[LLVMdev] Constraints

[Evan Cheng]

On Jun 17, 2008, at 1:36 PM, David Greene wrote:

> Can someone explain the Constraints system in X86*.td?
>
> For example:
>
> let Constraints = "$src1 = $dst"
>
> This replaces isTwoAddress (according to svn logs), which I gather  
> is how
> two-address instructions used to be marked for X86.

You're right. This is the same as isTwoAddress, just more flexible.

>
>
> Except isTwoAddress is still used in X86InstInfo.td.

Because I haven't replaced all uses of isTwoAddress with constraints,  
that's all.

Evan

>
>
> So what gives?  What do these two properties actually do?
>
>                                           -Dave
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