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Use bitand when checking for signed integer division overflow

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For `self == Self::MIN && rhs == -1`, LLVM does not realize that this is the
same check made by `self / rhs`, so the code generated may have some unnecessary
duplication. For `(self == Self::MIN) & (rhs == -1)`, LLVM realizes it is the
same check.
This commit is contained in:
Trevor Spiteri 2021-10-02 12:16:08 +02:00
parent 6e12110812
commit 1139ee32aa
1 changed files with 16 additions and 8 deletions
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24
library/core/src/num/int_macros.rs
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@ -543,7 +543,8 @@ macro_rules! int_impl {
without modifying the original"]
#[inline]
pub const fn checked_div(self, rhs: Self) -> Option<Self> {
if unlikely!(rhs == 0 || (self == Self::MIN && rhs == -1)) {
// Using `&` helps LLVM see that it is the same check made in division.
if unlikely!(rhs == 0 || ((self == Self::MIN) & (rhs == -1))) {
None
} else {
// SAFETY: div by zero and by INT_MIN have been checked above
@ -569,7 +570,8 @@ macro_rules! int_impl {
without modifying the original"]
#[inline]
pub const fn checked_div_euclid(self, rhs: Self) -> Option<Self> {
if unlikely!(rhs == 0 || (self == Self::MIN && rhs == -1)) {
// Using `&` helps LLVM see that it is the same check made in division.
if unlikely!(rhs == 0 || ((self == Self::MIN) & (rhs == -1))) {
None
} else {
Some(self.div_euclid(rhs))
@ -595,7 +597,8 @@ macro_rules! int_impl {
without modifying the original"]
#[inline]
pub const fn checked_rem(self, rhs: Self) -> Option<Self> {
if unlikely!(rhs == 0 || (self == Self::MIN && rhs == -1)) {
// Using `&` helps LLVM see that it is the same check made in division.
if unlikely!(rhs == 0 || ((self == Self::MIN) & (rhs == -1))) {
None
} else {
// SAFETY: div by zero and by INT_MIN have been checked above
@ -621,7 +624,8 @@ macro_rules! int_impl {
without modifying the original"]
#[inline]
pub const fn checked_rem_euclid(self, rhs: Self) -> Option<Self> {
if unlikely!(rhs == 0 || (self == Self::MIN && rhs == -1)) {
// Using `&` helps LLVM see that it is the same check made in division.
if unlikely!(rhs == 0 || ((self == Self::MIN) & (rhs == -1))) {
None
} else {
Some(self.rem_euclid(rhs))
@ -1466,7 +1470,8 @@ macro_rules! int_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
pub const fn overflowing_div(self, rhs: Self) -> (Self, bool) {
if unlikely!(self == Self::MIN && rhs == -1) {
// Using `&` helps LLVM see that it is the same check made in division.
if unlikely!((self == Self::MIN) & (rhs == -1)) {
(self, true)
} else {
(self / rhs, false)
@ -1496,7 +1501,8 @@ macro_rules! int_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
pub const fn overflowing_div_euclid(self, rhs: Self) -> (Self, bool) {
if unlikely!(self == Self::MIN && rhs == -1) {
// Using `&` helps LLVM see that it is the same check made in division.
if unlikely!((self == Self::MIN) & (rhs == -1)) {
(self, true)
} else {
(self.div_euclid(rhs), false)
@ -1527,7 +1533,8 @@ macro_rules! int_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
pub const fn overflowing_rem(self, rhs: Self) -> (Self, bool) {
if unlikely!(self == Self::MIN && rhs == -1) {
// Using `&` helps LLVM see that it is the same check made in division.
if unlikely!((self == Self::MIN) & (rhs == -1)) {
(0, true)
} else {
(self % rhs, false)
@ -1558,7 +1565,8 @@ macro_rules! int_impl {
without modifying the original"]
#[inline]
pub const fn overflowing_rem_euclid(self, rhs: Self) -> (Self, bool) {
if unlikely!(self == Self::MIN && rhs == -1) {
// Using `&` helps LLVM see that it is the same check made in division.
if unlikely!((self == Self::MIN) & (rhs == -1)) {
(0, true)
} else {
(self.rem_euclid(rhs), false)