[PATCH] D76608: [ARM][MVE] Add target flag for narrowing insts

[Sjoerd Meijer via Phabricator via llvm-commits]

SjoerdMeijer added a comment.

Looks like a good direction to me.

Question about the name `retainsPreviousHalf`. Since it is not immediately obvious what the `Half` refers to, that could e.g. be a registers, how do you feel about e.g. `retainsPreviousHalfElement`? That looks like the terminology used by the ArmARM, e.g one of the instruction descriptions is:

" ... writing the result to either the top half (T variant) or bottom half (B variant) of the result element. The other half of the destination vector element
retains its previous value."



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Comment at: llvm/lib/Target/ARM/ARMInstrFormats.td:411
   bit validForTailPredication = 0;
+  bit retainsPreviousHalf = 0;
 
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I wanted to add that a comment would be good here, but then noticed there is one in ARMBaseInfo.h. Looks like the comment for thumbArithFlagSetting is duplicated, and is present here and in ARMBaseInfo.h


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https://reviews.llvm.org/D76608