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Auto merge of rust-lang#119672 - cjgillot:dse-sandwich, r=oli-obk
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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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@bors
bors committed Jan 16, 2024
2 parents f9c2421 + bc35ee4 commit fa0dc20
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Showing 71 changed files with 549 additions and 290 deletions.
14 changes: 11 additions & 3 deletions compiler/rustc_mir_transform/src/dead_store_elimination.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -123,13 +123,21 @@ pub fn eliminate<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
let Operand::Copy(place) = *arg else { bug!() };
*arg = Operand::Move(place);
}

crate::simplify::simplify_locals(body, tcx)
}

pub struct DeadStoreElimination;
pub enum DeadStoreElimination {
Initial,
Final,
}

impl<'tcx> MirPass<'tcx> for DeadStoreElimination {
fn name(&self) -> &'static str {
match self {
DeadStoreElimination::Initial => "DeadStoreElimination-initial",
DeadStoreElimination::Final => "DeadStoreElimination-final",
}
}

fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
sess.mir_opt_level() >= 2
}
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9 changes: 5 additions & 4 deletions compiler/rustc_mir_transform/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -596,24 +596,25 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
&multiple_return_terminators::MultipleReturnTerminators,
&instsimplify::InstSimplify,
&simplify::SimplifyLocals::BeforeConstProp,
&copy_prop::CopyProp,
&dead_store_elimination::DeadStoreElimination::Initial,
&gvn::GVN,
&simplify::SimplifyLocals::AfterGVN,
// Perform `SeparateConstSwitch` after SSA-based analyses, as cloning blocks may
// destroy the SSA property. It should still happen before const-propagation, so the
// latter pass will leverage the created opportunities.
&separate_const_switch::SeparateConstSwitch,
&gvn::GVN,
&simplify::SimplifyLocals::AfterGVN,
&dataflow_const_prop::DataflowConstProp,
&const_debuginfo::ConstDebugInfo,
&o1(simplify_branches::SimplifyConstCondition::AfterConstProp),
&jump_threading::JumpThreading,
&early_otherwise_branch::EarlyOtherwiseBranch,
&simplify_comparison_integral::SimplifyComparisonIntegral,
&dead_store_elimination::DeadStoreElimination,
&dest_prop::DestinationPropagation,
&o1(simplify_branches::SimplifyConstCondition::Final),
&o1(remove_noop_landing_pads::RemoveNoopLandingPads),
&o1(simplify::SimplifyCfg::Final),
&copy_prop::CopyProp,
&dead_store_elimination::DeadStoreElimination::Final,
&nrvo::RenameReturnPlace,
&simplify::SimplifyLocals::Final,
&multiple_return_terminators::MultipleReturnTerminators,
Expand Down
15 changes: 9 additions & 6 deletions ...opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.32bit.panic-abort.diff
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Original file line number Diff line number Diff line change
Expand Up @@ -25,20 +25,21 @@
scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
debug ptr => _6;
let mut _8: *const [bool; 0];
let mut _9: *mut [bool; 0];
scope 12 {
scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
debug ptr => _6;
debug ptr => _9;
scope 14 (inlined std::ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
debug self => _6;
let mut _9: *mut u8;
debug self => _9;
let mut _10: *mut u8;
scope 15 {
scope 16 (inlined std::ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
debug ptr => _9;
debug ptr => _10;
scope 17 (inlined std::ptr::mut_ptr::<impl *mut u8>::addr) {
debug self => _9;
debug self => _10;
scope 18 {
scope 19 (inlined std::ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
debug self => _9;
debug self => _10;
}
}
}
Expand Down Expand Up @@ -74,8 +75,10 @@
StorageDead(_7);
StorageLive(_8);
StorageLive(_9);
StorageLive(_10);
_8 = const {0x1 as *mut [bool; 0]} as *const [bool; 0] (PointerCoercion(MutToConstPointer));
_5 = NonNull::<[bool; 0]> { pointer: _8 };
StorageDead(_10);
StorageDead(_9);
StorageDead(_8);
StorageDead(_6);
Expand Down
15 changes: 9 additions & 6 deletions ...pt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.32bit.panic-unwind.diff
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Original file line number Diff line number Diff line change
Expand Up @@ -25,20 +25,21 @@
scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
debug ptr => _6;
let mut _8: *const [bool; 0];
let mut _9: *mut [bool; 0];
scope 12 {
scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
debug ptr => _6;
debug ptr => _9;
scope 14 (inlined std::ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
debug self => _6;
let mut _9: *mut u8;
debug self => _9;
let mut _10: *mut u8;
scope 15 {
scope 16 (inlined std::ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
debug ptr => _9;
debug ptr => _10;
scope 17 (inlined std::ptr::mut_ptr::<impl *mut u8>::addr) {
debug self => _9;
debug self => _10;
scope 18 {
scope 19 (inlined std::ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
debug self => _9;
debug self => _10;
}
}
}
Expand Down Expand Up @@ -74,8 +75,10 @@
StorageDead(_7);
StorageLive(_8);
StorageLive(_9);
StorageLive(_10);
_8 = const {0x1 as *mut [bool; 0]} as *const [bool; 0] (PointerCoercion(MutToConstPointer));
_5 = NonNull::<[bool; 0]> { pointer: _8 };
StorageDead(_10);
StorageDead(_9);
StorageDead(_8);
StorageDead(_6);
Expand Down
15 changes: 9 additions & 6 deletions ...opt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.64bit.panic-abort.diff
View file
Original file line number Diff line number Diff line change
Expand Up @@ -25,20 +25,21 @@
scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
debug ptr => _6;
let mut _8: *const [bool; 0];
let mut _9: *mut [bool; 0];
scope 12 {
scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
debug ptr => _6;
debug ptr => _9;
scope 14 (inlined std::ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
debug self => _6;
let mut _9: *mut u8;
debug self => _9;
let mut _10: *mut u8;
scope 15 {
scope 16 (inlined std::ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
debug ptr => _9;
debug ptr => _10;
scope 17 (inlined std::ptr::mut_ptr::<impl *mut u8>::addr) {
debug self => _9;
debug self => _10;
scope 18 {
scope 19 (inlined std::ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
debug self => _9;
debug self => _10;
}
}
}
Expand Down Expand Up @@ -74,8 +75,10 @@
StorageDead(_7);
StorageLive(_8);
StorageLive(_9);
StorageLive(_10);
_8 = const {0x1 as *mut [bool; 0]} as *const [bool; 0] (PointerCoercion(MutToConstPointer));
_5 = NonNull::<[bool; 0]> { pointer: _8 };
StorageDead(_10);
StorageDead(_9);
StorageDead(_8);
StorageDead(_6);
Expand Down
15 changes: 9 additions & 6 deletions ...pt/dataflow-const-prop/default_boxed_slice.main.DataflowConstProp.64bit.panic-unwind.diff
View file
Original file line number Diff line number Diff line change
Expand Up @@ -25,20 +25,21 @@
scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
debug ptr => _6;
let mut _8: *const [bool; 0];
let mut _9: *mut [bool; 0];
scope 12 {
scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
debug ptr => _6;
debug ptr => _9;
scope 14 (inlined std::ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
debug self => _6;
let mut _9: *mut u8;
debug self => _9;
let mut _10: *mut u8;
scope 15 {
scope 16 (inlined std::ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
debug ptr => _9;
debug ptr => _10;
scope 17 (inlined std::ptr::mut_ptr::<impl *mut u8>::addr) {
debug self => _9;
debug self => _10;
scope 18 {
scope 19 (inlined std::ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
debug self => _9;
debug self => _10;
}
}
}
Expand Down Expand Up @@ -74,8 +75,10 @@
StorageDead(_7);
StorageLive(_8);
StorageLive(_9);
StorageLive(_10);
_8 = const {0x1 as *mut [bool; 0]} as *const [bool; 0] (PointerCoercion(MutToConstPointer));
_5 = NonNull::<[bool; 0]> { pointer: _8 };
StorageDead(_10);
StorageDead(_9);
StorageDead(_8);
StorageDead(_6);
Expand Down
15 changes: 9 additions & 6 deletions tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.32bit.panic-abort.diff
View file
Original file line number Diff line number Diff line change
Expand Up @@ -25,20 +25,21 @@
scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
debug ptr => _6;
let mut _8: *const [bool; 0];
let mut _9: *mut [bool; 0];
scope 12 {
scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
debug ptr => _6;
debug ptr => _9;
scope 14 (inlined std::ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
debug self => _6;
let mut _9: *mut u8;
debug self => _9;
let mut _10: *mut u8;
scope 15 {
scope 16 (inlined std::ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
debug ptr => _9;
debug ptr => _10;
scope 17 (inlined std::ptr::mut_ptr::<impl *mut u8>::addr) {
debug self => _9;
debug self => _10;
scope 18 {
scope 19 (inlined std::ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
debug self => _9;
debug self => _10;
}
}
}
Expand Down Expand Up @@ -76,9 +77,11 @@
StorageDead(_7);
StorageLive(_8);
StorageLive(_9);
StorageLive(_10);
- _8 = _6 as *const [bool; 0] (PointerCoercion(MutToConstPointer));
+ _8 = const {0x1 as *mut [bool; 0]} as *const [bool; 0] (PointerCoercion(MutToConstPointer));
_5 = NonNull::<[bool; 0]> { pointer: _8 };
StorageDead(_10);
StorageDead(_9);
StorageDead(_8);
StorageDead(_6);
Expand Down
15 changes: 9 additions & 6 deletions tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.32bit.panic-unwind.diff
View file
Original file line number Diff line number Diff line change
Expand Up @@ -25,20 +25,21 @@
scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
debug ptr => _6;
let mut _8: *const [bool; 0];
let mut _9: *mut [bool; 0];
scope 12 {
scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
debug ptr => _6;
debug ptr => _9;
scope 14 (inlined std::ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
debug self => _6;
let mut _9: *mut u8;
debug self => _9;
let mut _10: *mut u8;
scope 15 {
scope 16 (inlined std::ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
debug ptr => _9;
debug ptr => _10;
scope 17 (inlined std::ptr::mut_ptr::<impl *mut u8>::addr) {
debug self => _9;
debug self => _10;
scope 18 {
scope 19 (inlined std::ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
debug self => _9;
debug self => _10;
}
}
}
Expand Down Expand Up @@ -76,9 +77,11 @@
StorageDead(_7);
StorageLive(_8);
StorageLive(_9);
StorageLive(_10);
- _8 = _6 as *const [bool; 0] (PointerCoercion(MutToConstPointer));
+ _8 = const {0x1 as *mut [bool; 0]} as *const [bool; 0] (PointerCoercion(MutToConstPointer));
_5 = NonNull::<[bool; 0]> { pointer: _8 };
StorageDead(_10);
StorageDead(_9);
StorageDead(_8);
StorageDead(_6);
Expand Down
15 changes: 9 additions & 6 deletions tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.64bit.panic-abort.diff
View file
Original file line number Diff line number Diff line change
Expand Up @@ -25,20 +25,21 @@
scope 11 (inlined NonNull::<[bool; 0]>::new_unchecked) {
debug ptr => _6;
let mut _8: *const [bool; 0];
let mut _9: *mut [bool; 0];
scope 12 {
scope 13 (inlined NonNull::<T>::new_unchecked::runtime::<[bool; 0]>) {
debug ptr => _6;
debug ptr => _9;
scope 14 (inlined std::ptr::mut_ptr::<impl *mut [bool; 0]>::is_null) {
debug self => _6;
let mut _9: *mut u8;
debug self => _9;
let mut _10: *mut u8;
scope 15 {
scope 16 (inlined std::ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) {
debug ptr => _9;
debug ptr => _10;
scope 17 (inlined std::ptr::mut_ptr::<impl *mut u8>::addr) {
debug self => _9;
debug self => _10;
scope 18 {
scope 19 (inlined std::ptr::mut_ptr::<impl *mut u8>::cast::<()>) {
debug self => _9;
debug self => _10;
}
}
}
Expand Down Expand Up @@ -76,9 +77,11 @@
StorageDead(_7);
StorageLive(_8);
StorageLive(_9);
StorageLive(_10);
- _8 = _6 as *const [bool; 0] (PointerCoercion(MutToConstPointer));
+ _8 = const {0x1 as *mut [bool; 0]} as *const [bool; 0] (PointerCoercion(MutToConstPointer));
_5 = NonNull::<[bool; 0]> { pointer: _8 };
StorageDead(_10);
StorageDead(_9);
StorageDead(_8);
StorageDead(_6);
Expand Down
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