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VLD1 (single element to one lane)

Load single 1-element structure to one lane of one register loads one element from memory into one element of a register. Elements of the register that are not loaded are unchanged. For details of the addressing mode see Advanced SIMD addressing mode.

Depending on settings in the CPACR, NSACR, and HCPTR registers, and the Security state and PE mode in which the instruction is executed, an attempt to execute the instruction might be undefined, or trapped to Hyp mode. For more information see Enabling Advanced SIMD and floating-point support.

It has encodings from the following instruction sets: A32 ( A1 , A2 and A3 ) and T32 ( T1 , T2 and T3 ) .

A1

313029282726252423222120191817161514131211109876543210
111101001D10RnVd0000index_alignRm
size

Offset (Rm == 1111)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}]

Post-indexed (Rm == 1101)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}]!

Post-indexed (Rm != 11x1)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}], <Rm>

if size == '11' then SEE "VLD1 (single element to all lanes)";
if index_align<0> != '0' then UNDEFINED;
ebytes = 1;  index = UInt(index_align<3:1>);  alignment = 1;
d = UInt(D:Vd);  n = UInt(Rn);  m = UInt(Rm);
wback = (m != 15);  register_index = (m != 15 && m != 13);
if n == 15 then UNPREDICTABLE;

A2

313029282726252423222120191817161514131211109876543210
111101001D10RnVd0100index_alignRm
size

Offset (Rm == 1111)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}]

Post-indexed (Rm == 1101)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}]!

Post-indexed (Rm != 11x1)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}], <Rm>

if size == '11' then SEE "VLD1 (single element to all lanes)";
if index_align<1> != '0' then UNDEFINED;
ebytes = 2;  index = UInt(index_align<3:2>);
alignment = if index_align<0> == '0' then 1 else 2;
d = UInt(D:Vd);  n = UInt(Rn);  m = UInt(Rm);
wback = (m != 15);  register_index = (m != 15 && m != 13);
if n == 15 then UNPREDICTABLE;

A3

313029282726252423222120191817161514131211109876543210
111101001D10RnVd1000index_alignRm
size

Offset (Rm == 1111)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}]

Post-indexed (Rm == 1101)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}]!

Post-indexed (Rm != 11x1)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}], <Rm>

if size == '11' then SEE "VLD1 (single element to all lanes)";
if index_align<2> != '0' then UNDEFINED;
if index_align<1:0> != '00' && index_align<1:0> != '11' then UNDEFINED;
ebytes = 4;  index = UInt(index_align<3>);
alignment = if index_align<1:0> == '00' then 1 else 4;
d = UInt(D:Vd);  n = UInt(Rn);  m = UInt(Rm);
wback = (m != 15);  register_index = (m != 15 && m != 13);
if n == 15 then UNPREDICTABLE;

T1

15141312111098765432101514131211109876543210
111110011D10RnVd0000index_alignRm
size

Offset (Rm == 1111)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}]

Post-indexed (Rm == 1101)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}]!

Post-indexed (Rm != 11x1)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}], <Rm>

if size == '11' then SEE "VLD1 (single element to all lanes)";
if index_align<0> != '0' then UNDEFINED;
ebytes = 1;  index = UInt(index_align<3:1>);  alignment = 1;
d = UInt(D:Vd);  n = UInt(Rn);  m = UInt(Rm);
wback = (m != 15);  register_index = (m != 15 && m != 13);
if n == 15 then UNPREDICTABLE;

T2

15141312111098765432101514131211109876543210
111110011D10RnVd0100index_alignRm
size

Offset (Rm == 1111)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}]

Post-indexed (Rm == 1101)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}]!

Post-indexed (Rm != 11x1)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}], <Rm>

if size == '11' then SEE "VLD1 (single element to all lanes)";
if index_align<1> != '0' then UNDEFINED;
ebytes = 2;  index = UInt(index_align<3:2>);
alignment = if index_align<0> == '0' then 1 else 2;
d = UInt(D:Vd);  n = UInt(Rn);  m = UInt(Rm);
wback = (m != 15);  register_index = (m != 15 && m != 13);
if n == 15 then UNPREDICTABLE;

T3

15141312111098765432101514131211109876543210
111110011D10RnVd1000index_alignRm
size

Offset (Rm == 1111)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}]

Post-indexed (Rm == 1101)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}]!

Post-indexed (Rm != 11x1)

VLD1{<c>}{<q>}.<size> <list>, [<Rn>{:<align>}], <Rm>

if size == '11' then SEE "VLD1 (single element to all lanes)";
if index_align<2> != '0' then UNDEFINED;
if index_align<1:0> != '00' && index_align<1:0> != '11' then UNDEFINED;
ebytes = 4;  index = UInt(index_align<3>);
alignment = if index_align<1:0> == '00' then 1 else 4;
d = UInt(D:Vd);  n = UInt(Rn);  m = UInt(Rm);
wback = (m != 15);  register_index = (m != 15 && m != 13);
if n == 15 then UNPREDICTABLE;

For more information about the constrained unpredictable behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors.

Assembler Symbols

<c>

For encoding A1, A2 and A3: see Standard assembler syntax fields. This encoding must be unconditional.

For encoding T1, T2 and T3: see Standard assembler syntax fields.

<q>

See Standard assembler syntax fields.

<size> Is the data size, encoded in size:
size <size>
00 8
01 16
10 32
<list>

Is a list containing the single 64-bit name of the SIMD&FP register holding the element.

The list must be { <Dd>[<index>] }.

The register <Dd> is encoded in the "D:Vd" field.

The permitted values and encoding of <index> depend on <size>:

<size> == 8
<index> is in the range 0 to 7, encoded in the "index_align<3:1>" field.
<size> == 16
<index> is in the range 0 to 3, encoded in the "index_align<3:2>" field.
<size> == 32
<index> is 0 or 1, encoded in the "index_align<3>" field.
<Rn>

Is the general-purpose base register, encoded in the "Rn" field.

<align>

When <size> == 8, <align> must be omitted, otherwise it is the optional alignment.

Whenever <align> is omitted, the standard alignment is used, see Unaligned data access, and the encoding depends on <size>:

<size> == 8
Encoded in the "index_align<0>" field as 0.
<size> == 16
Encoded in the "index_align<1:0>" field as 0b00.
<size> == 32
Encoded in the "index_align<2:0>" field as 0b000.

Whenever <align> is present, the permitted values and encoding depend on <size>:

<size> == 16
<align> is 16, meaning 16-bit alignment, encoded in the "index_align<1:0>" field as 0b01.
<size> == 32
<align> is 32, meaning 32-bit alignment, encoded in the "index_align<2:0>" field as 0b011.

: is the preferred separator before the <align> value, but the alignment can be specified as @<align>, see Advanced SIMD addressing mode.

<Rm>

Is the general-purpose index register containing an offset applied after the access, encoded in the "Rm" field.

For more information about the variants of this instruction, see Advanced SIMD addressing mode.

Operation

if ConditionPassed() then
    EncodingSpecificOperations();  CheckAdvSIMDEnabled();
    address = R[n];  iswrite = FALSE;
    - = AArch32.CheckAlignment(address, alignment, AccType_VEC, iswrite);
    Elem[D[d],index] = MemU[address,ebytes];
    if wback then
        if register_index then
            R[n] = R[n] + R[m];
        else
            R[n] = R[n] + ebytes;
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