On 02/08/2016 10:09 AM, Richard Biener wrote:
The gcc.target/i386/addr-sel-1.c (for PR28940) seems to just started working at some point past in time and thus it was added and the bug closed. You could say RA does a better job after the patch as it uses 1 less register but that restricts the followup postreload combine attempts. Though I wonder about what's "better" RA here - isn't the best allocation one that avoids spills but uses as many registers as possible (at least when targeting a CPU that cannot to register renaming)? regrename doesn't help this testcase either (it runs too late and does a renaming that doesn't help).
I don't think regrename's place in the pass pipeline is set in stone. If we enable it for gcc-7. we could also experiment with putting it just before postreload, or schedule another reload-combine afterwards.
Bernd
