ADDHNB

Add narrow high part (bottom)

This instruction adds each vector element of the first source vector to the corresponding vector element of the second source vector, and places the most significant half of the result in the even-numbered half-width destination elements, while setting the odd-numbered elements to zero. This instruction is unpredicated.

SVE2 class

(FEAT_SVE2 || FEAT_SME)

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	1	0	0	0	1	0	1	size		1	Zm					0	1	1	0	0	0	Zn					Zd
																			S	R	T

Encoding

ADDHNB <Zd>.<T>, <Zn>.<Tb>, <Zm>.<Tb>

Decode

if !IsFeatureImplemented(FEAT_SVE2) && !IsFeatureImplemented(FEAT_SME) then EndOfDecode(Decode_UNDEF); if size == '00' then EndOfDecode(Decode_UNDEF); constant integer esize = 8 << UInt(size); constant integer n = UInt(Zn); constant integer m = UInt(Zm); constant integer d = UInt(Zd);

Assembler Symbols

<Zd>	Is the name of the destination scalable vector register, encoded in the "Zd" field.

<T>

Is the size specifier, encoded in size:

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

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

<Tb>

Is the size specifier, encoded in size:

size	<Tb>
00	RESERVED
01	H
10	S
11	D

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

Operation

CheckSVEEnabled(); constant integer VL = CurrentVL; constant integer elements = VL DIV esize; constant bits(VL) operand1 = Z[n, VL]; constant bits(VL) operand2 = Z[m, VL]; bits(VL) result; constant integer halfesize = esize DIV 2; for e = 0 to elements-1 constant integer element1 = UInt(Elem[operand1, e, esize]); constant integer element2 = UInt(Elem[operand2, e, esize]); constant integer res = (element1 + element2) >> halfesize; Elem[result, 2*e + 0, halfesize] = res<halfesize-1:0>; Elem[result, 2*e + 1, halfesize] = Zeros(halfesize); Z[d, VL] = result;

Operational information

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

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