bjoernager/rust
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Only introduce stable projections.

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This commit is contained in:
Camille GILLOT 2025-04-04 10:27:50 +00:00
parent 109edab245
commit d9caf840e1
4 changed files with 15 additions and 9 deletions
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16
compiler/rustc_mir_transform/src/gvn.rs
View file

@ -980,7 +980,9 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
}
}
if let Some(place) = self.try_as_place(copy_from_local_value, location) {
// Allow introducing places with non-constant offsets, as those are still better than
// reconstructing an aggregate.
if let Some(place) = self.try_as_place(copy_from_local_value, location, true) {
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));
@ -1665,7 +1667,7 @@ impl<'tcx> VnState<'_, 'tcx> {
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(place) = self.try_as_place(index, location) {
} else if let Some(place) = self.try_as_place(index, location, false) {
self.reused_locals.insert(place.local);
Some(Operand::Copy(place))
} else {
@ -1704,7 +1706,12 @@ impl<'tcx> VnState<'_, 'tcx> {
/// 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>> {
fn try_as_place(
&mut self,
mut index: VnIndex,
loc: Location,
allow_complex_projection: bool,
) -> Option<Place<'tcx>> {
let mut projection = SmallVec::<[PlaceElem<'tcx>; 1]>::new();
loop {
if let Some(local) = self.try_as_local(index, loc) {
@ -1713,6 +1720,7 @@ impl<'tcx> VnState<'_, 'tcx> {
Place { local, projection: self.tcx.mk_place_elems(projection.as_slice()) };
return Some(place);
} else if let Value::Projection(pointer, proj) = *self.get(index)
&& (allow_complex_projection || proj.is_stable_offset())
&& let Some(proj) = self.try_as_place_elem(proj, loc)
{
projection.push(proj);
@ -1773,7 +1781,7 @@ 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(place) = self.try_as_place(value, location)
} else if let Some(place) = self.try_as_place(value, location, false)
&& *rvalue != Rvalue::Use(Operand::Move(place))
&& *rvalue != Rvalue::Use(Operand::Copy(place))
{

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

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

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

@ -9,8 +9,7 @@
bb0: {
_3 = copy (*_1) as *const u8 (PtrToPtr);
_4 = copy _2 as *const u8 (PtrToPtr);
- _0 = Eq(copy _3, copy _4);
+ _0 = Eq(copy (*_1), copy _2);
_0 = Eq(copy _3, copy _4);
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 (*_1), copy _2);
// CHECK: _0 = Eq(copy [[A]], copy [[B]]);
RET = a == b;
Return()
}