rtlanal: Fix set_noop_p for volatile loads or stores [PR114768]

On the following testcase, combine propagates the mem/v load into mem store
with the same address and then removes it, because noop_move_p says it is a
no-op move.  If it was the other way around, i.e. mem/v store and mem load,
or both would be mem/v, it would be kept.
The problem is that rtx_equal_p never checks any kind of flags on the rtxes
(and I think it would be quite dangerous to change it at this point), and
set_noop_p checks side_effects_p on just one of the operands, not both.
In the MEM <- MEM set, it only checks it on the destination, in
store to ZERO_EXTRACT only checks it on the source.

The following patch adds the missing side_effects_p checks.

2024-04-19  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/114768
	* rtlanal.cc (set_noop_p): Don't return true for MEM <- MEM
	sets if src has side-effects or for stores into ZERO_EXTRACT
	if ZERO_EXTRACT operand has side-effects.

	* gcc.dg/pr114768.c: New test.