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Allow GVN to produce places and not just locals.

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This commit is contained in:
Camille GILLOT 2025-04-03 13:04:41 +00:00
parent f174fd716a
commit 109edab245
17 changed files with 203 additions and 58 deletions
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66
compiler/rustc_mir_transform/src/gvn.rs
View file

@ -980,27 +980,15 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
}
}
let tcx = self.tcx;
let mut projection = SmallVec::<[PlaceElem<'tcx>; 1]>::new();
loop {
if let Some(local) = self.try_as_local(copy_from_local_value, location) {
projection.reverse();
let place = Place { local, projection: tcx.mk_place_elems(projection.as_slice()) };
if rvalue.ty(self.local_decls, tcx) == place.ty(self.local_decls, tcx).ty {
self.reused_locals.insert(local);
*rvalue = Rvalue::Use(Operand::Copy(place));
return Some(copy_from_value);
}
return None;
} else if let Value::Projection(pointer, proj) = *self.get(copy_from_local_value)
&& let Some(proj) = self.try_as_place_elem(proj, location)
{
projection.push(proj);
copy_from_local_value = pointer;
} else {
return None;
if let Some(place) = self.try_as_place(copy_from_local_value, location) {
if rvalue.ty(self.local_decls, self.tcx) == place.ty(self.local_decls, self.tcx).ty {
self.reused_locals.insert(place.local);
*rvalue = Rvalue::Use(Operand::Copy(place));
return Some(copy_from_local_value);
}
}
None
}
fn simplify_aggregate(
@ -1672,14 +1660,14 @@ fn op_to_prop_const<'tcx>(
}
impl<'tcx> VnState<'_, 'tcx> {
/// If either [`Self::try_as_constant`] as [`Self::try_as_local`] succeeds,
/// If either [`Self::try_as_constant`] as [`Self::try_as_place`] succeeds,
/// returns that result as an [`Operand`].
fn try_as_operand(&mut self, index: VnIndex, location: Location) -> Option<Operand<'tcx>> {
if let Some(const_) = self.try_as_constant(index) {
Some(Operand::Constant(Box::new(const_)))
} else if let Some(local) = self.try_as_local(index, location) {
self.reused_locals.insert(local);
Some(Operand::Copy(local.into()))
} else if let Some(place) = self.try_as_place(index, location) {
self.reused_locals.insert(place.local);
Some(Operand::Copy(place))
} else {
None
}
@ -1712,6 +1700,29 @@ impl<'tcx> VnState<'_, 'tcx> {
Some(ConstOperand { span: DUMMY_SP, user_ty: None, const_ })
}
/// Construct a place which holds the same value as `index` and for which all locals strictly
/// dominate `loc`. If you used this place, add its base local to `reused_locals` to remove
/// storage statements.
#[instrument(level = "trace", skip(self), ret)]
fn try_as_place(&mut self, mut index: VnIndex, loc: Location) -> Option<Place<'tcx>> {
let mut projection = SmallVec::<[PlaceElem<'tcx>; 1]>::new();
loop {
if let Some(local) = self.try_as_local(index, loc) {
projection.reverse();
let place =
Place { local, projection: self.tcx.mk_place_elems(projection.as_slice()) };
return Some(place);
} else if let Value::Projection(pointer, proj) = *self.get(index)
&& let Some(proj) = self.try_as_place_elem(proj, loc)
{
projection.push(proj);
index = pointer;
} else {
return None;
}
}
}
/// If there is a local which is assigned `index`, and its assignment strictly dominates `loc`,
/// return it. If you used this local, add it to `reused_locals` to remove storage statements.
fn try_as_local(&mut self, index: VnIndex, loc: Location) -> Option<Local> {
@ -1762,11 +1773,12 @@ impl<'tcx> MutVisitor<'tcx> for VnState<'_, 'tcx> {
if let Some(value) = value {
if let Some(const_) = self.try_as_constant(value) {
*rvalue = Rvalue::Use(Operand::Constant(Box::new(const_)));
} else if let Some(local) = self.try_as_local(value, location)
&& *rvalue != Rvalue::Use(Operand::Move(local.into()))
} else if let Some(place) = self.try_as_place(value, location)
&& *rvalue != Rvalue::Use(Operand::Move(place))
&& *rvalue != Rvalue::Use(Operand::Copy(place))
{
*rvalue = Rvalue::Use(Operand::Copy(local.into()));
self.reused_locals.insert(local);
*rvalue = Rvalue::Use(Operand::Copy(place));
self.reused_locals.insert(place.local);
}
}
}

6
tests/mir-opt/const_prop/address_of_pair.fn0.GVN.diff
View file

@ -31,15 +31,13 @@
(*_3) = const true;
_4 = const ();
StorageDead(_4);
- StorageLive(_5);
+ nop;
StorageLive(_5);
StorageLive(_6);
_6 = copy (_2.1: bool);
_5 = Not(move _6);
StorageDead(_6);
_0 = copy _5;
- StorageDead(_5);
+ nop;
StorageDead(_5);
StorageDead(_3);
StorageDead(_2);
return;

8
tests/mir-opt/dont_reset_cast_kind_without_updating_operand.test.GVN.32bit.panic-abort.diff
View file

@ -69,8 +69,7 @@
bb0: {
StorageLive(_1);
- StorageLive(_2);
+ nop;
StorageLive(_2);
StorageLive(_3);
StorageLive(_11);
StorageLive(_12);
@ -119,8 +118,7 @@
StorageDead(_11);
_2 = &_3;
_1 = copy _2;
- StorageDead(_2);
+ nop;
StorageDead(_2);
StorageLive(_4);
- _9 = deref_copy _3;
+ _9 = copy _3;
@ -141,7 +139,7 @@
StorageLive(_8);
_8 = copy _5;
- _7 = copy _8 as *mut () (PtrToPtr);
+ _7 = copy _5 as *mut () (PtrToPtr);
+ _7 = copy ((_9.0: std::ptr::Unique<()>).0: std::ptr::NonNull<()>) as *mut () (Transmute);
StorageDead(_8);
StorageDead(_7);
- StorageDead(_5);

8
tests/mir-opt/dont_reset_cast_kind_without_updating_operand.test.GVN.32bit.panic-unwind.diff
View file

@ -35,8 +35,7 @@
bb0: {
StorageLive(_1);
- StorageLive(_2);
+ nop;
StorageLive(_2);
StorageLive(_3);
_3 = Box::<()>::new(const ()) -> [return: bb1, unwind continue];
}
@ -44,8 +43,7 @@
bb1: {
_2 = &_3;
_1 = copy _2;
- StorageDead(_2);
+ nop;
StorageDead(_2);
StorageLive(_4);
- _9 = deref_copy _3;
+ _9 = copy _3;
@ -66,7 +64,7 @@
StorageLive(_8);
_8 = copy _5;
- _7 = copy _8 as *mut () (PtrToPtr);
+ _7 = copy _5 as *mut () (PtrToPtr);
+ _7 = copy ((_9.0: std::ptr::Unique<()>).0: std::ptr::NonNull<()>) as *mut () (Transmute);
StorageDead(_8);
StorageDead(_7);
- StorageDead(_5);

8
tests/mir-opt/dont_reset_cast_kind_without_updating_operand.test.GVN.64bit.panic-abort.diff
View file

@ -69,8 +69,7 @@
bb0: {
StorageLive(_1);
- StorageLive(_2);
+ nop;
StorageLive(_2);
StorageLive(_3);
StorageLive(_11);
StorageLive(_12);
@ -119,8 +118,7 @@
StorageDead(_11);
_2 = &_3;
_1 = copy _2;
- StorageDead(_2);
+ nop;
StorageDead(_2);
StorageLive(_4);
- _9 = deref_copy _3;
+ _9 = copy _3;
@ -141,7 +139,7 @@
StorageLive(_8);
_8 = copy _5;
- _7 = copy _8 as *mut () (PtrToPtr);
+ _7 = copy _5 as *mut () (PtrToPtr);
+ _7 = copy ((_9.0: std::ptr::Unique<()>).0: std::ptr::NonNull<()>) as *mut () (Transmute);
StorageDead(_8);
StorageDead(_7);
- StorageDead(_5);

8
tests/mir-opt/dont_reset_cast_kind_without_updating_operand.test.GVN.64bit.panic-unwind.diff
View file

@ -35,8 +35,7 @@
bb0: {
StorageLive(_1);
- StorageLive(_2);
+ nop;
StorageLive(_2);
StorageLive(_3);
_3 = Box::<()>::new(const ()) -> [return: bb1, unwind continue];
}
@ -44,8 +43,7 @@
bb1: {
_2 = &_3;
_1 = copy _2;
- StorageDead(_2);
+ nop;
StorageDead(_2);
StorageLive(_4);
- _9 = deref_copy _3;
+ _9 = copy _3;
@ -66,7 +64,7 @@
StorageLive(_8);
_8 = copy _5;
- _7 = copy _8 as *mut () (PtrToPtr);
+ _7 = copy _5 as *mut () (PtrToPtr);
+ _7 = copy ((_9.0: std::ptr::Unique<()>).0: std::ptr::NonNull<()>) as *mut () (Transmute);
StorageDead(_8);
StorageDead(_7);
- StorageDead(_5);

3
tests/mir-opt/gvn.remove_casts_must_change_both_sides.GVN.panic-abort.diff
View file

@ -9,7 +9,8 @@
bb0: {
_3 = copy (*_1) as *const u8 (PtrToPtr);
_4 = copy _2 as *const u8 (PtrToPtr);
_0 = Eq(copy _3, copy _4);
- _0 = Eq(copy _3, copy _4);
+ _0 = Eq(copy (*_1), copy _2);
return;
}
}

3
tests/mir-opt/gvn.remove_casts_must_change_both_sides.GVN.panic-unwind.diff
View file

@ -9,7 +9,8 @@
bb0: {
_3 = copy (*_1) as *const u8 (PtrToPtr);
_4 = copy _2 as *const u8 (PtrToPtr);
_0 = Eq(copy _3, copy _4);
- _0 = Eq(copy _3, copy _4);
+ _0 = Eq(copy (*_1), copy _2);
return;
}
}

2
tests/mir-opt/gvn.rs
View file

@ -1048,7 +1048,7 @@ fn remove_casts_must_change_both_sides(mut_a: &*mut u8, mut_b: *mut u8) -> bool
let a = *mut_a as *const u8;
// CHECK: [[B:_.+]] = copy _2 as *const u8 (PtrToPtr);
let b = mut_b as *const u8;
// CHECK: _0 = Eq(copy [[A]], copy [[B]]);
// CHECK: _0 = Eq(copy (*_1), copy _2);
RET = a == b;
Return()
}

58
tests/mir-opt/gvn_copy_constant_projection.compare_constant_index.GVN.panic-abort.diff Normal file
View file

@ -0,0 +1,58 @@
- // MIR for `compare_constant_index` before GVN
+ // MIR for `compare_constant_index` after GVN
fn compare_constant_index(_1: [i32; 1], _2: [i32; 1]) -> std::cmp::Ordering {
debug x => _1;
debug y => _2;
let mut _0: std::cmp::Ordering;
let _3: &i32;
let _4: usize;
let mut _5: bool;
let _6: &i32;
let _7: usize;
let mut _8: bool;
scope 1 (inlined std::cmp::impls::<impl Ord for i32>::cmp) {
let mut _9: i32;
let mut _10: i32;
}
bb0: {
- StorageLive(_4);
+ nop;
_4 = const 0_usize;
- _5 = Lt(copy _4, const 1_usize);
- assert(move _5, "index out of bounds: the length is {} but the index is {}", const 1_usize, copy _4) -> [success: bb1, unwind unreachable];
+ _5 = const true;
+ assert(const true, "index out of bounds: the length is {} but the index is {}", const 1_usize, const 0_usize) -> [success: bb1, unwind unreachable];
}
bb1: {
- _3 = &_1[_4];
+ _3 = &_1[0 of 1];
StorageLive(_7);
_7 = const 0_usize;
- _8 = Lt(copy _7, const 1_usize);
- assert(move _8, "index out of bounds: the length is {} but the index is {}", const 1_usize, copy _7) -> [success: bb2, unwind unreachable];
+ _8 = const true;
+ assert(const true, "index out of bounds: the length is {} but the index is {}", const 1_usize, const 0_usize) -> [success: bb2, unwind unreachable];
}
bb2: {
- _6 = &_2[_7];
+ _6 = &_2[0 of 1];
StorageLive(_9);
- _9 = copy (*_3);
+ _9 = copy _1[0 of 1];
StorageLive(_10);
- _10 = copy (*_6);
+ _10 = copy _2[0 of 1];
_0 = Cmp(move _9, move _10);
StorageDead(_10);
StorageDead(_9);
StorageDead(_7);
- StorageDead(_4);
+ nop;
return;
}
}

58
tests/mir-opt/gvn_copy_constant_projection.compare_constant_index.GVN.panic-unwind.diff Normal file
View file

@ -0,0 +1,58 @@
- // MIR for `compare_constant_index` before GVN
+ // MIR for `compare_constant_index` after GVN
fn compare_constant_index(_1: [i32; 1], _2: [i32; 1]) -> std::cmp::Ordering {
debug x => _1;
debug y => _2;
let mut _0: std::cmp::Ordering;
let _3: &i32;
let _4: usize;
let mut _5: bool;
let _6: &i32;
let _7: usize;
let mut _8: bool;
scope 1 (inlined std::cmp::impls::<impl Ord for i32>::cmp) {
let mut _9: i32;
let mut _10: i32;
}
bb0: {
- StorageLive(_4);
+ nop;
_4 = const 0_usize;
- _5 = Lt(copy _4, const 1_usize);
- assert(move _5, "index out of bounds: the length is {} but the index is {}", const 1_usize, copy _4) -> [success: bb1, unwind continue];
+ _5 = const true;
+ assert(const true, "index out of bounds: the length is {} but the index is {}", const 1_usize, const 0_usize) -> [success: bb1, unwind continue];
}
bb1: {
- _3 = &_1[_4];
+ _3 = &_1[0 of 1];
StorageLive(_7);
_7 = const 0_usize;
- _8 = Lt(copy _7, const 1_usize);
- assert(move _8, "index out of bounds: the length is {} but the index is {}", const 1_usize, copy _7) -> [success: bb2, unwind continue];
+ _8 = const true;
+ assert(const true, "index out of bounds: the length is {} but the index is {}", const 1_usize, const 0_usize) -> [success: bb2, unwind continue];
}
bb2: {
- _6 = &_2[_7];
+ _6 = &_2[0 of 1];
StorageLive(_9);
- _9 = copy (*_3);
+ _9 = copy _1[0 of 1];
StorageLive(_10);
- _10 = copy (*_6);
+ _10 = copy _2[0 of 1];
_0 = Cmp(move _9, move _10);
StorageDead(_10);
StorageDead(_9);
StorageDead(_7);
- StorageDead(_4);
+ nop;
return;
}
}

18
tests/mir-opt/gvn_copy_constant_projection.rs Normal file
View file

@ -0,0 +1,18 @@
// EMIT_MIR_FOR_EACH_PANIC_STRATEGY
use std::cmp::Ordering;
fn compare_constant_index(x: [i32; 1], y: [i32; 1]) -> Ordering {
// CHECK-LABEL: fn compare_constant_index(
// CHECK-NOT: (*{{_.*}});
// CHECK: [[lhs:_.*]] = copy _1[0 of 1];
// CHECK-NOT: (*{{_.*}});
// CHECK: [[rhs:_.*]] = copy _2[0 of 1];
// CHECK: _0 = Cmp(move [[lhs]], move [[rhs]]);
Ord::cmp(&x[0], &y[0])
}
fn main() {
compare_constant_index([1], [2]);
}
// EMIT_MIR gvn_copy_constant_projection.compare_constant_index.GVN.diff

4
tests/mir-opt/inline_coroutine_body.run2-{closure#0}.Inline.panic-abort.diff
View file

@ -229,7 +229,6 @@
+ StorageDead(_24);
+ StorageLive(_45);
+ StorageLive(_46);
+ StorageLive(_49);
+ StorageLive(_51);
+ StorageLive(_42);
+ StorageLive(_43);
@ -243,9 +242,11 @@
+ _47 = Pin::<&mut std::future::Ready<()>> { __pointer: copy _45 };
+ StorageDead(_47);
+ _44 = &mut ((*_45).0: std::option::Option<()>);
+ StorageLive(_49);
+ _49 = Option::<()>::None;
+ _43 = copy ((*_45).0: std::option::Option<()>);
+ ((*_45).0: std::option::Option<()>) = copy _49;
+ StorageDead(_49);
+ StorageDead(_44);
+ StorageLive(_50);
+ _50 = discriminant(_43);
@ -322,7 +323,6 @@
+ _18 = Poll::<()>::Ready(move _42);
+ StorageDead(_42);
+ StorageDead(_51);
+ StorageDead(_49);
+ StorageDead(_46);
+ StorageDead(_45);
+ StorageDead(_22);

4
tests/mir-opt/inline_coroutine_body.run2-{closure#0}.Inline.panic-unwind.diff
View file

@ -246,7 +246,6 @@
+ StorageDead(_24);
+ StorageLive(_47);
+ StorageLive(_48);
+ StorageLive(_51);
+ StorageLive(_53);
+ StorageLive(_44);
+ StorageLive(_45);
@ -260,9 +259,11 @@
+ _49 = Pin::<&mut std::future::Ready<()>> { __pointer: copy _47 };
+ StorageDead(_49);
+ _46 = &mut ((*_47).0: std::option::Option<()>);
+ StorageLive(_51);
+ _51 = Option::<()>::None;
+ _45 = copy ((*_47).0: std::option::Option<()>);
+ ((*_47).0: std::option::Option<()>) = copy _51;
+ StorageDead(_51);
+ StorageDead(_46);
+ StorageLive(_52);
+ _52 = discriminant(_45);
@ -363,7 +364,6 @@
+ _18 = Poll::<()>::Ready(move _44);
+ StorageDead(_44);
+ StorageDead(_53);
+ StorageDead(_51);
+ StorageDead(_48);
+ StorageDead(_47);
+ StorageDead(_22);

3
tests/mir-opt/pre-codegen/derived_ord.demo_le.PreCodegen.after.mir
View file

@ -40,6 +40,7 @@ fn demo_le(_1: &MultiField, _2: &MultiField) -> bool {
StorageLive(_12);
StorageLive(_11);
StorageLive(_5);
StorageLive(_6);
StorageLive(_7);
StorageLive(_3);
_3 = copy ((*_1).0: char);
@ -65,6 +66,7 @@ fn demo_le(_1: &MultiField, _2: &MultiField) -> bool {
_11 = Option::<std::cmp::Ordering>::Some(move _10);
StorageDead(_10);
StorageDead(_7);
StorageDead(_6);
StorageDead(_5);
goto -> bb3;
}
@ -72,6 +74,7 @@ fn demo_le(_1: &MultiField, _2: &MultiField) -> bool {
bb2: {
_11 = copy _6;
StorageDead(_7);
StorageDead(_6);
StorageDead(_5);
goto -> bb3;
}

2
tests/mir-opt/pre-codegen/tuple_ord.demo_ge_partial.PreCodegen.after.mir
View file

@ -44,8 +44,10 @@ fn demo_ge_partial(_1: &(f32, f32), _2: &(f32, f32)) -> bool {
StorageDead(_5);
StorageDead(_4);
StorageDead(_3);
StorageLive(_8);
_8 = copy ((_7 as Break).0: bool);
_0 = copy _8;
StorageDead(_8);
goto -> bb3;
}

2
tests/mir-opt/pre-codegen/tuple_ord.demo_le_total.PreCodegen.after.mir
View file

@ -44,8 +44,10 @@ fn demo_le_total(_1: &(u16, i16), _2: &(u16, i16)) -> bool {
StorageDead(_5);
StorageDead(_4);
StorageDead(_3);
StorageLive(_8);
_8 = copy ((_7 as Break).0: bool);
_0 = copy _8;
StorageDead(_8);
goto -> bb3;
}