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Micro-fusion limited to 1-reg addressing modes
Author:  Date: 2015-11-15 12:23
This is a limitation of IDQ, so it happens after either decoder or uop-cache. Unlike Nhm, SnB introduced new rule for IDQ: microfused uops with index reg (and some other rare types) are unfused when writing to IDQ. Even if you have 4 of them per clock, IDQ would get all 8 «uop halfs» at once, but (as with any uops) can read just 4/cl. Reason: IDQ, ROB and RS buffers and queues have reduced uop format (for energy efficiency) without 6-bit (renamed) index field. There is no changes to this in IvB, but there may be in Hwl.
 
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