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This commit is contained in:
Wesley Wiser 2021-12-20 20:15:29 -05:00
parent ef57f249a2
commit ebc0d0d2a8
4 changed files with 59 additions and 36 deletions
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47
compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
View file

@ -273,7 +273,9 @@ fn save_function_record(
/// `codegened_and_inlined_items`).
///
/// These unused functions are then codegen'd in one of the CGUs which is marked as the
/// "code coverage dead code cgu" during the partitioning process.
/// "code coverage dead code cgu" during the partitioning process. This prevents us from generating
/// code regions for the same function more than once which can lead to linker errors regarding
/// duplicate symbols.
fn add_unused_functions<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) {
assert!(cx.codegen_unit.is_code_coverage_dead_code_cgu());
@ -281,12 +283,24 @@ fn add_unused_functions<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) {
let ignore_unused_generics = tcx.sess.instrument_coverage_except_unused_generics();
let all_def_ids: DefIdSet = tcx
let eligible_def_ids: DefIdSet = tcx
.mir_keys(())
.iter()
.filter_map(|local_def_id| {
let def_id = local_def_id.to_def_id();
if ignore_unused_generics && tcx.generics_of(def_id).requires_monomorphization(tcx) {
let kind = tcx.def_kind(def_id);
// `mir_keys` will give us `DefId`s for all kinds of things, not
// just "functions", like consts, statics, etc. Filter those out.
// If `ignore_unused_generics` was specified, filter out any
// generic functions from consideration as well.
if !matches!(
kind,
DefKind::Fn | DefKind::AssocFn | DefKind::Closure | DefKind::Generator
) {
return None;
} else if ignore_unused_generics
&& tcx.generics_of(def_id).requires_monomorphization(tcx)
{
return None;
}
Some(local_def_id.to_def_id())
@ -295,24 +309,17 @@ fn add_unused_functions<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) {
let codegenned_def_ids = tcx.codegened_and_inlined_items(());
for &non_codegenned_def_id in all_def_ids.difference(codegenned_def_ids) {
// `all_def_ids` contains things besides just "functions" such as constants,
// statics, etc. We need to filter those out.
let kind = tcx.def_kind(non_codegenned_def_id);
if matches!(kind, DefKind::Fn | DefKind::AssocFn | DefKind::Closure | DefKind::Generator) {
let codegen_fn_attrs = tcx.codegen_fn_attrs(non_codegenned_def_id);
for &non_codegenned_def_id in eligible_def_ids.difference(codegenned_def_ids) {
let codegen_fn_attrs = tcx.codegen_fn_attrs(non_codegenned_def_id);
// If a function is marked `#[no_coverage]`, then skip generating a
// dead code stub for it.
if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NO_COVERAGE) {
debug!("skipping unused fn marked #[no_coverage]: {:?}", non_codegenned_def_id);
continue;
}
debug!("generating unused fn: {:?}", non_codegenned_def_id);
cx.define_unused_fn(non_codegenned_def_id);
} else {
debug!("skipping unused {:?}: {:?}", kind, non_codegenned_def_id);
// If a function is marked `#[no_coverage]`, then skip generating a
// dead code stub for it.
if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NO_COVERAGE) {
debug!("skipping unused fn marked #[no_coverage]: {:?}", non_codegenned_def_id);
continue;
}
debug!("generating unused fn: {:?}", non_codegenned_def_id);
cx.define_unused_fn(non_codegenned_def_id);
}
}

32
compiler/rustc_monomorphize/src/partitioning/mod.rs
View file

@ -205,17 +205,33 @@ pub fn partition<'tcx>(
tcx.sess.instrument_coverage() && !tcx.sess.instrument_coverage_except_unused_functions();
if instrument_dead_code {
assert!(
post_inlining.codegen_units.len() > 0,
"There must be at least one CGU that code coverage data can be generated in."
);
// Find the smallest CGU that has exported symbols and put the dead
// function stubs in that CGU. We look for exported symbols to increase
// the likelyhood the linker won't throw away the dead functions.
let mut cgus_with_exported_symbols: Vec<_> = post_inlining
.codegen_units
.iter_mut()
.filter(|cgu| cgu.items().iter().any(|(_, (linkage, _))| *linkage == Linkage::External))
.collect();
cgus_with_exported_symbols.sort_by_key(|cgu| cgu.size_estimate());
// the likelihood the linker won't throw away the dead functions.
// FIXME(#92165): In order to truly resolve this, we need to make sure
// the object file (CGU) containing the dead function stubs is included
// in the final binary. This will probably require forcing these
// function symbols to be included via `-u` or `/include` linker args.
let mut cgus: Vec<_> = post_inlining.codegen_units.iter_mut().collect();
cgus.sort_by_key(|cgu| cgu.size_estimate());
let dead_code_cgu = cgus_with_exported_symbols.last_mut().unwrap();
let dead_code_cgu = if let Some(cgu) = cgus
.into_iter()
.rev()
.filter(|cgu| cgu.items().iter().any(|(_, (linkage, _))| *linkage == Linkage::External))
.next()
{
cgu
} else {
// If there are no CGUs that have externally linked items,
// then we just pick the first CGU as a fallback.
&mut post_inlining.codegen_units[0]
};
dead_code_cgu.make_code_coverage_dead_code_cgu();
}

8
src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.uses_crate.txt
View file

@ -19,12 +19,12 @@
18| 2| println!("used_only_from_bin_crate_generic_function with {:?}", arg);
19| 2|}
------------------
| used_crate::used_only_from_bin_crate_generic_function::<&str>:
| used_crate::used_only_from_bin_crate_generic_function::<&alloc::vec::Vec<i32>>:
| 17| 1|pub fn used_only_from_bin_crate_generic_function<T: Debug>(arg: T) {
| 18| 1| println!("used_only_from_bin_crate_generic_function with {:?}", arg);
| 19| 1|}
------------------
| used_crate::used_only_from_bin_crate_generic_function::<&alloc::vec::Vec<i32>>:
| used_crate::used_only_from_bin_crate_generic_function::<&str>:
| 17| 1|pub fn used_only_from_bin_crate_generic_function<T: Debug>(arg: T) {
| 18| 1| println!("used_only_from_bin_crate_generic_function with {:?}", arg);
| 19| 1|}
@ -36,12 +36,12 @@
22| 2| println!("used_only_from_this_lib_crate_generic_function with {:?}", arg);
23| 2|}
------------------
| used_crate::used_only_from_this_lib_crate_generic_function::<&str>:
| used_crate::used_only_from_this_lib_crate_generic_function::<alloc::vec::Vec<i32>>:
| 21| 1|pub fn used_only_from_this_lib_crate_generic_function<T: Debug>(arg: T) {
| 22| 1| println!("used_only_from_this_lib_crate_generic_function with {:?}", arg);
| 23| 1|}
------------------
| used_crate::used_only_from_this_lib_crate_generic_function::<alloc::vec::Vec<i32>>:
| used_crate::used_only_from_this_lib_crate_generic_function::<&str>:
| 21| 1|pub fn used_only_from_this_lib_crate_generic_function<T: Debug>(arg: T) {
| 22| 1| println!("used_only_from_this_lib_crate_generic_function with {:?}", arg);
| 23| 1|}

8
src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.uses_inline_crate.txt
View file

@ -42,12 +42,12 @@
40| 2| println!("used_only_from_bin_crate_generic_function with {:?}", arg);
41| 2|}
------------------
| used_inline_crate::used_only_from_bin_crate_generic_function::<&alloc::vec::Vec<i32>>:
| used_inline_crate::used_only_from_bin_crate_generic_function::<&str>:
| 39| 1|pub fn used_only_from_bin_crate_generic_function<T: Debug>(arg: T) {
| 40| 1| println!("used_only_from_bin_crate_generic_function with {:?}", arg);
| 41| 1|}
------------------
| used_inline_crate::used_only_from_bin_crate_generic_function::<&str>:
| used_inline_crate::used_only_from_bin_crate_generic_function::<&alloc::vec::Vec<i32>>:
| 39| 1|pub fn used_only_from_bin_crate_generic_function<T: Debug>(arg: T) {
| 40| 1| println!("used_only_from_bin_crate_generic_function with {:?}", arg);
| 41| 1|}
@ -61,12 +61,12 @@
46| 4| println!("used_only_from_this_lib_crate_generic_function with {:?}", arg);
47| 4|}
------------------
| used_inline_crate::used_only_from_this_lib_crate_generic_function::<alloc::vec::Vec<i32>>:
| used_inline_crate::used_only_from_this_lib_crate_generic_function::<&str>:
| 45| 2|pub fn used_only_from_this_lib_crate_generic_function<T: Debug>(arg: T) {
| 46| 2| println!("used_only_from_this_lib_crate_generic_function with {:?}", arg);
| 47| 2|}
------------------
| used_inline_crate::used_only_from_this_lib_crate_generic_function::<&str>:
| used_inline_crate::used_only_from_this_lib_crate_generic_function::<alloc::vec::Vec<i32>>:
| 45| 2|pub fn used_only_from_this_lib_crate_generic_function<T: Debug>(arg: T) {
| 46| 2| println!("used_only_from_this_lib_crate_generic_function with {:?}", arg);
| 47| 2|}