UDOT (4-way, indexed)

The unsigned integer indexed dot product instruction computes the dot product of a group of four unsigned 8-bit or 16-bit integer values held in each 32-bit or 64-bit element of the first source vector multiplied by a group of four unsigned 8-bit or 16-bit integer values in an indexed 32-bit or 64-bit element of the second source vector, and then destructively adds the widened dot product to the corresponding 32-bit or 64-bit element of the destination vector.

The groups within the second source vector are specified using an immediate index which selects the same group position within each 128-bit vector segment. The index range is from 0 to one less than the number of groups per 128-bit segment, encoded in 1 to 2 bits depending on the size of the group. This instruction is unpredicated.

32-bit

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then UNDEFINED; constant integer esize = 32; constant integer index = UInt(i2); constant integer n = UInt(Zn); constant integer m = UInt(Zm); constant integer da = UInt(Zda);

64-bit

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then UNDEFINED; constant integer esize = 64; constant integer index = UInt(i1); constant integer n = UInt(Zn); constant integer m = UInt(Zm); constant integer da = UInt(Zda);

Assembler Symbols

<Zda>

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

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

<Zm>	For the 32-bit variant: is the name of the second source scalable vector register Z0-Z7, encoded in the "Zm" field.
	For the 64-bit variant: is the name of the second source scalable vector register Z0-Z15, encoded in the "Zm" field.

<imm>	For the 32-bit variant: is the immediate index of a 32-bit group of four 8-bit values within each 128-bit vector segment, in the range 0 to 3, encoded in the "i2" field.
	For the 64-bit variant: is the immediate index of a 64-bit group of four 16-bit values within each 128-bit vector segment, in the range 0 to 1, encoded in the "i1" field.

Operation

CheckSVEEnabled(); constant integer VL = CurrentVL; constant integer PL = VL DIV 8; constant integer elements = VL DIV esize; constant integer eltspersegment = 128 DIV esize; constant bits(VL) operand1 = Z[n, VL]; constant bits(VL) operand2 = Z[m, VL]; constant bits(VL) operand3 = Z[da, VL]; bits(VL) result; for e = 0 to elements-1 constant integer segmentbase = e - (e MOD eltspersegment); constant integer s = segmentbase + index; bits(esize) res = Elem[operand3, e, esize]; for i = 0 to 3 constant integer element1 = UInt(Elem[operand1, 4 * e + i, esize DIV 4]); constant integer element2 = UInt(Elem[operand2, 4 * s + i, esize DIV 4]); res = res + element1 * element2; Elem[result, e, esize] = res; Z[da, VL] = result;

Operational information

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 must be unpredicated.
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	1	0	0	0	1	0	0	1	0	1	i2		Zm			0	0	0	0	0	1	Zn					Zda
								size<1>	size<0>												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
0	1	0	0	0	1	0	0	1	1	1	i1	Zm				0	0	0	0	0	1	Zn					Zda
								size<1>	size<0>												U