[LLVMdev] X86TargetLowering::LowerToBT

[Fiona Glaser]

Is that even a valid instruction? I thought TEST only took 32-bit immediates.

Fiona

> On Jan 22, 2015, at 2:48 PM, Chris Sears <chris.sears at gmail.com> wrote:
> 
> The problem is that REX TEST reg,#(1<<37) is 10 bytes vs 5 bytes for REX BT reg,37.
> That's a large space penalty to pay for a possible partial update stall.
> 
> So the idea of generating BT for -Os and TEST for -Ofast makes sense to me.
> Regardless, LowerToBT is generating TEST for small values.
> 
> I'm still tracking down the Clang issue and I'd like folks to look at that.
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