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VTST -- AArch32

VTST

Vector Test Bits takes each element in a vector, and bitwise ANDs it with the corresponding element of a second vector. If the result is not zero, the corresponding element in the destination vector is set to all ones. Otherwise, it is set to all zeros.

The operand vector elements can be any one of:

The result vector elements are fields the same size as the operand vector elements.

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 ) and T32 ( T1 ) .

A1

313029282726252423222120191817161514131211109876543210
111100100DsizeVnVd1000NQM1Vm
Uopco1

Encoding for the 64-bit SIMD vector variant

Applies when (Q == 0)

VTST{<c>}{<q>}.<dt> {<Dd>, }<Dn>, <Dm>

Encoding for the 128-bit SIMD vector variant

Applies when (Q == 1)

VTST{<c>}{<q>}.<dt> {<Qd>, }<Qn>, <Qm>

Decode for all variants of this encoding

if Q == '1' && (Vd[0] == '1' || Vn[0] == '1' || Vm[0] == '1') then Undefined(); end; if size == '11' then Undefined(); end; let esize : integer{} = 8 << UInt(size); let elements : integer = 64 DIV esize; let d : integer = UInt(D::Vd); let n : integer = UInt(N::Vn); let m : integer = UInt(M::Vm); let regs : integer = if Q == '0' then 1 else 2;

T1

15141312111098765432101514131211109876543210
111011110DsizeVnVd1000NQM1Vm
Uopco1

Encoding for the 64-bit SIMD vector variant

Applies when (Q == 0)

VTST{<c>}{<q>}.<dt> {<Dd>, }<Dn>, <Dm>

Encoding for the 128-bit SIMD vector variant

Applies when (Q == 1)

VTST{<c>}{<q>}.<dt> {<Qd>, }<Qn>, <Qm>

Decode for all variants of this encoding

if Q == '1' && (Vd[0] == '1' || Vn[0] == '1' || Vm[0] == '1') then Undefined(); end; if size == '11' then Undefined(); end; let esize : integer{} = 8 << UInt(size); let elements : integer = 64 DIV esize; let d : integer = UInt(D::Vd); let n : integer = UInt(N::Vn); let m : integer = UInt(M::Vm); let regs : integer = if Q == '0' then 1 else 2;

Assembler Symbols

<c>

For the "A1 128-bit SIMD vector" and "A1 64-bit SIMD vector" variants: see Standard assembler syntax fields. This encoding must be unconditional.

For the "T1 128-bit SIMD vector" and "T1 64-bit SIMD vector" variants: see Standard assembler syntax fields.

<q>

See Standard assembler syntax fields.

<dt>

Is the data type for the elements of the operands, encoded in size:

size <dt>
00 8
01 16
10 32
<Dd>

Is the 64-bit name of the SIMD&FP destination register, encoded in the "D:Vd" field.

<Dn>

Is the 64-bit name of the first SIMD&FP source register, encoded in the "N:Vn" field.

<Dm>

Is the 64-bit name of the second SIMD&FP source register, encoded in the "M:Vm" field.

<Qd>

Is the 128-bit name of the SIMD&FP destination register, encoded in the "D:Vd" field as <Qd>*2.

<Qn>

Is the 128-bit name of the first SIMD&FP source register, encoded in the "N:Vn" field as <Qn>*2.

<Qm>

Is the 128-bit name of the second SIMD&FP source register, encoded in the "M:Vm" field as <Qm>*2.

Operational information

This instruction is a data-independent-time instruction as described in About the DIT bit.


2025-09_rel_asl1 2026-03-12 12:57:38

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