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Auto merge of #83666 - Amanieu:instrprof-order, r=tmandry

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Run LLVM coverage instrumentation passes before optimization passes

This matches the behavior of Clang and allows us to remove several
hacks which were needed to ensure functions weren't optimized away
before reaching the instrumentation pass.

Fixes #83429

cc `@richkadel`

r? `@tmandry`
This commit is contained in:
bors 2021-03-31 03:20:33 +00:00
commit 6ff482bde5
9 changed files with 29 additions and 60 deletions
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9
compiler/rustc_codegen_llvm/src/back/write.rs
View file

@ -548,6 +548,15 @@ pub(crate) unsafe fn optimize(
llvm::LLVMRustAddPass(fpm, find_pass("lint").unwrap());
continue;
}
if pass_name == "insert-gcov-profiling" || pass_name == "instrprof" {
// Instrumentation must be inserted before optimization,
// otherwise LLVM may optimize some functions away which
// breaks llvm-cov.
//
// This mirrors what Clang does in lib/CodeGen/BackendUtil.cpp.
llvm::LLVMRustAddPass(mpm, find_pass(pass_name).unwrap());
continue;
}
if let Some(pass) = find_pass(pass_name) {
extra_passes.push(pass);

9
compiler/rustc_middle/src/mir/mono.rs
View file

@ -84,14 +84,7 @@ impl<'tcx> MonoItem<'tcx> {
.debugging_opts
.inline_in_all_cgus
.unwrap_or_else(|| tcx.sess.opts.optimize != OptLevel::No)
&& !tcx.sess.link_dead_code()
&& !tcx.sess.instrument_coverage();
// Disabled for `-Z instrument-coverage` because some LLVM optimizations can sometimes
// break coverage results. A test that failed at certain optimization levels is now
// validated at that optimization level (via `compile-flags` directive):
// * `src/test/run-make-fulldeps/coverage/closure.rs` broke with `-C opt-level=2`, and
// also required disabling `internalize_symbols` in
// `rustc_mir/monomorphize/partitioning/mod.rs`
&& !tcx.sess.link_dead_code();
match *self {
MonoItem::Fn(ref instance) => {

8
compiler/rustc_mir/src/monomorphize/partitioning/mod.rs
View file

@ -196,13 +196,7 @@ pub fn partition<'tcx>(
// Next we try to make as many symbols "internal" as possible, so LLVM has
// more freedom to optimize.
if !tcx.sess.link_dead_code() && !tcx.sess.instrument_coverage() {
// Disabled for `-Z instrument-coverage` because some LLVM optimizations can sometimes
// break coverage results. Tests that failed at certain optimization levels are now
// validated at those optimization levels (via `compile-flags` directive); for example:
// * `src/test/run-make-fulldeps/coverage/async.rs` broke with `-C opt-level=1`
// * `src/test/run-make-fulldeps/coverage/closure.rs` broke with `-C opt-level=2`, and
// also required disabling `generate_gcu_internal_copies` in `rustc_middle/mir/mono.rs`
if !tcx.sess.link_dead_code() {
let _prof_timer = tcx.prof.generic_activity("cgu_partitioning_internalize_symbols");
partitioner.internalize_symbols(cx, &mut post_inlining);
}

12
compiler/rustc_typeck/src/collect.rs
View file

@ -2890,17 +2890,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
.emit();
InlineAttr::None
} else if list_contains_name(&items[..], sym::always) {
if tcx.sess.instrument_coverage() {
// Fixes Issue #82875. Forced inlining allows LLVM to discard functions
// marked with `#[inline(always)]`, which can break coverage reporting if
// that function was referenced from a coverage map.
//
// FIXME(#83429): Is there a better place, e.g., in codegen, to check and
// convert `Always` to `Hint`?
InlineAttr::Hint
} else {
InlineAttr::Always
}
InlineAttr::Always
} else if list_contains_name(&items[..], sym::never) {
InlineAttr::Never
} else {