USADA8 -- AArch32

USADA8

Unsigned Sum of Absolute Differences and Accumulate performs four unsigned 8-bit subtractions, and adds the absolute values of the differences to a 32-bit accumulate operand.

It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 ) .

A1

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
!= 1111				0	1	1	1	1	0	0	0	Rd				!= 1111				Rm				0	0	0	1	Rn
cond																Ra

A1

USADA8{<c>}{<q>} <Rd>, <Rn>, <Rm>, <Ra>

if Ra == '1111' then SEE USAD8; d = UInt(Rd); n = UInt(Rn); m = UInt(Rm); a = UInt(Ra); if d == 15 || n == 15 || m == 15 then UNPREDICTABLE;

T1

15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
1	1	1	1	1	0	1	1	0	1	1	1	Rn				!= 1111				Rd				0	0	0	0	Rm
																Ra

T1

USADA8{<c>}{<q>} <Rd>, <Rn>, <Rm>, <Ra>

if Ra == '1111' then SEE USAD8; d = UInt(Rd); n = UInt(Rn); m = UInt(Rm); a = UInt(Ra); if d == 15 || n == 15 || m == 15 then UNPREDICTABLE; // ARMv8-A removes UNPREDICTABLE for R13

For more information about the constrained unpredictable behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors.

Assembler Symbols

<c>	See Standard assembler syntax fields.

<q>	See Standard assembler syntax fields.

<Rd>	Is the general-purpose destination register, encoded in the "Rd" field.

<Rn>	Is the first general-purpose source register, encoded in the "Rn" field.

<Rm>	Is the second general-purpose source register, encoded in the "Rm" field.

<Ra>	Is the third general-purpose source register holding the addend, encoded in the "Ra" field.

Operation

if ConditionPassed() then EncodingSpecificOperations(); absdiff1 = Abs(UInt(R[n]<7:0>) - UInt(R[m]<7:0>)); absdiff2 = Abs(UInt(R[n]<15:8>) - UInt(R[m]<15:8>)); absdiff3 = Abs(UInt(R[n]<23:16>) - UInt(R[m]<23:16>)); absdiff4 = Abs(UInt(R[n]<31:24>) - UInt(R[m]<31:24>)); result = UInt(R[a]) + absdiff1 + absdiff2 + absdiff3 + absdiff4; R[d] = result<31:0>;

Internal version only: isa v00_66, pseudocode v31.3