Skip to content

GVN: Use a VnIndex in Address projection. #144477

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Oct 6, 2025
+233 −138
Merged

GVN: Use a VnIndex in Address projection. #144477

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
1180278
Make Value Copy by arena-allocating vectors.
cjgillot Jul 2, 2025
3d96e54
Use a VnIndex in Address projection.
cjgillot Jul 1, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
322 changes: 191 additions & 131 deletions compiler/rustc_mir_transform/src/gvn.rs
View file
Open in desktop

Large diffs are not rendered by default.

3 changes: 2 additions & 1 deletion tests/mir-opt/gvn.dereference_indexing.GVN.panic-abort.diff
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,8 @@
+ nop;
StorageLive(_8);
StorageLive(_9);
_9 = copy (*_3);
- _9 = copy (*_3);
+ _9 = copy _1[_4];
_8 = opaque::<u8>(move _9) -> [return: bb2, unwind unreachable];
}

Expand Down
3 changes: 2 additions & 1 deletion tests/mir-opt/gvn.dereference_indexing.GVN.panic-unwind.diff
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,8 @@
+ nop;
StorageLive(_8);
StorageLive(_9);
_9 = copy (*_3);
- _9 = copy (*_3);
+ _9 = copy _1[_4];
_8 = opaque::<u8>(move _9) -> [return: bb2, unwind continue];
}

Expand Down
4 changes: 2 additions & 2 deletions tests/mir-opt/gvn.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1065,8 +1065,8 @@ fn dereference_indexing(array: [u8; 2], index: usize) {
&array[i]
};

// CHECK-NOT: [{{.*}}]
// CHECK: [[tmp:_.*]] = copy (*[[a]]);
// CHECK-NOT: StorageDead([[i]]);
// CHECK: [[tmp:_.*]] = copy _1[[[i]]];
// CHECK: opaque::<u8>(move [[tmp]])
opaque(*a);
}
Expand Down
15 changes: 15 additions & 0 deletions tests/mir-opt/gvn_repeat.index_place.GVN.diff
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
- // MIR for `index_place` before GVN
+ // MIR for `index_place` after GVN

fn index_place(_1: usize, _2: usize, _3: [i32; 5]) -> i32 {
let mut _0: i32;
let mut _4: &i32;

bb0: {
_4 = &_3[_1];
_1 = copy _2;
_0 = copy (*_4);
return;
}
}

3 changes: 1 addition & 2 deletions tests/mir-opt/gvn_repeat.repeat_local.GVN.diff
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -10,8 +10,7 @@
_4 = [copy _3; 5];
_5 = &_4[_1];
_1 = copy _2;
- _0 = copy (*_5);
+ _0 = copy _3;
_0 = copy (*_5);
return;
}
}
Expand Down
21 changes: 20 additions & 1 deletion tests/mir-opt/gvn_repeat.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,23 @@

use std::intrinsics::mir::*;

// EMIT_MIR gvn_repeat.index_place.GVN.diff
#[custom_mir(dialect = "runtime")]
pub fn index_place(mut idx1: usize, idx2: usize, array: [i32; 5]) -> i32 {
// CHECK-LABEL: fn index_place(
// CHECK: let mut [[ELEM:.*]]: &i32;
// CHECK: _0 = copy (*[[ELEM]])
mir! {
let elem;
{
elem = &array[idx1];
idx1 = idx2;
RET = *elem;
Return()
}
}
}

// EMIT_MIR gvn_repeat.repeat_place.GVN.diff
#[custom_mir(dialect = "runtime")]
pub fn repeat_place(mut idx1: usize, idx2: usize, val: &i32) -> i32 {
Expand All @@ -29,7 +46,8 @@ pub fn repeat_place(mut idx1: usize, idx2: usize, val: &i32) -> i32 {
#[custom_mir(dialect = "runtime")]
pub fn repeat_local(mut idx1: usize, idx2: usize, val: i32) -> i32 {
// CHECK-LABEL: fn repeat_local(
// CHECK: _0 = copy _3
// CHECK: let mut [[ELEM:.*]]: &i32;
// CHECK: _0 = copy (*[[ELEM]]);
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should we leave a FIXME here?

Copy link
Contributor Author

@cjgillot cjgillot Oct 6, 2025 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

The new result is more correct, so I'd rather not. The current annotation was more of a bug: idx1 is not SSA, so we should never have been able to refer to &array[idx1].

mir! {
let array;
let elem;
Expand All @@ -44,6 +62,7 @@ pub fn repeat_local(mut idx1: usize, idx2: usize, val: i32) -> i32 {
}

fn main() {
assert_eq!(index_place(0, 5, [0; 5]), 0);
assert_eq!(repeat_place(0, 5, &0), 0);
assert_eq!(repeat_local(0, 5, 0), 0);
}
Loading