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|
pub use super::ffi::*;
use rustc_index::vec::{IndexSlice, IndexVec};
use rustc_middle::mir::coverage::{
CodeRegion, CounterValueReference, ExpressionOperandId, InjectedExpressionId,
InjectedExpressionIndex, MappedExpressionIndex, Op,
};
use rustc_middle::ty::Instance;
use rustc_middle::ty::TyCtxt;
#[derive(Clone, Debug, PartialEq)]
pub struct Expression {
lhs: ExpressionOperandId,
op: Op,
rhs: ExpressionOperandId,
region: Option<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. Counters and counter expressions have non-overlapping `id`s because they
/// can both be operands in an expression. 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."
#[derive(Debug)]
pub struct FunctionCoverage<'tcx> {
instance: Instance<'tcx>,
source_hash: u64,
is_used: bool,
counters: IndexVec<CounterValueReference, Option<CodeRegion>>,
expressions: IndexVec<InjectedExpressionIndex, Option<Expression>>,
unreachable_regions: Vec<CodeRegion>,
}
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)
}
/// 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)
}
fn create(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>, is_used: bool) -> Self {
let coverageinfo = tcx.coverageinfo(instance.def);
debug!(
"FunctionCoverage::create(instance={:?}) has coverageinfo={:?}. is_used={}",
instance, coverageinfo, is_used
);
Self {
instance,
source_hash: 0, // will be set with the first `add_counter()`
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(),
}
}
/// Returns true for a used (called) function, and false for an unused function.
pub fn is_used(&self) -> bool {
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 a code region to be counted by an injected counter intrinsic.
pub fn add_counter(&mut self, id: CounterValueReference, region: CodeRegion) {
if let Some(previous_region) = self.counters[id].replace(region.clone()) {
assert_eq!(previous_region, region, "add_counter: code region for id changed");
}
}
/// Both counters and "counter expressions" (or simply, "expressions") can be operands in other
/// expressions. Expression IDs start from `u32::MAX` and go down, so the range of expression
/// IDs will not overlap with the range of counter IDs. Counters and expressions can be added in
/// any order, and expressions can still be assigned contiguous (though descending) IDs, without
/// knowing what the last counter ID will be.
///
/// When storing the expression data in the `expressions` vector in the `FunctionCoverage`
/// struct, its vector index is computed, from the given expression ID, by subtracting from
/// `u32::MAX`.
///
/// Since the expression operands (`lhs` and `rhs`) can reference either counters or
/// expressions, an operand that references an expression also uses its original ID, descending
/// from `u32::MAX`. Theses operands are translated only during code generation, after all
/// counters and expressions have been added.
pub fn add_counter_expression(
&mut self,
expression_id: InjectedExpressionId,
lhs: ExpressionOperandId,
op: Op,
rhs: ExpressionOperandId,
region: Option<CodeRegion>,
) {
debug!(
"add_counter_expression({:?}, lhs={:?}, op={:?}, rhs={:?} at {:?}",
expression_id, lhs, op, rhs, region
);
let expression_index = self.expression_index(u32::from(expression_id));
debug_assert!(
expression_index.as_usize() < self.expressions.len(),
"expression_index {} is out of range for expressions.len() = {}
for {:?}",
expression_index.as_usize(),
self.expressions.len(),
self,
);
if let Some(previous_expression) = self.expressions[expression_index].replace(Expression {
lhs,
op,
rhs,
region: region.clone(),
}) {
assert_eq!(
previous_expression,
Expression { lhs, op, rhs, region },
"add_counter_expression: expression for id changed"
);
}
}
/// Add a region that will be marked as "unreachable", with a constant "zero counter".
pub fn add_unreachable_region(&mut self, region: CodeRegion) {
self.unreachable_regions.push(region)
}
/// 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
}
/// Generate an array of CounterExpressions, and an iterator over all `Counter`s and their
/// associated `Regions` (from which the LLVM-specific `CoverageMapGenerator` will create
/// `CounterMappingRegion`s.
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 counter_regions = self.counter_regions();
let (counter_expressions, expression_regions) = self.expressions_with_regions();
let unreachable_regions = self.unreachable_regions();
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_map(|(index, entry)| {
// Option::map() will return None to filter out missing counters. This may happen
// if, for example, a MIR-instrumented counter is removed during an optimization.
entry.as_ref().map(|region| (Counter::counter_value_reference(index), region))
})
}
fn expressions_with_regions(
&self,
) -> (Vec<CounterExpression>, impl Iterator<Item = (Counter, &CodeRegion)>) {
let mut counter_expressions = Vec::with_capacity(self.expressions.len());
let mut expression_regions = Vec::with_capacity(self.expressions.len());
let mut new_indexes = IndexVec::from_elem_n(None, self.expressions.len());
// This closure converts any `Expression` operand (`lhs` or `rhs` of the `Op::Add` or
// `Op::Subtract` operation) into its native `llvm::coverage::Counter::CounterKind` type
// and value. Operand ID value `0` maps to `CounterKind::Zero`; values in the known range
// of injected LLVM counters map to `CounterKind::CounterValueReference` (and the value
// matches the injected counter index); and any other value is converted into a
// `CounterKind::Expression` with the expression's `new_index`.
//
// Expressions will be returned from this function in a sequential vector (array) of
// `CounterExpression`, so the expression IDs must be mapped from their original,
// potentially sparse set of indexes, originally in reverse order from `u32::MAX`.
//
// An `Expression` as an operand will have already been encountered as an `Expression` with
// operands, so its new_index will already have been generated (as a 1-up index value).
// (If an `Expression` as an operand does not have a corresponding new_index, it was
// probably optimized out, after the expression was injected into the MIR, so it will
// get a `CounterKind::Zero` instead.)
//
// In other words, an `Expression`s at any given index can include other expressions as
// operands, but expression operands can only come from the subset of expressions having
// `expression_index`s lower than the referencing `Expression`. Therefore, it is
// reasonable to look up the new index of an expression operand while the `new_indexes`
// vector is only complete up to the current `ExpressionIndex`.
let id_to_counter = |new_indexes: &IndexSlice<
InjectedExpressionIndex,
Option<MappedExpressionIndex>,
>,
id: ExpressionOperandId| {
if id == ExpressionOperandId::ZERO {
Some(Counter::zero())
} else if id.index() < self.counters.len() {
debug_assert!(
id.index() > 0,
"ExpressionOperandId indexes for counters are 1-based, but this id={}",
id.index()
);
// Note: Some codegen-injected Counters may be only referenced by `Expression`s,
// and may not have their own `CodeRegion`s,
let index = CounterValueReference::from(id.index());
// Note, the conversion to LLVM `Counter` adjusts the index to be zero-based.
Some(Counter::counter_value_reference(index))
} else {
let index = self.expression_index(u32::from(id));
self.expressions
.get(index)
.expect("expression id is out of range")
.as_ref()
// If an expression was optimized out, assume it would have produced a count
// of zero. This ensures that expressions dependent on optimized-out
// expressions are still valid.
.map_or(Some(Counter::zero()), |_| new_indexes[index].map(Counter::expression))
}
};
for (original_index, expression) in
self.expressions.iter_enumerated().filter_map(|(original_index, entry)| {
// Option::map() will return None to filter out missing expressions. This may happen
// if, for example, a MIR-instrumented expression is removed during an optimization.
entry.as_ref().map(|expression| (original_index, expression))
})
{
let optional_region = &expression.region;
let Expression { lhs, op, rhs, .. } = *expression;
if let Some(Some((lhs_counter, mut rhs_counter))) = id_to_counter(&new_indexes, lhs)
.map(|lhs_counter| {
id_to_counter(&new_indexes, rhs).map(|rhs_counter| (lhs_counter, rhs_counter))
})
{
if lhs_counter.is_zero() && op.is_subtract() {
// The left side of a subtraction was probably optimized out. As an example,
// a branch condition might be evaluated as a constant expression, and the
// branch could be removed, dropping unused counters in the process.
//
// Since counters are unsigned, we must assume the result of the expression
// can be no more and no less than zero. An expression known to evaluate to zero
// does not need to be added to the coverage map.
//
// Coverage test `loops_branches.rs` includes multiple variations of branches
// based on constant conditional (literal `true` or `false`), and demonstrates
// that the expected counts are still correct.
debug!(
"Expression subtracts from zero (assume unreachable): \
original_index={:?}, lhs={:?}, op={:?}, rhs={:?}, region={:?}",
original_index, lhs, op, rhs, optional_region,
);
rhs_counter = Counter::zero();
}
debug_assert!(
lhs_counter.is_zero()
// Note: with `as usize` the ID _could_ overflow/wrap if `usize = u16`
|| ((lhs_counter.zero_based_id() as usize)
<= usize::max(self.counters.len(), self.expressions.len())),
"lhs id={} > both counters.len()={} and expressions.len()={}
({:?} {:?} {:?})",
lhs_counter.zero_based_id(),
self.counters.len(),
self.expressions.len(),
lhs_counter,
op,
rhs_counter,
);
debug_assert!(
rhs_counter.is_zero()
// Note: with `as usize` the ID _could_ overflow/wrap if `usize = u16`
|| ((rhs_counter.zero_based_id() as usize)
<= usize::max(self.counters.len(), self.expressions.len())),
"rhs id={} > both counters.len()={} and expressions.len()={}
({:?} {:?} {:?})",
rhs_counter.zero_based_id(),
self.counters.len(),
self.expressions.len(),
lhs_counter,
op,
rhs_counter,
);
// Both operands exist. `Expression` operands exist in `self.expressions` and have
// been assigned a `new_index`.
let mapped_expression_index =
MappedExpressionIndex::from(counter_expressions.len());
let expression = CounterExpression::new(
lhs_counter,
match op {
Op::Add => ExprKind::Add,
Op::Subtract => ExprKind::Subtract,
},
rhs_counter,
);
debug!(
"Adding expression {:?} = {:?}, region: {:?}",
mapped_expression_index, expression, optional_region
);
counter_expressions.push(expression);
new_indexes[original_index] = Some(mapped_expression_index);
if let Some(region) = optional_region {
expression_regions.push((Counter::expression(mapped_expression_index), region));
}
} else {
bug!(
"expression has one or more missing operands \
original_index={:?}, lhs={:?}, op={:?}, rhs={:?}, region={:?}",
original_index,
lhs,
op,
rhs,
optional_region,
);
}
}
(counter_expressions, expression_regions.into_iter())
}
fn unreachable_regions(&self) -> impl Iterator<Item = (Counter, &CodeRegion)> {
self.unreachable_regions.iter().map(|region| (Counter::zero(), region))
}
fn expression_index(&self, id_descending_from_max: u32) -> InjectedExpressionIndex {
debug_assert!(id_descending_from_max >= self.counters.len() as u32);
InjectedExpressionIndex::from(u32::MAX - id_descending_from_max)
}
}
|