Memory Cloaking

1
Memory Cloaking Bypassing

• ???as?a st? µ???µa
• ?????µ??e? ????te?t?????? ?p?????st??

?atsa??? ???st?t???? ?473?sa?????? G??????
?479
2
???se?? t?? ???µ??

• ??? ßas???? ???se?? t?? µ??µ??
• ??s? ep????????a a??µesa se e?t????
• (store ? load)
• ADD R1, R4, R3
• Store R1, 0(R6)
• Load R2, 0(R6)
• ADD R4, R2, R3

???µ?
3
???se?? t?? ???µ??

1. ??s? d?aµ???asµ?? ded?µ????(1 store ?d??e? se
   p???ap?? loads)

4
???ß??µata

• ???s? d?e????se?? spata??e? ??????? ?a p???ap??
  Loads ep?s??.
• Ta µp????se ? epe?e??ast?? ?a a????e?e? ta ?e???
  s?et???µe??? e?t?????
• S??p?? µa? ?a µe??s??µe t? communication latency

5
???sµ??

• Memory Cloaking ? µetaf??? µ?a? t?µ?? ap? t?
  store st? load p??? t?? ?p?????sµ? t?? d?e????s??
  (address calculation)

6
???sµ??

• Memory Bypassing ? d?ad??as?a store-load
  pa?a?e?pteta? apt?? a??s?da DEF-store-load-USE.
  ?? t?µ?? ????? apt? s?µe?? t?? pa?as?e??? t???
  st? s?µe?? t?? ?ata?a??s?? t???.

7
???ß?e?? ????t?s??

• ???aµ??? p??pe? ?a µetas??µat??eta? ? ?µµes??
  s??desµ?? se ?µes?.
• ADD R1, R4, R3
• Store R1, 0(R6)
• Load R2, 0(R6)
• ADD R4, R2, R3
• Speculative memory cloaking p??pe? ?a
  epa???e?te?.

8
???ß?e?? ????t?s??

• ?t????µe ??a ?st????? e?a?t?se?? (dependence
  history) ???a?a? a????e?s?? e?a?t?se??.Record
  (load PC, address)Loads (load PC, address)
• S??d???µe s?????µa µe t?? a????e??µe?e?
  e?a?t?se??.

association
Store Load fsynonym
9
Transient Value Cache (TVC)

• ???f? µ??µ? µetaßat???? t?µ??
• ????? ap????e?s?? ??a ß?a??ß?e? t?µ??
• ???s?µ?p??e?ta? sa? f??t?? ??a t?? ???f? µ??µ?
  t?? ded?µ????.
• ?e?????µe t? bandwidth t?? data cache.

10
?p?d?s?

• ?p???e? d??at?t?ta e?a??et??? µe????? a???ße?a?
  st?? p??ß?e?? t?? e?a?t?se?? µ??µ??
• ?? Cloaking µe ep??e?t???? d??at?t?te? a????e?
  t?? ap?d?se?? t?? µ??µ?? t?f?? cloaking µp??e?
  ?a? ?a t?? µe??se? ???? ?a??asµ???? ep??????.
• ????? st???e?a ep??e????? t?? p??ß?e?? µa? p.?.
  t? address locality, t? base-register ?a?
  Address-Space distribution.