Its effect could be achieved by
-stop-after,-print-after,-print-after-all. But a few tests need to
print MIR after ISel which could not be done with
-print-after/-stop-after since isel pass does not have commandline name.
That's the reason --print-machineinstrs is downgraded to
--print-after-isel in this patch. --print-after-isel could be
removed after we switch to new pass manager since isel pass would have a
commandline text name to use print-after or equivalent switches.
The motivation of this patch is to reduce tests dependency on