UMAX (multiple vectors) -- A64

This instruction determines the unsigned maximum of elements of the two or four second source vectors and the corresponding elements of the two or four first source vectors and destructively places the results in the corresponding elements of the two or four first source vectors.

Two registers
(FEAT_SME2)

Decode for this encoding

if !IsFeatureImplemented(FEAT_SME2) then EndOfDecode(Decode_UNDEF); end; let esize : integer{} = 8 << UInt(size); let dn : integer = UInt(Zdn::'0'); let m : integer = UInt(Zm::'0'); let nreg : integer{} = 2; let unsigned : boolean = TRUE;

Four registers
(FEAT_SME2)

Decode for this encoding

if !IsFeatureImplemented(FEAT_SME2) then EndOfDecode(Decode_UNDEF); end; let esize : integer{} = 8 << UInt(size); let dn : integer = UInt(Zdn::'00'); let m : integer = UInt(Zm::'00'); let nreg : integer{} = 4; let unsigned : boolean = TRUE;

Assembler Symbols

<Zdn1>	For the "Two registers" variant: is the name of the first scalable vector register of the destination and first source multi-vector group, encoded as "Zdn" times 2.
	For the "Four registers" variant: is the name of the first scalable vector register of the destination and first source multi-vector group, encoded as "Zdn" times 4.

<T>

Is the size specifier, encoded in size:

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

<Zdn2>

Is the name of the second scalable vector register of the destination and first source multi-vector group, encoded as "Zdn" times 2 plus 1.

<Zm1>	For the "Two registers" variant: is the name of the first scalable vector register of the second source multi-vector group, encoded as "Zm" times 2.
	For the "Four registers" variant: is the name of the first scalable vector register of the second source multi-vector group, encoded as "Zm" times 4.

<Zm2>

Is the name of the second scalable vector register of the second source multi-vector group, encoded as "Zm" times 2 plus 1.

<Zdn4>

Is the name of the fourth scalable vector register of the destination and first source multi-vector group, encoded as "Zdn" times 4 plus 3.

<Zm4>

Is the name of the fourth scalable vector register of the second source multi-vector group, encoded as "Zm" times 4 plus 3.

Operation

CheckStreamingSVEEnabled(); let VL : integer{} = CurrentVL(); let elements : integer = VL DIV esize; var results : array [[4]] of bits(VL); for r = 0 to nreg-1 do let operand1 : bits(VL) = Z{}(dn+r); let operand2 : bits(VL) = Z{}(m+r); for e = 0 to elements-1 do let op1elt : bits(esize) = operand1[e*:esize]; let element1 : integer = if unsigned then UInt(op1elt) else SInt(op1elt); let op2elt : bits(esize) = operand2[e*:esize]; let element2 : integer = if unsigned then UInt(op2elt) else SInt(op2elt); let res : integer = Max(element1, element2); results[[r]][e*:esize] = res[esize-1:0]; end; end; for r = 0 to nreg-1 do Z{VL}(dn+r) = results[[r]]; end;

Operational information

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

2026-03_rel 2026-03-26 20:48:11

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	0	0	0	0	0	1	size		1	Zm				0	1	0	1	1	0	0	0	0	0	0	0	Zdn				1
																									opc						U

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	0	0	0	0	0	1	size		1	Zm			0	0	1	0	1	1	1	0	0	0	0	0	0	Zdn			0	1
																									opc						U