Skip to content

Handle all GVN binops in a single place. #125893

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 1 commit into from
Jun 5, 2024
Merged

Handle all GVN binops in a single place. #125893

Changes from all commits
Commits
Show all changes
1 commit
Select commit
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
70 changes: 40 additions & 30 deletions compiler/rustc_mir_transform/src/gvn.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -223,7 +223,6 @@ enum Value<'tcx> {
NullaryOp(NullOp<'tcx>, Ty<'tcx>),
UnaryOp(UnOp, VnIndex),
BinaryOp(BinOp, VnIndex, VnIndex),
CheckedBinaryOp(BinOp, VnIndex, VnIndex), // FIXME get rid of this, work like MIR instead
Cast {
kind: CastKind,
value: VnIndex,
Expand Down Expand Up @@ -508,17 +507,6 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
let val = self.ecx.binary_op(bin_op, &lhs, &rhs).ok()?;
val.into()
}
CheckedBinaryOp(bin_op, lhs, rhs) => {
let lhs = self.evaluated[lhs].as_ref()?;
let lhs = self.ecx.read_immediate(lhs).ok()?;
let rhs = self.evaluated[rhs].as_ref()?;
let rhs = self.ecx.read_immediate(rhs).ok()?;
let val = self
.ecx
.binary_op(bin_op.wrapping_to_overflowing().unwrap(), &lhs, &rhs)
.ok()?;
val.into()
}
Cast { kind, value, from: _, to } => match kind {
CastKind::IntToInt | CastKind::IntToFloat => {
let value = self.evaluated[value].as_ref()?;
Expand Down Expand Up @@ -829,17 +817,10 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
let lhs = lhs?;
let rhs = rhs?;

if let Some(op) = op.overflowing_to_wrapping() {
if let Some(value) = self.simplify_binary(op, true, ty, lhs, rhs) {
return Some(value);
}
Value::CheckedBinaryOp(op, lhs, rhs)
} else {
if let Some(value) = self.simplify_binary(op, false, ty, lhs, rhs) {
return Some(value);
}
Value::BinaryOp(op, lhs, rhs)
if let Some(value) = self.simplify_binary(op, ty, lhs, rhs) {
return Some(value);
}
Value::BinaryOp(op, lhs, rhs)
}
Rvalue::UnaryOp(op, ref mut arg) => {
let arg = self.simplify_operand(arg, location)?;
Expand Down Expand Up @@ -970,7 +951,6 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
fn simplify_binary(
&mut self,
op: BinOp,
checked: bool,
lhs_ty: Ty<'tcx>,
lhs: VnIndex,
rhs: VnIndex,
Expand Down Expand Up @@ -999,22 +979,39 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
use Either::{Left, Right};
let a = as_bits(lhs).map_or(Right(lhs), Left);
let b = as_bits(rhs).map_or(Right(rhs), Left);

let result = match (op, a, b) {
// Neutral elements.
(BinOp::Add | BinOp::BitOr | BinOp::BitXor, Left(0), Right(p))
(
BinOp::Add
| BinOp::AddWithOverflow
| BinOp::AddUnchecked
| BinOp::BitOr
| BinOp::BitXor,
Left(0),
Right(p),
)
| (
BinOp::Add
| BinOp::AddWithOverflow
| BinOp::AddUnchecked
| BinOp::BitOr
| BinOp::BitXor
| BinOp::Sub
| BinOp::SubWithOverflow
| BinOp::SubUnchecked
Copy link
Member

Choose a reason for hiding this comment

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

Thanks for this! It'll fix some things like https://rust.godbolt.org/z/4b8G5h6jc.

| BinOp::Offset
| BinOp::Shl
| BinOp::Shr,
Right(p),
Left(0),
)
| (BinOp::Mul, Left(1), Right(p))
| (BinOp::Mul | BinOp::Div, Right(p), Left(1)) => p,
| (BinOp::Mul | BinOp::MulWithOverflow | BinOp::MulUnchecked, Left(1), Right(p))
| (
BinOp::Mul | BinOp::MulWithOverflow | BinOp::MulUnchecked | BinOp::Div,
Right(p),
Left(1),
) => p,
// Attempt to simplify `x & ALL_ONES` to `x`, with `ALL_ONES` depending on type size.
(BinOp::BitAnd, Right(p), Left(ones)) | (BinOp::BitAnd, Left(ones), Right(p))
if ones == layout.size.truncate(u128::MAX)
Expand All @@ -1023,10 +1020,21 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
p
}
// Absorbing elements.
(BinOp::Mul | BinOp::BitAnd, _, Left(0))
(
BinOp::Mul | BinOp::MulWithOverflow | BinOp::MulUnchecked | BinOp::BitAnd,
_,
Left(0),
)
| (BinOp::Rem, _, Left(1))
| (
BinOp::Mul | BinOp::Div | BinOp::Rem | BinOp::BitAnd | BinOp::Shl | BinOp::Shr,
BinOp::Mul
| BinOp::MulWithOverflow
| BinOp::MulUnchecked
| BinOp::Div
| BinOp::Rem
| BinOp::BitAnd
| BinOp::Shl
| BinOp::Shr,
Left(0),
_,
) => self.insert_scalar(Scalar::from_uint(0u128, layout.size), lhs_ty),
Expand All @@ -1038,7 +1046,9 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
self.insert_scalar(Scalar::from_uint(ones, layout.size), lhs_ty)
}
// Sub/Xor with itself.
(BinOp::Sub | BinOp::BitXor, a, b) if a == b => {
(BinOp::Sub | BinOp::SubWithOverflow | BinOp::SubUnchecked | BinOp::BitXor, a, b)
if a == b =>
{
self.insert_scalar(Scalar::from_uint(0u128, layout.size), lhs_ty)
}
// Comparison:
Expand All @@ -1052,7 +1062,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
_ => return None,
};

if checked {
if op.is_overflowing() {
let false_val = self.insert_bool(false);
Some(self.insert_tuple(vec![result, false_val]))
} else {
Expand Down