ST64B -- A64

ST64B

Single-copy atomic 64-byte store without status result

This instruction stores eight 64-bit doublewords from consecutive registers to a memory location. The store starts at register Xt, with the data being formed as Data[511:0] = X(t+7)::X(t+6)::X(t+5)::X(t+4)::X(t+3)::X(t+2)::X(t+1)::Xt. The data is stored atomically and is required to be 64-byte aligned.

It is IMPLEMENTATION DEFINED which memory locations support this instruction. A memory location that supports ST64B also supports LD64B.

For more information, including about the memory types accessible and how the accesses are performed, see Single-copy atomic 64-byte load/store.

Integer
(FEAT_LS64)

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
1	1	1	1	1	0	0	0	0	0	1	1	1	1	1	1	1	0	0	1	0	0	Rn					Rt
size					VR			A	R		Rs					o3	opc

Encoding

ST64B <Xt>, [<Xn|SP> {, #0}]

Decode for this encoding

if !IsFeatureImplemented(FEAT_LS64) then EndOfDecode(Decode_UNDEF); end; if Rt[4:3] == '11' || Rt[0] == '1' then EndOfDecode(Decode_UNDEF); end; let withstatus : boolean = FALSE; let t : integer{} = UInt(Rt); let n : integer{} = UInt(Rn); let tagchecked : boolean = n != 31;

For information about the CONSTRAINED UNPREDICTABLE behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors, and particularly ST64B.

Assembler Symbols

<Xt>	Is the 64-bit name of the first general-purpose register to be transferred, encoded in the "Rt" field.

<Xn|SP>

Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field.

Operation

CheckLDST64BEnabled(); var data : bits(512); var address : bits(64); var value : bits(64); let accdesc : AccessDescriptor = CreateAccDescLS64(MemOp_STORE, withstatus, tagchecked); for i = 0 to 7 do value = X{64}(t+i); if BigEndian(accdesc.acctype) then value = BigEndianReverse{64}(value); end; data[63+64*i : 64*i] = value; end; if n == 31 then CheckSPAlignment(); address = SP{64}(); else address = X{64}(n); end; MemStore64B(address, data, accdesc);