Vector Count Leading Sign Bits counts the number of consecutive bits following the topmost bit, that are the same as the topmost bit, in each element in a vector, and places the results in a second vector. The count does not include the topmost bit itself.
The operand vector elements can be any one of 8-bit, 16-bit, or 32-bit signed integers.
The result vector elements are the same data type 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 ) .
| 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | D | 1 | 1 | size | 0 | 0 | Vd | 0 | 1 | 0 | 0 | 0 | Q | M | 0 | Vm | |||||||
if size == '11' then UNDEFINED; if Q == '1' && (Vd<0> == '1' || Vm<0> == '1') then UNDEFINED; constant integer esize = 8 << UInt(size); constant elements = 64 DIV esize; constant d = UInt(D:Vd); constant m = UInt(M:Vm); constant regs = if Q == '0' then 1 else 2;
| 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | D | 1 | 1 | size | 0 | 0 | Vd | 0 | 1 | 0 | 0 | 0 | Q | M | 0 | Vm | |||||||
if size == '11' then UNDEFINED; if Q == '1' && (Vd<0> == '1' || Vm<0> == '1') then UNDEFINED; constant integer esize = 8 << UInt(size); constant elements = 64 DIV esize; constant d = UInt(D:Vd); constant m = UInt(M:Vm); constant regs = if Q == '0' then 1 else 2;
| <c> |
For encoding A1: see Standard assembler syntax fields. This encoding must be unconditional. |
|
For encoding T1: see Standard assembler syntax fields. |
| <q> |
| <dt> |
Is the data type for the elements of the operands,
encoded in
|
| <Qd> |
Is the 128-bit name of the SIMD&FP destination register, encoded in the "D:Vd" field as <Qd>*2. |
| <Qm> |
Is the 128-bit name of the SIMD&FP source register, encoded in the "M:Vm" field as <Qm>*2. |
| <Dd> |
Is the 64-bit name of the SIMD&FP destination register, encoded in the "D:Vd" field. |
| <Dm> |
Is the 64-bit name of the SIMD&FP source register, encoded in the "M:Vm" field. |
if ConditionPassed() then EncodingSpecificOperations(); CheckAdvSIMDEnabled(); for r = 0 to regs-1 for e = 0 to elements-1 Elem[D[d+r],e,esize] = CountLeadingSignBits(Elem[D[m+r],e,esize])<esize-1:0>;
If CPSR.DIT is 1 and this instruction passes its condition execution check:
Internal version only: isa v01_31, pseudocode v2024-03_rel ; Build timestamp: 2024-03-25T10:05
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