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PFaut2
Beginner
123 Views

Encoding phsubsw with VEX.256

Hi,

I don't understand how to encode PHSUBSW with VEX.256. According to the documentation, VEX.L must be 0, otherwise the instruction will #UD. I thought we must use VEX.L = 1 to force the VEX.256.

Thanks

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1 Reply
MarkC_Intel
Moderator
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Hi. Thanks. Yeah that "VEX.L must be zero" thing is left over from before we introduced AVX2 which added the 256b encoding for this instruction. I'll ask our doc team to fix this (and possibly others that might have similar origin).

 

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