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| author | Scott McMurray <scottmcm@users.noreply.github.com> | 2017-06-08 21:29:45 -0700 |
|---|---|---|
| committer | Scott McMurray <scottmcm@users.noreply.github.com> | 2017-06-08 23:01:39 -0700 |
| commit | 6d86f0c018b57fcb9ca12c801939130b7f8e441e (patch) | |
| tree | 1563fcaaa1b22911c04c545af1969738a7d293f9 | |
| parent | 13e24003472c13636d4350a530d6e6495775afeb (diff) | |
| download | rust-6d86f0c018b57fcb9ca12c801939130b7f8e441e.tar.gz rust-6d86f0c018b57fcb9ca12c801939130b7f8e441e.zip | |
Use ctlz_nonzero to improve ASM from next_power_of_two
| -rw-r--r-- | src/libcore/num/mod.rs | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs index b76eac9e51f..62d75445cc9 100644 --- a/src/libcore/num/mod.rs +++ b/src/libcore/num/mod.rs @@ -1262,6 +1262,7 @@ macro_rules! uint_impl { ($SelfT:ty, $ActualT:ty, $BITS:expr, $ctpop:path, $ctlz:path, + $ctlz_nonzero:path, $cttz:path, $bswap:path, $add_with_overflow:path, @@ -2184,6 +2185,7 @@ macro_rules! uint_impl { // This method cannot overflow, as in the `next_power_of_two` // overflow cases it instead ends up returning the maximum value // of the type, and can return 0 for 0. + #[inline] fn one_less_than_next_power_of_two(self) -> Self { if self <= 1 { return 0; } @@ -2192,7 +2194,7 @@ macro_rules! uint_impl { // (such as intel pre-haswell) have more efficient ctlz // intrinsics when the argument is non-zero. let p = self - 1; - let z = p.leading_zeros(); + let z = unsafe { $ctlz_nonzero(p) }; <$SelfT>::max_value() >> z } @@ -2236,11 +2238,17 @@ macro_rules! uint_impl { } } +#[cfg(stage0)] +unsafe fn ctlz_nonzero<T>(x: T) -> T { intrinsics::ctlz(x) } +#[cfg(not(stage0))] +unsafe fn ctlz_nonzero<T>(x: T) -> T { intrinsics::ctlz_nonzero(x) } + #[lang = "u8"] impl u8 { uint_impl! { u8, u8, 8, intrinsics::ctpop, intrinsics::ctlz, + ctlz_nonzero, intrinsics::cttz, intrinsics::bswap, intrinsics::add_with_overflow, @@ -2253,6 +2261,7 @@ impl u16 { uint_impl! { u16, u16, 16, intrinsics::ctpop, intrinsics::ctlz, + ctlz_nonzero, intrinsics::cttz, intrinsics::bswap, intrinsics::add_with_overflow, @@ -2265,6 +2274,7 @@ impl u32 { uint_impl! { u32, u32, 32, intrinsics::ctpop, intrinsics::ctlz, + ctlz_nonzero, intrinsics::cttz, intrinsics::bswap, intrinsics::add_with_overflow, @@ -2277,6 +2287,7 @@ impl u64 { uint_impl! { u64, u64, 64, intrinsics::ctpop, intrinsics::ctlz, + ctlz_nonzero, intrinsics::cttz, intrinsics::bswap, intrinsics::add_with_overflow, @@ -2289,6 +2300,7 @@ impl u128 { uint_impl! { u128, u128, 128, intrinsics::ctpop, intrinsics::ctlz, + ctlz_nonzero, intrinsics::cttz, intrinsics::bswap, intrinsics::add_with_overflow, @@ -2302,6 +2314,7 @@ impl usize { uint_impl! { usize, u16, 16, intrinsics::ctpop, intrinsics::ctlz, + ctlz_nonzero, intrinsics::cttz, intrinsics::bswap, intrinsics::add_with_overflow, @@ -2314,6 +2327,7 @@ impl usize { uint_impl! { usize, u32, 32, intrinsics::ctpop, intrinsics::ctlz, + ctlz_nonzero, intrinsics::cttz, intrinsics::bswap, intrinsics::add_with_overflow, @@ -2327,6 +2341,7 @@ impl usize { uint_impl! { usize, u64, 64, intrinsics::ctpop, intrinsics::ctlz, + ctlz_nonzero, intrinsics::cttz, intrinsics::bswap, intrinsics::add_with_overflow, |