Skip to content

[mir-opt] Run SimplifyLocals to a fixedpoint and handle most rvalues #70755

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 5 commits into from
Apr 16, 2020
Merged

[mir-opt] Run SimplifyLocals to a fixedpoint and handle most rvalues #70755

Show file tree
Hide file tree
Changes from 2 commits
Commits
Show all changes
5 commits
Select commit Hold shift + click to select a range
0e0a71a
Add test case
wesleywiser Apr 3, 2020
7c0802b
Remove other Rvalues
wesleywiser Apr 3, 2020
de3cf6e
Run `SimplifyLocals` iteratively until we get to a fixedpoint
wesleywiser Apr 4, 2020
da8f3bb
Directly modify the `used_locals` vec
wesleywiser Apr 14, 2020
9666d31
Respond to code review feedback
wesleywiser Apr 16, 2020
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
42 changes: 30 additions & 12 deletions src/librustc_mir/transform/simplify.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -368,21 +368,39 @@ impl<'a, 'tcx> Visitor<'tcx> for DeclMarker<'a, 'tcx> {
if location.statement_index != block.statements.len() {
let stmt = &block.statements[location.statement_index];

fn can_skip_constant(c: &ty::Const<'tcx>) -> bool {
// Keep assignments from unevaluated constants around, since the
// evaluation may report errors, even if the use of the constant
// is dead code.
!matches!(c.val, ty::ConstKind::Unevaluated(..))
}

fn can_skip_operand(o: &Operand<'_>) -> bool {
match o {
Operand::Copy(p) | Operand::Move(p) => !p.is_indirect(),
Operand::Constant(c) => can_skip_constant(c.literal),
}
}

if let StatementKind::Assign(box (dest, rvalue)) = &stmt.kind {
if !dest.is_indirect() && dest.local == *local {
if let Rvalue::Use(Operand::Constant(c)) = rvalue {
match c.literal.val {
// Keep assignments from unevaluated constants around, since the
// evaluation may report errors, even if the use of the constant
// is dead code.
ty::ConstKind::Unevaluated(..) => {}
_ => {
trace!("skipping store of const value {:?} to {:?}", c, dest);
return;
}
let can_skip = match rvalue {
Rvalue::Use(op) => can_skip_operand(op),
Rvalue::Discriminant(_) => true,
Copy link
Member

Choose a reason for hiding this comment

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

Should this use !place.is_indirect()?

Copy link
Member Author

Choose a reason for hiding this comment

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

I think eliminating a read of an indirect place's discriminant is ok in the same way removing a read of its address is. Is there a situation you're thinking of where that wouldn't be true?

Rvalue::BinaryOp(_, l, r) | Rvalue::CheckedBinaryOp(_, l, r) => {
can_skip_operand(l) && can_skip_operand(r)
}
} else if let Rvalue::Discriminant(d) = rvalue {
trace!("skipping store of discriminant value {:?} to {:?}", d, dest);
Rvalue::Repeat(op, c) => can_skip_operand(op) && can_skip_constant(c),
Rvalue::AddressOf(_, _) => true,
Rvalue::Len(_) => true,
Rvalue::UnaryOp(_, op) => can_skip_operand(op),
Rvalue::Aggregate(_, operands) => operands.iter().all(can_skip_operand),

_ => false,
};

if can_skip {
trace!("skipping store of {:?} to {:?}", rvalue, dest);
return;
}
}
Expand Down
16 changes: 8 additions & 8 deletions src/test/mir-opt/const_allocation3/32bit/rustc.main.ConstProp.after.mir
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -30,30 +30,30 @@ fn main() -> () {
}

alloc0 (static: FOO, size: 4, align: 4) {
╾alloc10+0╼ │ ╾──╼
╾alloc9+0─╼ │ ╾──╼
}

alloc10 (size: 168, align: 1) {
alloc9 (size: 168, align: 1) {
0x00 │ ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab │ ................
0x10 │ ab ab ab ab ab ab ab ab ab ab ab ab ╾alloc5+0─╼ │ ............╾──╼
0x10 │ ab ab ab ab ab ab ab ab ab ab ab ab ╾alloc4+0─╼ │ ............╾──╼
0x20 │ 01 ef cd ab 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0x30 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0x40 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0x50 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0x60 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0x70 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0x80 │ 00 00 00 00 00 00 00 00 00 00 ╾alloc7+0─╼ 00 00 │ ..........╾──╼..
0x90 │ ╾alloc8+99╼ 00 00 00 00 00 00 00 00 00 00 00 00 │ ╾──╼............
0x80 │ 00 00 00 00 00 00 00 00 00 00 ╾alloc6+0─╼ 00 00 │ ..........╾──╼..
0x90 │ ╾alloc7+99╼ 00 00 00 00 00 00 00 00 00 00 00 00 │ ╾──╼............
0xa0 │ 00 00 00 00 00 00 00 00 │ ........
}

alloc5 (size: 4, align: 4) {
alloc4 (size: 4, align: 4) {
2a 00 00 00 │ *...
}

alloc7 (fn: main)
alloc6 (fn: main)

alloc8 (size: 100, align: 1) {
alloc7 (size: 100, align: 1) {
0x00 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0x10 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0x20 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
Expand Down
14 changes: 7 additions & 7 deletions src/test/mir-opt/const_allocation3/64bit/rustc.main.ConstProp.after.mir
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -30,31 +30,31 @@ fn main() -> () {
}

alloc0 (static: FOO, size: 8, align: 8) {
╾──────alloc10+0──────╼ │ ╾──────╼
╾──────alloc9+0───────╼ │ ╾──────╼
}

alloc10 (size: 180, align: 1) {
alloc9 (size: 180, align: 1) {
0x00 │ ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab │ ................
0x10 │ ab ab ab ab ab ab ab ab ab ab ab ab ╾─alloc5+0─ │ ............╾───
0x10 │ ab ab ab ab ab ab ab ab ab ab ab ab ╾─alloc4+0─ │ ............╾───
0x20 │ ──────────╼ 01 ef cd ab 00 00 00 00 00 00 00 00 │ ───╼............
0x30 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0x40 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0x50 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0x60 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0x70 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0x80 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ╾──── │ ..............╾─
0x90 │ ────alloc7+0────╼ 00 00 ╾──────alloc8+99──────╼ │ ─────╼..╾──────╼
0x90 │ ────alloc6+0────╼ 00 00 ╾──────alloc7+99──────╼ │ ─────╼..╾──────╼
0xa0 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0xb0 │ 00 00 00 00 │ ....
}

alloc5 (size: 4, align: 4) {
alloc4 (size: 4, align: 4) {
2a 00 00 00 │ *...
}

alloc7 (fn: main)
alloc6 (fn: main)

alloc8 (size: 100, align: 1) {
alloc7 (size: 100, align: 1) {
0x00 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0x10 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
0x20 │ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
Expand Down
60 changes: 10 additions & 50 deletions ...test/mir-opt/const_prop/optimizes_into_variable/32bit/rustc.main.SimplifyLocals.after.mir
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3,15 +3,14 @@
fn main() -> () {
let mut _0: (); // return place in scope 0 at $DIR/optimizes_into_variable.rs:11:11: 11:11
let _1: i32; // in scope 0 at $DIR/optimizes_into_variable.rs:12:9: 12:10
let mut _3: [i32; 6]; // in scope 0 at $DIR/optimizes_into_variable.rs:13:13: 13:31
scope 1 {
debug x => _1; // in scope 1 at $DIR/optimizes_into_variable.rs:12:9: 12:10
let _2: i32; // in scope 1 at $DIR/optimizes_into_variable.rs:13:9: 13:10
scope 2 {
debug y => _2; // in scope 2 at $DIR/optimizes_into_variable.rs:13:9: 13:10
let _4: u32; // in scope 2 at $DIR/optimizes_into_variable.rs:14:9: 14:10
let _3: u32; // in scope 2 at $DIR/optimizes_into_variable.rs:14:9: 14:10
scope 3 {
debug z => _4; // in scope 3 at $DIR/optimizes_into_variable.rs:14:9: 14:10
debug z => _3; // in scope 3 at $DIR/optimizes_into_variable.rs:14:9: 14:10
}
}
}
Expand All @@ -26,70 +25,31 @@ fn main() -> () {
// + span: $DIR/optimizes_into_variable.rs:12:13: 12:18
// + literal: Const { ty: i32, val: Value(Scalar(0x00000004)) }
StorageLive(_2); // bb0[2]: scope 1 at $DIR/optimizes_into_variable.rs:13:9: 13:10
StorageLive(_3); // bb0[3]: scope 1 at $DIR/optimizes_into_variable.rs:13:13: 13:31
_3 = [const 0i32, const 1i32, const 2i32, const 3i32, const 4i32, const 5i32]; // bb0[4]: scope 1 at $DIR/optimizes_into_variable.rs:13:13: 13:31
// ty::Const
// + ty: i32
// + val: Value(Scalar(0x00000000))
// mir::Constant
// + span: $DIR/optimizes_into_variable.rs:13:14: 13:15
// + literal: Const { ty: i32, val: Value(Scalar(0x00000000)) }
// ty::Const
// + ty: i32
// + val: Value(Scalar(0x00000001))
// mir::Constant
// + span: $DIR/optimizes_into_variable.rs:13:17: 13:18
// + literal: Const { ty: i32, val: Value(Scalar(0x00000001)) }
// ty::Const
// + ty: i32
// + val: Value(Scalar(0x00000002))
// mir::Constant
// + span: $DIR/optimizes_into_variable.rs:13:20: 13:21
// + literal: Const { ty: i32, val: Value(Scalar(0x00000002)) }
// ty::Const
// + ty: i32
// + val: Value(Scalar(0x00000003))
// mir::Constant
// + span: $DIR/optimizes_into_variable.rs:13:23: 13:24
// + literal: Const { ty: i32, val: Value(Scalar(0x00000003)) }
// ty::Const
// + ty: i32
// + val: Value(Scalar(0x00000004))
// mir::Constant
// + span: $DIR/optimizes_into_variable.rs:13:26: 13:27
// + literal: Const { ty: i32, val: Value(Scalar(0x00000004)) }
// ty::Const
// + ty: i32
// + val: Value(Scalar(0x00000005))
// mir::Constant
// + span: $DIR/optimizes_into_variable.rs:13:29: 13:30
// + literal: Const { ty: i32, val: Value(Scalar(0x00000005)) }
_2 = const 3i32; // bb0[5]: scope 1 at $DIR/optimizes_into_variable.rs:13:13: 13:34
_2 = const 3i32; // bb0[3]: scope 1 at $DIR/optimizes_into_variable.rs:13:13: 13:34
// ty::Const
// + ty: i32
// + val: Value(Scalar(0x00000003))
// mir::Constant
// + span: $DIR/optimizes_into_variable.rs:13:13: 13:34
// + literal: Const { ty: i32, val: Value(Scalar(0x00000003)) }
StorageDead(_3); // bb0[6]: scope 1 at $DIR/optimizes_into_variable.rs:13:34: 13:35
StorageLive(_4); // bb0[7]: scope 2 at $DIR/optimizes_into_variable.rs:14:9: 14:10
_4 = const 42u32; // bb0[8]: scope 2 at $DIR/optimizes_into_variable.rs:14:13: 14:38
StorageLive(_3); // bb0[4]: scope 2 at $DIR/optimizes_into_variable.rs:14:9: 14:10
_3 = const 42u32; // bb0[5]: scope 2 at $DIR/optimizes_into_variable.rs:14:13: 14:38
// ty::Const
// + ty: u32
// + val: Value(Scalar(0x0000002a))
// mir::Constant
// + span: $DIR/optimizes_into_variable.rs:14:13: 14:38
// + literal: Const { ty: u32, val: Value(Scalar(0x0000002a)) }
_0 = const (); // bb0[9]: scope 0 at $DIR/optimizes_into_variable.rs:11:11: 15:2
_0 = const (); // bb0[6]: scope 0 at $DIR/optimizes_into_variable.rs:11:11: 15:2
// ty::Const
// + ty: ()
// + val: Value(Scalar(<ZST>))
// mir::Constant
// + span: $DIR/optimizes_into_variable.rs:11:11: 15:2
// + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
StorageDead(_4); // bb0[10]: scope 2 at $DIR/optimizes_into_variable.rs:15:1: 15:2
StorageDead(_2); // bb0[11]: scope 1 at $DIR/optimizes_into_variable.rs:15:1: 15:2
StorageDead(_1); // bb0[12]: scope 0 at $DIR/optimizes_into_variable.rs:15:1: 15:2
return; // bb0[13]: scope 0 at $DIR/optimizes_into_variable.rs:15:2: 15:2
StorageDead(_3); // bb0[7]: scope 2 at $DIR/optimizes_into_variable.rs:15:1: 15:2
StorageDead(_2); // bb0[8]: scope 1 at $DIR/optimizes_into_variable.rs:15:1: 15:2
StorageDead(_1); // bb0[9]: scope 0 at $DIR/optimizes_into_variable.rs:15:1: 15:2
return; // bb0[10]: scope 0 at $DIR/optimizes_into_variable.rs:15:2: 15:2
}
}
Loading