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| author | Dylan DPC <dylan.dpc@gmail.com> | 2020-04-23 20:35:04 +0200 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2020-04-23 20:35:04 +0200 |
| commit | 199f4deef0ac8ccfe02a8290eadd0ab3ae66d71c (patch) | |
| tree | 2aff5b15c1c8cdeb21c21d052d9a4cac3bd834d3 /src | |
| parent | 1363a4b3522feccdba4e4fc19cacb80f50e26e9a (diff) | |
| parent | 99de3728f95d1a3fa6063aa4ef2974a45cf35f4c (diff) | |
| download | rust-199f4deef0ac8ccfe02a8290eadd0ab3ae66d71c.tar.gz rust-199f4deef0ac8ccfe02a8290eadd0ab3ae66d71c.zip | |
Rollup merge of #71446 - Amanieu:transmute_copy, r=sfackler
Only use read_unaligned in transmute_copy if necessary I've noticed that this causes LLVM to generate poor code on targets that don't support unaligned memory accesses.
Diffstat (limited to 'src')
| -rw-r--r-- | src/libcore/mem/mod.rs | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/src/libcore/mem/mod.rs b/src/libcore/mem/mod.rs index 3fa2b7a2d04..7fcfbf10814 100644 --- a/src/libcore/mem/mod.rs +++ b/src/libcore/mem/mod.rs @@ -924,7 +924,12 @@ pub fn drop<T>(_x: T) {} #[inline] #[stable(feature = "rust1", since = "1.0.0")] pub unsafe fn transmute_copy<T, U>(src: &T) -> U { - ptr::read_unaligned(src as *const T as *const U) + // If U has a higher alignment requirement, src may not be suitably aligned. + if align_of::<U>() > align_of::<T>() { + ptr::read_unaligned(src as *const T as *const U) + } else { + ptr::read(src as *const T as *const U) + } } /// Opaque type representing the discriminant of an enum. |