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Refactor MIR coverage instrumentation

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Lays a better foundation for injecting more counters in each function.
This commit is contained in:
Rich Kadel 2020-07-27 16:25:08 -07:00
parent 12ddd6073a
commit 20f55c193d
5 changed files with 151 additions and 120 deletions
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8
src/librustc_codegen_llvm/coverageinfo/mapgen.rs
View File

@ -24,7 +24,7 @@ use std::ffi::CString;
/// replicated for Rust's Coverage Map.
pub fn finalize<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) {
let function_coverage_map = cx.coverage_context().take_function_coverage_map();
if function_coverage_map.len() == 0 {
if function_coverage_map.is_empty() {
// This module has no functions with coverage instrumentation
return;
}
@ -81,7 +81,7 @@ struct CoverageMapGenerator {
impl CoverageMapGenerator {
fn new() -> Self {
Self { filenames: Vec::new(), filename_to_index: FxHashMap::<CString, u32>::default() }
Self { filenames: Vec::new(), filename_to_index: FxHashMap::default() }
}
/// Using the `expressions` and `counter_regions` collected for the current function, generate
@ -95,7 +95,7 @@ impl CoverageMapGenerator {
coverage_mappings_buffer: &RustString,
) {
let mut counter_regions = counter_regions.collect::<Vec<_>>();
if counter_regions.len() == 0 {
if counter_regions.is_empty() {
return;
}
@ -109,7 +109,7 @@ impl CoverageMapGenerator {
// `file_id` (indexing files referenced by the current function), and construct the
// function-specific `virtual_file_mapping` from `file_id` to its index in the module's
// `filenames` array.
counter_regions.sort_by_key(|(_counter, region)| *region);
counter_regions.sort_unstable_by_key(|(_counter, region)| *region);
for (counter, region) in counter_regions {
let (file_path, start_line, start_col, end_line, end_col) = region.file_start_and_end();
let same_file = current_file_path.as_ref().map_or(false, |p| p == file_path);

25
src/librustc_codegen_llvm/coverageinfo/mod.rs
View File

@ -110,36 +110,37 @@ impl CoverageInfoBuilderMethods<'tcx> for Builder<'a, 'll, 'tcx> {
}
}
/// Aligns to C++ struct llvm::coverage::Counter::CounterKind.
/// The order of discrimiators is important.
/// Aligns with [llvm::coverage::CounterMappingRegion::RegionKind](https://github.com/rust-lang/llvm-project/blob/rustc/10.0-2020-05-05/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L205-L221)
#[derive(Copy, Clone, Debug)]
#[repr(C)]
enum RegionKind {
/// A CodeRegion associates some code with a counter
CodeRegion,
CodeRegion = 0,
/// An ExpansionRegion represents a file expansion region that associates
/// a source range with the expansion of a virtual source file, such as
/// for a macro instantiation or #include file.
ExpansionRegion,
ExpansionRegion = 1,
/// A SkippedRegion represents a source range with code that was skipped
/// by a preprocessor or similar means.
SkippedRegion,
SkippedRegion = 2,
/// A GapRegion is like a CodeRegion, but its count is only set as the
/// line execution count when its the only region in the line.
GapRegion,
GapRegion = 3,
}
/// This struct provides LLVM's representation of a "CoverageMappingRegion", encoded into the
/// coverage map in accordance with LLVM's "Coverage Mapping Format". The struct composes fields
/// representing the `Counter` type and value(s) (injected counter ID, or expression type and
/// operands), the source file (an indirect index into a "filenames array", encoded separately),
/// and source location (start and end positions of the represented code region).
/// coverage map, in accordance with the
/// [LLVM Code Coverage Mapping Format](https://github.com/rust-lang/llvm-project/blob/llvmorg-8.0.0/llvm/docs/CoverageMappingFormat.rst#llvm-code-coverage-mapping-format).
/// The struct composes fields representing the `Counter` type and value(s) (injected counter ID,
/// or expression type and operands), the source file (an indirect index into a "filenames array",
/// encoded separately), and source location (start and end positions of the represented code
/// region).
///
/// Aligns to C++ struct llvm::coverage::CounterMappingRegion.
/// The order of fields is important.
/// Aligns with [llvm::coverage::CounterMappingRegion](https://github.com/rust-lang/llvm-project/blob/rustc/10.0-2020-05-05/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L223-L226)
/// Important: The Rust struct layout (order and types of fields) must match its C++ counterpart.
#[derive(Copy, Clone, Debug)]
#[repr(C)]
pub struct CounterMappingRegion {

32
src/librustc_codegen_ssa/coverageinfo/map.rs
View File

@ -7,26 +7,28 @@ use std::cmp::{Ord, Ordering};
use std::fmt;
use std::path::PathBuf;
/// Aligns to C++ struct llvm::coverage::Counter::CounterKind.
/// The order of discriminators is important.
/// Aligns with [llvm::coverage::Counter::CounterKind](https://github.com/rust-lang/llvm-project/blob/rustc/10.0-2020-05-05/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L91)
#[derive(Copy, Clone, Debug)]
#[repr(C)]
enum CounterKind {
Zero,
CounterValueReference,
Expression,
Zero = 0,
CounterValueReference = 1,
Expression = 2,
}
/// Aligns to C++ struct llvm::coverage::Counter. Note that `id` has
/// different interpretations, depending on the `kind`:
/// A reference to an instance of an abstract "counter" that will yield a value in a coverage
/// report. Note that `id` has different interpretations, depending on the `kind`:
/// * For `CounterKind::Zero`, `id` is assumed to be `0`
/// * For `CounterKind::CounterValueReference`, `id` matches the `counter_id` of the injected
/// instrumentation counter (the `index` argument to the LLVM intrinsic `instrprof.increment()`)
/// * For `CounterKind::Expression`, `id` is the index into the array of counter expressions.
/// The order of fields is important.
/// * For `CounterKind::Expression`, `id` is the index into the coverage map's array of counter
/// expressions.
/// Aligns with [llvm::coverage::Counter](https://github.com/rust-lang/llvm-project/blob/rustc/10.0-2020-05-05/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L98-L99)
/// Important: The Rust struct layout (order and types of fields) must match its C++ counterpart.
#[derive(Copy, Clone, Debug)]
#[repr(C)]
pub struct Counter {
// Important: The layout (order and types of fields) must match its C++ counterpart.
kind: CounterKind,
id: u32,
}
@ -45,21 +47,19 @@ impl Counter {
}
}
/// Aligns to C++ struct llvm::coverage::CounterExpression::ExprKind.
/// The order of discriminators is important.
/// Aligns with [llvm::coverage::CounterExpression::ExprKind](https://github.com/rust-lang/llvm-project/blob/rustc/10.0-2020-05-05/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L146)
#[derive(Copy, Clone, Debug)]
#[repr(C)]
pub enum ExprKind {
Subtract,
Add,
Subtract = 0,
Add = 1,
}
/// Aligns to C++ struct llvm::coverage::CounterExpression.
/// The order of fields is important.
/// Aligns with [llvm::coverage::CounterExpression](https://github.com/rust-lang/llvm-project/blob/rustc/10.0-2020-05-05/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h#L147-L148)
/// Important: The Rust struct layout (order and types of fields) must match its C++ counterpart.
#[derive(Copy, Clone, Debug)]
#[repr(C)]
pub struct CounterExpression {
// Note the field order is important.
kind: ExprKind,
lhs: Counter,
rhs: Counter,

184
src/librustc_mir/transform/instrument_coverage.rs
View File

@ -7,10 +7,9 @@ use rustc_middle::hir;
use rustc_middle::ich::StableHashingContext;
use rustc_middle::mir::coverage::*;
use rustc_middle::mir::interpret::Scalar;
use rustc_middle::mir::CoverageInfo;
use rustc_middle::mir::{
self, traversal, BasicBlock, BasicBlockData, Operand, Place, SourceInfo, StatementKind,
Terminator, TerminatorKind, START_BLOCK,
self, traversal, BasicBlock, BasicBlockData, CoverageInfo, Operand, Place, SourceInfo,
SourceScope, StatementKind, Terminator, TerminatorKind,
};
use rustc_middle::ty;
use rustc_middle::ty::query::Providers;
@ -41,14 +40,14 @@ fn coverageinfo_from_mir<'tcx>(tcx: TyCtxt<'tcx>, mir_def_id: DefId) -> Coverage
tcx.require_lang_item(lang_items::CoverageCounterSubtractFnLangItem, None);
// The `num_counters` argument to `llvm.instrprof.increment` is the number of injected
// counters, with each counter having an index from `0..num_counters-1`. MIR optimization
// counters, with each counter having a counter ID from `0..num_counters-1`. MIR optimization
// may split and duplicate some BasicBlock sequences. Simply counting the calls may not
// not work; but computing the num_counters by adding `1` to the highest index (for a given
// work; but computing the num_counters by adding `1` to the highest counter_id (for a given
// instrumented function) is valid.
//
// `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 their simple u32 indexes.
// code generate, to lookup counters and expressions by simple u32 indexes.
let mut num_counters: u32 = 0;
let mut num_expressions: u32 = 0;
for terminator in
@ -57,27 +56,26 @@ fn coverageinfo_from_mir<'tcx>(tcx: TyCtxt<'tcx>, mir_def_id: DefId) -> Coverage
if let TerminatorKind::Call { func: Operand::Constant(func), args, .. } = &terminator.kind {
match func.literal.ty.kind {
FnDef(id, _) if id == count_code_region_fn => {
let index_arg =
let counter_id_arg =
args.get(count_code_region_args::COUNTER_ID).expect("arg found");
let counter_index = mir::Operand::scalar_from_const(index_arg)
let counter_id = mir::Operand::scalar_from_const(counter_id_arg)
.to_u32()
.expect("index arg is u32");
num_counters = std::cmp::max(num_counters, counter_index + 1);
.expect("counter_id arg is u32");
num_counters = std::cmp::max(num_counters, counter_id + 1);
}
FnDef(id, _)
if id == coverage_counter_add_fn || id == coverage_counter_subtract_fn =>
{
let index_arg = args
let expression_id_arg = args
.get(coverage_counter_expression_args::EXPRESSION_ID)
.expect("arg found");
let translated_index = mir::Operand::scalar_from_const(index_arg)
let id_descending_from_max = mir::Operand::scalar_from_const(expression_id_arg)
.to_u32()
.expect("index arg is u32");
// Counter expressions start with "translated indexes", descending from
// `u32::MAX`, so the range of expression indexes is disjoint from the range of
// counter indexes. This way, both counters and expressions can be operands in
// other expressions.
let expression_index = u32::MAX - translated_index;
.expect("expression_id arg is u32");
// Counter expressions are initially assigned IDs descending from `u32::MAX`, so
// the range of expression IDs is disjoint from the range of counter IDs. This
// way, both counters and expressions can be operands in other expressions.
let expression_index = u32::MAX - id_descending_from_max;
num_expressions = std::cmp::max(num_expressions, expression_index + 1);
}
_ => {}
@ -97,12 +95,10 @@ fn call_terminators(data: &'tcx BasicBlockData<'tcx>) -> Option<&'tcx Terminator
impl<'tcx> MirPass<'tcx> for InstrumentCoverage {
fn run_pass(&self, tcx: TyCtxt<'tcx>, src: MirSource<'tcx>, mir_body: &mut mir::Body<'tcx>) {
if tcx.sess.opts.debugging_opts.instrument_coverage {
// If the InstrumentCoverage pass is called on promoted MIRs, skip them.
// See: https://github.com/rust-lang/rust/pull/73011#discussion_r438317601
if src.promoted.is_none() {
Instrumentor::new(tcx, src, mir_body).inject_counters();
}
// If the InstrumentCoverage pass is called on promoted MIRs, skip them.
// See: https://github.com/rust-lang/rust/pull/73011#discussion_r438317601
if src.promoted.is_none() {
Instrumentor::new(tcx, src, mir_body).inject_counters();
}
}
}
@ -113,6 +109,12 @@ enum Op {
Subtract,
}
struct InjectedCall<'tcx> {
func: Operand<'tcx>,
args: Vec<Operand<'tcx>>,
inject_at: Span,
}
struct Instrumentor<'a, 'tcx> {
tcx: TyCtxt<'tcx>,
mir_def_id: DefId,
@ -147,11 +149,8 @@ impl<'a, 'tcx> Instrumentor<'a, 'tcx> {
}
/// Expression IDs start from u32::MAX and go down because a CounterExpression can reference
/// (add or subtract counts) of both Counter regions and CounterExpression regions. The indexes
/// of each type of region must be contiguous, but also must be unique across both sets.
/// The expression IDs are eventually translated into region indexes (starting after the last
/// counter index, for the given function), during backend code generation, by the helper method
/// `rustc_codegen_ssa::coverageinfo::map::FunctionCoverage::translate_expressions()`.
/// (add or subtract counts) of both Counter regions and CounterExpression regions. The counter
/// expression operand IDs must be unique across both types.
fn next_expression(&mut self) -> u32 {
assert!(self.num_counters < u32::MAX - self.num_expressions);
let next = u32::MAX - self.num_expressions;
@ -171,17 +170,25 @@ impl<'a, 'tcx> Instrumentor<'a, 'tcx> {
}
fn inject_counters(&mut self) {
let mir_body = &self.mir_body;
let body_span = self.hir_body.value.span;
debug!(
"instrumenting {:?}, span: {}",
self.mir_def_id,
self.tcx.sess.source_map().span_to_string(body_span)
);
debug!("instrumenting {:?}, span: {:?}", self.mir_def_id, body_span);
// FIXME(richkadel): As a first step, counters are only injected at the top of each
// function. The complete solution will inject counters at each conditional code branch.
let next_block = START_BLOCK;
self.inject_counter(body_span, next_block);
let _ignore = mir_body;
let id = self.next_counter();
let function_source_hash = self.function_source_hash();
let code_region = body_span;
let scope = rustc_middle::mir::OUTERMOST_SOURCE_SCOPE;
let is_cleanup = false;
let next_block = rustc_middle::mir::START_BLOCK;
self.inject_call(
self.make_counter(id, function_source_hash, code_region),
scope,
is_cleanup,
next_block,
);
// FIXME(richkadel): The next step to implement source based coverage analysis will be
// instrumenting branches within functions, and some regions will be counted by "counter
@ -190,57 +197,68 @@ impl<'a, 'tcx> Instrumentor<'a, 'tcx> {
let fake_use = false;
if fake_use {
let add = false;
if add {
self.inject_counter_expression(body_span, next_block, 1, Op::Add, 2);
} else {
self.inject_counter_expression(body_span, next_block, 1, Op::Subtract, 2);
}
let lhs = 1;
let op = if add { Op::Add } else { Op::Subtract };
let rhs = 2;
let code_region = body_span;
let scope = rustc_middle::mir::OUTERMOST_SOURCE_SCOPE;
let is_cleanup = false;
let next_block = rustc_middle::mir::START_BLOCK;
let id = self.next_expression();
self.inject_call(
self.make_expression(id, code_region, lhs, op, rhs),
scope,
is_cleanup,
next_block,
);
}
}
fn inject_counter(&mut self, code_region: Span, next_block: BasicBlock) -> u32 {
let counter_id = self.next_counter();
let function_source_hash = self.function_source_hash();
let injection_point = code_region.shrink_to_lo();
fn make_counter(
&self,
id: u32,
function_source_hash: u64,
code_region: Span,
) -> InjectedCall<'tcx> {
let inject_at = code_region.shrink_to_lo();
let count_code_region_fn = function_handle(
let func = function_handle(
self.tcx,
self.tcx.require_lang_item(lang_items::CountCodeRegionFnLangItem, None),
injection_point,
inject_at,
);
let mut args = Vec::new();
use count_code_region_args::*;
debug_assert_eq!(FUNCTION_SOURCE_HASH, args.len());
args.push(self.const_u64(function_source_hash, injection_point));
args.push(self.const_u64(function_source_hash, inject_at));
debug_assert_eq!(COUNTER_ID, args.len());
args.push(self.const_u32(counter_id, injection_point));
args.push(self.const_u32(id, inject_at));
debug_assert_eq!(START_BYTE_POS, args.len());
args.push(self.const_u32(code_region.lo().to_u32(), injection_point));
args.push(self.const_u32(code_region.lo().to_u32(), inject_at));
debug_assert_eq!(END_BYTE_POS, args.len());
args.push(self.const_u32(code_region.hi().to_u32(), injection_point));
args.push(self.const_u32(code_region.hi().to_u32(), inject_at));
self.inject_call(count_code_region_fn, args, injection_point, next_block);
counter_id
InjectedCall { func, args, inject_at }
}
fn inject_counter_expression(
&mut self,
fn make_expression(
&self,
id: u32,
code_region: Span,
next_block: BasicBlock,
lhs: u32,
op: Op,
rhs: u32,
) -> u32 {
let expression_id = self.next_expression();
let injection_point = code_region.shrink_to_lo();
) -> InjectedCall<'tcx> {
let inject_at = code_region.shrink_to_lo();
let count_code_region_fn = function_handle(
let func = function_handle(
self.tcx,
self.tcx.require_lang_item(
match op {
@ -249,43 +267,51 @@ impl<'a, 'tcx> Instrumentor<'a, 'tcx> {
},
None,
),
injection_point,
inject_at,
);
let mut args = Vec::new();
use coverage_counter_expression_args::*;
debug_assert_eq!(EXPRESSION_ID, args.len());
args.push(self.const_u32(expression_id, injection_point));
args.push(self.const_u32(id, inject_at));
debug_assert_eq!(LEFT_ID, args.len());
args.push(self.const_u32(lhs, injection_point));
args.push(self.const_u32(lhs, inject_at));
debug_assert_eq!(RIGHT_ID, args.len());
args.push(self.const_u32(rhs, injection_point));
args.push(self.const_u32(rhs, inject_at));
debug_assert_eq!(START_BYTE_POS, args.len());
args.push(self.const_u32(code_region.lo().to_u32(), injection_point));
args.push(self.const_u32(code_region.lo().to_u32(), inject_at));
debug_assert_eq!(END_BYTE_POS, args.len());
args.push(self.const_u32(code_region.hi().to_u32(), injection_point));
args.push(self.const_u32(code_region.hi().to_u32(), inject_at));
self.inject_call(count_code_region_fn, args, injection_point, next_block);
expression_id
InjectedCall { func, args, inject_at }
}
fn inject_call(
&mut self,
func: Operand<'tcx>,
args: Vec<Operand<'tcx>>,
fn_span: Span,
call: InjectedCall<'tcx>,
scope: SourceScope,
is_cleanup: bool,
next_block: BasicBlock,
) {
let InjectedCall { func, args, inject_at } = call;
debug!(
" injecting {}call to {:?}({:?}) at: {:?}, scope: {:?}",
if is_cleanup { "cleanup " } else { "" },
func,
args,
inject_at,
scope,
);
let mut patch = MirPatch::new(self.mir_body);
let temp = patch.new_temp(self.tcx.mk_unit(), fn_span);
let new_block = patch.new_block(placeholder_block(fn_span));
let temp = patch.new_temp(self.tcx.mk_unit(), inject_at);
let new_block = patch.new_block(placeholder_block(inject_at, scope, is_cleanup));
patch.patch_terminator(
new_block,
TerminatorKind::Call {
@ -295,7 +321,7 @@ impl<'a, 'tcx> Instrumentor<'a, 'tcx> {
destination: Some((Place::from(temp), new_block)),
cleanup: None,
from_hir_call: false,
fn_span,
fn_span: inject_at,
},
);
@ -325,15 +351,15 @@ fn function_handle<'tcx>(tcx: TyCtxt<'tcx>, fn_def_id: DefId, span: Span) -> Ope
Operand::function_handle(tcx, fn_def_id, substs, span)
}
fn placeholder_block(span: Span) -> BasicBlockData<'tcx> {
fn placeholder_block(span: Span, scope: SourceScope, is_cleanup: bool) -> BasicBlockData<'tcx> {
BasicBlockData {
statements: vec![],
terminator: Some(Terminator {
source_info: SourceInfo::outermost(span),
source_info: SourceInfo { span, scope },
// this gets overwritten by the counter Call
kind: TerminatorKind::Unreachable,
}),
is_cleanup: false,
is_cleanup,
}
}

22
src/librustc_mir/transform/mod.rs
View File

@ -332,21 +332,25 @@ fn mir_validated(
body.required_consts = required_consts;
let promote_pass = promote_consts::PromoteTemps::default();
let promote: &[&dyn MirPass<'tcx>] = &[
// What we need to run borrowck etc.
&promote_pass,
&simplify::SimplifyCfg::new("qualify-consts"),
];
let opt_coverage: &[&dyn MirPass<'tcx>] = if tcx.sess.opts.debugging_opts.instrument_coverage {
&[&instrument_coverage::InstrumentCoverage]
} else {
&[]
};
run_passes(
tcx,
&mut body,
InstanceDef::Item(def.to_global()),
None,
MirPhase::Validated,
&[&[
// What we need to run borrowck etc.
&promote_pass,
&simplify::SimplifyCfg::new("qualify-consts"),
// If the `instrument-coverage` option is enabled, analyze the CFG, identify each
// conditional branch, construct a coverage map to be passed to LLVM, and inject
// counters where needed.
&instrument_coverage::InstrumentCoverage,
]],
&[promote, opt_coverage],
);
let promoted = promote_pass.promoted_fragments.into_inner();