ssbb

Speculative Store Bypass Barrier (A32)

SSBB

Prevents speculative loads bypassing earlier stores (v8.0).

Details

Speculative Store Bypass Barrier (v8.0) prevents speculative loads from bypassing earlier stores, ensuring that load operations wait for all prior store operations to complete. This is a lighter-weight barrier than SB, specifically targeting store-to-load forwarding speculation. Available in A32 instruction set; does not modify condition flags.

Pseudocode Operation

// Prevent speculative load execution past prior stores
StoreBypassBarrier()
// All prior stores complete before subsequent loads can execute

Example

SSBB

Encoding

Binary Layout
111101010111
1
1
1
1
1
1
1
1
0
0
0
0
0100
0000
 
Format System Hint
Opcode 0xF57FF040
Extension A32 (v8.0)

Operands

Reference (Arm AArch32 ISA)

Instruction Forms

Encoding Instruction ISA Bit pattern
0xF57FF040 SSBB{<q>} A32 111101010111 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 0100 | 0000
0xF3BF8F40 SSBB{<q>} T32 111100111011 | 1 | 1 | 1 | 1 | 10 | 0 | 0 | 1 | 1 | 1 | 1 | 0100 | 0000

Description

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:

Operation

if ConditionPassed() then
    EncodingSpecificOperations();
    SpeculativeStoreBypassBarrierToVA();