rs6000: Preserve REG_EH_REGION when replacing load/store [PR106091]

rs6000: Preserve REG_EH_REGION when replacing load/store [PR106091]

As test case in PR106091 shows, rs6000 specific pass swaps
doesn't preserve the reg_note REG_EH_REGION when replacing
some load insn at the end of basic block, it causes the
flow info verification to fail unexpectedly.  Since memory
reference rtx may trap, this patch is to ensure we copy
REG_EH_REGION reg_note while replacing swapped aligned load
or store.

	PR target/106091

gcc/ChangeLog:

	* config/rs6000/rs6000-p8swap.cc (replace_swapped_aligned_store): Copy
	REG_EH_REGION when replacing one store insn having it.
	(replace_swapped_aligned_load): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/pr106091.c: New test.

(cherry picked from commit f4286601933406142b46693660f7f4b682cb50a5)