Commits on Aug 30, 2023

1. build: use -muse-unaligned-vector-move for Windows …

   We currently work around a longstanding GCC issue with aligned vector
   instructions, in our release builds, by patching the behaviour we want
   into GCC (see discussion in bitcoin#24736).
   
   A new option now exists in the binutils assembler,
   `-muse-unaligned-vector-move`, which should also achieve the behaviour
   we want (at least for our code). This was added in the 2.38 release,
   see
   https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=c8480b58e1968f209b6365af7422678f348222c2.
   ```bash
   x86: Add -muse-unaligned-vector-move to assembler
   
   Unaligned load/store instructions on aligned memory or register are as
   fast as aligned load/store instructions on modern Intel processors.  Add
   a command-line option, -muse-unaligned-vector-move, to x86 assembler to
   encode encode aligned vector load/store instructions as unaligned
   vector load/store instructions.
   ```
   
   Even if we introduce this option into our build system, we'll have to
   maintain our GCC patching, as we want all code that ends up in the
   binary, to avoid these instructions. However, there may be some value in
   adding the option, as it could be an improvement for someone building
   (bitcoind.exe) with an unpatched compiler.

   

   fanquake committed Aug 30, 2023
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