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matthiaskrgrmatthiaskrgr
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Rollup merge of #105420 - tmiasko:dest-prop-dead-code, r=JakobDegen
Remove dead code after destination propagation Fixes #105428. cc `@JakobDegen`
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‎compiler/rustc_mir_transform/src/dest_prop.rs

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Original file line numberDiff line numberDiff line change
@@ -129,6 +129,7 @@
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use std::collections::hash_map::{Entry, OccupiedEntry};
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use crate::simplify::remove_dead_blocks;
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use crate::MirPass;
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use rustc_data_structures::fx::FxHashMap;
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use rustc_index::bit_set::BitSet;
@@ -235,6 +236,12 @@ impl<'tcx> MirPass<'tcx> for DestinationPropagation {
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apply_merges(body, tcx, &merges, &merged_locals);
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}
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if round_count != 0 {
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// Merging can introduce overlap between moved arguments and/or call destination in an
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// unreachable code, which validator considers to be ill-formed.
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remove_dead_blocks(tcx, body);
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}
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trace!(round_count);
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}
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}

‎src/test/mir-opt/dest-prop/unreachable.f.DestinationPropagation.diff

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,86 @@
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- // MIR for `f` before DestinationPropagation
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+ // MIR for `f` after DestinationPropagation
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fn f(_1: T) -> () {
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debug a => _1; // in scope 0 at $DIR/unreachable.rs:+0:19: +0:20
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let mut _0: (); // return place in scope 0 at $DIR/unreachable.rs:+0:25: +0:25
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let _2: T; // in scope 0 at $DIR/unreachable.rs:+1:9: +1:10
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let mut _3: bool; // in scope 0 at $DIR/unreachable.rs:+2:8: +2:13
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let _4: (); // in scope 0 at $DIR/unreachable.rs:+3:9: +3:16
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let mut _5: T; // in scope 0 at $DIR/unreachable.rs:+3:11: +3:12
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let mut _6: T; // in scope 0 at $DIR/unreachable.rs:+3:14: +3:15
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let _7: (); // in scope 0 at $DIR/unreachable.rs:+5:9: +5:16
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let mut _8: T; // in scope 0 at $DIR/unreachable.rs:+5:11: +5:12
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let mut _9: T; // in scope 0 at $DIR/unreachable.rs:+5:14: +5:15
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scope 1 {
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- debug b => _2; // in scope 1 at $DIR/unreachable.rs:+1:9: +1:10
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+ debug b => _1; // in scope 1 at $DIR/unreachable.rs:+1:9: +1:10
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}
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bb0: {
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- StorageLive(_2); // scope 0 at $DIR/unreachable.rs:+1:9: +1:10
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- _2 = _1; // scope 0 at $DIR/unreachable.rs:+1:13: +1:14
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+ nop; // scope 0 at $DIR/unreachable.rs:+1:9: +1:10
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+ nop; // scope 0 at $DIR/unreachable.rs:+1:13: +1:14
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StorageLive(_3); // scope 1 at $DIR/unreachable.rs:+2:8: +2:13
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_3 = const false; // scope 1 at $DIR/unreachable.rs:+2:8: +2:13
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- goto -> bb3; // scope 1 at $DIR/unreachable.rs:+2:8: +2:13
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+ goto -> bb1; // scope 1 at $DIR/unreachable.rs:+2:8: +2:13
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}
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bb1: {
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- StorageLive(_4); // scope 1 at $DIR/unreachable.rs:+3:9: +3:16
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- StorageLive(_5); // scope 1 at $DIR/unreachable.rs:+3:11: +3:12
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- _5 = _1; // scope 1 at $DIR/unreachable.rs:+3:11: +3:12
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- StorageLive(_6); // scope 1 at $DIR/unreachable.rs:+3:14: +3:15
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- _6 = _2; // scope 1 at $DIR/unreachable.rs:+3:14: +3:15
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- _4 = g::<T>(move _5, move _6) -> bb2; // scope 1 at $DIR/unreachable.rs:+3:9: +3:16
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- // mir::Constant
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- // + span: $DIR/unreachable.rs:11:9: 11:10
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- // + literal: Const { ty: fn(T, T) {g::<T>}, val: Value(<ZST>) }
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- }
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-
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- bb2: {
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- StorageDead(_6); // scope 1 at $DIR/unreachable.rs:+3:15: +3:16
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- StorageDead(_5); // scope 1 at $DIR/unreachable.rs:+3:15: +3:16
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- StorageDead(_4); // scope 1 at $DIR/unreachable.rs:+3:16: +3:17
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- _0 = const (); // scope 1 at $DIR/unreachable.rs:+2:14: +4:6
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- goto -> bb5; // scope 1 at $DIR/unreachable.rs:+2:5: +6:6
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- }
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-
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- bb3: {
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StorageLive(_7); // scope 1 at $DIR/unreachable.rs:+5:9: +5:16
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- StorageLive(_8); // scope 1 at $DIR/unreachable.rs:+5:11: +5:12
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- _8 = _2; // scope 1 at $DIR/unreachable.rs:+5:11: +5:12
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+ nop; // scope 1 at $DIR/unreachable.rs:+5:11: +5:12
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+ nop; // scope 1 at $DIR/unreachable.rs:+5:11: +5:12
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StorageLive(_9); // scope 1 at $DIR/unreachable.rs:+5:14: +5:15
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- _9 = _2; // scope 1 at $DIR/unreachable.rs:+5:14: +5:15
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- _7 = g::<T>(move _8, move _9) -> bb4; // scope 1 at $DIR/unreachable.rs:+5:9: +5:16
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+ _9 = _1; // scope 1 at $DIR/unreachable.rs:+5:14: +5:15
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+ _7 = g::<T>(move _1, move _9) -> bb2; // scope 1 at $DIR/unreachable.rs:+5:9: +5:16
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// mir::Constant
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// + span: $DIR/unreachable.rs:13:9: 13:10
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// + literal: Const { ty: fn(T, T) {g::<T>}, val: Value(<ZST>) }
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}
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- bb4: {
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+ bb2: {
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StorageDead(_9); // scope 1 at $DIR/unreachable.rs:+5:15: +5:16
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- StorageDead(_8); // scope 1 at $DIR/unreachable.rs:+5:15: +5:16
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+ nop; // scope 1 at $DIR/unreachable.rs:+5:15: +5:16
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StorageDead(_7); // scope 1 at $DIR/unreachable.rs:+5:16: +5:17
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_0 = const (); // scope 1 at $DIR/unreachable.rs:+4:12: +6:6
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- goto -> bb5; // scope 1 at $DIR/unreachable.rs:+2:5: +6:6
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+ goto -> bb3; // scope 1 at $DIR/unreachable.rs:+2:5: +6:6
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}
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- bb5: {
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+ bb3: {
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StorageDead(_3); // scope 1 at $DIR/unreachable.rs:+6:5: +6:6
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- StorageDead(_2); // scope 0 at $DIR/unreachable.rs:+7:1: +7:2
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+ nop; // scope 0 at $DIR/unreachable.rs:+7:1: +7:2
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return; // scope 0 at $DIR/unreachable.rs:+7:2: +7:2
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}
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}
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‎src/test/mir-opt/dest-prop/unreachable.rs

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@@ -0,0 +1,18 @@
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// Check that unreachable code is removed after the destination propagation.
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// Regression test for issue #105428.
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//
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// compile-flags: --crate-type=lib -Zmir-opt-level=0
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// compile-flags: -Zmir-enable-passes=+ConstProp,+SimplifyConstCondition-after-const-prop,+DestinationPropagation
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// EMIT_MIR unreachable.f.DestinationPropagation.diff
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pub fn f<T: Copy>(a: T) {
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let b = a;
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if false {
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g(a, b);
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} else {
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g(b, b);
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}
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}
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#[inline(never)]
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pub fn g<T: Copy>(_: T, _: T) {}

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