LSL (wide elements, predicated)

Shift left active elements of the first source vector by corresponding overlapping 64-bit elements of the second source vector and destructively place the results in the corresponding elements of the first source vector. The shift amount is a vector of unsigned 64-bit doubleword elements in which all bits are significant, and not used modulo the destination element size. Inactive elements in the destination vector register remain unmodified.

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then UNDEFINED; if size == '11' then UNDEFINED; constant integer esize = 8 << UInt(size); constant integer g = UInt(Pg); constant integer dn = UInt(Zdn); constant integer m = UInt(Zm);

Assembler Symbols

<Zdn>

Is the name of the first source and destination scalable vector register, encoded in the "Zdn" field.

<T>

Is the size specifier, encoded in size:

size	<T>
00	B
01	H
10	S
11	RESERVED

<Pg>	Is the name of the governing scalable predicate register P0-P7, encoded in the "Pg" field.

<Zm>	Is the name of the second source scalable vector register, encoded in the "Zm" field.

Operation

CheckSVEEnabled(); constant integer VL = CurrentVL; constant integer PL = VL DIV 8; constant integer elements = VL DIV esize; constant bits(PL) mask = P[g, PL]; constant bits(VL) operand1 = Z[dn, VL]; constant bits(VL) operand2 = if AnyActiveElement(mask, esize) then Z[m, VL] else Zeros(VL); bits(VL) result; for e = 0 to elements-1 if ActivePredicateElement(mask, e, esize) then constant bits(esize) element1 = Elem[operand1, e, esize]; constant bits(64) element2 = Elem[operand2, (e * esize) DIV 64, 64]; constant integer shift = Min(UInt(element2), esize); Elem[result, e, esize] = LSL(element1, shift); else Elem[result, e, esize] = Elem[operand1, e, esize]; Z[dn, VL] = result;

Operational information

If FEAT_SVE2 is implemented or FEAT_SME is implemented, then if PSTATE.DIT is 1:

The execution time of this instruction is independent of:
- The values of the data supplied in any of its operand registers when its governing predicate register contains the same value for each execution.
- The values of the NZCV flags.
The response of this instruction to asynchronous exceptions does not vary based on:
- The values of the data supplied in any of its operand registers when its governing predicate register contains the same value for each execution.
- The values of the NZCV flags.

This instruction might be immediately preceded in program order by a MOVPRFX instruction. The MOVPRFX must conform to all of the following requirements, otherwise the behavior of the MOVPRFX and this instruction is constrained unpredictable:

The MOVPRFX can be predicated or unpredicated.
A predicated MOVPRFX must use the same governing predicate register as this instruction.
A predicated MOVPRFX must use the larger of the destination element size and first source element size in the preferred disassembly of this instruction.
The MOVPRFX must specify the same destination register as this instruction.
The destination register must not refer to architectural register state referenced by any other source operand register of this instruction.

Internal version only: aarchmrs v2024-03_relA, pseudocode v2024-03_rel, sve v2024-03_rel ; Build timestamp: 2024-03-26T09:45

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	0	0	0	0	1	0	0	size		0	1	1	0	1	1	1	0	0	Pg			Zm					Zdn
													R	L	U