Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH 0/7] Add support to handle misaligned accesses in S-mode | Date | Wed, 4 Oct 2023 14:10:40 +0000 |
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... > Saying that you support misaligned access does not mean that they are > going to be efficient, just that they are supported (in fact, the uABI > state that they may perform poorly). The compiler is actually not so > stupid and will try to do as much aligned access as possible in what it > generates (unless forced by some assembly, cast or whatever that can > screw up alignment accesses). This is already the case and it will most > probably not change.
I did a quick check.
https://godbolt.org/z/j3e9drv4e
The code generated by both clang and gcc for misaligned reads is horrid. Gcc does a better job if the alignment is known but generates much the same as the clang code when it isn't.
The C code is much shorter. Even though both gcc and clang add a (different) instruction to it
David
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