LRA: Revert "Remove useless move insns"

LRA: Revert "Remove useless move insns"

Useless move insn removal was added to LRA just to avoid wasting CPU
cycles on such insn processing afterwards.  Such insns are removed
anyway later in the pass pipeline.  The CPU time savings are tiny but
the removal creates too many problems including PR target/90178.
Vladimir pre-approved the patch to remove the code:

https://gcc.gnu.org/ml/gcc-patches/2019-04/msg00834.html

gcc/

	PR target/90178
	Revert:
	2018-11-21  Uros Bizjak  <ubizjak@gmail.com>

	Revert the revert:
	2013-10-26  Vladimir Makarov  <vmakarov@redhat.com>

	Revert:
	2013-10-25  Vladimir Makarov  <vmakarov@redhat.com>

	* lra-spills.c (lra_final_code_change): Remove useless move insns.

gcc/testsuite/

	PR target/90178
	* gcc.target/i386/pr90178.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@270484 138bc75d-0d04-0410-961f-82ee72b054a4