https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78176
Maciej W. Rozycki <ma...@linux-mips.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |ma...@linux-mips.org
--- Comment #11 from Maciej W. Rozycki <ma...@linux-mips.org> ---
TBH this does look like trying to rely on UB to me, as per section
6.5.6 "Additive operators" clause 8 of the C language standard, which
states (among others):
"If both the pointer operand and the result point to elements of the
same array object, or one past the last element of the array object,
the evaluation shall not produce an overflow; otherwise, the behavior
is undefined."
Here under the triggering conditions the pointer the integer is added
to with LDXC1 does not point to an element of the array operated on (or
to one past the last), so the hardware operation matches the standard's
semantics WRT overflow and I don't think we ought to be pushing it.
So it looks like a middle end bug to me and the backend is fine in
faithfully assuming its RTL pattern won't be passed operands leading to
UB.
Have I missed anything?
Maciej
