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Auto merge of #119672 - cjgillot:dse-sandwich, r=oli-obk
Sandwich MIR optimizations between DSE. This PR reorders MIR optimization passes in an attempt to increase their efficiency. - Stop running CopyProp before GVN, it's useless as GVN will do the same thing anyway. Instead, we perform CopyProp at the end of the pipeline, to ensure we do not emit copy/move chains. - Run DSE before GVN, as it increases the probability to have single-assignment locals. - Run DSE after the final CopyProp to turn copies into moves. r? `@ghost`
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‎compiler/rustc_mir_transform/src/dead_store_elimination.rs‎

Lines changed: 11 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -123,13 +123,21 @@ pub fn eliminate<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
123123
let Operand::Copy(place) = *arg else { bug!() };
124124
*arg = Operand::Move(place);
125125
}
126-
127-
crate::simplify::simplify_locals(body, tcx)
128126
}
129127

130-
pub struct DeadStoreElimination;
128+
pub enum DeadStoreElimination {
129+
Initial,
130+
Final,
131+
}
131132

132133
impl<'tcx> MirPass<'tcx> for DeadStoreElimination {
134+
fn name(&self) -> &'static str {
135+
match self {
136+
DeadStoreElimination::Initial => "DeadStoreElimination-initial",
137+
DeadStoreElimination::Final => "DeadStoreElimination-final",
138+
}
139+
}
140+
133141
fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
134142
sess.mir_opt_level() >= 2
135143
}

‎compiler/rustc_mir_transform/src/lib.rs‎

Lines changed: 5 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -596,24 +596,25 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
596596
&multiple_return_terminators::MultipleReturnTerminators,
597597
&instsimplify::InstSimplify,
598598
&simplify::SimplifyLocals::BeforeConstProp,
599-
&copy_prop::CopyProp,
599+
&dead_store_elimination::DeadStoreElimination::Initial,
600+
&gvn::GVN,
601+
&simplify::SimplifyLocals::AfterGVN,
600602
// Perform `SeparateConstSwitch` after SSA-based analyses, as cloning blocks may
601603
// destroy the SSA property. It should still happen before const-propagation, so the
602604
// latter pass will leverage the created opportunities.
603605
&separate_const_switch::SeparateConstSwitch,
604-
&gvn::GVN,
605-
&simplify::SimplifyLocals::AfterGVN,
606606
&dataflow_const_prop::DataflowConstProp,
607607
&const_debuginfo::ConstDebugInfo,
608608
&o1(simplify_branches::SimplifyConstCondition::AfterConstProp),
609609
&jump_threading::JumpThreading,
610610
&early_otherwise_branch::EarlyOtherwiseBranch,
611611
&simplify_comparison_integral::SimplifyComparisonIntegral,
612-
&dead_store_elimination::DeadStoreElimination,
613612
&dest_prop::DestinationPropagation,
614613
&o1(simplify_branches::SimplifyConstCondition::Final),
615614
&o1(remove_noop_landing_pads::RemoveNoopLandingPads),
616615
&o1(simplify::SimplifyCfg::Final),
616+
&copy_prop::CopyProp,
617+
&dead_store_elimination::DeadStoreElimination::Final,
617618
&nrvo::RenameReturnPlace,
618619
&simplify::SimplifyLocals::Final,
619620
&multiple_return_terminators::MultipleReturnTerminators,

‎tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.32bit.panic-abort.diff‎

Lines changed: 9 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -25,20 +25,21 @@
2525
scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
2626
debug ptr => _6;
2727
let mut _8: *const [bool; 0];
28+
let mut _9: *mut [bool; 0];
2829
scope 12 {
2930
scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
30-
debug ptr => _6;
31+
debug ptr => _9;
3132
scope 14 (inlined std::ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
32-
debug self => _6;
33-
let mut _9: *mut u8;
33+
debug self => _9;
34+
let mut _10: *mut u8;
3435
scope 15 {
3536
scope 16 (inlined std::ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
36-
debug ptr => _9;
37+
debug ptr => _10;
3738
scope 17 (inlined std::ptr::mut_ptr::<impl *mut u8>::addr) {
38-
debug self => _9;
39+
debug self => _10;
3940
scope 18 {
4041
scope 19 (inlined std::ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
41-
debug self => _9;
42+
debug self => _10;
4243
}
4344
}
4445
}
@@ -74,8 +75,10 @@
7475
StorageDead(_7);
7576
StorageLive(_8);
7677
StorageLive(_9);
78+
StorageLive(_10);
7779
_8 = const {0x1 as *mut [bool; 0]} as *const [bool; 0] (PointerCoercion(MutToConstPointer));
7880
_5 = NonNull::<[bool; 0]> { pointer: _8 };
81+
StorageDead(_10);
7982
StorageDead(_9);
8083
StorageDead(_8);
8184
StorageDead(_6);

‎tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.32bit.panic-unwind.diff‎

Lines changed: 9 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -25,20 +25,21 @@
2525
scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
2626
debug ptr => _6;
2727
let mut _8: *const [bool; 0];
28+
let mut _9: *mut [bool; 0];
2829
scope 12 {
2930
scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
30-
debug ptr => _6;
31+
debug ptr => _9;
3132
scope 14 (inlined std::ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
32-
debug self => _6;
33-
let mut _9: *mut u8;
33+
debug self => _9;
34+
let mut _10: *mut u8;
3435
scope 15 {
3536
scope 16 (inlined std::ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
36-
debug ptr => _9;
37+
debug ptr => _10;
3738
scope 17 (inlined std::ptr::mut_ptr::<impl *mut u8>::addr) {
38-
debug self => _9;
39+
debug self => _10;
3940
scope 18 {
4041
scope 19 (inlined std::ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
41-
debug self => _9;
42+
debug self => _10;
4243
}
4344
}
4445
}
@@ -74,8 +75,10 @@
7475
StorageDead(_7);
7576
StorageLive(_8);
7677
StorageLive(_9);
78+
StorageLive(_10);
7779
_8 = const {0x1 as *mut [bool; 0]} as *const [bool; 0] (PointerCoercion(MutToConstPointer));
7880
_5 = NonNull::<[bool; 0]> { pointer: _8 };
81+
StorageDead(_10);
7982
StorageDead(_9);
8083
StorageDead(_8);
8184
StorageDead(_6);

‎tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.64bit.panic-abort.diff‎

Lines changed: 9 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -25,20 +25,21 @@
2525
scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
2626
debug ptr => _6;
2727
let mut _8: *const [bool; 0];
28+
let mut _9: *mut [bool; 0];
2829
scope 12 {
2930
scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
30-
debug ptr => _6;
31+
debug ptr => _9;
3132
scope 14 (inlined std::ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
32-
debug self => _6;
33-
let mut _9: *mut u8;
33+
debug self => _9;
34+
let mut _10: *mut u8;
3435
scope 15 {
3536
scope 16 (inlined std::ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
36-
debug ptr => _9;
37+
debug ptr => _10;
3738
scope 17 (inlined std::ptr::mut_ptr::<impl *mut u8>::addr) {
38-
debug self => _9;
39+
debug self => _10;
3940
scope 18 {
4041
scope 19 (inlined std::ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
41-
debug self => _9;
42+
debug self => _10;
4243
}
4344
}
4445
}
@@ -74,8 +75,10 @@
7475
StorageDead(_7);
7576
StorageLive(_8);
7677
StorageLive(_9);
78+
StorageLive(_10);
7779
_8 = const {0x1 as *mut [bool; 0]} as *const [bool; 0] (PointerCoercion(MutToConstPointer));
7880
_5 = NonNull::<[bool; 0]> { pointer: _8 };
81+
StorageDead(_10);
7982
StorageDead(_9);
8083
StorageDead(_8);
8184
StorageDead(_6);

‎tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.64bit.panic-unwind.diff‎

Lines changed: 9 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -25,20 +25,21 @@
2525
scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
2626
debug ptr => _6;
2727
let mut _8: *const [bool; 0];
28+
let mut _9: *mut [bool; 0];
2829
scope 12 {
2930
scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
30-
debug ptr => _6;
31+
debug ptr => _9;
3132
scope 14 (inlined std::ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
32-
debug self => _6;
33-
let mut _9: *mut u8;
33+
debug self => _9;
34+
let mut _10: *mut u8;
3435
scope 15 {
3536
scope 16 (inlined std::ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
36-
debug ptr => _9;
37+
debug ptr => _10;
3738
scope 17 (inlined std::ptr::mut_ptr::<impl *mut u8>::addr) {
38-
debug self => _9;
39+
debug self => _10;
3940
scope 18 {
4041
scope 19 (inlined std::ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
41-
debug self => _9;
42+
debug self => _10;
4243
}
4344
}
4445
}
@@ -74,8 +75,10 @@
7475
StorageDead(_7);
7576
StorageLive(_8);
7677
StorageLive(_9);
78+
StorageLive(_10);
7779
_8 = const {0x1 as *mut [bool; 0]} as *const [bool; 0] (PointerCoercion(MutToConstPointer));
7880
_5 = NonNull::<[bool; 0]> { pointer: _8 };
81+
StorageDead(_10);
7982
StorageDead(_9);
8083
StorageDead(_8);
8184
StorageDead(_6);

‎tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.32bit.panic-abort.diff‎

Lines changed: 9 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -25,20 +25,21 @@
2525
scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
2626
debug ptr => _6;
2727
let mut _8: *const [bool; 0];
28+
let mut _9: *mut [bool; 0];
2829
scope 12 {
2930
scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
30-
debug ptr => _6;
31+
debug ptr => _9;
3132
scope 14 (inlined std::ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
32-
debug self => _6;
33-
let mut _9: *mut u8;
33+
debug self => _9;
34+
let mut _10: *mut u8;
3435
scope 15 {
3536
scope 16 (inlined std::ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
36-
debug ptr => _9;
37+
debug ptr => _10;
3738
scope 17 (inlined std::ptr::mut_ptr::<impl *mut u8>::addr) {
38-
debug self => _9;
39+
debug self => _10;
3940
scope 18 {
4041
scope 19 (inlined std::ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
41-
debug self => _9;
42+
debug self => _10;
4243
}
4344
}
4445
}
@@ -76,9 +77,11 @@
7677
StorageDead(_7);
7778
StorageLive(_8);
7879
StorageLive(_9);
80+
StorageLive(_10);
7981
- _8 = _6 as *const [bool; 0] (PointerCoercion(MutToConstPointer));
8082
+ _8 = const {0x1 as *mut [bool; 0]} as *const [bool; 0] (PointerCoercion(MutToConstPointer));
8183
_5 = NonNull::<[bool; 0]> { pointer: _8 };
84+
StorageDead(_10);
8285
StorageDead(_9);
8386
StorageDead(_8);
8487
StorageDead(_6);

‎tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.32bit.panic-unwind.diff‎

Lines changed: 9 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -25,20 +25,21 @@
2525
scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
2626
debug ptr => _6;
2727
let mut _8: *const [bool; 0];
28+
let mut _9: *mut [bool; 0];
2829
scope 12 {
2930
scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
30-
debug ptr => _6;
31+
debug ptr => _9;
3132
scope 14 (inlined std::ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
32-
debug self => _6;
33-
let mut _9: *mut u8;
33+
debug self => _9;
34+
let mut _10: *mut u8;
3435
scope 15 {
3536
scope 16 (inlined std::ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
36-
debug ptr => _9;
37+
debug ptr => _10;
3738
scope 17 (inlined std::ptr::mut_ptr::<impl *mut u8>::addr) {
38-
debug self => _9;
39+
debug self => _10;
3940
scope 18 {
4041
scope 19 (inlined std::ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
41-
debug self => _9;
42+
debug self => _10;
4243
}
4344
}
4445
}
@@ -76,9 +77,11 @@
7677
StorageDead(_7);
7778
StorageLive(_8);
7879
StorageLive(_9);
80+
StorageLive(_10);
7981
- _8 = _6 as *const [bool; 0] (PointerCoercion(MutToConstPointer));
8082
+ _8 = const {0x1 as *mut [bool; 0]} as *const [bool; 0] (PointerCoercion(MutToConstPointer));
8183
_5 = NonNull::<[bool; 0]> { pointer: _8 };
84+
StorageDead(_10);
8285
StorageDead(_9);
8386
StorageDead(_8);
8487
StorageDead(_6);

‎tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.64bit.panic-abort.diff‎

Lines changed: 9 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -25,20 +25,21 @@
2525
scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
2626
debug ptr => _6;
2727
let mut _8: *const [bool; 0];
28+
let mut _9: *mut [bool; 0];
2829
scope 12 {
2930
scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
30-
debug ptr => _6;
31+
debug ptr => _9;
3132
scope 14 (inlined std::ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
32-
debug self => _6;
33-
let mut _9: *mut u8;
33+
debug self => _9;
34+
let mut _10: *mut u8;
3435
scope 15 {
3536
scope 16 (inlined std::ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
36-
debug ptr => _9;
37+
debug ptr => _10;
3738
scope 17 (inlined std::ptr::mut_ptr::<impl *mut u8>::addr) {
38-
debug self => _9;
39+
debug self => _10;
3940
scope 18 {
4041
scope 19 (inlined std::ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
41-
debug self => _9;
42+
debug self => _10;
4243
}
4344
}
4445
}
@@ -76,9 +77,11 @@
7677
StorageDead(_7);
7778
StorageLive(_8);
7879
StorageLive(_9);
80+
StorageLive(_10);
7981
- _8 = _6 as *const [bool; 0] (PointerCoercion(MutToConstPointer));
8082
+ _8 = const {0x1 as *mut [bool; 0]} as *const [bool; 0] (PointerCoercion(MutToConstPointer));
8183
_5 = NonNull::<[bool; 0]> { pointer: _8 };
84+
StorageDead(_10);
8285
StorageDead(_9);
8386
StorageDead(_8);
8487
StorageDead(_6);

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