From c981d67b509f1ba16c97683ad6dc430429899e49 Mon Sep 17 00:00:00 2001 From: Dylan MacKenzie Date: Sat, 8 Feb 2020 16:30:45 -0800 Subject: [PATCH 1/4] [!] Use `rustc_inherit_overflow_checks` in `next_power_of_two` I believe the previous code was calling `ops::Add::add` instead of the `+` operator to get this behavior. --- src/libcore/num/mod.rs | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs index ed37b48b3e855..f86376cac888a 100644 --- a/src/libcore/num/mod.rs +++ b/src/libcore/num/mod.rs @@ -8,7 +8,6 @@ use crate::convert::Infallible; use crate::fmt; use crate::intrinsics; use crate::mem; -use crate::ops; use crate::str::FromStr; macro_rules! impl_nonzero_fmt { @@ -4042,9 +4041,9 @@ assert_eq!(3", stringify!($SelfT), ".next_power_of_two(), 4);", $EndFeature, " ```"), #[stable(feature = "rust1", since = "1.0.0")] #[inline] + #[rustc_inherit_overflow_checks] pub fn next_power_of_two(self) -> Self { - // Call the trait to get overflow checks - ops::Add::add(self.one_less_than_next_power_of_two(), 1) + self.one_less_than_next_power_of_two() + 1 } } From 2afa99379d9623e50efd290e609447bdc5059af8 Mon Sep 17 00:00:00 2001 From: Dylan MacKenzie Date: Sat, 8 Feb 2020 16:31:59 -0800 Subject: [PATCH 2/4] Use bespoke macro instead of `?` inside const fns --- src/libcore/num/mod.rs | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs index f86376cac888a..c38f51a0f55bc 100644 --- a/src/libcore/num/mod.rs +++ b/src/libcore/num/mod.rs @@ -10,6 +10,16 @@ use crate::intrinsics; use crate::mem; use crate::str::FromStr; +// Used because the `?` operator is not allowed in a const context. +macro_rules! try_opt { + ($e:expr) => { + match $e { + Some(x) => x, + None => return None, + } + }; +} + macro_rules! impl_nonzero_fmt { ( #[$stability: meta] ( $( $Trait: ident ),+ ) for $Ty: ident ) => { $( @@ -1000,17 +1010,17 @@ $EndFeature, " while exp > 1 { if (exp & 1) == 1 { - acc = acc.checked_mul(base)?; + acc = try_opt!(acc.checked_mul(base)); } exp /= 2; - base = base.checked_mul(base)?; + base = try_opt!(base.checked_mul(base)); } // Deal with the final bit of the exponent separately, since // squaring the base afterwards is not necessary and may cause a // needless overflow. if exp == 1 { - acc = acc.checked_mul(base)?; + acc = try_opt!(acc.checked_mul(base)); } Some(acc) @@ -3126,17 +3136,17 @@ assert_eq!(", stringify!($SelfT), "::max_value().checked_pow(2), None);", $EndFe while exp > 1 { if (exp & 1) == 1 { - acc = acc.checked_mul(base)?; + acc = try_opt!(acc.checked_mul(base)); } exp /= 2; - base = base.checked_mul(base)?; + base = try_opt!(base.checked_mul(base)); } // Deal with the final bit of the exponent separately, since // squaring the base afterwards is not necessary and may cause a // needless overflow. if exp == 1 { - acc = acc.checked_mul(base)?; + acc = try_opt!(acc.checked_mul(base)); } Some(acc) From 269bf89865536964546242589bb186a8a7e3c566 Mon Sep 17 00:00:00 2001 From: Dylan MacKenzie Date: Sat, 8 Feb 2020 16:32:30 -0800 Subject: [PATCH 3/4] Make integer power methods const --- src/libcore/lib.rs | 3 +++ src/libcore/num/mod.rs | 42 ++++++++++++++++++++++++++++-------------- 2 files changed, 31 insertions(+), 14 deletions(-) diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs index 1fd70e1a1b049..56117a5406284 100644 --- a/src/libcore/lib.rs +++ b/src/libcore/lib.rs @@ -72,11 +72,14 @@ #![feature(concat_idents)] #![feature(const_alloc_layout)] #![feature(const_if_match)] +#![feature(const_loop)] #![feature(const_checked_int_methods)] #![feature(const_euclidean_int_methods)] #![feature(const_overflowing_int_methods)] #![feature(const_saturating_int_methods)] #![feature(const_int_unchecked_arith)] +#![feature(const_int_pow)] +#![feature(constctlz)] #![feature(const_panic)] #![feature(const_fn_union)] #![feature(const_generics)] diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs index c38f51a0f55bc..a8c71fc208a80 100644 --- a/src/libcore/num/mod.rs +++ b/src/libcore/num/mod.rs @@ -1001,10 +1001,11 @@ $EndFeature, " ```"), #[stable(feature = "no_panic_pow", since = "1.34.0")] + #[rustc_const_unstable(feature = "const_int_pow", issue = "53718")] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] - pub fn checked_pow(self, mut exp: u32) -> Option { + pub const fn checked_pow(self, mut exp: u32) -> Option { let mut base = self; let mut acc: Self = 1; @@ -1188,10 +1189,11 @@ assert_eq!(", stringify!($SelfT), "::MIN.saturating_pow(3), ", stringify!($SelfT $EndFeature, " ```"), #[stable(feature = "no_panic_pow", since = "1.34.0")] + #[rustc_const_unstable(feature = "const_int_pow", issue = "53718")] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] - pub fn saturating_pow(self, exp: u32) -> Self { + pub const fn saturating_pow(self, exp: u32) -> Self { match self.checked_pow(exp) { Some(x) => x, None if self < 0 && exp % 2 == 1 => Self::min_value(), @@ -1531,10 +1533,11 @@ assert_eq!(3i8.wrapping_pow(6), -39);", $EndFeature, " ```"), #[stable(feature = "no_panic_pow", since = "1.34.0")] + #[rustc_const_unstable(feature = "const_int_pow", issue = "53718")] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] - pub fn wrapping_pow(self, mut exp: u32) -> Self { + pub const fn wrapping_pow(self, mut exp: u32) -> Self { let mut base = self; let mut acc: Self = 1; @@ -1908,10 +1911,11 @@ assert_eq!(3i8.overflowing_pow(5), (-13, true));", $EndFeature, " ```"), #[stable(feature = "no_panic_pow", since = "1.34.0")] + #[rustc_const_unstable(feature = "const_int_pow", issue = "53718")] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] - pub fn overflowing_pow(self, mut exp: u32) -> (Self, bool) { + pub const fn overflowing_pow(self, mut exp: u32) -> (Self, bool) { let mut base = self; let mut acc: Self = 1; let mut overflown = false; @@ -1957,11 +1961,12 @@ assert_eq!(x.pow(5), 32);", $EndFeature, " ```"), #[stable(feature = "rust1", since = "1.0.0")] + #[rustc_const_unstable(feature = "const_int_pow", issue = "53718")] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] #[rustc_inherit_overflow_checks] - pub fn pow(self, mut exp: u32) -> Self { + pub const fn pow(self, mut exp: u32) -> Self { let mut base = self; let mut acc = 1; @@ -3127,10 +3132,11 @@ Basic usage: assert_eq!(", stringify!($SelfT), "::max_value().checked_pow(2), None);", $EndFeature, " ```"), #[stable(feature = "no_panic_pow", since = "1.34.0")] + #[rustc_const_unstable(feature = "const_int_pow", issue = "53718")] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] - pub fn checked_pow(self, mut exp: u32) -> Option { + pub const fn checked_pow(self, mut exp: u32) -> Option { let mut base = self; let mut acc: Self = 1; @@ -3242,10 +3248,11 @@ assert_eq!(", stringify!($SelfT), "::MAX.saturating_pow(2), ", stringify!($SelfT $EndFeature, " ```"), #[stable(feature = "no_panic_pow", since = "1.34.0")] + #[rustc_const_unstable(feature = "const_int_pow", issue = "53718")] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] - pub fn saturating_pow(self, exp: u32) -> Self { + pub const fn saturating_pow(self, exp: u32) -> Self { match self.checked_pow(exp) { Some(x) => x, None => Self::max_value(), @@ -3535,10 +3542,11 @@ Basic usage: assert_eq!(3u8.wrapping_pow(6), 217);", $EndFeature, " ```"), #[stable(feature = "no_panic_pow", since = "1.34.0")] + #[rustc_const_unstable(feature = "const_int_pow", issue = "53718")] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] - pub fn wrapping_pow(self, mut exp: u32) -> Self { + pub const fn wrapping_pow(self, mut exp: u32) -> Self { let mut base = self; let mut acc: Self = 1; @@ -3861,10 +3869,11 @@ Basic usage: assert_eq!(3u8.overflowing_pow(6), (217, true));", $EndFeature, " ```"), #[stable(feature = "no_panic_pow", since = "1.34.0")] + #[rustc_const_unstable(feature = "const_int_pow", issue = "53718")] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] - pub fn overflowing_pow(self, mut exp: u32) -> (Self, bool) { + pub const fn overflowing_pow(self, mut exp: u32) -> (Self, bool) { let mut base = self; let mut acc: Self = 1; let mut overflown = false; @@ -3907,11 +3916,12 @@ Basic usage: ", $Feature, "assert_eq!(2", stringify!($SelfT), ".pow(5), 32);", $EndFeature, " ```"), #[stable(feature = "rust1", since = "1.0.0")] + #[rustc_const_unstable(feature = "const_int_pow", issue = "53718")] #[must_use = "this returns the result of the operation, \ without modifying the original"] #[inline] #[rustc_inherit_overflow_checks] - pub fn pow(self, mut exp: u32) -> Self { + pub const fn pow(self, mut exp: u32) -> Self { let mut base = self; let mut acc = 1; @@ -4022,7 +4032,8 @@ assert!(!10", stringify!($SelfT), ".is_power_of_two());", $EndFeature, " // overflow cases it instead ends up returning the maximum value // of the type, and can return 0 for 0. #[inline] - fn one_less_than_next_power_of_two(self) -> Self { + #[rustc_const_unstable(feature = "const_int_pow", issue = "53718")] + const fn one_less_than_next_power_of_two(self) -> Self { if self <= 1 { return 0; } let p = self - 1; @@ -4050,9 +4061,10 @@ Basic usage: assert_eq!(3", stringify!($SelfT), ".next_power_of_two(), 4);", $EndFeature, " ```"), #[stable(feature = "rust1", since = "1.0.0")] + #[rustc_const_unstable(feature = "const_int_pow", issue = "53718")] #[inline] #[rustc_inherit_overflow_checks] - pub fn next_power_of_two(self) -> Self { + pub const fn next_power_of_two(self) -> Self { self.one_less_than_next_power_of_two() + 1 } } @@ -4075,7 +4087,8 @@ $EndFeature, " ```"), #[inline] #[stable(feature = "rust1", since = "1.0.0")] - pub fn checked_next_power_of_two(self) -> Option { + #[rustc_const_unstable(feature = "const_int_pow", issue = "53718")] + pub const fn checked_next_power_of_two(self) -> Option { self.one_less_than_next_power_of_two().checked_add(1) } } @@ -4099,7 +4112,8 @@ $EndFeature, " ```"), #[unstable(feature = "wrapping_next_power_of_two", issue = "32463", reason = "needs decision on wrapping behaviour")] - pub fn wrapping_next_power_of_two(self) -> Self { + #[rustc_const_unstable(feature = "const_int_pow", issue = "53718")] + pub const fn wrapping_next_power_of_two(self) -> Self { self.one_less_than_next_power_of_two().wrapping_add(1) } } From 7fe5eaf7d8cb23ceb71d8e509be13d20ef836114 Mon Sep 17 00:00:00 2001 From: Dylan MacKenzie Date: Sat, 8 Feb 2020 16:50:00 -0800 Subject: [PATCH 4/4] Test integer exponentiation in a const context --- src/test/ui/consts/const-int-pow-rpass.rs | 37 +++++++++++++++++++++++ 1 file changed, 37 insertions(+) diff --git a/src/test/ui/consts/const-int-pow-rpass.rs b/src/test/ui/consts/const-int-pow-rpass.rs index 8e84a900605f5..b0fba19455ba8 100644 --- a/src/test/ui/consts/const-int-pow-rpass.rs +++ b/src/test/ui/consts/const-int-pow-rpass.rs @@ -1,11 +1,48 @@ // run-pass +#![feature(const_int_pow)] +#![feature(wrapping_next_power_of_two)] + const IS_POWER_OF_TWO_A: bool = 0u32.is_power_of_two(); const IS_POWER_OF_TWO_B: bool = 32u32.is_power_of_two(); const IS_POWER_OF_TWO_C: bool = 33u32.is_power_of_two(); +const POW: u8 = 3u8.pow(5); + +const CHECKED_POW_OK: Option = 3u8.checked_pow(5); +const CHECKED_POW_OVERFLOW: Option = 3u8.checked_pow(6); + +const WRAPPING_POW: u8 = 3u8.wrapping_pow(6); +const OVERFLOWING_POW: (u8, bool) = 3u8.overflowing_pow(6); +const SATURATING_POW: u8 = 3u8.saturating_pow(6); + +const NEXT_POWER_OF_TWO: u32 = 3u32.next_power_of_two(); + +const CHECKED_NEXT_POWER_OF_TWO_OK: Option = 3u32.checked_next_power_of_two(); +const CHECKED_NEXT_POWER_OF_TWO_OVERFLOW: Option = + u32::max_value().checked_next_power_of_two(); + +const WRAPPING_NEXT_POWER_OF_TWO: u32 = + u32::max_value().wrapping_next_power_of_two(); + fn main() { assert!(!IS_POWER_OF_TWO_A); assert!(IS_POWER_OF_TWO_B); assert!(!IS_POWER_OF_TWO_C); + + assert_eq!(POW, 243); + + assert_eq!(CHECKED_POW_OK, Some(243)); + assert_eq!(CHECKED_POW_OVERFLOW, None); + + assert_eq!(WRAPPING_POW, 217); + assert_eq!(OVERFLOWING_POW, (217, true)); + assert_eq!(SATURATING_POW, u8::max_value()); + + assert_eq!(NEXT_POWER_OF_TWO, 4); + + assert_eq!(CHECKED_NEXT_POWER_OF_TWO_OK, Some(4)); + assert_eq!(CHECKED_NEXT_POWER_OF_TWO_OVERFLOW, None); + + assert_eq!(WRAPPING_NEXT_POWER_OF_TWO, 0); }