USUBLT

Unsigned subtract long (top)

This instruction subtracts the odd-numbered unsigned elements of the second source vector from the corresponding unsigned elements of the first source vector, and places the results in the overlapping double-width elements of the destination vector. 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		0	Zm					0	0	0	1	1	1	Zn					Zd
																		op	S	U	T

Encoding

USUBLT <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); constant integer sel1 = 1; constant integer sel2 = 1; constant boolean unsigned = TRUE;

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	H
10	S
11	D

<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	B
10	H
11	S

<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; for e = 0 to elements-1 constant bits(esize DIV 2) op1elt = Elem[operand1, 2*e + sel1, esize DIV 2]; constant bits(esize DIV 2) op2elt = Elem[operand2, 2*e + sel2, esize DIV 2]; constant integer element1 = if unsigned then UInt(op1elt) else SInt(op1elt); constant integer element2 = if unsigned then UInt(op2elt) else SInt(op2elt); constant integer res = element1 - element2; Elem[result, e, esize] = res<esize-1:0>; Z[d, VL] = result;

Operational information

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

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