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Use BinOp::Cmp for iNN::signum

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This way it can use the nice new LLVM intrinsic in LLVM20.
This commit is contained in:
Scott McMurray
2025-02-28 19:55:42 -08:00
parent 8c392966a0
commit 80046158ba
5 changed files with 10 additions and 11 deletions
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10
library/core/src/intrinsics/mod.rs
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@@ -2528,13 +2528,15 @@ pub const fn bswap<T: Copy>(_x: T) -> T;
#[rustc_intrinsic] #[rustc_intrinsic]
pub const fn bitreverse<T: Copy>(_x: T) -> T; pub const fn bitreverse<T: Copy>(_x: T) -> T;
/// Does a three-way comparison between the two integer arguments. /// Does a three-way comparison between the two arguments,
/// which must be of character or integer (signed or unsigned) type.
/// ///
/// This is included as an intrinsic as it's useful to let it be one thing /// This was originally added because it greatly simplified the MIR in `cmp`
/// in MIR, rather than the multiple checks and switches that make its IR /// implementations, and then LLVM 20 added a backend intrinsic for it too.
/// large and difficult to optimize.
/// ///
/// The stabilized version of this intrinsic is [`Ord::cmp`]. /// The stabilized version of this intrinsic is [`Ord::cmp`].
#[rustc_intrinsic_const_stable_indirect]
#[rustc_nounwind]
#[rustc_intrinsic] #[rustc_intrinsic]
pub const fn three_way_compare<T: Copy>(_lhs: T, _rhss: T) -> crate::cmp::Ordering; pub const fn three_way_compare<T: Copy>(_lhs: T, _rhss: T) -> crate::cmp::Ordering;

5
library/core/src/num/int_macros.rs
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@@ -3571,10 +3571,7 @@ macro_rules! int_impl {
// so delegate it to `Ord` which is already producing -1/0/+1 // so delegate it to `Ord` which is already producing -1/0/+1
// exactly like we need and can be the place to deal with the complexity. // exactly like we need and can be the place to deal with the complexity.
// FIXME(const-hack): replace with cmp crate::intrinsics::three_way_compare(self, 0) as Self
if self < 0 { -1 }
else if self == 0 { 0 }
else { 1 }
} }
/// Returns `true` if `self` is positive and `false` if the number is zero or /// Returns `true` if `self` is positive and `false` if the number is zero or

2
tests/mir-opt/lower_intrinsics.three_way_compare_char.LowerIntrinsics.panic-unwind.diff
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@@ -18,7 +18,7 @@
_4 = copy _1; _4 = copy _1;
StorageLive(_5); StorageLive(_5);
_5 = copy _2; _5 = copy _2;
- _3 = three_way_compare::<char>(move _4, move _5) -> [return: bb1, unwind continue]; - _3 = three_way_compare::<char>(move _4, move _5) -> [return: bb1, unwind unreachable];
+ _3 = Cmp(move _4, move _5); + _3 = Cmp(move _4, move _5);
+ goto -> bb1; + goto -> bb1;
} }

2
tests/mir-opt/lower_intrinsics.three_way_compare_signed.LowerIntrinsics.panic-unwind.diff
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@@ -15,7 +15,7 @@
_4 = copy _1; _4 = copy _1;
StorageLive(_5); StorageLive(_5);
_5 = copy _2; _5 = copy _2;
- _3 = three_way_compare::<i16>(move _4, move _5) -> [return: bb1, unwind continue]; - _3 = three_way_compare::<i16>(move _4, move _5) -> [return: bb1, unwind unreachable];
+ _3 = Cmp(move _4, move _5); + _3 = Cmp(move _4, move _5);
+ goto -> bb1; + goto -> bb1;
} }

2
tests/mir-opt/lower_intrinsics.three_way_compare_unsigned.LowerIntrinsics.panic-unwind.diff
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@@ -18,7 +18,7 @@
_4 = copy _1; _4 = copy _1;
StorageLive(_5); StorageLive(_5);
_5 = copy _2; _5 = copy _2;
- _3 = three_way_compare::<u32>(move _4, move _5) -> [return: bb1, unwind continue]; - _3 = three_way_compare::<u32>(move _4, move _5) -> [return: bb1, unwind unreachable];
+ _3 = Cmp(move _4, move _5); + _3 = Cmp(move _4, move _5);
+ goto -> bb1; + goto -> bb1;
} }