On Wed, Aug 7, 2013 at 2:50 AM, Weiliang Lin <[email protected]>wrote:

> Yes, I agree with you, especially on IA32 which does not have much
> registers.
>

That platform is my main concern, too, especially because it is still the
most important platform we have.


> So could I have a conclusion here. The branchless code is suitable for the
> stub call where there is no register pressure, but not suitable for
> lithium. Right?
>

I jumped into the discussion a little bit late, so I don't know exactly
which stub is meant, but in general, yes: For the Lithium code generators
using an additional register just to avoid a tiny branch is a no-go, but if
you have a spare register in some stub you can of course use it. Adding a
comment plus a URL describing the bit twiddling hack would be good, too,
because if you haven't seen such code before, it is totally unclear what it
is doing and how.

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