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Rollup merge of #43159 - cuviper:ptr-swap-simd, r=arielb1

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Disable big-endian simd in swap_nonoverlapping_bytes

This is a workaround for #42778, which was git-bisected to #40454's
optimizations to `mem::swap`, later moved to `ptr` in #42819.  Natively
compiled rustc couldn't even compile stage1 libcore on powerpc64 and
s390x, but they work fine without this `repr(simd)`.  Since powerpc64le
works OK, it seems probably related to being big-endian.

The underlying problem is not yet known, but this at least makes those
architectures functional again in the meantime.

cc @arielb1
This commit is contained in:
Corey Farwell 2017-07-14 20:57:15 -07:00 • committed by GitHub
commit 721f736b1b
1 changed files with 4 additions and 1 deletions
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5
src/libcore/ptr.rs
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@ -160,7 +160,10 @@ unsafe fn swap_nonoverlapping_bytes(x: *mut u8, y: *mut u8, len: usize) {
// #[repr(simd)], even if we don't actually use this struct directly.
//
// FIXME repr(simd) broken on emscripten and redox
#[cfg_attr(not(any(target_os = "emscripten", target_os = "redox")), repr(simd))]
// It's also broken on big-endian powerpc64 and s390x. #42778
#[cfg_attr(not(any(target_os = "emscripten", target_os = "redox",
target_endian = "big")),
repr(simd))]
struct Block(u64, u64, u64, u64);
struct UnalignedBlock(u64, u64, u64, u64);