bjoernager/rust
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coverage: Store the number of counters/expressions in function coverage info

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Coverage codegen can now allocate arrays based on the number of
counters/expressions originally used by the instrumentor.

The existing query that inspects coverage statements is still used for
determining the number of counters passed to `llvm.instrprof.increment`. If
some high-numbered counters were removed by MIR optimizations, the instrumented
binary can potentially use less memory and disk space at runtime.
This commit is contained in:
Zalathar 2023-09-13 12:15:40 +10:00
parent c479bc7f3b
commit a18c5f3b75
8 changed files with 69 additions and 102 deletions
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8
compiler/rustc_mir_transform/src/coverage/counters.rs
View file

@ -126,6 +126,14 @@ impl CoverageCounters {
next
}
pub(super) fn num_counters(&self) -> usize {
self.next_counter_id.as_usize()
}
pub(super) fn num_expressions(&self) -> usize {
self.next_expression_id.as_usize()
}
fn set_bcb_counter(
&mut self,
bcb: BasicCoverageBlock,

2
compiler/rustc_mir_transform/src/coverage/mod.rs
View file

@ -214,6 +214,8 @@ impl<'a, 'tcx> Instrumentor<'a, 'tcx> {
self.mir_body.function_coverage_info = Some(Box::new(FunctionCoverageInfo {
function_source_hash: self.function_source_hash,
num_counters: self.coverage_counters.num_counters(),
num_expressions: self.coverage_counters.num_expressions(),
}));
}

89
compiler/rustc_mir_transform/src/coverage/query.rs
View file

@ -2,92 +2,33 @@ use super::*;
use rustc_data_structures::captures::Captures;
use rustc_middle::mir::coverage::*;
use rustc_middle::mir::{self, Body, Coverage, CoverageInfo};
use rustc_middle::mir::{self, Body, Coverage, CoverageIdsInfo};
use rustc_middle::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.coverage_ids_info = |tcx, def_id| coverage_ids_info(tcx, def_id);
providers.covered_code_regions = |tcx, def_id| covered_code_regions(tcx, def_id);
}
/// Coverage codegen needs to know the total number of counter IDs and expression IDs that have
/// been used by a function's coverage mappings. These totals are used to create vectors to hold
/// the relevant counter and expression data, and the maximum counter ID (+ 1) is also needed by
/// the `llvm.instrprof.increment` intrinsic.
///
/// 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.
///
/// It's possible for a coverage expression to remain in MIR while one or both of its operands
/// have been optimized away. To avoid problems in codegen, we include those operands' IDs when
/// determining the maximum counter/expression ID, even if the underlying counter/expression is
/// no longer present.
struct CoverageVisitor {
max_counter_id: CounterId,
max_expression_id: ExpressionId,
}
impl CoverageVisitor {
/// Updates `max_counter_id` to the maximum encountered counter ID.
#[inline(always)]
fn update_max_counter_id(&mut self, counter_id: CounterId) {
self.max_counter_id = self.max_counter_id.max(counter_id);
}
/// Updates `max_expression_id` to the maximum encountered expression ID.
#[inline(always)]
fn update_max_expression_id(&mut self, expression_id: ExpressionId) {
self.max_expression_id = self.max_expression_id.max(expression_id);
}
fn update_from_expression_operand(&mut self, operand: Operand) {
match operand {
Operand::Counter(id) => self.update_max_counter_id(id),
Operand::Expression(id) => self.update_max_expression_id(id),
Operand::Zero => {}
}
}
fn visit_body(&mut self, body: &Body<'_>) {
for coverage in all_coverage_in_mir_body(body) {
self.visit_coverage(coverage);
}
}
fn visit_coverage(&mut self, coverage: &Coverage) {
match coverage.kind {
CoverageKind::Counter { id, .. } => self.update_max_counter_id(id),
CoverageKind::Expression { id, lhs, rhs, .. } => {
self.update_max_expression_id(id);
self.update_from_expression_operand(lhs);
self.update_from_expression_operand(rhs);
}
CoverageKind::Unreachable => {}
}
}
}
fn coverageinfo<'tcx>(tcx: TyCtxt<'tcx>, instance_def: ty::InstanceDef<'tcx>) -> CoverageInfo {
/// Query implementation for `coverage_ids_info`.
fn coverage_ids_info<'tcx>(
tcx: TyCtxt<'tcx>,
instance_def: ty::InstanceDef<'tcx>,
) -> CoverageIdsInfo {
let mir_body = tcx.instance_mir(instance_def);
let mut coverage_visitor = CoverageVisitor {
max_counter_id: CounterId::START,
max_expression_id: ExpressionId::START,
};
let max_counter_id = all_coverage_in_mir_body(mir_body)
.filter_map(|coverage| match coverage.kind {
CoverageKind::Counter { id } => Some(id),
_ => None,
})
.max()
.unwrap_or(CounterId::START);
coverage_visitor.visit_body(mir_body);
// Add 1 to the highest IDs to get the total number of IDs.
CoverageInfo {
num_counters: (coverage_visitor.max_counter_id + 1).as_u32(),
num_expressions: (coverage_visitor.max_expression_id + 1).as_u32(),
}
CoverageIdsInfo { max_counter_id }
}
fn covered_code_regions(tcx: TyCtxt<'_>, def_id: DefId) -> Vec<&CodeRegion> {