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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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18
compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
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@@ -114,7 +114,7 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
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, function_coverage_info));
.or_insert_with(|| FunctionCoverage::new(instance, function_coverage_info));
let Coverage { kind, code_regions } = coverage;
match *kind {
@@ -124,11 +124,21 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
// as that needs an exclusive borrow.
drop(coverage_map);
let coverageinfo = bx.tcx().coverageinfo(instance.def);
// The number of counters passed to `llvm.instrprof.increment` might
// be smaller than the number originally inserted by the instrumentor,
// if some high-numbered counters were removed by MIR optimizations.
// If so, LLVM's profiler runtime will use fewer physical counters.
let num_counters =
bx.tcx().coverage_ids_info(instance.def).max_counter_id.as_u32() + 1;
assert!(
num_counters as usize <= function_coverage_info.num_counters,
"num_counters disagreement: query says {num_counters} but function info only has {}",
function_coverage_info.num_counters
);
let fn_name = bx.get_pgo_func_name_var(instance);
let hash = bx.const_u64(function_coverage_info.function_source_hash);
let num_counters = bx.const_u32(coverageinfo.num_counters);
let num_counters = bx.const_u32(num_counters);
let index = bx.const_u32(id.as_u32());
debug!(
"codegen intrinsic instrprof.increment(fn_name={:?}, hash={:?}, num_counters={:?}, index={:?})",
@@ -208,7 +218,7 @@ fn add_unused_function_coverage<'tcx>(
) {
let tcx = cx.tcx;
let mut function_coverage = FunctionCoverage::unused(tcx, instance, function_coverage_info);
let mut function_coverage = FunctionCoverage::unused(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);