SSBB

Speculative Store Bypass Barrier is a memory barrier which prevents speculative loads from bypassing earlier stores to the same virtual address under certain conditions.

The semantics of the Speculative Store Bypass Barrier are:

• When a load to a location appears in program order after the SSBB, then the load does not speculatively read an entry earlier in the coherence order for that location than the entry generated by the latest store satisfying all of the following conditions:
  • The store is to the same location as the load.
  • The store uses the same virtual address as the load.
  • The store appears in program order before the SSBB.
• When a load to a location appears in program order before the SSBB, then the load does not speculatively read data from any store satisfying all of the following conditions:
  • The store is to the same location as the load.
  • The store uses the same virtual address as the load.
  • The store appears in program order after the SSBB.

This is an alias of DSB. This means:

• The encodings in this description are named to match the encodings of DSB.
• The description of DSB gives the operational pseudocode for this instruction.