"no regressions" meaning?

[Larry Evans <jcampbell3 at prodigy dot net>]

I've read several postings to this news group which use this phrase.  If
I plan to make some changes in some
files in $(src.dir)/gcc/cp, should I do the following in order to see
whether there are "no regressions"?

  1.  Before making any changes, in $(obj.dir):
        1.1 make check-gcc
        1.2 mv gcc/testsuite/g++.sum gcc/testsuite/g++.sum.orig
   2.  Make the changes om $(src.dir)/gcc/cp.
   3.  in $(obj.dir)
         3.1 make check-gcc
         3.2 diff gcc/test/suite/g++.sum gcc/testsuite/g++.sum.orig
   4.  There are "no regressions" iff there are no differences shown in
step 3.2

In the above, $(obj.dir) is the top level object directory and
$(src.dir) is the top level source directory.