One useful thing in the gcc testsuite is the ability to run make check
for one particular test.
Usually what I do is run make check, let it finish, and then rename
testsuite/gcc.log so it doesn't get clobbered when I run make check again.
Then go through the tests one by one.
After patching gcc (assuming it's a gcc bug) I can test the patch
for the particular testcase I'm interested in with
make check RUNTESTFLAGS=foo.exp=bar.c
e.g.
make check RUNTESTFLAGS=compile.exp=20010605-1.c
And if you wanted a few -v's:
make check RUNTESTFLAGS='compile.exp=20010605-1.c -v -v'
Sorry about the foo=bar=baz syntax, but I kinda like it.