diff options
| -rw-r--r-- | src/libcore/mem.rs | 2 | ||||
| -rw-r--r-- | src/libcore/ptr.rs | 13 | ||||
| -rw-r--r-- | src/test/codegen/swap-small-types.rs | 27 |
3 files changed, 41 insertions, 1 deletions
diff --git a/src/libcore/mem.rs b/src/libcore/mem.rs index 8fb4e0d6a02..a0fe6e98806 100644 --- a/src/libcore/mem.rs +++ b/src/libcore/mem.rs @@ -638,7 +638,7 @@ pub unsafe fn uninitialized<T>() -> T { #[stable(feature = "rust1", since = "1.0.0")] pub fn swap<T>(x: &mut T, y: &mut T) { unsafe { - ptr::swap_nonoverlapping(x, y, 1); + ptr::swap_nonoverlapping_one(x, y); } } diff --git a/src/libcore/ptr.rs b/src/libcore/ptr.rs index d8e061496d9..d020e14be4c 100644 --- a/src/libcore/ptr.rs +++ b/src/libcore/ptr.rs @@ -188,6 +188,19 @@ pub unsafe fn swap_nonoverlapping<T>(x: *mut T, y: *mut T, count: usize) { } #[inline] +pub(crate) unsafe fn swap_nonoverlapping_one<T>(x: *mut T, y: *mut T) { + // For types smaller than the block optimization below, + // just swap directly to avoid pessimizing codegen. + if mem::size_of::<T>() < 32 { + let z = read(x); + copy_nonoverlapping(y, x, 1); + write(y, z); + } else { + swap_nonoverlapping(x, y, 1); + } +} + +#[inline] unsafe fn swap_nonoverlapping_bytes(x: *mut u8, y: *mut u8, len: usize) { // The approach here is to utilize simd to swap x & y efficiently. Testing reveals // that swapping either 32 bytes or 64 bytes at a time is most efficient for intel diff --git a/src/test/codegen/swap-small-types.rs b/src/test/codegen/swap-small-types.rs new file mode 100644 index 00000000000..46406ee5182 --- /dev/null +++ b/src/test/codegen/swap-small-types.rs @@ -0,0 +1,27 @@ +// Copyright 2018 The Rust Project Developers. See the COPYRIGHT +// file at the top-level directory of this distribution and at +// http://rust-lang.org/COPYRIGHT. +// +// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or +// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license +// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +// compile-flags: -O +// only-x86_64 + +#![crate_type = "lib"] + +use std::mem::swap; + +type RGB48 = [u16; 3]; + +// CHECK-LABEL: @swap_rgb48 +#[no_mangle] +pub fn swap_rgb48(x: &mut RGB48, y: &mut RGB48) { +// CHECK-NOT: alloca +// CHECK: load i48 +// CHECK: store i48 + swap(x, y) +} |