diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs index f80f839282781..d34173dafb351 100644 --- a/src/libcore/num/mod.rs +++ b/src/libcore/num/mod.rs @@ -882,17 +882,38 @@ $EndFeature, " ```"), #[stable(feature = "rust1", since = "1.0.0")] #[inline] + #[cfg(stage0)] pub fn saturating_add(self, rhs: Self) -> Self { - #[cfg(stage0)] match self.checked_add(rhs) { Some(x) => x, None if rhs >= 0 => Self::max_value(), None => Self::min_value(), } - #[cfg(not(stage0))] - { - intrinsics::saturating_add(self, rhs) - } + } + + } + + doc_comment! { + concat!("Saturating integer addition. Computes `self + rhs`, saturating at the numeric +bounds instead of overflowing. + +# Examples + +Basic usage: + +``` +", $Feature, "assert_eq!(100", stringify!($SelfT), ".saturating_add(1), 101); +assert_eq!(", stringify!($SelfT), "::max_value().saturating_add(100), ", stringify!($SelfT), +"::max_value());", +$EndFeature, " +```"), + + #[stable(feature = "rust1", since = "1.0.0")] + #[rustc_const_unstable(feature = "const_saturating_int_methods")] + #[inline] + #[cfg(not(stage0))] + pub const fn saturating_add(self, rhs: Self) -> Self { + intrinsics::saturating_add(self, rhs) } } @@ -912,17 +933,36 @@ $EndFeature, " ```"), #[stable(feature = "rust1", since = "1.0.0")] #[inline] + #[cfg(stage0)] pub fn saturating_sub(self, rhs: Self) -> Self { - #[cfg(stage0)] match self.checked_sub(rhs) { Some(x) => x, None if rhs >= 0 => Self::min_value(), None => Self::max_value(), } - #[cfg(not(stage0))] - { - intrinsics::saturating_sub(self, rhs) - } + } + } + + doc_comment! { + concat!("Saturating integer subtraction. Computes `self - rhs`, saturating at the +numeric bounds instead of overflowing. + +# Examples + +Basic usage: + +``` +", $Feature, "assert_eq!(100", stringify!($SelfT), ".saturating_sub(127), -27); +assert_eq!(", stringify!($SelfT), "::min_value().saturating_sub(100), ", stringify!($SelfT), +"::min_value());", +$EndFeature, " +```"), + #[stable(feature = "rust1", since = "1.0.0")] + #[rustc_const_unstable(feature = "const_saturating_int_methods")] + #[inline] + #[cfg(not(stage0))] + pub const fn saturating_sub(self, rhs: Self) -> Self { + intrinsics::saturating_sub(self, rhs) } } @@ -2753,16 +2793,34 @@ assert_eq!(200u8.saturating_add(127), 255);", $EndFeature, " ```"), #[stable(feature = "rust1", since = "1.0.0")] #[inline] + #[cfg(stage0)] pub fn saturating_add(self, rhs: Self) -> Self { - #[cfg(stage0)] match self.checked_add(rhs) { Some(x) => x, None => Self::max_value(), } - #[cfg(not(stage0))] - { - intrinsics::saturating_add(self, rhs) - } + } + } + + doc_comment! { + concat!("Saturating integer addition. Computes `self + rhs`, saturating at +the numeric bounds instead of overflowing. + +# Examples + +Basic usage: + +``` +", $Feature, "assert_eq!(100", stringify!($SelfT), ".saturating_add(1), 101); +assert_eq!(200u8.saturating_add(127), 255);", $EndFeature, " +```"), + + #[stable(feature = "rust1", since = "1.0.0")] + #[rustc_const_unstable(feature = "const_saturating_int_methods")] + #[inline] + #[cfg(not(stage0))] + pub const fn saturating_add(self, rhs: Self) -> Self { + intrinsics::saturating_add(self, rhs) } } @@ -2780,16 +2838,33 @@ assert_eq!(13", stringify!($SelfT), ".saturating_sub(127), 0);", $EndFeature, " ```"), #[stable(feature = "rust1", since = "1.0.0")] #[inline] + #[cfg(stage0)] pub fn saturating_sub(self, rhs: Self) -> Self { - #[cfg(stage0)] match self.checked_sub(rhs) { Some(x) => x, None => Self::min_value(), } - #[cfg(not(stage0))] - { - intrinsics::saturating_sub(self, rhs) - } + } + } + + doc_comment! { + concat!("Saturating integer subtraction. Computes `self - rhs`, saturating +at the numeric bounds instead of overflowing. + +# Examples + +Basic usage: + +``` +", $Feature, "assert_eq!(100", stringify!($SelfT), ".saturating_sub(27), 73); +assert_eq!(13", stringify!($SelfT), ".saturating_sub(127), 0);", $EndFeature, " +```"), + #[stable(feature = "rust1", since = "1.0.0")] + #[rustc_const_unstable(feature = "const_saturating_int_methods")] + #[inline] + #[cfg(not(stage0))] + pub const fn saturating_sub(self, rhs: Self) -> Self { + intrinsics::saturating_sub(self, rhs) } } diff --git a/src/librustc_mir/interpret/intrinsics.rs b/src/librustc_mir/interpret/intrinsics.rs index d8778dfeef7a1..dcbf6a52ba9f5 100644 --- a/src/librustc_mir/interpret/intrinsics.rs +++ b/src/librustc_mir/interpret/intrinsics.rs @@ -4,7 +4,7 @@ use syntax::symbol::Symbol; use rustc::ty; -use rustc::ty::layout::{LayoutOf, Primitive}; +use rustc::ty::layout::{LayoutOf, Primitive, Size}; use rustc::mir::BinOp; use rustc::mir::interpret::{ EvalResult, EvalErrorKind, Scalar, @@ -122,6 +122,49 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> self.binop_with_overflow(bin_op, lhs, rhs, dest)?; } } + "saturating_add" | "saturating_sub" => { + let l = self.read_immediate(args[0])?; + let r = self.read_immediate(args[1])?; + let is_add = intrinsic_name == "saturating_add"; + let (val, overflowed) = self.binary_op_imm(if is_add { + BinOp::Add + } else { + BinOp::Sub + }, l, r)?; + let val = if overflowed { + let num_bits = l.layout.size.bits(); + if l.layout.abi.is_signed() { + // For signed ints the saturated value depends on the sign of the first + // term since the sign of the second term can be inferred from this and + // the fact that the operation has overflowed (if either is 0 no + // overflow can occur) + let first_term: u128 = l.to_scalar()?.to_bits(l.layout.size)?; + let first_term_positive = first_term & (1 << (num_bits-1)) == 0; + if first_term_positive { + // Negative overflow not possible since the positive first term + // can only increase an (in range) negative term for addition + // or corresponding negated positive term for subtraction + Scalar::from_uint((1u128 << (num_bits - 1)) - 1, // max positive + Size::from_bits(num_bits)) + } else { + // Positive overflow not possible for similar reason + // max negative + Scalar::from_uint(1u128 << (num_bits - 1), Size::from_bits(num_bits)) + } + } else { // unsigned + if is_add { + // max unsigned + Scalar::from_uint(u128::max_value() >> (128 - num_bits), + Size::from_bits(num_bits)) + } else { // underflow to 0 + Scalar::from_uint(0u128, Size::from_bits(num_bits)) + } + } + } else { + val + }; + self.write_scalar(val, dest)?; + } "unchecked_shl" | "unchecked_shr" => { let l = self.read_immediate(args[0])?; let r = self.read_immediate(args[1])?; diff --git a/src/librustc_mir/transform/qualify_consts.rs b/src/librustc_mir/transform/qualify_consts.rs index 2d941902debc3..d6ec207434243 100644 --- a/src/librustc_mir/transform/qualify_consts.rs +++ b/src/librustc_mir/transform/qualify_consts.rs @@ -820,6 +820,8 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> { | "add_with_overflow" | "sub_with_overflow" | "mul_with_overflow" + | "saturating_add" + | "saturating_sub" // no need to check feature gates, intrinsics are only callable // from the libstd or with forever unstable feature gates => is_const_fn = true, diff --git a/src/librustc_mir/transform/qualify_min_const_fn.rs b/src/librustc_mir/transform/qualify_min_const_fn.rs index 85bf1e70ebf42..d8dc6c2845b28 100644 --- a/src/librustc_mir/transform/qualify_min_const_fn.rs +++ b/src/librustc_mir/transform/qualify_min_const_fn.rs @@ -374,6 +374,8 @@ fn is_intrinsic_whitelisted(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> bool | "overflowing_add" // ~> .wrapping_add | "overflowing_sub" // ~> .wrapping_sub | "overflowing_mul" // ~> .wrapping_mul + | "saturating_add" // ~> .saturating_add + | "saturating_sub" // ~> .saturating_sub | "unchecked_shl" // ~> .wrapping_shl | "unchecked_shr" // ~> .wrapping_shr | "rotate_left" // ~> .rotate_left diff --git a/src/test/run-pass/const-int-saturating-arith.rs b/src/test/run-pass/const-int-saturating-arith.rs new file mode 100644 index 0000000000000..dae4c7216b2c0 --- /dev/null +++ b/src/test/run-pass/const-int-saturating-arith.rs @@ -0,0 +1,34 @@ +// ignore-emscripten no i128 support +#![feature(const_saturating_int_methods)] + +const INT_U32_NO: u32 = (42 as u32).saturating_add(2); +const INT_U32: u32 = u32::max_value().saturating_add(1); +const INT_U128: u128 = u128::max_value().saturating_add(1); +const INT_I128: i128 = i128::max_value().saturating_add(1); +const INT_I128_NEG: i128 = i128::min_value().saturating_add(-1); + +const INT_U32_NO_SUB: u32 = (42 as u32).saturating_sub(2); +const INT_U32_SUB: u32 = (1 as u32).saturating_sub(2); +const INT_I32_NO_SUB: i32 = (-42 as i32).saturating_sub(2); +const INT_I32_NEG_SUB: i32 = i32::min_value().saturating_sub(1); +const INT_I32_POS_SUB: i32 = i32::max_value().saturating_sub(-1); +const INT_U128_SUB: u128 = (0 as u128).saturating_sub(1); +const INT_I128_NEG_SUB: i128 = i128::min_value().saturating_sub(1); +const INT_I128_POS_SUB: i128 = i128::max_value().saturating_sub(-1); + +fn main() { + assert_eq!(INT_U32_NO, 44); + assert_eq!(INT_U32, u32::max_value()); + assert_eq!(INT_U128, u128::max_value()); + assert_eq!(INT_I128, i128::max_value()); + assert_eq!(INT_I128_NEG, i128::min_value()); + + assert_eq!(INT_U32_NO_SUB, 40); + assert_eq!(INT_U32_SUB, 0); + assert_eq!(INT_I32_NO_SUB, -44); + assert_eq!(INT_I32_NEG_SUB, i32::min_value()); + assert_eq!(INT_I32_POS_SUB, i32::max_value()); + assert_eq!(INT_U128_SUB, 0); + assert_eq!(INT_I128_NEG_SUB, i128::min_value()); + assert_eq!(INT_I128_POS_SUB, i128::max_value()); +}