[PR115568][LRA]: Use more strict output reload check in rematerialization

[PR115568][LRA]: Use more strict output reload check in rematerialization

  In this PR case LRA rematerialized a value from inheritance insn
instead of output reload one.  This resulted in considering a
rematerilization candidate value available when it was actually
not.  As a consequence an insn after rematerliazation used the
unexpected value and this use resulted in fp exception.  The patch
fixes this bug.

gcc/ChangeLog:

	PR rtl-optimization/115568
	* lra-remat.cc (create_cands): Check that output reload insn is
	adjacent to given insn.  Update a comment.

gcc/testsuite/ChangeLog:

	PR rtl-optimization/115568
	* gcc.target/i386/pr115568.c: New.