From adf53d4b068e216f0705ba2baae4cc21dd0988a3 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Tomasz=20Mi=C4=85sko?= Date: Fri, 16 Dec 2022 00:00:00 +0000 Subject: [PATCH] Remove dead code after destination propagation --- compiler/rustc_mir_transform/src/dest_prop.rs | 7 ++ .../unreachable.f.DestinationPropagation.diff | 86 +++++++++++++++++++ src/test/mir-opt/dest-prop/unreachable.rs | 18 ++++ 3 files changed, 111 insertions(+) create mode 100644 src/test/mir-opt/dest-prop/unreachable.f.DestinationPropagation.diff create mode 100644 src/test/mir-opt/dest-prop/unreachable.rs diff --git a/compiler/rustc_mir_transform/src/dest_prop.rs b/compiler/rustc_mir_transform/src/dest_prop.rs index 3e45319431cec..74d8337653f03 100644 --- a/compiler/rustc_mir_transform/src/dest_prop.rs +++ b/compiler/rustc_mir_transform/src/dest_prop.rs @@ -129,6 +129,7 @@ use std::collections::hash_map::{Entry, OccupiedEntry}; +use crate::simplify::remove_dead_blocks; use crate::MirPass; use rustc_data_structures::fx::FxHashMap; use rustc_index::bit_set::BitSet; @@ -235,6 +236,12 @@ impl<'tcx> MirPass<'tcx> for DestinationPropagation { apply_merges(body, tcx, &merges, &merged_locals); } + if round_count != 0 { + // Merging can introduce overlap between moved arguments and/or call destination in an + // unreachable code, which validator considers to be ill-formed. + remove_dead_blocks(tcx, body); + } + trace!(round_count); } } diff --git a/src/test/mir-opt/dest-prop/unreachable.f.DestinationPropagation.diff b/src/test/mir-opt/dest-prop/unreachable.f.DestinationPropagation.diff new file mode 100644 index 0000000000000..9ea756c271298 --- /dev/null +++ b/src/test/mir-opt/dest-prop/unreachable.f.DestinationPropagation.diff @@ -0,0 +1,86 @@ +- // MIR for `f` before DestinationPropagation ++ // MIR for `f` after DestinationPropagation + + fn f(_1: T) -> () { + debug a => _1; // in scope 0 at $DIR/unreachable.rs:+0:19: +0:20 + let mut _0: (); // return place in scope 0 at $DIR/unreachable.rs:+0:25: +0:25 + let _2: T; // in scope 0 at $DIR/unreachable.rs:+1:9: +1:10 + let mut _3: bool; // in scope 0 at $DIR/unreachable.rs:+2:8: +2:13 + let _4: (); // in scope 0 at $DIR/unreachable.rs:+3:9: +3:16 + let mut _5: T; // in scope 0 at $DIR/unreachable.rs:+3:11: +3:12 + let mut _6: T; // in scope 0 at $DIR/unreachable.rs:+3:14: +3:15 + let _7: (); // in scope 0 at $DIR/unreachable.rs:+5:9: +5:16 + let mut _8: T; // in scope 0 at $DIR/unreachable.rs:+5:11: +5:12 + let mut _9: T; // in scope 0 at $DIR/unreachable.rs:+5:14: +5:15 + scope 1 { +- debug b => _2; // in scope 1 at $DIR/unreachable.rs:+1:9: +1:10 ++ debug b => _1; // in scope 1 at $DIR/unreachable.rs:+1:9: +1:10 + } + + bb0: { +- StorageLive(_2); // scope 0 at $DIR/unreachable.rs:+1:9: +1:10 +- _2 = _1; // scope 0 at $DIR/unreachable.rs:+1:13: +1:14 ++ nop; // scope 0 at $DIR/unreachable.rs:+1:9: +1:10 ++ nop; // scope 0 at $DIR/unreachable.rs:+1:13: +1:14 + StorageLive(_3); // scope 1 at $DIR/unreachable.rs:+2:8: +2:13 + _3 = const false; // scope 1 at $DIR/unreachable.rs:+2:8: +2:13 +- goto -> bb3; // scope 1 at $DIR/unreachable.rs:+2:8: +2:13 ++ goto -> bb1; // scope 1 at $DIR/unreachable.rs:+2:8: +2:13 + } + + bb1: { +- StorageLive(_4); // scope 1 at $DIR/unreachable.rs:+3:9: +3:16 +- StorageLive(_5); // scope 1 at $DIR/unreachable.rs:+3:11: +3:12 +- _5 = _1; // scope 1 at $DIR/unreachable.rs:+3:11: +3:12 +- StorageLive(_6); // scope 1 at $DIR/unreachable.rs:+3:14: +3:15 +- _6 = _2; // scope 1 at $DIR/unreachable.rs:+3:14: +3:15 +- _4 = g::(move _5, move _6) -> bb2; // scope 1 at $DIR/unreachable.rs:+3:9: +3:16 +- // mir::Constant +- // + span: $DIR/unreachable.rs:11:9: 11:10 +- // + literal: Const { ty: fn(T, T) {g::}, val: Value() } +- } +- +- bb2: { +- StorageDead(_6); // scope 1 at $DIR/unreachable.rs:+3:15: +3:16 +- StorageDead(_5); // scope 1 at $DIR/unreachable.rs:+3:15: +3:16 +- StorageDead(_4); // scope 1 at $DIR/unreachable.rs:+3:16: +3:17 +- _0 = const (); // scope 1 at $DIR/unreachable.rs:+2:14: +4:6 +- goto -> bb5; // scope 1 at $DIR/unreachable.rs:+2:5: +6:6 +- } +- +- bb3: { + StorageLive(_7); // scope 1 at $DIR/unreachable.rs:+5:9: +5:16 +- StorageLive(_8); // scope 1 at $DIR/unreachable.rs:+5:11: +5:12 +- _8 = _2; // scope 1 at $DIR/unreachable.rs:+5:11: +5:12 ++ nop; // scope 1 at $DIR/unreachable.rs:+5:11: +5:12 ++ nop; // scope 1 at $DIR/unreachable.rs:+5:11: +5:12 + StorageLive(_9); // scope 1 at $DIR/unreachable.rs:+5:14: +5:15 +- _9 = _2; // scope 1 at $DIR/unreachable.rs:+5:14: +5:15 +- _7 = g::(move _8, move _9) -> bb4; // scope 1 at $DIR/unreachable.rs:+5:9: +5:16 ++ _9 = _1; // scope 1 at $DIR/unreachable.rs:+5:14: +5:15 ++ _7 = g::(move _1, move _9) -> bb2; // scope 1 at $DIR/unreachable.rs:+5:9: +5:16 + // mir::Constant + // + span: $DIR/unreachable.rs:13:9: 13:10 + // + literal: Const { ty: fn(T, T) {g::}, val: Value() } + } + +- bb4: { ++ bb2: { + StorageDead(_9); // scope 1 at $DIR/unreachable.rs:+5:15: +5:16 +- StorageDead(_8); // scope 1 at $DIR/unreachable.rs:+5:15: +5:16 ++ nop; // scope 1 at $DIR/unreachable.rs:+5:15: +5:16 + StorageDead(_7); // scope 1 at $DIR/unreachable.rs:+5:16: +5:17 + _0 = const (); // scope 1 at $DIR/unreachable.rs:+4:12: +6:6 +- goto -> bb5; // scope 1 at $DIR/unreachable.rs:+2:5: +6:6 ++ goto -> bb3; // scope 1 at $DIR/unreachable.rs:+2:5: +6:6 + } + +- bb5: { ++ bb3: { + StorageDead(_3); // scope 1 at $DIR/unreachable.rs:+6:5: +6:6 +- StorageDead(_2); // scope 0 at $DIR/unreachable.rs:+7:1: +7:2 ++ nop; // scope 0 at $DIR/unreachable.rs:+7:1: +7:2 + return; // scope 0 at $DIR/unreachable.rs:+7:2: +7:2 + } + } + diff --git a/src/test/mir-opt/dest-prop/unreachable.rs b/src/test/mir-opt/dest-prop/unreachable.rs new file mode 100644 index 0000000000000..32b5def984a80 --- /dev/null +++ b/src/test/mir-opt/dest-prop/unreachable.rs @@ -0,0 +1,18 @@ +// Check that unreachable code is removed after the destination propagation. +// Regression test for issue #105428. +// +// compile-flags: --crate-type=lib -Zmir-opt-level=0 +// compile-flags: -Zmir-enable-passes=+ConstProp,+SimplifyConstCondition-after-const-prop,+DestinationPropagation + +// EMIT_MIR unreachable.f.DestinationPropagation.diff +pub fn f(a: T) { + let b = a; + if false { + g(a, b); + } else { + g(b, b); + } +} + +#[inline(never)] +pub fn g(_: T, _: T) {}