* Linaro GCC
Continued work on 64-bit shifts. My patch for shifts in core registers
was rejected because I used conditional-execution before it's safe,
apparently, so I've spent some time looking at the alternatives.
First, conditional move instructions were unsatisfactory - the final
instruction sequence was longer and therefore less efficient.
Second, if_then_else instructions (basically conditional execution
expressed a different way) was to limited - there were no patterns
compatible with "or with shifted input" available in ARM mode, and no
patterns available at all in Thumb mode. I solved that easily enough, of
course, but the result was still unsatisfactory. In Thumb mode the
result was roughly equivalent (conditional-execution is constrained by
IT blocks), but in ARM mode it uses patterns that output two opposing
instructions at once, without allowing for the possibility of scheduling
or other optimization.
Third, I've tried putting in ordinary branches and relying on the
if-conversion pass to transform that to conditional execution. I had not
done this initially, partially because I didn't know how, but mostly
because the original implementation I was trying to replace resulted in
branches in the output code, and I was trying to improve on that.
Anyway, I've now figured out how to do that, and initial testing
suggests that the if-conversion really is working this time. Even if it
doesn't always, the other improvements to the shift sequence should
still give a boost.
My other patch, to do 64-bits shifts in NEON (and fall back to the above
code when register allocation sees fit) has not yet been reviewed.
* Linaro Connect
This week was Linaro Connect week. I could not attend the event in San
Francisco in person this time, so I took part in some of the morning
sessions remotely.
Linaro have switched to using Google Hangouts for the remote
participation, and it went really rather well. In the old system there
was an audio stream to listen to (on a 20 second delay or so, usually),
and an IRC room projected onto a large screen for remote attendees to
respond. The new Hangout system is effectively a simple in-browser
video-conference system that allowed us to not only see the room, but
also respond verbally in real time. The only disadvantage is the
10-person limit, but I never saw any room get near that all week.
I successfully attended several sessions and one regular meeting
remotely by these means. And no jet lag or eating so much!
_______________________________________________
linaro-toolchain mailing list
[email protected]
http://lists.linaro.org/mailman/listinfo/linaro-toolchain
