[LLVMdev] X86TargetLowering::LowerToBT

[Stephen Canon]

> On Jan 22, 2015, at 5:59 PM, Chris Sears <chris.sears at gmail.com> wrote:
> 
> My bad on that. So that's what the comment meant.
> That means BT is pretty much req'd in the 64b case.

In the 64b case we can TEST with mask from memory.  This is *still* preferable to BT in most instruction streams.

One can reasonably argue that we should generate BT under –Os (I disagree, but only because I think that optimizing for code size to the point of completely disregarding performance is pointlessly stupid; if that’s what Os is meant to be, then by all means use BT).  I don’t think one can make a case for BT outside of –Os.

– Steve