enable strict alignment (+strict-align) on ARMv6 #45094
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As discovered in rust-lang#44538 ARMv6 devices may or may not support unaligned memory accesses. ARMv6 Linux *seems* to have no problem with unaligned accesses but this is because the kernel is stepping in to fix each unaligned memory access -- this incurs in a performance penalty. This commit enforces aligned memory accesses on all our in-tree ARM targets that may be used with ARMv6 devices. This should improve performance of Rust programs on ARMv6 devices. For the record, clang also applies this attribute when targeting ARMv6 devices that are not running Darwin or NetBSD.
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Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @alexcrichton (or someone else) soon. If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes. Please see the contribution instructions for more information. |
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@bors: r+ rollup Thanks! |
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📌 Commit 2b8f190 has been approved by |
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enable strict alignment (+strict-align) on ARMv6 As discovered in rust-lang#44538 ARMv6 devices may or may not support unaligned memory accesses. ARMv6 Linux *seems* to have no problem with unaligned accesses but this is because the kernel is stepping in to fix each unaligned memory access -- this incurs in a performance penalty. This commit enforces aligned memory accesses on all our in-tree ARM targets that may be used with ARMv6 devices. This should improve performance of Rust programs on ARMv6 devices. For the record, clang also applies this attribute when targeting ARMv6 devices that are not running Darwin or NetBSD. closes rust-lang#44538 r? @alexcrichton
This was referenced Jan 22, 2018
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As discovered in #44538 ARMv6 devices may or may not support unaligned memory accesses. ARMv6
Linux seems to have no problem with unaligned accesses but this is because the kernel is stepping
in to fix each unaligned memory access -- this incurs in a performance penalty.
This commit enforces aligned memory accesses on all our in-tree ARM targets that may be used with
ARMv6 devices. This should improve performance of Rust programs on ARMv6 devices. For the record,
clang also applies this attribute when targeting ARMv6 devices that are not running Darwin or
NetBSD.
closes #44538
r? @alexcrichton