage) = statement.kind { + if is_inlined(body, statement) { + continue; + } + self.visit_coverage(coverage); + } + } + } + } + + fn visit_coverage(&mut self, coverage: &Coverage) { + if self.add_missing_operands { + match coverage.kind { + CoverageKind::Expression { lhs, rhs, .. } => { + self.update_from_expression_operand(u32::from(lhs)); + self.update_from_expression_operand(u32::from(rhs)); + } + _ => {} + } + } else { + match coverage.kind { + CoverageKind::Counter { id, .. } => { + self.update_num_counters(u32::from(id)); + } + CoverageKind::Expression { id, .. } => { + self.update_num_expressions(u32::from(id)); + } + _ => {} + } + } + } +} + +fn coverageinfo<'tcx>(tcx: TyCtxt<'tcx>, instance_def: ty::InstanceDef<'tcx>) -> CoverageInfo { + let mir_body = tcx.instance_mir(instance_def); + + let mut coverage_visitor = CoverageVisitor { + // num_counters always has at least the `ZERO` counter. + info: CoverageInfo { num_counters: 1, num_expressions: 0 }, + add_missing_operands: false, + }; + + coverage_visitor.visit_body(mir_body); + + coverage_visitor.add_missing_operands = true; + coverage_visitor.visit_body(mir_body); + + coverage_visitor.info +} + +fn covered_file_name<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> Option<Symbol> { + if tcx.is_mir_available(def_id) { + let body = mir_body(tcx, def_id); + for bb_data in body.basic_blocks().iter() { + for statement in bb_data.statements.iter() { + if let StatementKind::Coverage(box ref coverage) = statement.kind { + if let Some(code_region) = coverage.code_region.as_ref() { + if is_inlined(body, statement) { + continue; + } + return Some(code_region.file_name); + } + } + } + } + } + return None; +} + +fn covered_code_regions<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> Vec<&'tcx CodeRegion> { + let body = mir_body(tcx, def_id); + body.basic_blocks() + .iter() + .map(|data| { + data.statements.iter().filter_map(|statement| match statement.kind { + StatementKind::Coverage(box ref coverage) => { + if is_inlined(body, statement) { + None + } else { + coverage.code_region.as_ref() // may be None + } + } + _ => None, + }) + }) + .flatten() + .collect() +} + +fn is_inlined(body: &Body<'_>, statement: &Statement<'_>) -> bool { + let scope_data = &body.source_scopes[statement.source_info.scope]; + scope_data.inlined.is_some() || scope_data.inlined_parent_scope.is_some() +} + +/// This function ensures we obtain the correct MIR for the given item irrespective of +/// whether that means const mir or runtime mir. For `const fn` this opts for runtime +/// mir. +fn mir_body<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx mir::Body<'tcx> { + let id = ty::WithOptConstParam::unknown(def_id); + let def = ty::InstanceDef::Item(id); + tcx.instance_mir(def) +} |