STRD (immediate)
Store Register Dual (immediate)
Store Register Dual (immediate) calculates an address from a base register value and an immediate offset, and stores two words from two registers to memory. It can use offset, post-indexed, or pre-indexed addressing. For information about memory accesses see Memory accesses.
For more information about the constrained unpredictable behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors.
Related encodings: Load/store dual, load/store exclusive, table branch.
If CPSR.DIT is 1, the timing of this instruction is insensitive to the value of the data being loaded or stored.
It has encodings from the following instruction sets:
A32 (
A1
)
and
T32 (
T1
)
.
!= 1111
0
0
0
1
0
1
1
1
1
1
0
STRD{<c>}{<q>} <Rt>, <Rt2>, [<Rn> {, #{+/-}<imm>}]
0
0
STRD{<c>}{<q>} <Rt>, <Rt2>, [<Rn>], #{+/-}<imm>
1
1
STRD{<c>}{<q>} <Rt>, <Rt2>, [<Rn>, #{+/-}<imm>]!
if Rt<0> == '1' then UNPREDICTABLE;
t = UInt(Rt); t2 = t+1; n = UInt(Rn); imm32 = ZeroExtend(imm4H:imm4L, 32);
index = (P == '1'); add = (U == '1'); wback = (P == '0') || (W == '1');
if P == '0' && W == '1' then UNPREDICTABLE;
if wback && (n == 15 || n == t || n == t2) then UNPREDICTABLE;
if t2 == 15 then UNPREDICTABLE;
t == 15 || t2 == 15
The store instruction performs the store using the specified addressing mode but the value corresponding to R15 is unknown.
wback && (n == t || n == t2)
wback && n == 15
The instruction uses the addressing mode described in the equivalent immediate offset instruction.
Rt<0> == '1'
The instruction executes as described, with no change to its behavior and no additional side-effects. This does not apply when Rt == '1111'.
P == '0' && W == '1'
The instruction executes as an LDRD using one of offset, post-indexed, or pre-indexed addressing.
1
1
1
0
1
0
0
1
0
!= 1111
1
0
STRD{<c>}{<q>} <Rt>, <Rt2>, [<Rn> {, #{+/-}<imm>}]
0
1
STRD{<c>}{<q>} <Rt>, <Rt2>, [<Rn>], #{+/-}<imm>
1
1
STRD{<c>}{<q>} <Rt>, <Rt2>, [<Rn>, #{+/-}<imm>]!
if P == '0' && W == '0' then SEE "Related encodings";
t = UInt(Rt); t2 = UInt(Rt2); n = UInt(Rn); imm32 = ZeroExtend(imm8:'00', 32);
index = (P == '1'); add = (U == '1'); wback = (W == '1');
if wback && (n == t || n == t2) then UNPREDICTABLE;
if n == 15 || t == 15 || t2 == 15 then UNPREDICTABLE; // Armv8-A removes UNPREDICTABLE for R13
t == 15 || t2 == 15
The store instruction performs the store using the specified addressing mode but the value corresponding to R15 is unknown.
wback && (n == t || n == t2)
wback && n == 15
The instruction uses the addressing mode described in the equivalent immediate offset instruction.
<c>
See Standard assembler syntax fields.
<q>
See Standard assembler syntax fields.
<Rt>
For encoding A1: is the first general-purpose register to be transferred, encoded in the "Rt" field. This register must be even-numbered and not R14.
<Rt>
For encoding T1: is the first general-purpose register to be transferred, encoded in the "Rt" field.
<Rt2>
For encoding A1: is the second general-purpose register to be transferred. This register must be <R(t+1)>.
<Rt2>
For encoding T1: is the second general-purpose register to be transferred, encoded in the "Rt2" field.
<Rn>
For encoding A1: is the general-purpose base register, encoded in the "Rn" field. The PC can be used in the offset variant, but this is deprecated.
<Rn>
For encoding T1: is the general-purpose base register, encoded in the "Rn" field.
+/-
Specifies the offset is added to or subtracted from the base register, defaulting to + if omitted and
<imm>
For encoding A1: is the 8-bit unsigned immediate byte offset, in the range 0 to 255, defaulting to 0 if omitted, and encoded in the "imm4H:imm4L" field.
<imm>
For encoding T1: is the unsigned immediate byte offset, a multiple of 4, in the range 0 to 1020, defaulting to 0 if omitted, and encoded in the "imm8" field as <imm>/4.
if ConditionPassed() then
EncodingSpecificOperations();
offset_addr = if add then (R[n] + imm32) else (R[n] - imm32);
address = if index then offset_addr else R[n];
if IsAligned(address, 8) then
bits(64) data;
if BigEndian(AccessType_GPR) then
data<63:32> = R[t];
data<31:0> = R[t2];
else
data<31:0> = R[t];
data<63:32> = R[t2];
MemA[address,8] = data;
else
MemA[address,4] = R[t];
MemA[address+4,4] = R[t2];
if wback then R[n] = offset_addr;