Use LLVM intrinsics for saturating add/sub
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Nikita Popov
parent
d8a0dd7ae8
commit
4a4186e4d1
5 changed files with 101 additions and 3 deletions
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@ -1493,6 +1493,19 @@ extern "rust-intrinsic" {
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/// [`std::u32::wrapping_mul`](../../std/primitive.u32.html#method.wrapping_mul)
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pub fn overflowing_mul<T>(a: T, b: T) -> T;
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/// Computes `a + b`, while saturating at numeric bounds.
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/// The stabilized versions of this intrinsic are available on the integer
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/// primitives via the `saturating_add` method. For example,
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/// [`std::u32::saturating_add`](../../std/primitive.u32.html#method.saturating_add)
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#[cfg(not(stage0))]
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pub fn saturating_add<T>(a: T, b: T) -> T;
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/// Computes `a - b`, while saturating at numeric bounds.
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/// The stabilized versions of this intrinsic are available on the integer
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/// primitives via the `saturating_sub` method. For example,
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/// [`std::u32::saturating_sub`](../../std/primitive.u32.html#method.saturating_sub)
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#[cfg(not(stage0))]
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pub fn saturating_sub<T>(a: T, b: T) -> T;
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/// Returns the value of the discriminant for the variant in 'v',
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/// cast to a `u64`; if `T` has no discriminant, returns 0.
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pub fn discriminant_value<T>(v: &T) -> u64;
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@ -883,11 +883,16 @@ $EndFeature, "
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn saturating_add(self, rhs: Self) -> Self {
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#[cfg(stage0)]
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match self.checked_add(rhs) {
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Some(x) => x,
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None if rhs >= 0 => Self::max_value(),
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None => Self::min_value(),
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}
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#[cfg(not(stage0))]
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{
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intrinsics::saturating_add(self, rhs)
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}
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}
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}
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@ -908,11 +913,16 @@ $EndFeature, "
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn saturating_sub(self, rhs: Self) -> Self {
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#[cfg(stage0)]
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match self.checked_sub(rhs) {
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Some(x) => x,
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None if rhs >= 0 => Self::min_value(),
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None => Self::max_value(),
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}
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#[cfg(not(stage0))]
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{
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intrinsics::saturating_sub(self, rhs)
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}
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}
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}
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@ -2744,10 +2754,15 @@ assert_eq!(200u8.saturating_add(127), 255);", $EndFeature, "
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn saturating_add(self, rhs: Self) -> Self {
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#[cfg(stage0)]
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match self.checked_add(rhs) {
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Some(x) => x,
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None => Self::max_value(),
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}
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#[cfg(not(stage0))]
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{
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intrinsics::saturating_add(self, rhs)
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}
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}
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}
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@ -2766,10 +2781,15 @@ assert_eq!(13", stringify!($SelfT), ".saturating_sub(127), 0);", $EndFeature, "
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn saturating_sub(self, rhs: Self) -> Self {
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#[cfg(stage0)]
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match self.checked_sub(rhs) {
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Some(x) => x,
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None => Self::min_value(),
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}
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#[cfg(not(stage0))]
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{
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intrinsics::saturating_sub(self, rhs)
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}
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}
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}
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@ -757,6 +757,30 @@ impl CodegenCx<'b, 'tcx> {
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ifn!("llvm.umul.with.overflow.i64", fn(t_i64, t_i64) -> mk_struct!{t_i64, i1});
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ifn!("llvm.umul.with.overflow.i128", fn(t_i128, t_i128) -> mk_struct!{t_i128, i1});
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ifn!("llvm.sadd.sat.i8", fn(t_i8, t_i8) -> t_i8);
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ifn!("llvm.sadd.sat.i16", fn(t_i16, t_i16) -> t_i16);
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ifn!("llvm.sadd.sat.i32", fn(t_i32, t_i32) -> t_i32);
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ifn!("llvm.sadd.sat.i64", fn(t_i64, t_i64) -> t_i64);
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ifn!("llvm.sadd.sat.i128", fn(t_i128, t_i128) -> t_i128);
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ifn!("llvm.uadd.sat.i8", fn(t_i8, t_i8) -> t_i8);
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ifn!("llvm.uadd.sat.i16", fn(t_i16, t_i16) -> t_i16);
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ifn!("llvm.uadd.sat.i32", fn(t_i32, t_i32) -> t_i32);
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ifn!("llvm.uadd.sat.i64", fn(t_i64, t_i64) -> t_i64);
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ifn!("llvm.uadd.sat.i128", fn(t_i128, t_i128) -> t_i128);
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ifn!("llvm.ssub.sat.i8", fn(t_i8, t_i8) -> t_i8);
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ifn!("llvm.ssub.sat.i16", fn(t_i16, t_i16) -> t_i16);
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ifn!("llvm.ssub.sat.i32", fn(t_i32, t_i32) -> t_i32);
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ifn!("llvm.ssub.sat.i64", fn(t_i64, t_i64) -> t_i64);
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ifn!("llvm.ssub.sat.i128", fn(t_i128, t_i128) -> t_i128);
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ifn!("llvm.usub.sat.i8", fn(t_i8, t_i8) -> t_i8);
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ifn!("llvm.usub.sat.i16", fn(t_i16, t_i16) -> t_i16);
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ifn!("llvm.usub.sat.i32", fn(t_i32, t_i32) -> t_i32);
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ifn!("llvm.usub.sat.i64", fn(t_i64, t_i64) -> t_i64);
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ifn!("llvm.usub.sat.i128", fn(t_i128, t_i128) -> t_i128);
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ifn!("llvm.lifetime.start", fn(t_i64,i8p) -> void);
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ifn!("llvm.lifetime.end", fn(t_i64, i8p) -> void);
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@ -14,7 +14,7 @@ use type_::Type;
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use type_of::LayoutLlvmExt;
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use rustc::ty::{self, Ty};
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use rustc::ty::layout::{self, LayoutOf, HasTyCtxt, Primitive};
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use rustc_codegen_ssa::common::TypeKind;
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use rustc_codegen_ssa::common::{IntPredicate, TypeKind};
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use rustc::hir;
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use syntax::ast::{self, FloatTy};
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use syntax::symbol::Symbol;
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@ -28,7 +28,7 @@ use rustc::session::Session;
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use syntax_pos::Span;
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use std::cmp::Ordering;
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use std::iter;
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use std::{iter, i128, u128};
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fn get_simple_intrinsic(cx: &CodegenCx<'ll, '_>, name: &str) -> Option<&'ll Value> {
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let llvm_name = match name {
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@ -342,7 +342,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
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"bitreverse" | "add_with_overflow" | "sub_with_overflow" |
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"mul_with_overflow" | "overflowing_add" | "overflowing_sub" | "overflowing_mul" |
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"unchecked_div" | "unchecked_rem" | "unchecked_shl" | "unchecked_shr" | "exact_div" |
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"rotate_left" | "rotate_right" => {
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"rotate_left" | "rotate_right" | "saturating_add" | "saturating_sub" => {
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let ty = arg_tys[0];
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match int_type_width_signed(ty, self) {
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Some((width, signed)) =>
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@ -468,6 +468,44 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
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self.or(shift1, shift2)
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}
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},
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"saturating_add" | "saturating_sub" => {
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let is_add = name == "saturating_add";
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let lhs = args[0].immediate();
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let rhs = args[1].immediate();
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if llvm_util::get_major_version() >= 8 {
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let llvm_name = &format!("llvm.{}{}.sat.i{}",
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if signed { 's' } else { 'u' },
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if is_add { "add" } else { "sub" },
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width);
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let llfn = self.get_intrinsic(llvm_name);
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self.call(llfn, &[lhs, rhs], None)
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} else {
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let llvm_name = &format!("llvm.{}{}.with.overflow.i{}",
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if signed { 's' } else { 'u' },
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if is_add { "add" } else { "sub" },
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width);
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let llfn = self.get_intrinsic(llvm_name);
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let pair = self.call(llfn, &[lhs, rhs], None);
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let val = self.extract_value(pair, 0);
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let overflow = self.extract_value(pair, 1);
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let llty = self.type_ix(width);
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let limit = if signed {
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let limit_lo = self.const_uint_big(
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llty, (i128::MIN >> (128 - width)) as u128);
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let limit_hi = self.const_uint_big(
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llty, (i128::MAX >> (128 - width)) as u128);
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let neg = self.icmp(
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IntPredicate::IntSLT, val, self.const_uint(llty, 0));
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self.select(neg, limit_hi, limit_lo)
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} else if is_add {
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self.const_uint_big(llty, u128::MAX >> (128 - width))
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} else {
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self.const_uint(llty, 0)
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};
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self.select(overflow, limit, val)
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}
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},
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_ => bug!(),
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},
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None => {
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@ -68,6 +68,7 @@ pub fn intrisic_operation_unsafety(intrinsic: &str) -> hir::Unsafety {
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"size_of" | "min_align_of" | "needs_drop" |
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"add_with_overflow" | "sub_with_overflow" | "mul_with_overflow" |
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"overflowing_add" | "overflowing_sub" | "overflowing_mul" |
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"saturating_add" | "saturating_sub" |
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"rotate_left" | "rotate_right" |
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"ctpop" | "ctlz" | "cttz" | "bswap" | "bitreverse"
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=> hir::Unsafety::Normal,
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@ -307,6 +308,8 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
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"overflowing_add" | "overflowing_sub" | "overflowing_mul" =>
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(1, vec![param(0), param(0)], param(0)),
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"saturating_add" | "saturating_sub" =>
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(1, vec![param(0), param(0)], param(0)),
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"fadd_fast" | "fsub_fast" | "fmul_fast" | "fdiv_fast" | "frem_fast" =>
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(1, vec![param(0), param(0)], param(0)),
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