lb.aq
Load Byte Acquire
This instruction is defined by:
Synopsis
Load 8 bits of data from the address in xs1 into register xd, sign-extending
the result to XLEN bits.
This instruction has acquire semantics, which means that no subsequent memory operations (in program order) from this hart can be observed to occur before this load completes. Acquire semantics provide ordering guarantees useful for synchronization, such as reading a lock variable.
The address must be naturally aligned; if not, an address-misaligned or access-fault exception will be raised.
Execution
-
Pruned, XLEN == 64
-
Original
XReg virtual_address = X[xs1];
X[xd] = sext(read_memory_aligned(8, virtual_address, $encoding, 1'b1, 1'b0), 8);XReg virtual_address = X[xs1];
if (!is_naturally_aligned(8, virtual_address)) {
raise(ExceptionCode::LoadAddressMisaligned, mode(), virtual_address);
}
X[xd] = sext(read_memory_aligned(8, virtual_address, $encoding, 1'b1, 1'b0), 8);