Fix patcher for ppc and aarch64 #13027
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Prevent the compiler from reordering the instructions in the patcher by marking the assembly code as clobbering memory. Thanks @pinskia for the patch and for bringing the discussion on the gcc bugzilla. Fixes open-mpi#13014. Signed-off-by: George Bosilca <gbosilca@nvidia.com>
devreal
reviewed
Jan 9, 2025
| asm volatile("std 2, %0" : "=m"(toc_save)); \ | ||
| asm volatile("nop; nop; nop; nop; nop"); | ||
| # define OPAL_PATCHER_END asm volatile("ld 2, %0" : : "m"(toc_save)); | ||
| asm volatile("std 2, %0" : "=m"(toc_save) :: "memory"); \ |
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Should we add a reference to the GCC ticket to remember why we globber the memory here? Just in case someone looks at this in 3 years from now and tries to save some cycles...
janjust
approved these changes
Jan 13, 2025
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Prevent the compiler from reordering the instructions in the patcher by marking the assembly code as clobbering memory.
Thanks @pinskia for the patch and for bringing the discussion on the gcc bugzilla.
I was not able to test this. The code generated by godbolt seems legit, but I did not yet figured out how to look at the disassembled code in OMPI.
Fixes #13014.