[LLVMdev] X86TargetLowering::LowerToBT

[Eric Christopher]

On Thu Jan 22 2015 at 3:32:53 PM Chris Sears <chris.sears at gmail.com> wrote:

> The status quo is:
>
> a) 40b REX+BT instruction for the 64b case
> b) 48b TEST for the 32b case
> c) unless it's small TEST
>
>
> You are currently paying a 16b penalty for TEST vs BT in the 32b case.
> That may be worth testing the -Os flag.
>

You'll want -Oz here, Os isn't supposed to affect the runtime as much as
this is going to.

-eric
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