https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113045
--- Comment #25 from Mark Wielaard <mark at gcc dot gnu.org> ---
Note comment #16 which explains that valgrind seems to translate this large
read into smaller chunks. Which most likely causes memcheck to flag the (last)
8 bytes read as fully invalid. See
--partial-loads-ok=<yes|no> [default: yes]
Controls how Memcheck handles 32-, 64-, 128- and 256-bit naturally
aligned loads from addresses for which some bytes are addressable and others
are not. When yes, such loads do not produce an address error. Instead, loaded
bytes originating from illegal addresses are marked as uninitialised, and those
corresponding to legal addresses are handled in the normal way.
When no, loads from partially invalid addresses are treated the same as
loads from completely invalid addresses: an illegal-address error is issued,
and the resulting bytes are marked as initialised.
It would be helpful to see if someone with arm knowledge (and valgrind VEX
knowledge) can see if there is a better translation of the vld1 instruction so
that it is one big read. That way memcheck at least has a chance of detecting
that the part that is invalid isn't actually used. See
https://sourceware.org/cgit/valgrind/tree/VEX/priv/guest_arm_toIR.c#n8383
But maybe there is no good/natural translation of these vector loads that would
help memcheck see it is a valid read and only the defined bytes are used.
