STRB (register)

Store Register Byte (register) calculates an address from a base register value and an offset register value, and stores a byte from a register to memory. The offset register value can optionally be shifted. For information about memory accesses see Memory accesses.

It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 and T2 ) .

A1

if P == '0' && W == '1' then SEE "STRBT"; t = UInt(Rt); n = UInt(Rn); m = UInt(Rm); index = (P == '1'); add = (U == '1'); wback = (P == '0') || (W == '1'); (shift_t, shift_n) = DecodeImmShift(stype, imm5); if t == 15 || m == 15 then UNPREDICTABLE; if wback && (n == 15 || n == t) then UNPREDICTABLE;

CONSTRAINED UNPREDICTABLE behavior

If t == 15, then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• The store instruction performs the store using the specified addressing mode but the value corresponding to R15 is unknown.

If wback && n == t, then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• The store instruction executes but the value stored is unknown.

If wback && n == 15, then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• The instruction executes without writeback of the base address.
• The instruction uses the addressing mode described in the equivalent immediate offset instruction.

T1

t = UInt(Rt); n = UInt(Rn); m = UInt(Rm); index = TRUE; add = TRUE; wback = FALSE; (shift_t, shift_n) = (SRType_LSL, 0);

T2

if Rn == '1111' then UNDEFINED; t = UInt(Rt); n = UInt(Rn); m = UInt(Rm); index = TRUE; add = TRUE; wback = FALSE; (shift_t, shift_n) = (SRType_LSL, UInt(imm2)); if t == 15 || m == 15 then UNPREDICTABLE; // Armv8-A removes UNPREDICTABLE for R13

CONSTRAINED UNPREDICTABLE behavior

If t == 15, then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• The store instruction performs the store using the specified addressing mode but the value corresponding to R15 is unknown.

Assembler Symbols