Count Leading Zero bits (vector). This instruction counts the number of consecutive zeros, starting from the most significant bit, in each vector element in the source SIMD&FP register, places the result into a vector, and writes the vector to the destination SIMD&FP register.
Depending on the settings in the CPACR_EL1, CPTR_EL2, and CPTR_EL3 registers, and the current Security state and Exception level, an attempt to execute the instruction might be trapped.
| 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 |
| 0 | Q | 1 | 0 | 1 | 1 | 1 | 0 | size | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 0 | Rn | Rd | |||||||||
| U | |||||||||||||||||||||||||||||||
integer d = UInt(Rd); integer n = UInt(Rn); if size == '11' then UNDEFINED; integer esize = 8 << UInt(size); integer datasize = if Q == '1' then 128 else 64; integer elements = datasize DIV esize; CountOp countop = if U == '1' then CountOp_CLZ else CountOp_CLS;
| <Vd> |
Is the name of the SIMD&FP destination register, encoded in the "Rd" field. |
| <T> |
Is an arrangement specifier,
encoded in
|
| <Vn> |
Is the name of the SIMD&FP source register, encoded in the "Rn" field. |
CheckFPAdvSIMDEnabled64(); bits(datasize) operand = V[n]; bits(datasize) result; integer count; for e = 0 to elements-1 if countop == CountOp_CLS then count = CountLeadingSignBits(Elem[operand, e, esize]); else count = CountLeadingZeroBits(Elem[operand, e, esize]); Elem[result, e, esize] = count<esize-1:0>; V[d] = result;
If PSTATE.DIT is 1:
Internal version only: isa v33.11seprel, AdvSIMD v29.05, pseudocode v2021-09_rel, sve v2021-09_rc3d ; Build timestamp: 2021-10-06T11:41
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