https://bugs.kde.org/show_bug.cgi?id=377966
Bug ID: 377966
Summary: disInstr(arm64): unhandled instruction 0xD50B7425
Product: valgrind
Version: 3.12.0
Platform: Fedora RPMs
OS: Linux
Status: UNCONFIRMED
Severity: normal
Priority: NOR
Component: memcheck
Assignee: jsew...@acm.org
Reporter: jrei...@bitwagon.com
Target Milestone: ---
On aarch64 (64-bit ARM) memcheck complains "unhandled instruction 0xD50B7425"
which is "dc zva, x5". This is a data cache control instruction; it [allocates
and] clears the cache line whose address corresponds to the contents of
register x5. Optimized code uses "dc zva," when it will be writing the entire
cache line. Therefore the hardware need not read the line from memory (which
otherwise would be required upon the first write to the line), which saves
time.
Other related instructions which are used soon afterwards: "dc cvau," [Clean
data cache line by Virtual Address to point of Unification] to force the cache
line to be written to memory; and "ic ivau," [Invalidate icache line by Virtual
Address to point of Unification] to force the icache to forget the old contents
of a newly-overwritten instruction stream.
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