bjoernager/rust
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coverage: Attach an optional FunctionCoverageInfo to mir::Body

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This allows coverage information to be attached to the function as a whole when
appropriate, instead of being smuggled through coverage statements in the
function's basic blocks.

As an example, this patch moves the `function_source_hash` value out of
individual `CoverageKind::Counter` statements and into the per-function info.

When synthesizing unused functions for coverage purposes, the absence of this
info is taken to indicate that a function was not eligible for coverage and
should not be synthesized.
This commit is contained in:
Zalathar 2023-09-10 16:35:37 +10:00
parent 6d7160ce97
commit c479bc7f3b
7 changed files with 74 additions and 54 deletions
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28
compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
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@ -16,7 +16,7 @@ use rustc_hir as hir;
use rustc_hir::def_id::DefId;
use rustc_llvm::RustString;
use rustc_middle::bug;
use rustc_middle::mir::coverage::{CounterId, CoverageKind};
use rustc_middle::mir::coverage::{CounterId, CoverageKind, FunctionCoverageInfo};
use rustc_middle::mir::Coverage;
use rustc_middle::ty;
use rustc_middle::ty::layout::{FnAbiOf, HasTyCtxt};
@ -91,31 +91,34 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
/// codegenned, collect the coverage `CodeRegion`s from the MIR and add
/// them. Since the function is never called, all of its `CodeRegion`s can be
/// added as `unreachable_region`s.
fn define_unused_fn(&self, def_id: DefId) {
fn define_unused_fn(&self, def_id: DefId, function_coverage_info: &'tcx FunctionCoverageInfo) {
let instance = declare_unused_fn(self, def_id);
codegen_unused_fn_and_counter(self, instance);
add_unused_function_coverage(self, instance, def_id);
add_unused_function_coverage(self, instance, def_id, function_coverage_info);
}
}
impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
#[instrument(level = "debug", skip(self))]
fn add_coverage(&mut self, instance: Instance<'tcx>, coverage: &Coverage) {
let bx = self;
let Some(function_coverage_info) =
bx.tcx.instance_mir(instance.def).function_coverage_info.as_deref()
else {
debug!("function has a coverage statement but no coverage info");
return;
};
let Some(coverage_context) = bx.coverage_context() else { return };
let mut coverage_map = coverage_context.function_coverage_map.borrow_mut();
let func_coverage = coverage_map
.entry(instance)
.or_insert_with(|| FunctionCoverage::new(bx.tcx(), instance));
.or_insert_with(|| FunctionCoverage::new(bx.tcx(), instance, function_coverage_info));
let Coverage { kind, code_regions } = coverage;
match *kind {
CoverageKind::Counter { function_source_hash, id } => {
debug!(
"ensuring function source hash is set for instance={:?}; function_source_hash={}",
instance, function_source_hash,
);
func_coverage.set_function_source_hash(function_source_hash);
CoverageKind::Counter { id } => {
func_coverage.add_counter(id, code_regions);
// We need to explicitly drop the `RefMut` before calling into `instrprof_increment`,
// as that needs an exclusive borrow.
@ -124,7 +127,7 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
let coverageinfo = bx.tcx().coverageinfo(instance.def);
let fn_name = bx.get_pgo_func_name_var(instance);
let hash = bx.const_u64(function_source_hash);
let hash = bx.const_u64(function_coverage_info.function_source_hash);
let num_counters = bx.const_u32(coverageinfo.num_counters);
let index = bx.const_u32(id.as_u32());
debug!(
@ -201,10 +204,11 @@ fn add_unused_function_coverage<'tcx>(
cx: &CodegenCx<'_, 'tcx>,
instance: Instance<'tcx>,
def_id: DefId,
function_coverage_info: &'tcx FunctionCoverageInfo,
) {
let tcx = cx.tcx;
let mut function_coverage = FunctionCoverage::unused(tcx, instance);
let mut function_coverage = FunctionCoverage::unused(tcx, instance, function_coverage_info);
for &code_region in tcx.covered_code_regions(def_id) {
let code_region = std::slice::from_ref(code_region);
function_coverage.add_unreachable_regions(code_region);