https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100232
--- Comment #4 from Tom de Vries <vries at gcc dot gnu.org> ---
This commit:
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commit 3af3bec2e4d344bd54a134d8b2263f44d788c3d8
Author: Richard Sandiford <richard.sandif...@arm.com>
Date: Mon May 4 21:21:16 2020 +0100
internal-fn: Avoid dropping the lhs of some calls [PR94941]
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adds:
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expand_insn (get_multi_vector_move (type, optab), 2, ops);
+ if (!rtx_equal_p (target, ops[0].value))
+ emit_move_insn (target, ops[0].value);
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in expand_load_lanes_optab_fn and mentions:
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create_output_operand coerces an output operand to the insn's
predicates, using a suggested rtx location if convenient.
But if that rtx location is actually required rather than
optional, the builder of the insn has to emit a move afterwards.
(We could instead add a new interface that does this automatically,
but that's future work.)
This PR shows that we were failing to emit the move for some of the
vector load internal functions. I think there are other routines in
internal-fn.c that potentially have the same problem, but this patch is
supposed to be a conservative subset suitable for backporting to GCC 10.
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