From 6691d11234c017217797d70c5d54e03891b39a14 Mon Sep 17 00:00:00 2001
From: Dylan MacKenzie <ecstaticmorse@gmail.com>
Date: Thu, 1 Oct 2020 11:31:43 -0700
Subject: [PATCH] Add `-Zprecise-enum-drop-elaboration`
Its purpose is to assist in debugging #77382 and #74551.
---
compiler/rustc_interface/src/tests.rs | 1 +
compiler/rustc_mir/src/dataflow/impls/mod.rs | 8 ++++++++
compiler/rustc_session/src/options.rs | 4 ++++
3 files changed, 13 insertions(+)
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index 72e10bc4304d0..07ce9d0cd9484 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -568,6 +568,7 @@ fn test_debugging_options_tracking_hash() {
tracked!(osx_rpath_install_name, true);
tracked!(panic_abort_tests, true);
tracked!(plt, Some(true));
+ tracked!(precise_enum_drop_elaboration, false);
tracked!(print_fuel, Some("abc".to_string()));
tracked!(profile, true);
tracked!(profile_emit, Some(PathBuf::from("abc")));
diff --git a/compiler/rustc_mir/src/dataflow/impls/mod.rs b/compiler/rustc_mir/src/dataflow/impls/mod.rs
index d4b9600f766f8..185f0edfeb6bc 100644
--- a/compiler/rustc_mir/src/dataflow/impls/mod.rs
+++ b/compiler/rustc_mir/src/dataflow/impls/mod.rs
@@ -358,6 +358,10 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeInitializedPlaces<'_, 'tcx> {
discr: &mir::Operand<'tcx>,
edge_effects: &mut impl SwitchIntEdgeEffects<G>,
) {
+ if !self.tcx.sess.opts.debugging_opts.precise_enum_drop_elaboration {
+ return;
+ }
+
let enum_ = discr.place().and_then(|discr| {
switch_on_enum_discriminant(self.tcx, &self.body, &self.body[block], discr)
});
@@ -469,6 +473,10 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeUninitializedPlaces<'_, 'tcx> {
discr: &mir::Operand<'tcx>,
edge_effects: &mut impl SwitchIntEdgeEffects<G>,
) {
+ if !self.tcx.sess.opts.debugging_opts.precise_enum_drop_elaboration {
+ return;
+ }
+
if !self.mark_inactive_variants_as_uninit {
return;
}
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index 712c9cb87c9d5..b705ab6d9313a 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -1008,6 +1008,10 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
"a single extra argument to prepend the linker invocation (can be used several times)"),
pre_link_args: Vec<String> = (Vec::new(), parse_list, [UNTRACKED],
"extra arguments to prepend to the linker invocation (space separated)"),
+ precise_enum_drop_elaboration: bool = (true, parse_bool, [TRACKED],
+ "use a more precise version of drop elaboration for matches on enums (default: yes). \
+ This results in better codegen, but has caused miscompilations on some tier 2 platforms. \
+ See #77382 and #74551."),
print_fuel: Option<String> = (None, parse_opt_string, [TRACKED],
"make rustc print the total optimization fuel used by a crate"),
print_link_args: bool = (false, parse_bool, [UNTRACKED],