Rollup merge of #73938 - nbdd0121:checked_opt, r=nagisa

Optimise fast path of checked_ops with `unlikely`

This PR marks paths returning `None` in checked_ops as unlikely to improvde codegen.

Fixes #73731

Author: Manishearth

src/libcore/num/mod.rs

@@ -21,6 +21,21 @@ macro_rules! try_opt {
     };
 }
 
+#[cfg(bootstrap)]
+macro_rules! unlikely {
+    ($e: expr) => {
+        $e
+    };
+}
+
+#[cfg(not(bootstrap))]
+#[allow_internal_unstable(const_likely)]
+macro_rules! unlikely {
+    ($e: expr) => {
+        intrinsics::unlikely($e)
+    };
+}
+
 macro_rules! impl_nonzero_fmt {
     ( #[$stability: meta] ( $( $Trait: ident ),+ ) for $Ty: ident ) => {
         $(
@@ -746,7 +761,7 @@ $EndFeature, "
             #[inline]
             pub const fn checked_add(self, rhs: Self) -> Option<Self> {
                 let (a, b) = self.overflowing_add(rhs);
-                if b {None} else {Some(a)}
+                if unlikely!(b) {None} else {Some(a)}
             }
         }
 
@@ -790,7 +805,7 @@ $EndFeature, "
             #[inline]
             pub const fn checked_sub(self, rhs: Self) -> Option<Self> {
                 let (a, b) = self.overflowing_sub(rhs);
-                if b {None} else {Some(a)}
+                if unlikely!(b) {None} else {Some(a)}
             }
         }
 
@@ -834,7 +849,7 @@ $EndFeature, "
             #[inline]
             pub const fn checked_mul(self, rhs: Self) -> Option<Self> {
                 let (a, b) = self.overflowing_mul(rhs);
-                if b {None} else {Some(a)}
+                if unlikely!(b) {None} else {Some(a)}
             }
         }
 
@@ -878,7 +893,7 @@ $EndFeature, "
                           without modifying the original"]
             #[inline]
             pub const fn checked_div(self, rhs: Self) -> Option<Self> {
-                if rhs == 0 || (self == Self::MIN && rhs == -1) {
+                if unlikely!(rhs == 0 || (self == Self::MIN && rhs == -1)) {
                     None
                 } else {
                     // SAFETY: div by zero and by INT_MIN have been checked above
@@ -907,7 +922,7 @@ assert_eq!((1", stringify!($SelfT), ").checked_div_euclid(0), None);
                           without modifying the original"]
             #[inline]
             pub const fn checked_div_euclid(self, rhs: Self) -> Option<Self> {
-                if rhs == 0 || (self == Self::MIN && rhs == -1) {
+                if unlikely!(rhs == 0 || (self == Self::MIN && rhs == -1)) {
                     None
                 } else {
                     Some(self.div_euclid(rhs))
@@ -936,7 +951,7 @@ $EndFeature, "
                           without modifying the original"]
             #[inline]
             pub const fn checked_rem(self, rhs: Self) -> Option<Self> {
-                if rhs == 0 || (self == Self::MIN && rhs == -1) {
+                if unlikely!(rhs == 0 || (self == Self::MIN && rhs == -1)) {
                     None
                 } else {
                     // SAFETY: div by zero and by INT_MIN have been checked above
@@ -964,7 +979,7 @@ assert_eq!(", stringify!($SelfT), "::MIN.checked_rem_euclid(-1), None);
                           without modifying the original"]
             #[inline]
             pub const fn checked_rem_euclid(self, rhs: Self) -> Option<Self> {
-                if rhs == 0 || (self == Self::MIN && rhs == -1) {
+                if unlikely!(rhs == 0 || (self == Self::MIN && rhs == -1)) {
                     None
                 } else {
                     Some(self.rem_euclid(rhs))
@@ -990,7 +1005,7 @@ $EndFeature, "
             #[inline]
             pub const fn checked_neg(self) -> Option<Self> {
                 let (a, b) = self.overflowing_neg();
-                if b {None} else {Some(a)}
+                if unlikely!(b) {None} else {Some(a)}
             }
         }
 
@@ -1014,7 +1029,7 @@ $EndFeature, "
             #[inline]
             pub const fn checked_shl(self, rhs: u32) -> Option<Self> {
                 let (a, b) = self.overflowing_shl(rhs);
-                if b {None} else {Some(a)}
+                if unlikely!(b) {None} else {Some(a)}
             }
         }
 
@@ -1038,7 +1053,7 @@ $EndFeature, "
             #[inline]
             pub const fn checked_shr(self, rhs: u32) -> Option<Self> {
                 let (a, b) = self.overflowing_shr(rhs);
-                if b {None} else {Some(a)}
+                if unlikely!(b) {None} else {Some(a)}
             }
         }
 
@@ -1745,7 +1760,7 @@ $EndFeature, "
             #[must_use = "this returns the result of the operation, \
                           without modifying the original"]
             pub const fn overflowing_div(self, rhs: Self) -> (Self, bool) {
-                if self == Self::MIN && rhs == -1 {
+                if unlikely!(self == Self::MIN && rhs == -1) {
                     (self, true)
                 } else {
                     (self / rhs, false)
@@ -1778,7 +1793,7 @@ assert_eq!(", stringify!($SelfT), "::MIN.overflowing_div_euclid(-1), (", stringi
             #[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 self == Self::MIN && rhs == -1 {
+                if unlikely!(self == Self::MIN && rhs == -1) {
                     (self, true)
                 } else {
                     (self.div_euclid(rhs), false)
@@ -1812,7 +1827,7 @@ $EndFeature, "
             #[must_use = "this returns the result of the operation, \
                           without modifying the original"]
             pub const fn overflowing_rem(self, rhs: Self) -> (Self, bool) {
-                if self == Self::MIN && rhs == -1 {
+                if unlikely!(self == Self::MIN && rhs == -1) {
                     (0, true)
                 } else {
                     (self % rhs, false)
@@ -1845,7 +1860,7 @@ assert_eq!(", stringify!($SelfT), "::MIN.overflowing_rem_euclid(-1), (0, true));
                           without modifying the original"]
             #[inline]
             pub const fn overflowing_rem_euclid(self, rhs: Self) -> (Self, bool) {
-                if self == Self::MIN && rhs == -1 {
+                if unlikely!(self == Self::MIN && rhs == -1) {
                     (0, true)
                 } else {
                     (self.rem_euclid(rhs), false)
@@ -1876,7 +1891,7 @@ assert_eq!(", stringify!($SelfT), "::MIN.overflowing_neg(), (", stringify!($Self
             #[allow(unused_attributes)]
             #[cfg_attr(bootstrap, allow_internal_unstable(const_if_match))]
             pub const fn overflowing_neg(self) -> (Self, bool) {
-                if self == Self::MIN {
+                if unlikely!(self == Self::MIN) {
                     (Self::MIN, true)
                 } else {
                     (-self, false)
@@ -2988,7 +3003,7 @@ assert_eq!((", stringify!($SelfT), "::MAX - 2).checked_add(3), None);", $EndFeat
             #[inline]
             pub const fn checked_add(self, rhs: Self) -> Option<Self> {
                 let (a, b) = self.overflowing_add(rhs);
-                if b {None} else {Some(a)}
+                if unlikely!(b) {None} else {Some(a)}
             }
         }
 
@@ -3030,7 +3045,7 @@ assert_eq!(0", stringify!($SelfT), ".checked_sub(1), None);", $EndFeature, "
             #[inline]
             pub const fn checked_sub(self, rhs: Self) -> Option<Self> {
                 let (a, b) = self.overflowing_sub(rhs);
-                if b {None} else {Some(a)}
+                if unlikely!(b) {None} else {Some(a)}
             }
         }
 
@@ -3072,7 +3087,7 @@ assert_eq!(", stringify!($SelfT), "::MAX.checked_mul(2), None);", $EndFeature, "
             #[inline]
             pub const fn checked_mul(self, rhs: Self) -> Option<Self> {
                 let (a, b) = self.overflowing_mul(rhs);
-                if b {None} else {Some(a)}
+                if unlikely!(b) {None} else {Some(a)}
             }
         }
 
@@ -3113,11 +3128,12 @@ assert_eq!(1", stringify!($SelfT), ".checked_div(0), None);", $EndFeature, "
                           without modifying the original"]
             #[inline]
             pub const fn checked_div(self, rhs: Self) -> Option<Self> {
-                match rhs {
-                    0 => None,
+                if unlikely!(rhs == 0) {
+                    None
+                } else {
                     // SAFETY: div by zero has been checked above and unsigned types have no other
                     // failure modes for division
-                    rhs => Some(unsafe { intrinsics::unchecked_div(self, rhs) }),
+                    Some(unsafe { intrinsics::unchecked_div(self, rhs) })
                 }
             }
         }
@@ -3140,7 +3156,7 @@ assert_eq!(1", stringify!($SelfT), ".checked_div_euclid(0), None);
                           without modifying the original"]
             #[inline]
             pub const fn checked_div_euclid(self, rhs: Self) -> Option<Self> {
-                if rhs == 0 {
+                if unlikely!(rhs == 0) {
                     None
                 } else {
                     Some(self.div_euclid(rhs))
@@ -3167,7 +3183,7 @@ assert_eq!(5", stringify!($SelfT), ".checked_rem(0), None);", $EndFeature, "
                           without modifying the original"]
             #[inline]
             pub const fn checked_rem(self, rhs: Self) -> Option<Self> {
-                if rhs == 0 {
+                if unlikely!(rhs == 0) {
                     None
                 } else {
                     // SAFETY: div by zero has been checked above and unsigned types have no other
@@ -3195,7 +3211,7 @@ assert_eq!(5", stringify!($SelfT), ".checked_rem_euclid(0), None);
                           without modifying the original"]
             #[inline]
             pub const fn checked_rem_euclid(self, rhs: Self) -> Option<Self> {
-                if rhs == 0 {
+                if unlikely!(rhs == 0) {
                     None
                 } else {
                     Some(self.rem_euclid(rhs))
@@ -3222,7 +3238,7 @@ assert_eq!(1", stringify!($SelfT), ".checked_neg(), None);", $EndFeature, "
             #[inline]
             pub const fn checked_neg(self) -> Option<Self> {
                 let (a, b) = self.overflowing_neg();
-                if b {None} else {Some(a)}
+                if unlikely!(b) {None} else {Some(a)}
             }
         }
 
@@ -3245,7 +3261,7 @@ assert_eq!(0x10", stringify!($SelfT), ".checked_shl(129), None);", $EndFeature,
             #[inline]
             pub const fn checked_shl(self, rhs: u32) -> Option<Self> {
                 let (a, b) = self.overflowing_shl(rhs);
-                if b {None} else {Some(a)}
+                if unlikely!(b) {None} else {Some(a)}
             }
         }
 
@@ -3268,7 +3284,7 @@ assert_eq!(0x10", stringify!($SelfT), ".checked_shr(129), None);", $EndFeature,
             #[inline]
             pub const fn checked_shr(self, rhs: u32) -> Option<Self> {
                 let (a, b) = self.overflowing_shr(rhs);
-                if b {None} else {Some(a)}
+                if unlikely!(b) {None} else {Some(a)}
             }
         }