Rules to Remember

• Branches must be resolved in Program Order

• Stores cannot be dispatched while under speculative execution

  • No way to recover memory consistency if misprediction made.

• Only NON-speculative instructions can be retired

• The spec_flag which follows an instruction throughout its life within the CPU is KEY for correct operation

  • If instruction’s context value ever equal to firstctx, then spec_flag is set to FALSE.
  • A speculative instruction can become non-speculative, but not vice-versa.

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