[LLVMdev] Instruction Constraints Question

Tim Northover t.p.northover at gmail.com
Wed Jan 23 13:40:41 PST 2013

>> It doesn't look like TableGen supports Constraints beyond EARLY_CLOBBER
>> and TIED_TO.  We would need to add a constraint such as "$dst != $src1,
>> $dst != $mask, $src1 != $mask" to the current patterns to enforce the
>> rules.
> You can emulate such constraints via early clobbing. Just mark dst as
> early clobbing.

How would that (or any early clobbering) enforce $src1 != $mask? Or is
it a fortuitous side-effect of implementation?


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