Arm® A64 Instruction Set Architecture: Armv8, for Armv8-A architecture profile | STURB: Store Register Byte (unscaled).

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STURB

Store Register Byte (unscaled) calculates an address from a base register value and an immediate offset, and stores a byte to the calculated address, from a 32-bit register. For information about memory accesses, see Load/Store addressing modes.

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0	0	1	1	1	0	0	0	0	0	0	imm9									0	0	Rn					Rt
size								opc

STURB <Wt>, [<Xn|SP>{, #<simm>}]

bits(64) offset = SignExtend(imm9, 64);

Assembler Symbols

<Wt>	Is the 32-bit name of the 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.

<simm>

Is the optional signed immediate byte offset, in the range -256 to 255, defaulting to 0 and encoded in the "imm9" field.

Shared Decode

integer n = UInt(Rn);
integer t = UInt(Rt);

boolean tag_checked = n != 31;

Operation

if HaveMTEExt() then
    SetTagCheckedInstruction(tag_checked);

bits(64) address;
bits(8) data;

if n == 31 then
    CheckSPAlignment();
    address = SP[];
else
    address = X[n];

address = address + offset;

data = X[t];
Mem[address, 1, AccType_NORMAL] = data;

Operational information

If PSTATE.DIT is 1, the timing of this instruction is insensitive to the value of the data being loaded or stored.

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