i386: Require in peephole2 that memory is offsettable [PR119450]

i386: Require in peephole2 that memory is offsettable [PR119450]

The following testcase ICEs because a peephole2 attempts to offset
memory which is not offsettable (in particular address is a ZERO_EXTEND
in this case).

Because peephole2s don't support constraints, I've added a check for this
in the peephole2's condition.

2025-03-26  Jakub Jelinek  <jakub@redhat.com>

	PR target/119450
	* config/i386/i386.md (narrow test peephole2): Test for
	offsettable_memref_p in condition.

	* gcc.target/i386/pr119450.c: New test.