[PATCH] D21798: [ARM] Do not test for CPUs, use SubtargetFeatures. Also remove 1 flag

[Renato Golin via llvm-commits]

rengolin added a comment.

> In particular, in the past MLx expansion was enabled for

>  subtargets with hasVFP2(), until r129775 [1] switched from that to isCortexA9,

>  without too much justification.


Now I remember this patch! This is about the VMLA+VMLA having a huge pipeline stall on A9, so VMLA+VMUL+VADD is preferred.

This is *exactly* the semantics of VMLxHazard and can be encoded in the way you do in this patch.

I remember this being a problem in A9, it may very well be present in A8 (though I don't remember exactly). I'm just surprised that A7 has the hazard as well. I'd have thought that, if A15 has fixed it, A7 would have carried the fix with it.

Regardless, this is a conversation for another patch. I think your fix is correct and it retains the current behaviour.

cheers,
--renato


http://reviews.llvm.org/D21798